TY - JOUR T1 - Carbon Accumulation, Flux, and Fate in Stordalen Mire, a Permafrost Peatland in Transition JF - Global Biogeochemical Cycles Y1 - 2022 A1 - Holmes, M. E. A1 - Crill, P. M. A1 - Burnett, W. C. A1 - McCalley, C. K. A1 - Wilson, R. M. A1 - Frolking, S. A1 - Chang, K.‐Y. A1 - Riley, W. J. A1 - Varner, R. K. A1 - Hodgkins, S. B. A1 - McNichol, A. P. A1 - Saleska, S. R. A1 - Rich, V. I. A1 - Chanton, J. P. AB - Stordalen Mire is a peatland in the discontinuous permafrost zone in arctic Sweden that exhibits a habitat gradient from permafrost palsa, to Sphagnum bog underlain by permafrost, to Eriophorum‐dominated fully thawed fen. We used three independent approaches to evaluate the annual, multi‐decadal, and millennial apparent carbon accumulation rates (aCAR) across this gradient: seven years of direct semi‐continuous measurement of CO2 and CH4 exchange, and 21 core profiles for 210Pb and 14C peat dating. Year‐round chamber measurements indicated net carbon balance of −13 ± 8, −49 ± 15, and −91 ± 43 g C m−2 y−1 for the years 2012–2018 in palsa, bog, and fen, respectively. Methane emission offset 2%, 7%, and 17% of the CO2 uptake rate across this gradient. Recent aCAR indicates higher C accumulation rates in surface peats in the palsa and bog compared to current CO2 fluxes, but these assessments are more similar in the fen. aCAR increased from low millennial‐scale levels (17–29 g C m−2 y−1) to moderate aCAR of the past century (72–81 g C m−2 y−1) to higher recent aCAR of 90–147 g C m−2 y−1. Recent permafrost collapse, greater inundation and vegetation response has made the landscape a stronger CO2 sink, but this CO2 sink is increasingly offset by rising CH4 emissions, dominated by modern carbon as determined by 14C. The higher CH4 emissions result in higher net CO2‐equivalent emissions, indicating that radiative forcing of this mire and similar permafrost ecosystems will exert a warming influence on future climate. Stordalen Mire, a permafrost peatland, has become a stronger carbon sink due to shifts in vegetation and inundation accompanying thaw This stronger carbon sink is offset by an increase in methane emission, resulting in higher net CO2‐equivalent emissions Analysis of respiration products indicates that methane emission from the fen and bog are dominated by modern carbon Stordalen Mire, a permafrost peatland, has become a stronger carbon sink due to shifts in vegetation and inundation accompanying thaw This stronger carbon sink is offset by an increase in methane emission, resulting in higher net CO2‐equivalent emissions Analysis of respiration products indicates that methane emission from the fen and bog are dominated by modern carbon VL - 36 UR - https://onlinelibrary.wiley.com/doi/10.1029/2021GB007113 IS - 1 ER - TY - JOUR T1 - Radiocarbon Content of Dissolved Organic Carbon in the South Indian Ocean JF - Geophysical Research Letters Y1 - 2018 A1 - Bercovici, S. K. A1 - McNichol, A. P. A1 - Xu, L. A1 - Hansell, D. A. KW - dissolved organic carbon KW - indian ocean KW - radiocarbon AB - We report four profiles of the radiocarbon content of dissolved organic carbon (DOC) spanning the South Indian Ocean (SIO), ranging from the Polar Front (56°S) to the subtropics (29°S). Surface waters held mean DOC Δ14C values of −426 ± 6‰ (~4,400 14C years) at the Polar Front and DOC Δ14C values of −252 ± 22‰ (~2,000 14C years) in the subtropics. At depth, Circumpolar Deep Waters held DOC Δ14C values of −491 ± 13‰ (~5,400 years), while values in Indian Deep Water were more depleted, holding DOC Δ14C values of −503 ± 8‰ (~5,600 14C years). High‐salinity North Atlantic Deep Water intruding into the deep SIO had a distinctly less depleted DOC Δ14C value of −481 ± 8‰ (~5,100 14C years). We use multiple linear regression to assess the dynamics of DOC Δ14C values in the deep Indian Ocean, finding that their distribution is characteristic of water masses in that region. VL - 45 UR - https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1002/2017GL076295 IS - 2 ER - TY - JOUR T1 - Rapid extraction of dissolved inorganic carbon from seawater and groundwater samples for radiocarbon dating JF - LIMNOLOGY AND OCEANOGRAPHY-METHODS Y1 - 2016 A1 - Gospodinova, K. A1 - McNichol, A. P. A1 - Gagnon, A. A1 - Walter, S. R. Shah AB - We designed and developed a system to efficiently extract dissolved inorganic carbon (DIC) from seawater and groundwater samples for radiocarbon dating. The Rapid Extraction of Dissolved Inorganic Carbon System (REDICS) utilizes a gas-permeable polymer membrane contactor to extract the DIC from an acidified water sample in the form of carbon dioxide (CO2), introduce it to a helium gas stream, cryogenically isolate it, and store it for stable and radiocarbon isotope analysis. The REDICS system offers multiple advantages to the DIC extraction method which has been used for the last several decades at the National Ocean Sciences Accelerator Mass Spectrometry Facility (NOSAMS) at the Woods Hole Oceanographic Institution, including faster DIC extraction, streamlined analysis, and minimized set-up and prep time. The system was tested using sodium carbonate and seawater standards, duplicates of which were also processed on the water stripping line (WSL) at NOSAMS. The results demonstrate that the system successfully extracts, quantifies, and stores more than 99% of the DIC in less than 20 min. Stable and radiocarbon isotope analysis demonstrated system precision of 0.04 parts per thousand and 7.8 parts per thousand, respectively. A Sargasso Sea depth profile was used to further validate the system. The results show high precision for both stable and radiocarbon analysis with pooled standard deviations of 0.02 parts per thousand and 5.6 parts per thousand, respectively. A comparison between the REDICS and WSL analyses indicates a good accuracy for both stable and radio-isotope analysis. VL - 14 ER - TY - JOUR T1 - Transfer of organic carbon through marine water columns to sediments - insights from stable and radiocarbon isotopes of lipid biomarkers JF - Biogeosciences Y1 - 2014 A1 - Wakeham, S. G. A1 - McNichol, A. P. AB - Compound-specific C-13 and C-14 compositions of diverse lipid biomarkers (fatty acids, alkenones, hydrocarbons, sterols and fatty alcohols) were measured in sinking particulate matter collected in sediment traps and from underlying surface sediments in the Black Sea, the Arabian Sea and the Ross Sea. The goal was to develop a multiparameter approach to constrain relative inputs of organic carbon (OC) from marine biomass, terrigenous vascular-plant and relict-kerogen sources. Using an isotope mass balance, we calculate that marine biomass in sediment trap material from the Black Sea and Arabian Sea accounted for 66-100% of OC, with lower terrigenous (3-8 %) and relict (4-16 %) contributions. Marine biomass in sediments constituted lower proportions of OC (66-90 %), with consequentially higher proportions of terrigenous and relict carbon (3-17 and 713 %, respectively). Ross Sea data were insufficient to allow similar mass balance calculations. These results suggest that, whereas particulate organic carbon is overwhelmingly marine in origin, pre-aged allochthonous terrigenous and relict OC become proportionally more important in sediments, consistent with pre-aged OC being better preserved during vertical transport to and burial at the seafloor than the upper-ocean-derived marine OC. VL - 11 IS - 23 N1 - PT: J; TC: 0; UT: WOS:000346357100026 JO - Transfer of organic carbon through marine water columns to sediments - insights from stable and radiocarbon isotopes of lipid biomarkers ER - TY - JOUR T1 - Carbon isotopic evidence for microbial control of carbon supply to Orca Basin at the seawater-brine interface JF - BIOGEOSCIENCES Y1 - 2013 A1 - Shah, S. R. A1 - Joye, S. B. A1 - Brandes, J. A. A1 - McNichol, A. P. AB - Orca Basin, an intraslope basin on the Texas-Louisiana continental slope, hosts a hypersaline, anoxic brine in its lowermost 200m in which limited microbial activity has been reported. This brine contains a large reservoir of reduced and aged carbon, and appears to be stable at decadal time scales: concentrations and isotopic composition of dissolved inorganic (DIC) and organic carbon (DOC) are similar to measurements made in the 1970s. Both DIC and DOC are more ``aged{''} within the brine pool than in overlying water, and the isotopic contrast between brine carbon and seawater carbon is much greater for DIC than DOC. While the stable carbon isotopic composition of brine DIC points towards a combination of methane and organic carbon remineralization as its source, radiocarbon and box model results point to the brine interface as the major source region for DIC, allowing for only limited oxidation of methane diffusing upwards from sediments. This conclusion is consistent with previous studies that identify the seawater-brine interface as the focus of microbial activity associated with Orca Basin brine. Isotopic similarities between DIC and DOC suggest a different relationship between these two carbon reservoirs than is typically observed in deep ocean basins. Radiocarbon values implicate the seawater-brine interface region as the likely source region for DOC to the brine as well as DIC. VL - 10 ER - TY - JOUR T1 - Prominent bacterial heterotrophy and sources of C-13-depleted fatty acids to the interior Canada Basin JF - BIOGEOSCIENCES Y1 - 2013 A1 - Shah, S. R. A1 - Griffith, D. R. A1 - Galy, V. A1 - McNichol, A. P. A1 - Eglinton, T. I. AB - In recent decades, the Canada Basin of the Arctic Ocean has experienced rapidly decreasing summer sea ice coverage and freshening of surface waters. It is unclear how these changes translate to deeper waters, particularly as our baseline understanding of organic carbon cycling in the deep basin is quite limited. In this study, we describe full-depth profiles of the abundance, distribution and carbon isotopic composition of fatty acids from suspended particulate matter at a seasonally ice-free station and a semi-permanently ice-covered station. Fatty acids, along with suspended particulate organic carbon (POC), are more concentrated and C-13-enriched under ice cover than in ice-free waters. But this influence, apparent at 50 m depth, does not propagate downward below 150m depth, likely due to the weak biological pump in the central Canada Basin. Branched fatty acids have delta C-13 values that are similar to suspended POC at all depths and are more C-13-enriched than even-numbered saturated fatty acids at depths above 3000 m. These are likely to be produced in situ by heterotrophic bacteria incorporating organic carbon that is isotopically similar to total suspended POC. Below surface waters, there is also the suggestion of a source of saturated even-numbered fatty acids which could represent contributions from laterally advected organic carbon and/or from chemoautotrophic bacteria. At 3000 m depth and below, a greater relative abundance of long-chain (C20-24), branched and unsaturated fatty acids is consistent with a stronger influence of re-suspended sedimentary organic carbon. At these deep depths, two individual fatty acids (C-12 and iso-C-17) are significantly depleted in C-13, allowing for the possibility that methane oxidizing bacteria contribute fatty acids, either directly to suspended particulate matter or to shallow sediments that are subsequently mobilized and incorporated into suspended particulate matter within the deep basin. VL - 10 ER - TY - JOUR T1 - Carbon dynamics in the western Arctic Ocean: insights from full-depth carbon isotope profiles of DIC, DOC, and POC JF - Biogeosciences Y1 - 2012 A1 - Griffith, D. R. A1 - McNichol, A. P. A1 - Xu, L. A1 - McLaughlin, F. A. A1 - Macdonald, R. W. A1 - Brown, K. A. A1 - Eglinton, T. I. AB - Arctic warming is projected to continue throughout the coming century. Yet, our currently limited understanding of the Arctic Ocean carbon cycle hinders our ability to predict how changing conditions will affect local Arctic ecosystems, regional carbon budgets, and global climate. We present here the first set of concurrent, full-depth, dual-isotope profiles for dissolved inorganic carbon (DIC), dissolved organic carbon (DOC), and suspended particulate organic carbon (POCsusp) at two sites in the Canada Basin of the Arctic Ocean. The carbon isotope composition of sinking and suspended POC in the Arctic contrasts strongly with open ocean Atlantic and Pacific sites, pointing to a combination of inputs to Arctic POCsusp at depth, including surface-derived organic carbon (OC), sorbed/advected OC, and OC derived from in situ DIC fixation. The latter process appears to be particularly important at intermediate depths, where mass balance calculations suggest that OC derived from in situ DIC fixation contributes up to 22% of POCsusp. As in other oceans, surface-derived OC is still a dominant source to Arctic POCsusp. Yet, we suggest that significantly smaller vertical POC fluxes in the Canada Basin make it possible to see evidence of DIC fixation in the POCsusp pool even at the bulk isotope level. VL - 9 IS - 3 N1 - id: 2254; PT: J; TC: 4; UT: WOS:000302179500026 JO - Carbon dynamics in the western Arctic Ocean: insights from full-depth carbon isotope profiles of DIC, DOC, and POC ER - TY - JOUR T1 - Age and Growth Rate Dynamics of an Old African Baobab Determined by Radiocarbon Dating JF - Radiocarbon Y1 - 2010 A1 - Patrut, A. A1 - Mayne, D. H. A1 - von Reden, K. F. A1 - Lowy, D. A. A1 - Venter, S. A1 - McNichol, A. P. A1 - Roberts, M. L. A1 - Margineanu, D. KW - cal kyr bp KW - Calibration KW - southern-hemisphere AB - In 2008, a large African baobab (Adansonia digitata L.) from Makulu Makete, South Africa, split vertically into 2 sections, revealing a large enclosed cavity. Several wood samples collected from the cavity were processed and radiocarbon dated by accelerator mass spectrometry (AMS) for determining the age and growth rate dynamics of the tree. The C-14 date of the oldest sample was found to be of 1016 +/- 22 BP, which corresponds to a calibrated age of 1000 +/- 15 yr. Thus, the Makulu Makete tree, which eventually collapsed to the ground and died, becomes the second oldest African baobab dated accurately to at least 1000 yr. The conventional growth rate of the trunk, estimated by the radial increase, declined gradually over its life cycle. However, the growth rate expressed more adequately by the cross-sectional area increase and by the volume increase accelerated up to the age of 650 yr and remained almost constant over the past 450 yr. VL - 52 SN - 0033-8222 IS - 2 N1 - Sp. Iss. 1696jn Times Cited:2 Cited References Count:21 JO - Radiocarbon ER - TY - JOUR T1 - A Continuous-Flow Gas Chromatography C-14 Accelerator Mass Spectrometry System JF - Radiocarbon Y1 - 2010 A1 - McIntyre, C. P. A1 - Galutschek, E. A1 - Roberts, M. L. A1 - von Reden, K. F. A1 - McNichol, A. P. A1 - Jenkins, W. J. KW - ams system KW - gc-ams KW - negative-ion source KW - RADIOCARBON ANALYSIS AB - Gas-accepting ion sources for radiocarbon accelerator mass spectrometry (AMS) have permitted the direct analysis of CO2 gas, eliminating the need to graphitize samples. As a result, a variety of analytical instruments can be interfaced to an AMS system, processing time is decreased, and smaller samples can be analyzed (albeit with lower precision). We have coupled a gas chromatograph to a compact C-14 AMS system fitted with a microwave ion source for real-time compound-specific C-14 analysis. As an initial test of the system, we have analyzed a sample of fatty acid methyl esters and biodiesel. Peak shape and memory was better then existing systems fitted with a hybrid ion source while precision was comparable. C-14/C-12 ratios of individual components at natural abundance levels were consistent with those determined by conventional methods. Continuing refinements to the ion source are expected to improve the performance and scope of the instrument. VL - 52 SN - 0033-8222 IS - 2 N1 - Sp. Iss. 1696jn Times Cited:4 Cited References Count:24 JO - Radiocarbon ER - TY - JOUR T1 - Fire History of a Giant African Baobab Evinced by Radiocarbon Dating JF - Radiocarbon Y1 - 2010 A1 - Patrut, A. A1 - Mayne, D. H. A1 - von Reden, K. F. A1 - Lowy, D. A. A1 - van Pelt, R. A1 - McNichol, A. P. A1 - Roberts, M. L. A1 - Margineanu, D. KW - age calibration KW - bomb c-14 data KW - bombacaceae KW - cal kyr bp KW - southern-hemisphere KW - system AB - The article reports the first radiocarbon dating of a live African baobab (Adansonia digitata L.), by investigating wood samples collected from 2 inner cavities of the very large 2-stemmed Platland tree of South Africa. Some 16 segments extracted from determined positions of the samples, which correspond to a depth of up to 15-20 cm in the wood, were processed and analyzed by accelerator mass spectrometry (AMS). Calibrated ages of segments are not correlated with their positions in the stems of the tree. Dating results indicate that the segments originate from new growth layers, with a thickness of several centimeters, which cover the original old wood. Four new growth layers were dated before the reference year AD 1950 and 2 layers were dated post-AD 1950, in the post-bomb period. Formation of these layers was triggered by major damage inside the cavities. Fire episodes are the only possible explanation for such successive major wounds over large areas or over the entire area of the inner cavities of the Platland tree, able to trigger regrowth. VL - 52 SN - 0033-8222 IS - 2 N1 - Sp. Iss. 1696jn Times Cited:11 Cited References Count:28 JO - Radiocarbon ER - TY - JOUR T1 - A High-Performance (14)c Accelerator Mass Spectrometry System JF - Radiocarbon Y1 - 2010 A1 - Roberts, M. L. A1 - Burton, J. R. A1 - Elder, K. L. A1 - Longworth, B. E. A1 - McIntyre, C. P. A1 - von Reden, K. F. A1 - Han, B. X. A1 - Rosenheim, B. E. A1 - W. J. Jenkins A1 - Galutschek, E. A1 - McNichol, A. P. AB - A new and unique radiocarbon accelerator mass spectrometry (AMS) facility has been constructed at the Woods Hole Oceanographic Institution. The defining characteristic of the new system is its large-gap optical elements that provide a larger-than-standard beam acceptance. Such a system is ideally suited for high-throughput, high-precision measurements of (14)C. Details and performance of the new system are presented. VL - 52 IS - 2 N1 - id: 2095; PT: J; CT: 20th International Radiocarbon Conference; CY: MAY 31-JUN 05, 2009; CL: Big Isl, HI; SI: 1; UT: WOS:000285437800005 JO - A High-Performance (14)c Accelerator Mass Spectrometry System ER - TY - JOUR T1 - Molecular and Isotopic Analysis of Motor Oil from a Biodiesel-Driven Vehicle JF - Energy & Fuels Y1 - 2010 A1 - Peacock, E. E. A1 - Arey, J. S. A1 - DeMello, J. A. A1 - McNichol, A. P. A1 - Nelson, R. K. A1 - Reddy, C. M. AB - Biodiesel, a mixture of fatty acid methyl esters (FAMEs), is increasingly recognized as a renewable fuel. While some environmental impacts of biodiesel usage have been investigated, accumulation of organic compounds in motor oil, which can subsequently leak onto roads, has not been studied. Because studies have shown that toxic polycyclic aromatic hydrocarbons (PAHs) accumulate in the motor oil of engines fueled with fossil diesel or gasoline, the objective of this study was to determine if this also occurs for engines fueled with biodiesel. Here, we sampled and analyzed motor oil of a biodiesel-powerd 2005 Volkswagen Passat Wagon over 3240 km for personal-use driving. Using gas chromatography with flame ionization detection (GC-FID), we found a total of 0.5% FAMEs in the motor oil after 3240 km. We also used gas chromatography-mass spectrometry and comprehensive two-dimensional gas chromatography and did not detect PAHs or other organic compounds not present in the initial motor oil. Using natural radiocarbon analysis, a powerful technique capable of detecting biodiesel-derived carbon that would be otherwise undetectable by gas chromatography, we found a total of 0.68% biodiesel-derived carbon after 3240 km. This is similar to the amount of FAMEs found in these samples with GC-FID, indicating that the primary source of biodiesel-derived carbon in the motor oil is FAMEs (and not PAHs or other carbonaceous species). This result suggests that used motor oil of biodiesel vehicles can be less toxic based on PAH content than vehicles fueled with fossil diesel or gasoline. VL - 24 N1 - id: 816; 555MH Times Cited:0 Cited References Count:63; YY JO - Molecular and Isotopic Analysis of Motor Oil from a Biodiesel-Driven Vehicle ER - TY - JOUR T1 - The Passage of the Bomb Radiocarbon Pulse into the Pacific Ocean JF - Radiocarbon Y1 - 2010 A1 - Jenkins, W. J. A1 - Elder, K. L. A1 - McNichol, A. P. A1 - von Reden, K. KW - AMS KW - antarctic intermediate water KW - anthropogenic co2 KW - atlantic KW - c-14 data KW - carbon KW - distributions KW - graphite KW - south-pacific KW - tritium AB - We report and compare radiocarbon observations made on 2 meridional oceanographic sections along 150 degrees W in the South Pacific in 1991 and 2005. The distributions reflect the progressive penetration of nuclear weapons-produced (14)C into the oceanic thermocline. The changes over the 14 yr between occupations are demonstrably large relative to any possible drift in our analytical standardization. The computed difference field based on the gridded data in the upper 1600 m of the section exhibits a significant decrease over time (approaching 40 to 50 parts per thousand in Delta(14)C) in the upper 200-300 m, consistent with the decadal post-bomb decline in atmospheric (14)C levels. A strong positive anomaly (increase with time), centered on the low salinity core of the Antarctic Intermediate Water (AAIW), approaches 50-60 parts per thousand in Delta(14)C, a clear signature of the downstream evolution of the (14)C transient in this water mass. We use this observation to estimate the transit time of AAIW from its "source region" in the southeast South Pacific and to compute the effective reservoir age of this water mass. The 2 sections show small but significant changes in the abyssal (14)C distributions. Between 1991 and 2005, Delta(14)C has increased by 9 parts per thousand below 2000 m north of 55 degrees S. This change is accompanied overall by a modest increase in salinity and dissolved oxygen, as well as a slight decrease in dissolved silica. Such changes are indicative of greater ventilation. Calculation of "phosphate star" also indicates that this may be due to a shift from the Southern Ocean toward North Atlantic Deep Water as the ventilation source of the abyssal South Pacific. VL - 52 SN - 0033-8222 IS - 3 N1 - Sp. Iss. 2696jo Times Cited:7 Cited References Count:38 JO - Radiocarbon ER - TY - JOUR T1 - Software development for continuous-gas-flow AMS JF - Nuclear Instruments & Methods in Physics Research Section B-Beam Interactions with Materials and Atoms Y1 - 2008 A1 - von Reden, K. F. A1 - Roberts, M. L. A1 - W. J. Jenkins A1 - Rosenheim, B. E. A1 - McNichol, A. P. A1 - Schneider, R. J. AB - The National Ocean Sciences Accelerator Mass Spectrometry (NOSAMS) Facility at Woods Hole Oceanographic institution is presently completing installation of a novel continuous-flow AMS system. A multi-year development of an AMS microwave gas ion source in collaboration with Atomic Energy Canada Limited (AECL), Chalk River, has preceded this final step of an implementation that is expected to add a new dimension to (14)C AMS. National Instruments, NIM, and CAMAC modules have been programmed with Lab-VIEW on a Windows XP platform to form the basis for data acquisition. In this paper we discuss possible applications and include simulations of expected data acquisition scenarios like real-time AMS analysis of chromatograms. Particular attention will have to be given to issues of synchronization between rapidly changing input amplitudes and signal processing cycles in hardware and software. (C) 2008 Elsevier B.V. All rights reserved. VL - 266 IS - 10 N1 - id: 2091; PT: J; CT: 9th European Conference on Accelerators in Applied Research and Technology; CY: SEP 03-07, 2007; CL: Florence, ITALY; SP: Univ Florence, Dept Phys, Ist Nazl Fis Nucl; UT: WOS:000257185600033 JO - Software development for continuous-gas-flow AMS ER - TY - JOUR T1 - Evaluation of gas chromatographic isotope fractionation and process contamination by carbon in compound-specific radiocarbon analysis JF - Analytical Chemistry Y1 - 2007 A1 - Zencak, Z. A1 - Reddy, C. M. A1 - Teuten, E. L. A1 - Xu, L. A1 - McNichol, A. P. A1 - Gustafsson, O. AB - The relevance of both modern and fossil carbon contamination as well as isotope fractionation during preparative gas chromatography for compound-specific radiocarbon analysis (CSRA) was evaluated. Two independent laboratories investigated the influence of modern carbon contamination in the sample cleanup procedure and preparative capillary gas chromatography (pcGC) of a radiocarbon-dead 3,3',4,4',5,5'-hexachlorobiphenyl (PCB 169) reference. The isolated samples were analyzed for their C-14/C-12 ratio by accelerator mass spectrometry. Sample Delta C-14 values of -996 +/- 20 and -985 +/- 20% agreed with a Delta C-14 of -995 +/- 20% for the unprocessed PCB 169, suggesting that no significant contamination by nonfossil carbon was introduced during the sample preparation process at either laboratory. A reference compound containing a modern C-14/C-12 ratio (vanillin) was employed to evaluate process contamination from fossil C. No negative bias due to fossil C was observed (sample Delta C-14 value of 165 +/- 20% agreed with Delta C-14 of 155 +/- 12% for the unprocessed vanillin). The extent of isotopic fractionation that can be induced during pcGC was evaluated by partially collecting the vanillin model compound of modern C-14/C-12 abundance. A significant change in the delta C-13 and delta C-14 values was observed when only parts of the eluting peak were collected (delta C-13 values ranged from -15.75 to -49.91% and delta C-14 values from -82.4 to +4.71%). Delta C-14 values, which are normalized to a delta C-13 of -25%, did not deviate significantly (-58.9 to -5.8%, considering the uncertainty of similar to +/- 20%). This means that normalization of radiocarbon results to a delta C-13 of -25%, normally performed to remove effects of environmental isotope fractionation on C-14-based age determinations, also cor-rects sufficiently for putative isotopic fractionation that may occur during pcGC isolation of individual compounds for CSRA. VL - 79 IS - 5 N1 - id: 615; 140ID Times Cited:11 Cited References Count:32 JO - Evaluation of gas chromatographic isotope fractionation and process contamination by carbon in compound-specific radiocarbon analysis ER - TY - JOUR T1 - The power of radiocarbon in biogeochemical studies of the marine carbon cycle: insights from studies of dissolved and particulate organic carbon (DOC and POC) JF - Chem Rev Y1 - 2007 A1 - McNichol, A. P. A1 - Aluwihare, L. I. VL - 107 IS - 2 N1 - McNichol, Ann PAluwihare, Lihini IengResearch Support, U.S. Gov't, Non-P.H.S.Review2007/02/16 09:00Chem Rev. 2007 Feb;107(2):443-66. JO - The power of radiocarbon in biogeochemical studies of the marine carbon cycle: insights from studies of dissolved and particulate organic carbon (DOC and POC) ER - TY - JOUR T1 - Absence of 14C in PM2.5 Emissions from Gasohol Combustion in Small Engines JF - Aerosol Science and Technology Y1 - 2006 A1 - Lewis, C. W. A1 - Volkens, J. A1 - Braddock, J. N. A1 - Crews, W. S. A1 - Lonneman, W. A. A1 - McNichol, A. P. N1 - id: 1699 ER - TY - JOUR T1 - Carbon flow in salt marsh sediments: Natural-level radiocarbon as a tracer for incorporation of petroleum-derived carbon into bacteria JF - Geochim. Cosmochim. Acta Y1 - 2006 A1 - Wakeham, S. G. A1 - McNichol, A. P. A1 - Kostka, J. A1 - Pease, T. K. VL - 70 N1 - id: 762 ER - TY - JOUR T1 - Natural abundance radiocarbon as a tracer of assimilation of petrolleum carbon by bacteria in salt marsh sediments JF - Geochim. Cosmochim. Acta Y1 - 2006 A1 - Wakeham, S. G. A1 - McNichol, A. P. A1 - Kostka, J. A1 - Pease, T. K. VL - 70 N1 - id: 520 ER - TY - JOUR T1 - Natural-abundance radiocarbon as a tracer of assimilation of petroleum carbon by bacteria in salt marsh sediments JF - Geochimica Et Cosmochimica Acta Y1 - 2006 A1 - Wakeham, S. G. A1 - McNichol, A. P. A1 - Kostka, J. E. A1 - Pease, T. K. AB - The natural abundance of radiocarbon ((14)C) provides unique insight into the source and cycling of sedimentary organic matter. Radiocarbon analysis of bacterial phospholipid lipid fatty acids (PLFAs) in salt-marsh sediments of southeast Georgia (USA)-one heavily contaminated by petroleum residues-was used to assess the fate of petroleum-derived carbon in sediments and incorporation of fossil carbon into microbial biomass. PLFAs that are common components of eubacterial cell membranes (e.g., branched C(15) and C(17), 10-methyl-C(16)) were depleted in (14)C in the contaminated sediment (mean Delta(14)C value of +25 +/- 19 parts per thousand for bacterial PLFAs) relative to PLFAs in uncontaminated "control" sediment (Delta(14)C = +101 +/- 12 parts per thousand). We suggest that the (14)C-depletion in bacterial PLFAs at the contaminated site results from microbial metabolism of petroleum and subsequent incorporation of petroleum-derived carbon into bacterial membrane lipids. A mass balance calculation indicates that 6-10% of the carbon in bacterial PLFAs at the oiled site could derive from petroleum residues. These results demonstrate that even weathered petroleum may contain components of sufficient lability to be a carbon source for biomass production by marsh sediment microorganisms. Furthermore, a small but significant fraction of fossil carbon is assimilated even in the presence of a much larger pool of presumably more-labile and faster-cycling carbon substrates. (c) 2006 Elsevier Inc. All rights reserved. VL - 70 IS - 7 N1 - 030olTimes Cited:27Cited References Count:65 JO - Natural-abundance radiocarbon as a tracer of assimilation of petroleum carbon by bacteria in salt marsh sediments ER - TY - JOUR T1 - 14C Measurements JF - Aerosol Science & Technol Y1 - 2004 A1 - Tanner, R. L. A1 - Parkhurst, W. J. A1 - McNichol, A. P. VL - 38 IS - S1 N1 - id: 972 ER - TY - JOUR T1 - Plans for Expanded 14C Analyses at the NOSAMS Facility--a status and progress report. 9th International Conference on Accelerator Mass Spectrometry, Nagoya, Japan, 9/2002 JF - Nuclear Instruments and Methods in Physics Research Y1 - 2004 A1 - von Reden, K. A1 - Donoghue, J. A1 - Elder, K. A1 - Gagnon, A. A1 - Gerlach, D. A1 - Griffin, V. S. A1 - Healy, R. A1 - Long, P. A1 - McNichol, A. P. A1 - Percy, D. A1 - Roberts, M. L. A1 - Schneider, R. J. A1 - Xu, L. A1 - Hayes, J. VL - B 223-224 N1 - id: 1810 ER - TY - JOUR T1 - Changes of the 13C/12C of dissolved inorganic carbon in the ocean as a tracer of anthropogenic C)2 uptake JF - Global Biogeochemical Cycles Y1 - 2003 A1 - Quay, P. D. A1 - Sonnerup, T. A1 - Westby, J. A1 - Stutsman, J. A1 - McNichol, A. P. VL - 17 IS - 1004 N1 - id: 1689 ER - TY - JOUR T1 - Fossil Sources of Ambient Aerosol Carbon Based on 14C Measurements JF - Aerosol Science and Technology Y1 - 2003 A1 - Tanner, R. L. A1 - Parker, W. J. A1 - McNichol, A. P. N1 - id: 1690 ER - TY - JOUR T1 - Challenges in radiocarbon dating organic carbon in opal-rich marine sediments JF - Radiocarbon Y1 - 2002 A1 - Zheng, Y. A1 - Anderson, R. F. A1 - Froelich, P. N. A1 - Beck, W. A1 - McNichol, A. P. A1 - Guilderson, T. AB - We explored the reliability of radiocarbon ages obtained on organic carbon phases in opal-rich Southern Ocean sediments. Paired biogenic carbonate and total organic carbon (TOC) C-14 analyses for three Southern Ocean cores showed that the TOC ages were systematically younger than the carbonate ages. Carbonate ages were consistent with oxygen isotopic and bio-stratigraphy, indicating error in TOC ages that could be explained by 5-24% of modern carbon contamination of TOC samples. Two possible sources of contamination are: 1) adsorption of atmospheric CO2 or volatile organic compounds to reactive opal surface sites, and 2) fixation of atmospheric CO2 by chemosynthetic bacteria during core storage. In an effort to reduce the modem carbon contamination, diatoms were separated from sediments, purified, and pre-oxidized by concentrated nitric and perchloric acids to permit dating of opal-intrinsic organic carbon (similar to0.1-0.3% by weight). C-14 ages of chemically pre-oxidized opal showed a significant amount of modem carbon contamination, from 11 to 32%, indicating adsorption from the atmosphere of modem carbon onto opal surfaces that were previously cleaned by acid oxidation. Several experiments designed to eliminate the modern C contamination were attempted, but so far we have not been able to obtain a radiocarbon age on C-14-dead Southern Ocean opal-rich sediments, either bulk TOC or purified diatom opal samples, as old as our procedural blank. VL - 44 UR - https://journals.uair.arizona.edu/index.php/radiocarbon/article/view/4084/3509 IS - 1 N1 - 591keTimes Cited:13Cited References Count:28 JO - Challenges in radiocarbon dating organic carbon in opal-rich marine sediments ER - TY - JOUR T1 - Changes in the 13C/12C of dissolved inorganic carbon in the ocean as a tracer of anthropogenic CO2 uptake JF - Global Biogeochemical Cycles Y1 - 2002 A1 - Quay, P. D. A1 - Sonnerup, R. A1 - Westby, T. A1 - Stutsman, J. A1 - McNichol, A. P. VL - 17 IS - 1 N1 - id: 1715 ER - TY - JOUR T1 - Converting AMS data to radiocarbon values: considerations and conventions JF - Radiocarbon Y1 - 2002 A1 - McNichol, A. P. A1 - Jull, A. J. T. A1 - Burr, G. S. VL - 43 IS - 2A N1 - id: 1818 ER - TY - CONF T1 - Fossil sources of PM2.5 aerosol carbon based on 14C measurements T2 - PM2.5 and electric power generation: recent findings and implications Y1 - 2002 A1 - Tanner, R. L. A1 - Parkhurst, W. J. A1 - McNichol, A. P. JF - PM2.5 and electric power generation: recent findings and implications CY - Pittsburgh, PA N1 - id: 353 ER - TY - JOUR T1 - Radiocarbon as a tool to apportion the sources of polycyclic aromatic hydrocarbons and black carbon in environmental samples JF - Environmental Science & Technology Y1 - 2002 A1 - Reddy, C. M. A1 - Pearson, A. A1 - Xu, L. A1 - McNichol, A. P. A1 - Benner, B. A. A1 - Wise, S. A. A1 - Klouda, G. A. A1 - Currie, L. A. A1 - Eglinton, T. I. AB - To determine the relative inputs of polycyclic aromatic hydrocarbons (PAHs) and black carbon (BC) in environmental samples from the combustion of fossil fuels and biomass we have developed two independent analytical methods for determining the C-14 abundance of PAHs and BC. The 5730 yr half-life of C-14 makes it an ideal tracer for identifying combustion products derived from fossil fuels (C-14-free) versus those stemming from modern biomass (contemporary C-14). The C-14 abundance of PAHs in several environmental Standard Reference Materials was measured by accelerator mass spectrometry after extraction and then purification by high-performance liquid chromatography and preparative capillary gas chromatography. This method yields pure compounds that allow for a high degree of confidence in the C-14 results. The PAHs data were then used to compare and evaluate results from an operationally defined thermal oxidation method used to isolate a BC fraction. The C-14 compositions of PAHs and BC were very similar and suggest that the thermal oxidation method employed for isolating BC is robust and free from interferences by non-BC components. In addition, these data indicate that both the PAHs and the BC species derive mostly from fossil fuels and/or their combustion products. VL - 36 IS - 8 N1 - 541gfTimes Cited:133Cited References Count:59 JO - Radiocarbon as a tool to apportion the sources of polycyclic aromatic hydrocarbons and black carbon in environmental samples ER - TY - JOUR T1 - WOCE radiocarbon IV: Pacific Ocean results; P10, P13N, P14C, P18, P19 & S4P JF - Radiocarbon Y1 - 2002 A1 - Key, R. M. A1 - Quay, P. D. A1 - Schlosser, P. A1 - McNichol, A. P. A1 - von Reden, K. F. A1 - Schneider, R. J. A1 - Elder, K. L. A1 - Stuiver, M. A1 - Ostlund, H. G. AB - The World Ocean Circulation Experiment, carried out between 1990 and 1997, provided the most comprehensive oceanic survey of radiocarbon to date. Approximately 10,000 samples were collected in the Pacific Ocean by U.S. investigators for both conventional large volume P counting and small volume accelerator mass spectrometry analysis techniques. Results from six cruises are presented. The data quality is as good or better than previous large-scale surveys. The C-14 distribution for the entire WOCE Pacific data set is graphically described using mean vertical profiles and sections, and property-property plots. VL - 44 UR - https://journals.uair.arizona.edu/index.php/radiocarbon/article/view/4097 IS - 1 N1 - 591keTimes Cited:33Cited References Count:56 JO - WOCE radiocarbon IV: Pacific Ocean results; P10, P13N, P14C, P18, P19 & S4P ER - TY - JOUR T1 - Converting AMS data to radiocarbon values: Considerations and conventions JF - Radiocarbon Y1 - 2001 A1 - McNichol, A. P. A1 - Jull, A. J. T. A1 - Burr, G. S. KW - accelerator mass-spectrometry KW - NOSAMS KW - ratio AB - We summarize the basic operation of accelerator mass spectrometry (AMS) systems used to measure radiocarbon and discuss the calculations used to convert AMS output to C-14 data. VL - 43 SN - 0033-8222 IS - 2a N1 - 1531yc Times Cited:24 Cited References Count:19 JO - Radiocarbon ER - TY - JOUR T1 - Origins of lipid biomarkers in Santa Monica Basin surface sediment: A case study using compound-specific D14C analysis JF - Geochimica et Cosmochimica Acta Y1 - 2001 A1 - Pearson, A. A1 - McNichol, A. P. A1 - Benitez-Nelson, B. C. A1 - Hayes, J. M. A1 - Eglinton, T. I. VL - 65 IS - 18 N1 - id: 1419 ER - TY - JOUR T1 - The Indian Ocean 13C Suess effect JF - Global Biogeochemical Cycles Y1 - 2000 A1 - Sonnerup, R. E. A1 - Quay, P. D. A1 - McNichol, A. P. VL - 14 N1 - id: 1816 ER - TY - JOUR T1 - Low-level (submicromole) environmental 14C metrology JF - Nucl. Instr. and Meth. in Phys. Res. Y1 - 2000 A1 - Currie, L. A. A1 - Kessler, J. D. A1 - Marolf, J. V. A1 - McNichol, A. P. A1 - Stuart, D. R. A1 - Donoghue, J. C. VL - B IS - 172 N1 - id: 1713 ER - TY - JOUR T1 - The NOSAMS sample preparation laboratory in the next millenium: Progress after the WOCE program JF - Nuclear Instruments & Methods in Physics Research Section B-Beam Interactions with Materials and Atoms Y1 - 2000 A1 - Gagnon, A. R. A1 - McNichol, A. P. A1 - Donoghue, J. C. A1 - Stuart, D. R. A1 - von Reden, K. AB - Since 1991, the primary charge of the National Ocean Sciences AMS (NOSAMS) facility at the Woods Hole Oceanographic Institution has been to supply high throughput, high precision AMS C-14 analyses for seawater samples collected as part of the World Ocean Circulation Experiment (WOCE). Approximately 13,000 samples taken as part of WOCE should be fully analyzed by the end of Y2K. Additional sample sources and techniques must be identified and incorporated if NOSAMS is to continue in its present operation mode.A trend in AMS today is the ability to routinely process and analyze radiocarbon samples that contain tiny amounts (<100 g) of carbon. The capability to mass-produce small samples for C-14 analysis has been recognized as a major facility goal. The installation of a new 134-position MC-SNICS ion source, which utilizes a smaller graphite target cartridge than presently used, is one step towards realizing this goal. New preparation systems constructed in the sample preparation laboratory (SPL) include an automated bank of 10 small-volume graphite reactors, an automated system to process organic carbon samples, and a multi-dimensional preparative capillary gas chromatograph (PCGC). (C) 2000 Elsevier Science B.V. All rights reserved. VL - 172 IS - 172 N1 - 372jrTimes Cited:20Cited References Count:12 JO - The NOSAMS sample preparation laboratory in the next millenium: Progress after the WOCE program ER - TY - JOUR T1 - Oceanic uptake of CO2 re-estimated through d13C in WOCE samples JF - Nuclear Instruments and Methods in Physics Research Y1 - 2000 A1 - Lerperger, M. A1 - McNichol, A. P. A1 - Peden, J. A1 - Gagnon, A. R. A1 - Elder, K. L. A1 - Kutschera, W. A1 - Rom, W. A1 - Steier, P. VL - B (172) IS - 1-4 N1 - id: 1817 ER - TY - CONF T1 - An ocean-wide DIC-13 data set T2 - AGU Ocean Sciences Meeting Y1 - 2000 A1 - McNichol, A. P. A1 - Quay, P. D. A1 - Stuart, D. R. A1 - Sonnerup, R. E. A1 - Key, R. M. JF - AGU Ocean Sciences Meeting CY - San Antonio, TX N1 - id: 1444 ER - TY - JOUR T1 - An organic tracer for surface ocean radiocarbon JF - Paleoceanography Y1 - 2000 A1 - Pearson, A. A1 - Eglinton, T. I. A1 - McNichol, A. P. AB - The Delta(14)C of surface water dissolved inorganic carbon (DIC) in the Southern California Eight was compared to Delta(14)C as recorded by the sterols in Santa Monica and Santa Barbara Basin sediments. All of the C-26, C-27, C-28, and C-29 sterols as well as dinosterol had C-14 concentrations equal to surface water DIG, indicating that all of the major sterols were derived from phytoplanktonic production. There is no detectable terrestrial component. Their tracer capability was confirmed by comparing the "bomb C-14"-derived change in surface water Delta(14)C(DIC) With the change in Delta(14)C(sterol). The "prebomb" Delta(14)C(DIC) was similar to 82 parts per thousand, and prebomb sterols averaged -75 +/- 19 parts per thousand. The Delta(14)C value in 1996 was +71 parts per thousand, Eighteen measurements representing eight different sterols from the sediment-water interface of both Santa Monica and Santa Barbara Basins averaged +62 +/- 23 parts per thousand. When three of these values were eliminated because of suspected contamination, the remaining data averaged +71 +/- 12 parts per thousand. The entire compound class could serve as an excellent proxy for the C-14 concentration of ocean surface waters. VL - 15 IS - 5 N1 - 358wyTimes Cited:37Cited References Count:58 JO - An organic tracer for surface ocean radiocarbon ER - TY - JOUR T1 - The radiocarbon age of calcite dissolving at the sea floor: Estimates from pore water data JF - Geochimica Et Cosmochimica Acta Y1 - 2000 A1 - Martin, W. R. A1 - McNichol, A. P. A1 - McCorkle, D. C. AB - We measured the radiocarbon content and stable isotopic composition of pore water and bottom water Sigma CO2, sedimentary organic carbon, and CaCO3 at two sites on the Ceara Rise, one underlying bottom water that is supersaturated with respect to calcite (Site B), the other underlying undersaturated bottom water (Site G). The results were combined with pore water O-2, Sigma CO2, and Ca2+ profiles (Martin and Sayles, 1996) to estimate the radiocarbon content of the CaCO3 that is dissolving in the sediment mixed layer. At Site G, the CaCO3 that is dissolving in the upper 2 cm of the sediments is clearly younger (richer in C-14) than the bulk sedimentary CaCO3, indicating that nonhomogeneous CaCO3 dissolution occurs there. The case for nonhomogeneous dissolution is much weaker at the site underlying supersaturated bottom water. The results indicate that nonhomogeneous dissolution occurs in sediments underlying undersaturated bottom water, that the dissolution is rapid relative to the rate of homogenization of the CaCO3 in the mixed layer by bioturbation, and that the dissolution rate of CaCO3 decreases as it ages in the sediment mixed layer. The results support the hypothesis, based on solid phase analyses, that the preferential dissolution of young (i.e., radiocarbon-rich) CaCO3 leads to a pattern of increasing radiocarbon age of mixed-layer CaCO3 as the degree of undersaturation of bottom water increases (Keir, 1984; Broecker et al., 1991). Copyright (C) 2000 Elsevier Science Ltd. VL - 64 IS - 8 N1 - 303ueTimes Cited:26Cited References Count:31 JO - The radiocarbon age of calcite dissolving at the sea floor: Estimates from pore water data ER - TY - JOUR T1 - The radiocarbon content of individual lignin-derived phenols: Technique and initial results JF - Radiocarbon Y1 - 2000 A1 - McNichol, A. P. A1 - Ertel, J. R. A1 - Eglinton, T. I. KW - AMS KW - isotope-ratio KW - NOSAMS KW - oxidation-products AB - We present a method for the isolation of phenolic compounds derived from lignin for radiocarbon analysis. These phenols are generated by chemical oxidation of polymeric materials and derivatized for separation and recovery by preparative capillary gas chromatography (PCGC). This technique yields tens of micrograms of pure, stable compounds that can he converted to graphite and analyzed by accelerator mass spectrometry (AMS). Analysis of model flavor compounds and dated woods indicates that, in most cases, the radiocarbon (C-14) contents of the individual compounds, corrected for the contribution of the derivative, agree with that of the bulk material to within 20 parts per thousand. VL - 42 SN - 0033-8222 IS - 2 N1 - 365vkTimes Cited:19 Cited References Count:17 JO - Radiocarbon ER - TY - CONF T1 - The radiocarbon gradient at the Antarctic Polar Front T2 - AGU Ocean Sciences Meeting Y1 - 2000 A1 - Schneider, R. J. A1 - McNichol, A. P. A1 - von Reden, K. F. A1 - Elder, K. L. A1 - Gagnon, A. R. A1 - Key, R. M. A1 - Quay, P. D. A1 - Schlosser, P. M. JF - AGU Ocean Sciences Meeting CY - San Antonio, TX N1 - id: 317 ER - TY - CONF T1 - Ten years after - the WOCE AMS radiocarbon program T2 - Accelerator Mass Spectrometer Conference Y1 - 2000 A1 - McNichol, A. P. A1 - Schneider, R. J. A1 - von Reden, K. F. A1 - Gagnon, A. R. A1 - Elder, K. L. A1 - Key, R. M. A1 - Quay, P. D. JF - Accelerator Mass Spectrometer Conference N1 - id: 316 ER - TY - JOUR T1 - Ten years after - The WOCE AMS radiocarbon program JF - Nuclear Instruments & Methods in Physics Research Section B-Beam Interactions with Materials and Atoms Y1 - 2000 A1 - McNichol, A. P. A1 - Schneider, R. J. A1 - von Reden, K. F. A1 - Gagnon, A. R. A1 - Elder, K. L. A1 - Key, R. M. A1 - Quay, P. D. AB - The National Ocean Sciences Accelerator Mass Spectrometry (NOSAMS) Facility is measuring all of the samples collected as part of the US WOCE Program - over 13,000 samples. We designed our extraction lines so that we also measure precise, oceanographically useful delta C-13-Sigma CO2 values. We have completed the analysis of samples from the Pacific and Southern Oceans and are processing those from the Indian Ocean now. At present, this constitutes the world's largest AMS data set. Reviews of the Pacific radiocarbon data are available and demonstrate the increased penetration of the "bomb signal" into the water column since the 1970s. Stable isotope data are being combined with those collected as part of NOAA's Ocean-Atmosphere Carbon Exchange Study to study the ocean's role in the anthropogenic CO2 cycle. The relationship of delta C-13 to other chemical tracers, e.g., PO4, O-2 and chlorofluorocarbons, will further our understanding of basic oceanographic processes. We present preliminary results from these studies as well as investigate the relationship of C-14 to C-13 in the ocean. (C) 2000 Elsevier Science B.V. All rights reserved. VL - 172 IS - 1-4 N1 - 372jrTimes Cited:14Cited References Count:12 JO - Ten years after - The WOCE AMS radiocarbon program ER - TY - CONF T1 - Installation and First Results of a 134-Sample MC-SNICS Ion Source at NOSAMS T2 - 8th International Conference on Accelerator Mass Spectrometry Y1 - 1999 A1 - von Reden, K. F. A1 - Schneider, R. J. A1 - McNichol, A. P. A1 - Elder, K. F. A1 - Gagnon, A. R. JF - 8th International Conference on Accelerator Mass Spectrometry CY - Vienna, Austria N1 - id: 1802 ER - TY - CHAP T1 - New Developments at the NOSAMS Facility T2 - Proceeding of the International Workshop on Frontiers in Accelerator Mass Spectrometry Y1 - 1999 A1 - von Reden, K. F. A1 - Schneider, R. J. A1 - McNichol, A. P. A1 - Hayes, J. M. A1 - Pearson, A. A1 - Eglinton, T. I. ED - Science, Japan International ED - Technology Exchange, Center JF - Proceeding of the International Workshop on Frontiers in Accelerator Mass Spectrometry PB - National Institute for Environmental Studies, Tsukuba, National Museum of Japanese History CY - Tsukuba, Japan N1 - id: 1723(JISTEC) ER - TY - CONF T1 - New Developments at the NOSAMS Facility T2 - International Workshop on Frontiers in Accelerator Mass Spectrometry Y1 - 1999 A1 - von Reden, K. F. A1 - Schneider, R. J. A1 - McNichol, A. P. A1 - Hayes, J. M. A1 - Pearson, A. A1 - Eglinton, T. I. ED - Shibata, Y. JF - International Workshop on Frontiers in Accelerator Mass Spectrometry PB - National Institute for Environmental Studies Reprot CY - Tsukuba, Japan N1 - id: 1679 ER - TY - JOUR T1 - Reconstructing the oceanic 13C Suess effect JF - Global Biogeochemical Cycles Y1 - 1999 A1 - Sonnerup, R. E. A1 - Quay, P. D. A1 - McNichol, A. P. A1 - Bullister, J. L. A1 - Westby, T. A. A1 - Anderson, H. L. VL - 13 N1 - id: 1710 ER - TY - CONF T1 - AMS measurement of T2 - Sixteenth International Radiocarbon Conference Y1 - 1998 A1 - von Reden, K. F. A1 - McNichol, A. P. A1 - Pearson, A. A1 - Schneider, R. J. JF - Sixteenth International Radiocarbon Conference CY - Groningen VL - 40(1) N1 - id: 1643 ER - TY - JOUR T1 - Carbon cycling in sediments from the western equatorial Atlantic: Stable and radiocarbon isotopes in pore waters on the Ceara Rise JF - EOS Y1 - 1998 A1 - McNichol, A. P. A1 - McCorkle, D. C. A1 - Martin, W. R. A1 - Berry, J. N. VL - 79 IS - 1 N1 - id: 108 ER - TY - JOUR T1 - Challenges in application of radiocarbon dating of organic carbon phases in opal-rich marine sediments from the Southern Ocean JF - Trans. AGU 79 Y1 - 1998 A1 - Zheng, Y. A1 - Anderson, R. F. A1 - Froelich, P. N. A1 - Beck, W. A1 - McNichol, A. P. A1 - Guilderson, T. N1 - id: 266 ER - TY - CONF T1 - High-precision Measurements of 14C as a Circulation Tracer in the Pacific, Indian, and Southern Oceans with Accelerator Mass Spectrometry (AMS) T2 - 8th International Conference on Heavy Ion Accelerator Technology Y1 - 1998 A1 - von Reden, K. F. A1 - Peden, J. C. A1 - Schneider, R. J. A1 - Bellino, M. A1 - Donoghue, J. A1 - Elder, K. L. A1 - Gagnon, A. R. A1 - Long, P. A1 - McNichol, A. P. A1 - Morin, T. A1 - Stuart, D. A1 - Hayes, J. M. A1 - Key, R. M. ED - Shepard, K. American Institute of Physics JF - 8th International Conference on Heavy Ion Accelerator Technology CY - Argonne National Lab N1 - id: 1636 ER - TY - JOUR T1 - Microscale AMS 14C measurements at NOSAMS JF - Radiocarbon Y1 - 1998 A1 - Pearson, A. A1 - McNichol, A. P. A1 - Schneider, R. J. A1 - von Reden, K. F. A1 - Zheng, Y. VL - 40 IS - 1 N1 - id: 1621 ER - TY - JOUR T1 - Microscale AMS 14C measurements at NOSAMS: (Proceedings of the 16th International Radiocarbon Conference, 1997) JF - Radiocarbon Y1 - 1998 A1 - Pearson, A. A1 - McNichol, A. P. A1 - Schneider, R. J. A1 - von Reden, K. F. A1 - Zheng, Y. VL - 40 IS - 1 N1 - id: 1814 ER - TY - CONF T1 - The NOSAMS Sample Preparation Laboratory: Systems and graphite performance analysis T2 - 16th International 14C Conference Y1 - 1998 A1 - Gagnon, A. R. A1 - McNichol, A. P. A1 - Donaghue, J. C. A1 - Morin, T. J. A1 - Peden, J. C. JF - 16th International 14C Conference CY - Groninghen N1 - id: 1628 ER - TY - JOUR T1 - Preparation for continuous flow accelerator mass spectrometry Radiocarbon JF - Radiocarbon Y1 - 1998 A1 - Schneider, R. J. A1 - Hayes, J. M. A1 - von Reden, K. F. A1 - McNichol, A. P. A1 - Eglinton, T. A1 - Wills, J. S. C. VL - 1 IS - 95-102 N1 - id: 1623 ER - TY - CONF T1 - Reproducibility of seawater, inorganic and organic 14C results at NOSAMS T2 - Sixteenth International 14C Conference Y1 - 1998 A1 - Elder, K. L. A1 - McNichol, A. P. A1 - Gagnon, A. R. JF - Sixteenth International 14C Conference CY - Groningen VL - 40(1) N1 - id: 1625 ER - TY - JOUR T1 - Status Report of the National Ocean Sciences AMS Facility at Woods Hole Oceanographic Institution: Operations and Recent Developments JF - 15th International Conference on the Applications of Accelerators in Research and Industry Y1 - 1998 A1 - Bellino, M. A1 - von Reden, K. F. A1 - Schneider, R. J. A1 - Peden, J. C. A1 - Donoghue, J. A1 - Elder, K. L. A1 - Gagnon, A. R. A1 - Long, P. A1 - McNichol, A. P. A1 - Odegaard, A. P. A1 - Stuart, D. A1 - Handwork, S. A1 - Hayes, J. M. VL - A.I.P. Conference Proceedings IS - 475, part 2 N1 - id: 1647 ER - TY - JOUR T1 - Target preparation for continuous flow accelerator mass spectrometry JF - Radiocarbon Y1 - 1998 A1 - Schneider, R. J. A1 - Hayes, J. M. A1 - von Reden, K. F. A1 - McNichol, A. P. A1 - Eglinton, T. I. A1 - Wills, J. S. C. KW - gas KW - ion-source AB - For very small samples, it is difficult to prepare graphitic targets that will yield a useful and steady sputtered ion beam. Working with materials separated by preparative capillary gas chromatography, we have succeeded with amounts as small as 20 mu g C. This seems to be a practical limit, as it involves 1) multiple chromatographic runs with trapping of effluent fractions, 2) recovery and combustion of the fractions, 3) graphitization and 4) compression of the resultant graphite/cobalt matrix into a good sputter target. Through such slow and intricate work, radiocarbon ages of lignin derivatives and hydrocarbons from coastal sediments have been determined. If this could be accomplished as an "online" measurement by flowing the analytes directly into a microwave gas ion source, with a carrier gas, then the number of processing steps could be minimized. Such a system would be useful not just for chromatographic effluents, but for any gaseous material, such as CO2 produced from carbonates. We describe tests using such an ion source. VL - 40 SN - 0033-8222 IS - 1 N1 - 1 Sp. Iss. SI113kt Times Cited:11 Cited References Count:10 JO - Radiocarbon ER - TY - CONF T1 - AMS measurements of the 14C distribution in the Pacific Ocean T2 - Proceedings of the Seventh International Conference on Accelerator Mass Spectrometry Y1 - 1997 A1 - von Reden, K. F. A1 - McNichol, A. P. A1 - Peden, J. C. A1 - Elder, K. L. A1 - Gagnon, A. R. A1 - Schneider, R. J. ED - Jull, A. J. T. JF - Proceedings of the Seventh International Conference on Accelerator Mass Spectrometry CY - Tucson, AZ VL - B123 N1 - id: 1644; B123 ER - TY - JOUR T1 - AMS measurements of the 14C distribution in the Pacific Ocean JF - Nuclear Instruments and Methods in Physics Research Y1 - 1997 A1 - von Reden, K. F. A1 - McNichol, A. P. A1 - Peden, J. C. A1 - Elder, K. L. A1 - Gagnon, A. R. A1 - Schneider, R. J. VL - B123 N1 - id: 1673 ER - TY - CONF T1 - Determination of the radiocarbon ages of individual PAH extracted from urban aerosol and marine sediment T2 - 16th International Radiocarbon Conference Y1 - 1997 A1 - Pearson, A. A1 - Eglinton, T. I. A1 - McNichol, A. P. A1 - Currie, L. A. A1 - Schneider, R. J. A1 - von Reden, K. F. A1 - Benner, B. A. A1 - Wise, S. A. JF - 16th International Radiocarbon Conference CY - Groningen VL - Book of Abstracts N1 - id: 951 ER - TY - CONF T1 - Evaluating reproducibility of seawater, inorganic and organic carbon 14C results at the National Ocean Sciences AMS Facility (NOSAMS) T2 - 16th International Radiocarbon Conference Y1 - 1997 A1 - Elder, K. L. A1 - McNichol, A. P. A1 - Gagnon, A. R. JF - 16th International Radiocarbon Conference T3 - Book of Abstracts CY - Groningen N1 - id: 956 ER - TY - CONF T1 - The National Ocean Sciences AMS (NOSAMS) Sample Preparation Laboratory: Systems and Graphite Performance Analysis T2 - International Radiocarbon Conference Y1 - 1997 A1 - Gagnon, A. R. A1 - McNichol, A. P. A1 - Donoghue, J. C. A1 - Morin, T. J. A1 - Peden, J. C. JF - International Radiocarbon Conference CY - Groningen, Nethlands N1 - id: 962 ER - TY - CONF T1 - Reproducibility of 14C AMS analyses at NOSAMS T2 - 16th International Radiocarbon Conference Y1 - 1997 A1 - Elder, K. L. A1 - Gagnon, A. R. A1 - McNichol, A. P. JF - 16th International Radiocarbon Conference PB - Book of Abstracts CY - Groningen N1 - id: 961 ER - TY - CONF T1 - Target preparation for continuous flow accelerator mass spectrometry T2 - 16th International Radiocarbon Conference Y1 - 1997 A1 - Schneider, R. J. A1 - Hayes, J. M. A1 - Eglinton, T. I. A1 - McNichol, A. P. A1 - von Reden, K. F. JF - 16th International Radiocarbon Conference CY - Groningen VL - Book of Abstracts N1 - id: 953 ER - TY - JOUR T1 - Target preparation for continuous flow accelerator mass spectrometry JF - Radiocarbon Y1 - 1997 A1 - Schneider, R. J. A1 - Hayes, J. M. A1 - von Reden, K. F. A1 - McNichol, A. P. A1 - Eglinton, T. I. VL - 40 N1 - id: 1661 ER - TY - JOUR T1 - Target preparation for continuous flow accelerator mass spectrometry: (Proceedings of the 16th International Radiocarbon Conference, 1997) JF - Radiocarbon Y1 - 1997 A1 - Schneider, R. J. A1 - Hayes, J. M. A1 - von Reden, K. F. A1 - McNichol, A. P. A1 - Eglinton, T. VL - 40 N1 - id: 1752 ER - TY - JOUR T1 - Variability in radiocarbon ages of individual organic compounds from marine sediments JF - Science Y1 - 1997 A1 - Eglinton, T. I. A1 - BenitezNelson, B. C. A1 - Pearson, A. A1 - McNichol, A. P. A1 - Bauer, J. E. A1 - Druffel, E. R. M. AB - Organic carbon (OC) from multiple sources can be delivered contemporaneously to aquatic sediments. The influence of different OC inputs on carbon-14-based sediment chronologies is illustrated in the carbon-14 ages of purified, source-specific (biomarker) organic compounds from near-surface sediments underlying two contrasting marine systems, the Black Sea and the Arabian Sea, In the Black Sea, isotopic heterogeneity of n-alkanes indicated that OC was contributed from both fossil and contemporary sources. Compounds reflecting different source inputs to the Arabian Sea exhibit a 10,000-year range in conventional carbon-14 ages. Radiocarbon measurements of biomarkers of marine photoautotrophy enable sediment chronologies to be constructed independent of detrital OC influences. VL - 277 IS - 5327 N1 - Xq247Times Cited:175Cited References Count:37 JO - Variability in radiocarbon ages of individual organic compounds from marine sediments ER - TY - CONF T1 - AMS measurements of the 14C distribution in the Pacific Ocean T2 - 7th International Conference on Accelerator Mass Spectrometry Y1 - 1996 A1 - von Reden, K. F. A1 - McNichol, A. P. A1 - Schneider, R. J. JF - 7th International Conference on Accelerator Mass Spectrometry PB - Radiocarbon CY - Tucson, AZ VL - 38 N1 - id: 950; 1 ER - TY - JOUR T1 - Automated systems and techniques utilized at the NOSAMS sample preparation laboratory: An update of productivity and quality issues JF - Radiocarbon Y1 - 1996 A1 - Gagnon, A. R. A1 - McNichol, A. P. A1 - Hutton, D. L. A1 - Osborne, E. A. A1 - Donoghue, J. C. VL - 38 IS - 1 N1 - id: 959 ER - TY - JOUR T1 - Compound specific radiocarbon analysis as a tool to quantitatively apportion modern and fossil sources of polycyclic aromatic hydrocarbons in environmental matrices. JF - Abstracts of Papers of the American Chemical Society Y1 - 1996 A1 - Eglinton, T. I. A1 - Pearson, A. A1 - McNichol, A. P. A1 - Currie, L. A. A1 - Benner, B. A. A1 - Wise, S. A. VL - 212 SN - 0065-7727 IS - 2 N1 - 1Va915 Times Cited:0 Cited References Count:0 JO - Abstr Pap Am Chem S ER - TY - JOUR T1 - Concentrations of carbonyl compounds and the carbon isotopy of formaldehyde at a coastal site in Nova Scotia during the NARE summer intensive JF - Journal of Geophysical Research-Atmospheres Y1 - 1996 A1 - Tanner, R. L. A1 - Zielinska, B. A1 - Uberna, E. A1 - Harshfield, G. A1 - McNichol, A. P. AB - The concentrations of gaseous atmospheric carbonyl compounds have been measured at a coastal site on the southern tip of Nova Scotia during August 1993 as part of the National Oceanic and Atmospheric Administration's North Atlantic Regional Experiment (NARE) summer intensive. The DNPH-cartridge technique was used for sampling, with analysis by HPLC with UV absorbance detection. The carbon isotopic content of formaldehyde was measured using a novel collection technique on bisulfite-coated fillers followed by accelerator mass spectrometric determination of C-14 content and C-13/C-12 isotopic ratios. Results from this study indicate that quantifiable levels above about 100 parts per trillion by volume were found at the Chebogue Point, Nova Scotia, site for several carbonyls, formaldehyde, acetaldehyde, acetone, propionaldehyde, methyl ethyl ketone, and benzaldehyde, for most 6-hour sampling periods. Six-hour averaged formaldehyde levels of <0.5 to about 3.5 parts per billion were found during periods of local influence and during influence of continental air masses crossing eastern Canada and northeastern US. In contrast, background levels of formaldehyde of 200-400 pptv were found under conditions of predominantly marine back trajectories. Large fractions of contemporary carbon (of the order of 80%) were found in collected formaldehyde samples for all transport regimes and formaldehyde concentrations, suggesting that biogenic sources of hydrocarbon precursors to formaldehyde predominated during the summer season. VL - 101 IS - D22 N1 - Vz788Times Cited:38Cited References Count:42 JO - Concentrations of carbonyl compounds and the carbon isotopy of formaldehyde at a coastal site in Nova Scotia during the NARE summer intensive ER - TY - CONF T1 - Expanded Small Sample Capabilities at NOSAMS: Preparation and Analysis of Conventional Graphite Targets Containing 0.15 mg Carbon T2 - 7th International Conference on Accelerator Mass Spectrometry Y1 - 1996 A1 - Pearson, A. A1 - McNichol, A. P. A1 - Schneider, R. J. A1 - von Reden, K. F. JF - 7th International Conference on Accelerator Mass Spectrometry PB - Radiocarbon CY - Tucson, AZ VL - 38 N1 - id: 946; 1 ER - TY - JOUR T1 - Gas chromatographic isolation of individual compounds from complex matrices for radiocarbon dating JF - Anal Chem Y1 - 1996 A1 - Eglinton, T. I. A1 - Aluwihare, L. I. A1 - Bauer, J. E. A1 - Druffel, E. R. A1 - McNichol, A. P. AB - This paper describes the application of a novel, practical approach for isolation of individual compounds from complex organic matrices for natural abundance radiocarbon measurement. This is achieved through the use of automated preparative capillary gas chromatography (PCGC) to separate and recover sufficient quantities of individual target compounds for (14)C analysis by accelerator mass spectrometry (AMS). We developed and tested this approach using a suite of samples (plant lipids, petroleums) whose ages spanned the (14)C time scale and which contained a variety of compound types (fatty acids, sterols, hydrocarbons). Comparison of individual compound and bulk radiocarbon signatures for the isotopically homogeneous samples studied revealed that Delta(14)C values generally agreed well (+/-10%). Background contamination was assessed at each stage of the isolation procedure, and incomplete solvent removal prior to combustion was the only significant source of additional carbon. Isotope fractionation was addressed through compound-specific stable carbon isotopic analyses. Fractionation of isotopes during isolation of individual compounds was minimal (<5 per thousand for delta(13)C), provided the entire peak was collected during PCGC. Trapping of partially coeluting peaks did cause errors, and these results highlight the importance of conducting stable carbon isotopic measurements of each trapped compound in concert with AMS for reliable radiocarbon measurements. The addition of carbon accompanying derivatization of functionalized compounds (e.g., fatty acids and sterols) prior to chromatographic separation represents a further source of potential error. This contribution can be removed using a simple isotopic mass balance approach. Based on these preliminary results, the PCGC-based approach holds promise for accurately determining (14)C ages on compounds specific to a given source within complex, heterogeneous samples. VL - 68 IS - 5 N1 - Eglinton, T IAluwihare, L IBauer, J EDruffel, E RMcNichol, A Peng1996/03/01 00:00Anal Chem. 1996 Mar 1;68(5):904-12. doi: 10.1021/ac9508513. JO - Gas chromatographic isolation of individual compounds from complex matrices for radiocarbon dating ER - TY - JOUR T1 - Isolation of Individual Organic Compounds for AMS Radiocarbon Analysis--A Novel Approach JF - Radiocarbon Y1 - 1996 A1 - Eglinton, T. I. A1 - McNichol, A. P. A1 - Benitez-Nelson, B. C. A1 - Pearson, A. A1 - von Reden, K. F. A1 - Schneider, R. J. A1 - Bauer, J. E. A1 - Druffel, E. R. M. VL - 38 IS - 1 N1 - id: 1650 ER - TY - CONF T1 - Isolation of Individual Organic Compounds for AMS Radiocarbon Analysis -- A Novel Approach T2 - 7th International Conference on Accelerator Mass Spectrometry Y1 - 1996 A1 - Eglinton, T. I. A1 - McNichol, A. P. A1 - Benitez-Nelson, B. C. A1 - Pearson, A. A1 - von Reden, K. F. A1 - Schneider, R. J. A1 - Bauer, J. E. A1 - Druffel, E. R. M. JF - 7th International Conference on Accelerator Mass Spectrometry PB - Radiocarbon CY - Tucson, AZ VL - 38 N1 - id: 1800; 1 ER - TY - CONF T1 - Kinematic Effects in the Sputtering of Carbon Isotopes T2 - 7th International Conference on Accelerator Mass Spectrometry Y1 - 1996 A1 - Schneider, R. J. A1 - Hartman, J. A1 - von Reden, K. F. A1 - McNichol, A. P. JF - 7th International Conference on Accelerator Mass Spectrometry PB - Radiocarbon CY - Tucson, AZ VL - 38 N1 - id: 1801; 1 ER - TY - JOUR T1 - Kinematic Effects in the Sputtering of Carbon Isotopes JF - Radiocarbon Y1 - 1996 A1 - Schneider, R. J. A1 - Hartman, J. A1 - von Reden, K. F. A1 - McNichol, A. P. VL - 1 IS - 108 N1 - id: 1660 ER - TY - JOUR T1 - Preparative capillary gas chromatographic isolation of individual compounds from complex matrices for radiocarbon dating JF - Analytical Chemistry Y1 - 1996 A1 - Eglinton, T. I. A1 - Aluwihare, L. I. A1 - Bauer, J. E. A1 - Druffel, E. R. M. A1 - McNichol, A. P. VL - 68 N1 - id: 1340 ER - TY - JOUR T1 - Progress of the NOSAMS Facility WOCE 14C Data Analysis JF - Radiocarbon Y1 - 1996 A1 - von Reden, K. F. A1 - McNichol, A. P. A1 - Schneider, R. J. VL - 38 IS - 1 N1 - id: 1672 ER - TY - CONF T1 - Progress of the NOSAMS Facility WOCE 14C data analysis T2 - 7th International Conference on Accelerator Mass Spectrometry Y1 - 1996 A1 - von Reden, K. F. A1 - McNichol, A. P. A1 - Schneider, R. J. JF - 7th International Conference on Accelerator Mass Spectrometry PB - Radiocarbon CY - Tucson, AZ VL - 38 N1 - id: 948; 1 ER - TY - CONF T1 - Progress of the NOSAMS Facility WOCE 14C Data Analysis T2 - Workshop on Applications of AMS to Global Climate Change Y1 - 1996 A1 - von Reden, K. F. A1 - McNichol, A. P. A1 - Schneider, R. J. JF - Workshop on Applications of AMS to Global Climate Change PB - Radiocarbon CY - La Jolla VL - 38 N1 - id: 1768; 1 ER - TY - CONF T1 - Progress of the NOSAMS Facility WOCE 14C Data Analysis, Workshop on Applications of AMS to Global Climate Change T2 - Workshop on Applications of AMS to Global Climate Change Y1 - 1996 A1 - von Reden, K. F. A1 - McNichol, A. P. A1 - Schneider, R. J. JF - Workshop on Applications of AMS to Global Climate Change PB - Radiocarbon CY - La Jolla VL - 38 N1 - id: 954; 8 ER - TY - CONF T1 - Progress of the NOSAMS facility WOCE (super 14) C data analysis Y1 - 1996 A1 - von Reden, K. F. A1 - McNichol, A. P. A1 - Schneider, Robert J. KW - 02D KW - 07 KW - accelerator mass spectroscopy KW - C-14 KW - carbon KW - Isotope geochemistry KW - isotopes KW - mass spectroscopy KW - Oceanography KW - Pacific Ocean KW - progress report KW - radioactive isotopes KW - report KW - sea water KW - spectroscopy PB - University of Arizona, Department of Geosciences, Tucson, AZ, United States (USA) CY - United States (USA) VL - 38 N1 - id: 2242; Source type: conferencepapers&proceedings; Object type: Article; Object type: Conference Paper; Copyright: GeoRef, Copyright 2007, American Geological Institute.; CSAUnique: 1999-071631; AccNum: 1999-071631; ISSN: 0033-8222; CODEN: RACAAT ER - TY - CONF T1 - Stable and radio-carbon isotope measurements in the Pacific Ocean; contributions from NOSAMS Y1 - 1996 A1 - McNichol, A. P. A1 - von Reden, K. F. A1 - Schneider, R. J. A1 - Key, R. M. A1 - Jones, G. A. KW - 02D KW - 07 KW - accelerator mass spectroscopy KW - C-13/C-12 KW - C-14 KW - carbon KW - chemical analysis KW - geochemical indicators KW - high-resolution methods KW - Isotope geochemistry KW - isotope ratios KW - isotopes KW - marine geology KW - mass spectroscopy KW - National Ocean Sciences Accelerator Mass Spectrometry KW - NOSAMS KW - Oceanography KW - Pacific Ocean KW - radioactive isotopes KW - radioactive tracers KW - sampling KW - sea water KW - spectroscopy KW - Stable isotopes KW - tracers KW - Woods Hole Oceanographic Institution PB - American Geophysical Union, Washington, DC, United States (USA) CY - United States (USA) VL - 77 N1 - id: 2240; Source type: conferencepapers&proceedings; Object type: Article; Object type: Conference Paper; Copyright: GeoRef, Copyright 2007, American Geological Institute.; CSAUnique: 1997-047916; AccNum: 1997-047916; ISSN: 0096-3941; CODEN: EOSTAJ ER - TY - JOUR T1 - Stable and radio-carbon isotope measurements in the Pacific Ocean: Contribution from NOSAMS JF - Supplement to Trans. Amer. Geophysical Union Y1 - 1996 A1 - McNichol, A. P. A1 - Key, R. A1 - Jones, G. VL - 76 IS - 3 N1 - id: 1266 ER - TY - CONF T1 - Stable and radiocarbon isotope measurements in the Pacific Ocean: Contributions from NOSAMS T2 - AGU/ASLO 1996 Ocean Sciences Meeting Y1 - 1996 A1 - McNichol, A. P. A1 - von Reden, K. F. A1 - Schneider, R. J. A1 - Key, R. M. A1 - Jones, G. A. JF - AGU/ASLO 1996 Ocean Sciences Meeting CY - San Diego, CA N1 - id: 960 ER - TY - JOUR T1 - WOCE AMS Radiocarbon I: Pacific Ocean results (P6, P16, and P17) JF - Radiocarbon Y1 - 1996 A1 - Key, R. M. A1 - Quay, P. D. A1 - Jones, G. A. A1 - McNichol, A. P. A1 - von Reden, K. F. A1 - Schneider, R. J. AB - AMS radiocarbon results from the World Ocean Circulation Experiment in the Pacific Ocean show dramatic changes in the inventory and distribution of bomb-produced 14C since the time of the GEOSECS survey (8/73-6/74). Nearsurface 4C values for the eastern portion of both the northern and southern subtropical gyres decreased by 25-50%, with the change being greater in the north. Equatorial near-surface values have increased by ca. 25%. Changes in the 250-750-m depth range are dramatically different between the northern and southern basins. The intermediate and mode waters of the southern basin have increased by as much as 75%o since GEOSECS. Waters of similar density in the northern hemisphere are not exposed to the Southern Ocean circulation regime and are significantly less ventilated, showing maximum changes of ca. 50%. VL - 38 UR - https://journals.uair.arizona.edu/index.php/radiocarbon/article/view/1918 IS - 3 N1 - id: 38 JO - WOCE AMS Radiocarbon I: Pacific Ocean results (P6, P16, and P17) ER - TY - CONF T1 - Improvements in procedural blanks at NOSAMS: Reflections of improvements in sample preparation and accelerator operation T2 - 15th International 14C Conference Y1 - 1995 A1 - McNichol, A. P. A1 - Gagnon, A. R. A1 - Osborne, E. a A1 - Hutton, D. L. A1 - von Reden, K. F. A1 - Schneider, R. J. JF - 15th International 14C Conference PB - Radiocarbon VL - 37 N1 - id: 1641; 15th International Radiocarbon Conference, Glasgow, Scotland, August 15-19, 1994 ER - TY - JOUR T1 - Improvements in procedural blanks at NOSAMS: Reflections of improvements in sample preparation and accelerator operation JF - Radiocarbon Y1 - 1995 A1 - McNichol, A. P. A1 - Gagnon, A. R. A1 - Osborne, E. A. A1 - Hutton, D. L. A1 - vonReden, K. F. A1 - Schneider, R. J. KW - SPECTROMETRY AB - During the four years the Sample Preparation Laboratory (SPL) at the National Ocean Sciences Accelerator Mass Spectrometer (NOSAMS) Facilty has been in operation we have accumulated much data from which we can assess our progress. We evaluate our procedural blanks here and describe modifications in our procedures that have improved our analyses of older samples. In the SPL, we convert three distinct types of samples-seawater, CaCO3 and organic carbon-to CO2 prior to preparing graphite for the accelerator and have distinct procedural blanks for each procedure. Dissolved inorganic carbon (Sigma CO2) is extracted from acidified seawater samples by sparging with a nitrogen carrier gas. We routinely analyze ''line blanks'' by processing CO2 from a C-14-dead source through the entire stripping procedure. Our hydrolysis blank, IAEA C-1, is prepared by acidifying in vacuo with 100% H3PO4 at 60 degrees C overnight, identical to our sample preparation. We use a dead graphite, NBS-21, or a commercially available carbon powder for our organic combustion blank; organic samples are combusted at 850 degrees C for 5 h using CuO to provide the oxidant. Analysis of our water stripping data suggests that one step in the procedure contributes the major portion of the line blank. At present, the contribution from the line blank has no effect on our seawater analyses (fraction modern (fm) between 0.7 and 1.2). Our hydrolysis blanks can have an fm value as low as 0.0006, but are more routinely between 0.0020 and 0.0025. The fm of our best organic combustion blanks is higher than those routinely achieved in other laboratories and we are currently altering our methods to reduce it. VL - 37 SN - 0033-8222 IS - 2 N1 - Ud868Times Cited:16 Cited References Count:6 JO - Radiocarbon ER - TY - JOUR T1 - Measurements of the OX-II/OX-1 ratio as a quality control parameter at NOSAMS JF - Radiocarbon Y1 - 1995 A1 - Schneider, R. J. A1 - McNichol, A. P. A1 - Nadeau, M. J. A1 - von Reden, K. F. VL - 37 IS - 3 N1 - id: 1630 ER - TY - CONF T1 - Measurements of the OX-II/OX-I ratio as a quality control parameter at NOSAMS T2 - 15th International Radiocarbon Conference Y1 - 1995 A1 - Schneider, R. J. A1 - McNichol, A. P. A1 - Nadeau, M. J. A1 - von Reden, K. F. JF - 15th International Radiocarbon Conference CY - Glasgow, Scotland N1 - id: 944 ER - TY - JOUR T1 - The Application of AMS to Organic Geochemistry--Constraints Imposed by Sample Preparation and Machine Operations JF - EOS, Transactions of the American Geophysical Union Y1 - 1994 A1 - McNichol, A. P. A1 - von Reden, K. F. A1 - Schneider, R. J. A1 - Jones, G. A. VL - 75 IS - 3 N1 - id: 1798 ER - TY - JOUR T1 - Automated Sample Processing at the National Ocean Sciences Ams Facility JF - Nuclear Instruments & Methods in Physics Research Section B-Beam Interactions with Materials and Atoms Y1 - 1994 A1 - Cohen, G. J. A1 - Hutton, D. L. A1 - Osborne, E. A. A1 - vonReden, K. F. A1 - Gagnon, A. R. A1 - McNichol, A. P. A1 - Jones, G. A. AB - The high throughput and high precision requirements for the NOSAMS facility have made it essential to automate many of the stages in sample processing. These automated procedures increase the sample capacity for the lab while reducing errors in sample preparation. Automation has also allowed sample histories to be recorded and saved in Sybase, a relational data base. VL - 92 IS - 1-4 N1 - Nv547Times Cited:9Cited References Count:1 JO - Automated Sample Processing at the National Ocean Sciences Ams Facility ER - TY - JOUR T1 - Comparative-Study of Fe-C Bead and Graphite Target Performance with the National-Ocean-Science-Ams (Nosams) Facility Recombinator Ion-Source JF - Nuclear Instruments & Methods in Physics Research Section B-Beam Interactions with Materials and Atoms Y1 - 1994 A1 - Klinedinst, D. B. A1 - McNichol, A. P. A1 - Currie, L. A. A1 - Schneider, R. J. A1 - Klouda, G. A. A1 - vonReden, K. F. A1 - Verkouteren, R. M. A1 - Jones, G. A. AB - An accelerator mass spectrometry (AMS) experiment was designed to investigate C-14 target performance for two target types over a range of isotopic concentrations and sample sizes, with a special focus on the ability to measure C-14 in environmental samples having only microgram amounts of carbon. The findings were positive, showing that precision, accuracy, and stability were adequate to determine C-14 to 1% or better in samples containing as little as 25 mug carbon. Satisfactory Poisson uncertainty and target stability were demonstrated down to a level of 7 mug carbon, but experimental data showed that accurate measurements at that level require detailed knowledge of blank variability and mass dependence of the modern carbon calibration factor. VL - 92 IS - 1-4 N1 - Nv547Times Cited:23Cited References Count:13 JO - Comparative-Study of Fe-C Bead and Graphite Target Performance with the National-Ocean-Science-Ams (Nosams) Facility Recombinator Ion-Source ER - TY - JOUR T1 - Constraints Imposed by Sample Preparation and Machine Operations JF - EOS, Transactions of the American Geophysical Union Y1 - 1994 A1 - McNichol, A. P. A1 - von Reden, K. F. A1 - Schneider, R. J. A1 - Jones, G. A. VL - 75 IS - 3 N1 - id: 937 ER - TY - JOUR T1 - High Precision Sea Water 14C Analyses at the National Ocean Sciences AMS Facility JF - EOS, Transactions of the American Geophysical Union Y1 - 1994 A1 - von Reden, K. F. A1 - Jones, G. A. A1 - Schneider, R. J. A1 - McNichol, A. P. VL - 75 IS - 3 N1 - id: 939 ER - TY - JOUR T1 - High-precision AMS radiocarbon measurements of central Arctic Ocean seawaters JF - Nuclear Instruments and Methods in Physics Research Y1 - 1994 A1 - Jones, G. A. A1 - Gagnon, A. R. A1 - Schneider, R. J. A1 - von Reden, K. F. A1 - McNichol, A. P. VL - B92 N1 - id: 52 ER - TY - JOUR T1 - High-precision sea water 14C analyses by accelerator mass spectrometry. 15th International Radiocarbon Conference, Glasgow, Scotland, August 15-19 JF - EOS, Transactions of the American Geophysical Union Y1 - 1994 A1 - von Reden, K. F. A1 - Jones, G. A. A1 - Schneider, R. J. A1 - McNichol, A. P. VL - 75 IS - 3 N1 - id: 941 ER - TY - JOUR T1 - Internal and External Checks in the Nosams Sample Preparation Laboratory for Target Quality and Homogeneity JF - Nuclear Instruments & Methods in Physics Research Section B-Beam Interactions with Materials and Atoms Y1 - 1994 A1 - Osborne, E. A. A1 - McNichol, A. P. A1 - Gagnon, A. R. A1 - Hutton, D. L. A1 - Jones, G. A. AB - In the NOSAMS sample preparation laboratory (SPL) we have developed rigorous internal procedures aimed at ensuring that sample preparation introduces as little error into our analyses as possible and identifying problems rapidly. Our three major CO2 preparation procedures are: stripping inorganic carbon from seawater, hydrolyzing CaCO3, and oxidizing organic matter. For seawater, approximately 10% of our analyses are standards or blanks which we use to demonstrate extraction of virtually all the inorganic carbon. Analysis of the stable carbon isotopic composition of the CO2 extracted from our standards indicates a precision of better than 0.15-0.20 parts per thousand. We also routinely process C-14-free CO2 in our stripping lines to demonstrate the absence of a significant process-dependent blank. For organic combustions and CaCO3 hydrolyses, we use the carbon yield (% organic carbon (OC) or % CaCO3 by weight) as a check on our sample procedures. We have analyzed the blank contribution of these procedures as a function of sample size. Our organic carbon blank is constant at approximately 0.4% modem for samples containing greater than 1 mg C and our carbonate blank is less than 0.2% modern for samples containing more than 0.5 mg C. We use a standard Fe/H-2 catalytic reduction to prepare graphite from CO2. We check the completeness of our reactions with the pressure data stored during the reaction as well as use a robot to determine a gravimetric yield. All graphite undergoes a visual inspection and is rejected if any heterogeneities are present. We have recombusted graphite made from CO2 with deltaC-13 values ranging from -42 to 1 parts per thousand and determined that the deltaC-13 of the recombusted carbon agrees with that from the pure gas to within 0.05 parts per thousand, demonstrating little or no fractionation during the treatment of the sample. The deltaC-13 we measure on the CO2 generated from more than 75% of our samples is compared to the deltaC-13 measured on the AMS as a further check of our procedures. As further external checks, we analyzed the International Atomic Energy Association (IAEA) samples during the establishment of our laboratory and are presently participating in the third international radiocarbon intercalibration (TIRI) exercise. VL - 92 IS - 1-4 N1 - Nv547Times Cited:14Cited References Count:5 JO - Internal and External Checks in the Nosams Sample Preparation Laboratory for Target Quality and Homogeneity ER - TY - JOUR T1 - Methods for Data Screening, Flagging and Error Analysis at the National-Ocean-Sciences-Ams-Facility JF - Nuclear Instruments & Methods in Physics Research Section B-Beam Interactions with Materials and Atoms Y1 - 1994 A1 - Schneider, R. J. A1 - Jones, G. A. A1 - McNichol, A. P. A1 - vonReden, K. F. A1 - Elder, K. L. A1 - Huang, K. A1 - Kessel, E. D. AB - All data collection, from sample submittal through processing into targets and AMS analysis, is integrated within a large relational database (Sybase). Over 50 tables are linked through key fields. Through structured queries, the information is analysed and presented for a wide variety of applications. Benefits include enhanced quality control, more complete reports to users and more accurate transfer of data among the several laboratories on the network. VL - 92 IS - 1-4 N1 - Nv547Times Cited:14Cited References Count:4 JO - Methods for Data Screening, Flagging and Error Analysis at the National-Ocean-Sciences-Ams-Facility ER - TY - JOUR T1 - The National Ocean Sciences Accelerator Mass Spectrometry Facility: Recent Developments JF - EOS, Transactions of the American Geophysical Union Y1 - 1994 A1 - Schneider, R. J. A1 - Jones, G. A. A1 - von Reden, K. F. A1 - McNichol, A. P. VL - 75 IS - 3 N1 - id: 938 ER - TY - JOUR T1 - Rapid analysis of seawater samples at the National Ocean Sciences Accelerator Mass Spectrometry Facility, Woods Hole, MA JF - Radiocarbon Y1 - 1994 A1 - McNichol, A. P. A1 - Jones, G. A. A1 - Hutton, D. L. A1 - Gagnon, A. R. A1 - Key, R. M. VL - 36 IS - 2 N1 - id: 305 ER - TY - JOUR T1 - The Rapid Preparation of Seawater Sigma-Co2 for Radiocarbon Analysis at the National Ocean Sciences Ams Facility JF - Radiocarbon Y1 - 1994 A1 - McNichol, A. P. A1 - Jones, G. A. A1 - Hutton, D. L. A1 - Gagnon, A. R. A1 - Key, R. M. KW - accelerator mass-spectrometry KW - C-14 KW - samples AB - We have established a laboratory for extracting Sigma CO2 from seawater samples for AMS analysis of the radiocarbon content. The seawater samples are collected at sea, poisoned and stored until analysis in the laboratory. Each sample is acidified; the inorganic carbon is stripped out as CO2 with an inert carrier gas and then converted to graphite. We present results for Buzzards Bay surface H2O and Na2CO3 standards that demonstrate we strip > 98% of inorganic carbon from seawater. Stable isotope analyses are performed to better than 0.2 parts per thousand, and the reproducibility of C-14 measurements on Buzzards Bay seawater is better than 13 parts per thousand. Finally, we compare data from samples collected in 1991 to those collected in the 1970s and to large volume samples. VL - 36 SN - 0033-8222 IS - 2 N1 - Pz926Times Cited:61 Cited References Count:14 JO - Radiocarbon ER - TY - MGZN T1 - Thermocline Ventilation Rates in the North Pacific Y1 - 1994 A1 - Sonnerup, R. E. A1 - Quay, P. D. A1 - Bullister, J. L. A1 - Key, R. M. A1 - McNichol, A. P. A1 - Jones, G. A. JF - American Geophysical Union, San Francisco N1 - id: 917 ER - TY - JOUR T1 - Tic, Toc, Dic, Doc, Pic, Poc - Unique Aspects in the Preparation of Oceanographic Samples for C-14 Ams JF - Nuclear Instruments & Methods in Physics Research Section B-Beam Interactions with Materials and Atoms Y1 - 1994 A1 - McNichol, A. P. A1 - Osborne, E. A. A1 - Gagnon, A. R. A1 - Fry, B. A1 - Jones, G. A. AB - The radiocarbon content of discrete carbon pools (total (T), dissolved (D), and particulate (P) inorganic (I) and organic (O) carbon (C)) is a useful tracer of carbon cycling within the modem and past ocean. The isolation of different carbon pools in the ocean environment and conversion to CO2 presents unique analytical problems for the radiocarbon chemist. In general, isolation and preparation of inorganic carbon presents few problems; dissolved carbon is easily extracted by acidifying the sample and stripping with an inert gas. Carbon is also readily isolated from particulate carbonate samples; in this case, CO2 is prepared by hydrolysis of the substrate with phosphoric acid. The isolation and preparation of organic carbon presents a much greater problem. Dissolved organic carbon (DOC) must first be isolated from DIC and then oxidized in the presence of very high salt concentrations. We present results from a closed-tube combustion method in which the DIC-free seawater is evaporated to dryness, transferred to a clean combustion tube, and oxidized overnight at 550-degrees-C. Combustion of total organic carbon (TOC) in sediments with a high inorganic carbon content is also difficult. Removal of CaCO3 with acid leaves severely deliquescent salts which, if not thoroughly dried, cause combustion tubes to explode. Removal of the salts by rinsing can also remove significant amounts of organic matter. Finally, we present results from a local coastal region. VL - 92 IS - 1-4 N1 - Nv547Times Cited:82Cited References Count:9 JO - Tic, Toc, Dic, Doc, Pic, Poc - Unique Aspects in the Preparation of Oceanographic Samples for C-14 Ams ER - TY - CONF T1 - Comparative study of Fe-C Bead vs. graphite target performance with the NOSAMS Facility recombinator ion source T2 - 6th International Conference on Accelerator Mass Spectrometry Y1 - 1993 A1 - Kleindinst, D. B. A1 - McNichol, A. P. A1 - Currie, L. A. A1 - Jones, G. A. A1 - Verkouteren, R. M. A1 - von Reden, K. F. A1 - Klouda, G. A. A1 - Schneider, R. J. JF - 6th International Conference on Accelerator Mass Spectrometry CY - Canberra, Australia N1 - id: 931 ER - TY - CONF T1 - The high-precision AMS 14C program on seawater at the National Ocean Sciences AMS Facility T2 - European Community Workshop on Development of Ocean Tracer Measurements Y1 - 1993 A1 - von Reden, K. F. A1 - Jones, G. A. A1 - Schneider, R. J. A1 - McNichol, A. P. JF - European Community Workshop on Development of Ocean Tracer Measurements CY - Bremen, Germany N1 - id: 1767 ER - TY - CONF T1 - High-precision AMS radiocarbon measurements of seawater at the National Ocean Sciences AMS Facility T2 - 6th International Conference on Accelerator Mass Spectrometry Y1 - 1993 A1 - Jones, G. A. A1 - Schneider, R. J. A1 - McNichol, A. P. A1 - von Reden, K. F. JF - 6th International Conference on Accelerator Mass Spectrometry CY - Canberra, Australia N1 - id: 929 ER - TY - CONF T1 - Internal and external checks in the NOSAMS Sample Preparation Laboratory for target quality and homogeneity T2 - 6th International Conference on Accelerator Mass Spectrometry Y1 - 1993 A1 - McNichol, A. P. A1 - Gagnon, A. R. A1 - Osborne, E. A. A1 - Hutton, D. L. A1 - Jones, G. A. JF - 6th International Conference on Accelerator Mass Spectrometry CY - Canberra, Australia N1 - id: 958 ER - TY - CONF T1 - Laboratory automation at the National Ocean Sciences AMS Facility T2 - 6th Internation Conference on Accelerator Mass Spectrometry Y1 - 1993 A1 - Cohen, G. J. A1 - Hutton, D. L. A1 - von Reden, K. F. A1 - Osborne, E. A. A1 - McNichol, A. P. A1 - Jones, G. A. JF - 6th Internation Conference on Accelerator Mass Spectrometry CY - Canberra, Australia N1 - id: 927 ER - TY - CONF T1 - Methods for data screening, flagging and error analysis at the National Ocean Sciences AMS Facility T2 - 6th International Conference on Accelerator Mass Spectrometry Y1 - 1993 A1 - Schneider, R. J. A1 - Jones, G. A. A1 - McNichol, A. P. A1 - von Reden, K. F. A1 - Elder, K. L. A1 - Kessel, E. D. JF - 6th International Conference on Accelerator Mass Spectrometry CY - Canberra, Australia N1 - id: 933 ER - TY - JOUR T1 - The National Ocean Sciences Accelerator Mass Spectrometry Facility JF - WOCE Notes Y1 - 1993 A1 - Jones, G. A. A1 - McNichol, A. P. A1 - von Reden, K. F. A1 - Schneider, R. J. VL - 5 N1 - id: 1639 ER - TY - CONF T1 - The National Ocean Sciences Accelerator Mass Spectrometry Facility and the WOCE Hydrographic Program. Measurement of 14C in seawater by AMS T2 - Third Scientific Meeting, Oceanography Society Y1 - 1993 A1 - McNichol, A. P. A1 - Jones, G. A. A1 - Schneider, R. J. A1 - von Reden, K. F. A1 - Key, R. M. JF - Third Scientific Meeting, Oceanography Society CY - Seattle, WA VL - 95 N1 - id: 1656 ER - TY - JOUR T1 - The National Ocean Sciences Accelerator Mass Spectrometry Facility (WOCE) JF - WOCE Notes Y1 - 1993 A1 - Jones, G. A. A1 - McNichol, A. P. A1 - von Reden, K. F. A1 - Schneider, R. J. VL - 5 N1 - id: 1651 ER - TY - CONF T1 - The National Ocean Sciences AMS Facility at Woods Hole Oceanographic Institution T2 - 6th International Conference on Accelerator Mass Spectrometry Y1 - 1993 A1 - Jones, G. A. A1 - Schneider, R. J. A1 - von Reden, K. F. A1 - McNichol, A. P. A1 - Gagnon, A. R. A1 - Cohen, G. J. A1 - Osborne, E. A. A1 - Hutton, D. L. A1 - Kessel, E. D. A1 - Elder, K. L. JF - 6th International Conference on Accelerator Mass Spectrometry CY - Canberra, Australia N1 - id: 930 ER - TY - CONF T1 - The National Ocean Sciences AMS System at Woods Hole Oceanographic Institution T2 - European Community Workshop on Tracers in Physical Oceanography Y1 - 1993 A1 - von Reden, K. F. A1 - Jones, G. A. A1 - Schneider, R. J. A1 - McNichol, A. P. JF - European Community Workshop on Tracers in Physical Oceanography CY - Bremen, Germany N1 - id: 935 ER - TY - MGZN T1 - Putting Ourselves to the Test: Analysis of the IAEA Intercomparison Samples Y1 - 1993 A1 - McNichol, A. P. JF - AMS Pulse VL - 1 N1 - id: 1612 ER - TY - CONF T1 - Role of the United States National Ocean Sciences Accelerator Mass Spectrometry Facility in Global Climate Change Studies T2 - International Symposium on Applications of Isotope Techniques in Studying Past and Current Environmental Change in the Hydrosphere and the Atmosphere Y1 - 1993 A1 - Jones, G. A. A1 - Schneider, R. J. A1 - von Reden, K. F. A1 - McNichol, A. P. JF - International Symposium on Applications of Isotope Techniques in Studying Past and Current Environmental Change in the Hydrosphere and the Atmosphere CY - Vienna N1 - id: 928 ER - TY - CONF T1 - Application of AMS to Oceanography: Progress at the National Ocean Sciences AMS Facility (abstract) T2 - AMS Symposium Division of Nuclear Chemistry and Technology, 203rd American Chemical Society National Meeting Y1 - 1992 A1 - McNichol, A. P. A1 - Jones, G. A. A1 - Schneider, R. J. A1 - von Reden, K. F. JF - AMS Symposium Division of Nuclear Chemistry and Technology, 203rd American Chemical Society National Meeting N1 - id: 1796 ER - TY - JOUR T1 - Illumination of a Black-Box - Analysis of Gas-Composition during Graphite Target Preparation JF - Radiocarbon Y1 - 1992 A1 - McNichol, A. P. A1 - Gagnon, A. R. A1 - Jones, G. A. A1 - Osborne, E. A. KW - deposition AB - We conducted a study of relative gas composition changes of CO2, CO and CH4 during the formation of graphite targets using different temperatures, catalysts and methods. Reduction with H-2 increases the reaction rate without compromising the quality of the AMS target produced. Methane is produced at virtually any temperature, and the amount produced is greater at very low temperatures. The reduction of CO to graphite is very slow when H-2 is not included in the reaction. VL - 34 SN - 0033-8222 IS - 3 N1 - Kf389Times Cited:63 Cited References Count:10 JO - Radiocarbon ER - TY - JOUR T1 - The National Ocean Sciences Accelerator Mass Spectrometer for Precision C-14 at Woods Hole Oceanographic Institution -- Status and new results JF - EOS, Transactions of the American Geophysical Union Y1 - 1992 A1 - von Reden, K. F. A1 - Jones, G. A. A1 - Schneider, R. J. A1 - McNichol, A. P. A1 - Cohen, G. J. VL - 72 N1 - id: 926 ER - TY - JOUR T1 - The new National Ocean Sciences Accelerator Mass Spectrometer Facility at Woods Hole Oceanographic Institution-Progress and first results (Proceedings of the 14th International Radiocarbon Conference, 1991) JF - Radiocarbon Y1 - 1992 A1 - von Reden, K. F. A1 - Jones, G. A. A1 - Schneider, R. J. A1 - McNichol, A. P. A1 - Cohen, G. J. A1 - Purser, K. H. VL - 34 N1 - id: 1787 ER - TY - CONF T1 - The new National Ocean Sciences Accelerator Mass Spectrometer Facility at Woods Hole Oceanographic Institution - Progress and First Results T2 - 14th International Radiocarbon Conference 1991 Y1 - 1992 A1 - von Reden, K. F. A1 - Jones, G. A. A1 - Schneider, R. J. A1 - McNichol, A. P. A1 - Cohen, G. J. A1 - Purser, K. H. ED - Long, A. JF - 14th International Radiocarbon Conference 1991 PB - Radiocarbon VL - 34 N1 - id: 1618 ER - TY - JOUR T1 - Rapid Analysis of Seawater Inorganic Carbon at the National Ocean Sciences AMS Facility: Progress and Preliminary Results (abstract) JF - EOS, Transactions of the American Geophysical Union Meeting Y1 - 1992 A1 - McNichol, A. P. A1 - Jones, G. A. A1 - Schneider, R. J. A1 - von Reden, K. F. A1 - Key, R. M. VL - 72 IS - 65 N1 - id: 1655 ER - TY - JOUR T1 - Variability of the delta13C of dissolved inorganic carbon at a site in the North Pacific Ocean JF - Geochimica et Cosmochimica Acta Y1 - 1992 A1 - McNichol, A. P. A1 - Druffel, E. R. M. VL - 56 N1 - id: 1746 ER - TY - CHAP T1 - Carbon cycling in coastal sediments: 2. An investigation of the sources of CO2 to pore water using carbon isotopes T2 - Organic Substances and Sediments in Water, Processes and Analytical Y1 - 1991 A1 - McNichol, A. P. A1 - Druffel, E. R. M. A1 - Lee, C. ED - Baker, R. A. JF - Organic Substances and Sediments in Water, Processes and Analytical PB - CRC Press CY - Boca Raton, FL VL - 2 N1 - id: 1743 ER - TY - JOUR T1 - Carbon cycling in coastal sediments: 2. Estimating remineralization in Buzzards Bay, MA--A comment JF - Geochimica et Cosmochimica Y1 - 1991 A1 - Rowe, G. T. A1 - McNichol, A. P. VL - 55 N1 - id: 1786 ER - TY - JOUR T1 - Illumination of a black box: Gas composition changes during graphite target preparation for AMS (Proceedings of the 14th International Radiocarbon Conference, 1991) JF - Radiocarbon Y1 - 1991 A1 - McNichol, A. P. A1 - Gagnon, A. R. A1 - Jones, G. A. A1 - Osborne, E. A. VL - 34 N1 - id: 1745 ER - TY - RPRT T1 - Measuring 14C in seawater by Accelerator Mass Spectrometry Y1 - 1991 A1 - McNichol, A. P. A1 - Jones, G. A. PB - WOCE Hydrographic Programme Office/Woods Hole Oceanographic Institution CY - Woods Hole, MA VL - WOCE Report No. 68/91 N1 - id: 1610 ER - TY - CONF T1 - The optimization of target production for AMS T2 - 14th International Radiocarbon Conference Y1 - 1991 A1 - McNichol, A. P. A1 - Gagnon, A. R. A1 - Jones, G. A. A1 - Schneider, R. J. A1 - von Reden, K. F. JF - 14th International Radiocarbon Conference CY - Tucson, AZ N1 - id: 922 ER - TY - CHAP T1 - Quantification and characterization of porewater organic colloids T2 - Organic Substances and Sediments in Water. Processes and Analytical Y1 - 1991 A1 - Chin, Y. P. A1 - McNichol, A. P. A1 - Gschwend, P. M. ED - Baker, R. A. JF - Organic Substances and Sediments in Water. Processes and Analytical PB - CRC Press CY - Boca Raton, FL VL - 2 N1 - id: 1744 ER -