@article {2921, title = {Climate control on terrestrial biospheric carbon turnover}, journal = {Proceedings of the National Academy of Sciences}, volume = {118}, year = {2021}, month = {Nov-02-2022}, pages = {e2011585118}, abstract = {Terrestrial vegetation and soils hold three times more carbon than the atmosphere. Much debate concerns how anthropogenic activity will perturb these surface reservoirs, potentially exacerbating ongoing changes to the climate system. Uncertainties specifically persist in extrapolating point-source observations to ecosystem-scale budgets and fluxes, which require consideration of vertical and lateral processes on multiple temporal and spatial scales. To explore controls on organic carbon (OC) turnover at the river basin scale, we present radiocarbon (C-14) ages on two groups of molecular tracers of plant-derived carbon-leaf-wax lipids and lignin phenols-from a globally distributed suite of rivers. We find significant negative relationships between the C-14 age of these biomarkers and mean annual temperature and precipitation. Moreover, riverine biospheric-carbon ages scale proportionally with basin-wide soil carbon turnover times and soil C-14 ages, implicating OC cycling within soils as a primary control on exported biomarker ages and revealing a broad distribution of soil OC reactivities. The ubiquitous occurrence of a long-lived soil OC pool suggests soil OC is globally vulnerable to perturbations by future temperature and precipitation increase. Scaling of riverine biospheric-carbon ages with soil OC turnover shows the former can constrain the sensitivity of carbon dynamics to environmental controls on broad spatial scales. Extracting this information from fluvially dominated sedimentary sequences may inform past variations in soil OC turnover in response to anthropogenic and/or climate perturbations. In turn, monitoring riverine OC composition may help detect future climate-change-induced perturbations of soil OC turnover and stocks.}, keywords = {Carbon cycle, carbon turnover times, fluvial carbon, plant biomarkers, radiocarbon}, issn = {0027-8424}, doi = {10.1073/pnas.2011585118}, url = {https://www.researchgate.net/publication/349357864_Climate_control_on_terrestrial_biospheric_carbon_turnover}, author = {Eglinton, Timothy I. and Galy, Valier V. and Hemingway, Jordon D. and Feng, Xiaojuan and Bao, Hongyan and Blattmann, Thomas M. and Dickens, Angela F. and Gies, Hannah and Giosan, Liviu and Haghipour, Negar and Hou, Pengfei and Lupker, Maarten and McIntyre, Cameron P. and Montlu{\c c}on, Daniel B. and Peucker-Ehrenbrink, Bernhard and Ponton, Camilo and Schefu{\ss}, Enno and Schwab, Melissa S. and Voss, Britta M. and Wacker, Lukas and Wu, Ying and Zhao, Meixun} } @article {2661, title = {On the Origin of Aged Sedimentary Organic Matter Along a River-Shelf-Deep Ocean Transect}, journal = {Journal of Geophysical Research: Biogeosciences}, volume = {124}, year = {2019}, month = {Jun-08-2021}, pages = {2582 - 2594}, abstract = {To assess the influences of carbon sources and transport processes on the C-14 age of organic matter (OM) in continental margin sediments, we examined a suite of samples collected along a river-shelf-deep ocean transect in the East China Sea (ECS). Ramped pyrolysis-oxidiation was conducted on suspended particulate matter in the Yangtze River and on surface sediments from the ECS shelf and northern Okinawa Trough. C-14 ages were determined on OM decomposition products within different temperature windows. These measurements suggest that extensive amounts of pre-old (i.e., millennial age) organic carbon (OC) are subject to degradation within and beyond the Yangtze River Delta, and this process is accompanied by an exchange of terrestrial and marine OM. These results, combined with fatty acid concentration data, suggest that both the nature and extent of OM preservation/degradation as well as the modes of transport influence the C-14 ages of sedimentary OM. Additionally, we find that the age of (thermally) refractory OC increases during across-shelf transport and that the age offset between the lowest and highest temperature OC decomposition fractions also increases along the shelf-to-trough transect. Amplified interfraction spread or C-14 heterogeneity is the greatest in the Okinawa Trough. Aged sedimentary OM across the transect may be a consequence of several reasons including fossil OC input, selective degradation of younger OC, hydrodynamic sorting processes, and aging during lateral transport. Consequently, each of them should be considered in assessing the C-14 results of sedimentary OM and its implications for the carbon cycle and interpretation of sedimentary records.}, keywords = {Carbon cycle, hydrodynamic processes, organic carbon, radiocarbon, sediments}, issn = {2169-8953}, doi = {10.1029/2019JG005107}, url = { https://doi.org/10.1029/2019JG005107}, author = {Bao, Rui and Zhao, Meixun and McNichol, Ann and Wu, Ying and Guo, Xinyu and Haghipour, Negar and Eglinton, Timothy I.} } @article {2626, title = {Spatiotemporal Variation of the Quality, Origin, and Age of Particulate Organic Matter Transported by the Yangtze River (Changjiang)}, journal = {Journal of Geophysical Research: Biogeosciences}, volume = {123}, year = {2018}, month = {Jan-09-2018}, pages = {2908 - 2921}, abstract = {Information on the age dynamics of particulate organic matter (POM) in large river systems is currently sparse and represents an important knowledge gap in our understanding of the global carbon cycle. Here we examine variations in organic geochemical characteristics of suspended sediments from the Changjiang (Yangtze River) system collected between 1997 and 2010. Higher particulate organic carbon content (POC\%) values were observed in the middle reach, especially after 2003, and are attributed to the increase of in situ (aquatic) primary production associated with decreased total suspended matter concentrations. Corresponding C-14 values from depth profiles taken in 2009 and 2010 indicate spatial and temporal variations in POC sources within the basin. Two isotopic mass balance approaches were explored to quantitatively apportion different sources of Changjiang POM. Results indicate that contributions of biomass and pre-aged soil organic matter are dominant, regardless of hydrological conditions, with soil-derived organic carbon comprising 17-56\% of POC based on a Monte Carlo three-end-member mixing model. In contrast, binary mixing model calculations suggest that up to 80\% of POC (2009 samples only) derived from biospheric sources. The emplacement of the Three Gorges Dam and resulting trapping of sediment from the upper reach of the watershed resulted in a modification of POM C-14 ages in the reservoir. With the resulting decline in sediment load and increase in the proportion of modern POC in the lower reach, these changes in POM flux and composition of the Changjiang have significant implications for downstream carbon cycle processes.}, keywords = {Changjiang, organic carbon, radiocarbon, suspended particulate matter, Three Gorges Dam}, issn = {2169-8953}, doi = {10.1029/2017JG004285}, url = {http://doi.wiley.com/10.1029/2017JG004285http://onlinelibrary.wiley.com/wol1/doi/10.1029/2017JG004285/fullpdfhttps://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1029\%2F2017JG004285}, author = {Wu, Ying and Eglinton, Timothy I. and Zhang, Jing and Montlu{\c c}on, Daniel B.} }