@article {2882,
	title = {Carbon geochemistry of plankton-dominated samples in the Laptev and East Siberian shelves: contrasts in suspended particle composition},
	journal = {Ocean Science},
	volume = {13},
	year = {2017},
	month = {Jan-01-2017},
	pages = {735 - 748},
	abstract = {Recent Arctic studies suggest that sea ice decline and permafrost thawing will affect phytoplankton dynamics and stimulate heterotrophic communities. However, in what way the plankton composition will change as the warming proceeds remains elusive. Here we investigate the chemical signature of the plankton-dominated fraction of particulate organic matter (POM) collected along the Siberian Shelf. POM (> 10 {\textmu}m) samples were analysed using molecular biomarkers (CuO oxidation and IP25) and dual-carbon isotopes (δ13C and Δ14C). In addition, surface water chemical properties were integrated with the POM (> 10 {\textmu}m) dataset to understand the link between plankton composition and environmental conditions.

δ13C and Δ14C exhibited a large variability in the POM (> 10 {\textmu}m) distribution while the content of terrestrial biomarkers in the POM was negligible. In the Laptev Sea (LS), δ13C and Δ14C of POM (> 10 {\textmu}m) suggested a heterotrophic environment in which dissolved organic carbon (DOC) from the Lena River was the primary source of metabolisable carbon. Within the Lena plume, terrestrial DOC probably became part of the food web via bacteria uptake and subsequently transferred to relatively other heterotrophic communities (e.g. dinoflagellates). Moving eastwards toward the sea-ice-dominated East Siberian Sea (ESS), the system became progressively more autotrophic. Comparison between δ13C of POM (> 10 {\textmu}m) samples and CO2aq concentrations revealed that the carbon isotope fractionation increased moving towards the easternmost and most productive stations.

In a warming scenario characterised by enhanced terrestrial DOC release (thawing permafrost) and progressive sea ice decline, heterotrophic conditions might persist in the LS while the nutrient-rich Pacific inflow will likely stimulate greater primary productivity in the ESS. The contrasting trophic conditions will result in a sharp gradient in δ13C between the LS and ESS, similar to what is documented in our semi-synoptic study.},
	doi = {10.5194/os-13-735-2017},
	url = {https://os.copernicus.org/articles/13/735/2017/},
	author = {Tesi, Tommaso and Geibel, Marc C. and Pearce, Christof and Panova, Elena and Vonk, Jorien E. and Karlsson, Emma and Salvado, Joan A. and Krus{\r a}, Martin and Broder, Lisa and Humborg, Christoph and Semiletov, Igor and Gustafsson, {\"O}rjan}
}
@article {226,
	title = {14C-Based source assessment of soot aerosols in Stockholm and the Swedish EMEP-Aspvreten regional background site},
	journal = {Atmospheric Environment},
	volume = {45},
	year = {2011},
	note = {id: 2148},
	pages = {215-222},
	abstract = {Combustion-derived soot or black carbon (BC) in the atmosphere has a strong influence on both climate and human health. In order to propose effective mitigation strategies for BC emissions it is of importance to investigate geographical distributions and seasonal variations of BC emission sources. Here, a radiocarbon methodology is used to distinguish between fossil fuel and biomass burning sources of soot carbon (SC). SC is isolated for subsequent off-line 14C quantification with the chemothermal oxidation method at 375 {\textdegree}C (CTO-375 method), which reflects a recalcitrant portion of the BC continuum known to minimize inadvertent inclusion of any non-pyrogenic organic matter. Monitored wind directions largely excluded impact from the Stockholm metropolitan region at the EMEP-Aspvreten rural station 70 km to the south-west. Nevertheless, the Stockholm city and the rural stations yielded similar relative source contributions with fraction biomass (fbiomass) for fall and winter periods in the range of one-third to half. Large temporal variations in 14C-based source apportionment was noted for both the 6 week fall and the 4 month winter observations. The fbiomass appeared to be related to the SC concentration suggesting that periods of elevated BC levels may be caused by increased wood fuel combustion. These results for the largest metropolitan area in Scandinavia combine with other recent 14C-based studies of combustion-derived aerosol fractions to suggest that biofuel combustion is contributing a large portion of the BC load to the northern European atmosphere.},
	issn = {1352-2310},
	doi = {10.1016/j.atmosenv.2010.09.015},
	url = {http://www.sciencedirect.com/science/article/pii/S1352231010007697},
	author = {Andersson, August and Sheesley, Rebecca J. and Krus{\r a}, Martin and Johansson, Christer and Gustafsson, {\"O}rjan}
}
@conference {958,
	title = {Year-round probing of soot carbon and secondary organic carbon contributions and sources to the South Asian Atmospheric Brown Cloud using radiocarbon (14C) measurements},
	booktitle = {EGU General Assembly 2010, held 2-7 May, 2010 in Vienna, Austria},
	volume = {12},
	year = {2010},
	note = {id: 870Y},
	month = {05/2010},
	abstract = {South Asia is one region of vital importance for assessing human impact on radiative forcing by atmospheric aerosols. Previous research in the region has indicated that black carbon is a significant component of the regional aerosol load. In contrast, there is more ambiguous information regarding the contribution of secondary organic aerosols (SOA) to the total carbonaceous (TC) aerosol composition. Here we primarily address the SOA component of the South Asian Atmospheric Brown Cloud (ABC) by a combination of measurements of SOA concentrations and the 14C signature of TC. Atmospheric particulate matter was collected during fourteen-month continuous sampling campaigns Jan 2008 - March 2009 at both the Maldives Climate Observatory at Hannimaadho (MCO-H) and at the Sinhagad hilltop sampling site of the Indian Institute of Tropical Meteorology (SIN) in central-western India. The radiocarbon method is an ideal approach to identify fossil sources (14C "dead") compared to biogenic and biomass combustion products (with a contemporary 14C signal). The radiocarbon source apportionment of TC revealed very similar contribution from biogenic/biomass combustion (60-70\%) for Indian SIN site and the MCOH receptor regions for much of the year. However, during the summer monsoon season biomass contribution to TC at the Indian Ocean site increases to 70-80\%, while it decreases to 40-50\% at the Indian site. Source apportionment of a soot carbon (SC) isolate (CTO-375 method; a tracer of black carbon) shows a similar trend. According to preliminary data in summer biomass contribution is higher at the MCOH receptor site (70\%) compared to the SIN background site (45\%). These unique year-round 14C data will be interpreted in view of the SOA concentration and the varying origin of the air masses.},
	author = {Kirillova, Elena and Sheesley, Rebecca J. and Andersson, August and Krus{\r a}, Martin and Safai, P. D. and Budhavant, Krishnakant and Rao, P. S. P. and Praveen, P. S. and Gustafsson, {\"O}rjan}
}
