Decadal Variations Of Black Carbon In Continental Shelf Sediments In Antarctica And The South China Sea And Their Environmental Implications

Sediment cores collected adjacent to the northeast Antarctic Peninsula during the 32nd Antarctic expedition and in the northern South China Sea in the spring of 2014 were studied.21 0Pb and 226Ra were determined to construct the chronologies of sediments deposited during the past 150 years.The contents and burial fluxes of black carbon(BC),'4C of black carbon(B'4C)and ?13Ctoc were analyzed to reveal their decadal variations.Further,the burial of BC was compared to illustrate the role of the study shelves in budgeting the global BC.Sources of BC in sediment cores adjacent to the northeast Antarctic Peninsula differed a lot between pre-and post-industrialization.Before the 1860s,BC originated mainly from rock weathering and biomass burning.After the 1860s,signals on the combustion of fossil fuel was observed.The decadal variations in the burial flux of BC recorded the enhanced erosion of the South Orkney Islands and the elevated glacial melting since the 1960s.The difference between two cores indicated that current(s)play an important role in affecting the decadal variability of BC.The annual BC burial flux in Antarctic shelf sediment is 2316 Gg,accounting for 13.5-79.9%of the global flux.These results indicated that the Antarctic shelves are efficient areas given BC burial.In view of the significant positive correlation between the BC content and TOC,813Ctoc,we speculated that the regulation of primary productivity by Fe accompanying the BC input may be the mechanism of coupling BC and TOC.Thus,BC may be a potential proxy as primary production in Antarctica.The South China Sea is located in the Southeast Asia,the world's largest source region of BC emission.In addition to documenting the enhanced fossil fuel utilization since the reform and opening up in the mainland of China,the decadal changes in BC also recorded the primary processing industry in the early Hong Kong.The decadal variations of BC content and burial flux are controlled by the coastal erosion and combustion emission intensity.The difference in BC variations between different cores was ascribed to the local sedimentary environments.Overall,the decadal variations in BC burial flux reflected the fossil fuel combustion.Recently,the reduced burial flux implied the changes in industrial structure.The annual BC burial in the shelf sediments of the South China Sea was 353 Gg.The South China Sea accounts for 4.8%of the global shelf area,and the BC annual burial accounts for 2.1-12.2%of global BC burial in shelves.Studies in the two typical sea areas showed that the B14C data could provide crucial information on qualitative and semi-quantitative constraining the sources of BC.Lithogenic graphite-type BC in sediments is an unneglectable BC fraction.The buried BC in cores contain information of fuel combustion and coastal erosion.In the same area,the difference in the decadal variations of BC at different sites illustrated the important role of local environments in controlling sedimentation.Thus,the intensity of source emission may not correspond to the burial of BC in sediments.