Organic Carbon Distribution in the Yangtze River Estuary-Hangzhou Bay and Its Adjacent Sea Area

A study of environmentally sensitive grain-size population was used by the grain size class vs standard deviation values of the surface sediment samples in the Yangtze River Estuary,Hangzhou Bay,Zhoushan archipelago sea area and the East China Sea shelf.Results indicated that there were three similar grain size populations between the East China Sea shelf and the Yangtze River estuary and two similar populations between the Hangzhou Bay and the Zhoushan archipelago sea area.According to the environmentally sensitive grain-size population,wet sieving was performed to separate the four area sediments into six size fractions(0.250 mm,0.125~0.250 mm,0.063~0.125 mm,0.025~0.063 mm,0.004~0.025 mm,and 0.004 mm).Each of these size fractions and the bulk samples were analyzed for the total organic carbon(TOC) and stable organic carbon isotopic ratios(δ13Corg).The further quantitative analysis of TOC and δ13Corg for each fraction indicated that there was the highest TOC content in the 0.004 mm fraction except the coarse size fractions of the Hangzhou bay where they were rich in the organic matter from the terrestrial source plant debris,and the particle size and type of the sediment component played important role in the organic matter distribution.