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To evaluate the sources and budgets of sedimentary organic matter in the East China Sea (ECS), bulk organic matter properties (total organic carbon (TOC), C/N ratio, carbon and nitrogen isotopic composition (δ 13 C and δ 15 N)) and sterols in surface sediments were analyzed. The distributions of bulk organic matter properties and sterols showed a strong regionality with higher contents in the southern inner shelf as well as the offshore upwelling area. It was consistent with the increasing mud and chlorophyll a ( Chl a) contents southwards. These distribution patterns were attributed to the terrestrial inputs by shelf circulations and phytoplankton contribution. Both of bulk organic matter properties and sterols indicated a mixture of terrestrial and marine derived organic matter inputs with marine source as a dominant input. Budgets suggested that organic carbon (OC) and sterol influxes from terrestrial source were 5.15 × 10 6 and 3.32 × 10 3 t/yr, with the Changjiang River input as the primary contributor; and while their influxes from marine source were 26.3 × 10 6 and 2.19 × 10 3 t/yr, respectively. The burial fluxes of OC and sterol were 3.99 × 10 6 t C/yr and 0.21 × 10 3 t/yr, with the inner shelf as main accumulation area. Although there was a huge amount of OC influx from terrestrial and marine sources, but only 24.6% and 10% of them could be preserved in sediments. Consequently, the combined effect of riverine input, marine primary productivity and deposition decided the organic matter behaviors in the ECS. [ABSTRACT FROM AUTHOR]

Surface and core sediments were collected to study distributions, phases and potential environmental risk of Hg and to reconstruct anthropogenic Hg change over the past one hundred years in the East China Sea (ECS). Hg contents in surface sediments displayed a decreasing gradient from the Changjiang Estuary to the outer sea. Sequential extraction analysis showed that Hg mainly existed as residual fraction (70.18% of total), and while organic matter fraction (22.96% of total) was the main component of labile fraction, indicating the strong adsorption of organic matters on Hg. Enrichment factor and sediment quality guidelines suggested that Hg in sediments of ECS were at minor enrichment and low adverse effect. Temporal distributions of total Hg content, labile fraction, burial flux and anthropogenic Hg flux showed that anthropogenic Hg input increased since the 1960s, which was related to riverine input and atmospheric transport. [ABSTRACT FROM AUTHOR]