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Wu, B.; Jin, H.; Gao, S.; Xu, J., and Chen, J., 2020. Nutrient budgets and recent decadal variations in a highly eutrophic estuary: Hangzhou Bay, China. Journal of Coastal Research, 36(1), 63–71. Coconut Creek (Florida), ISSN 0749-0208. Hangzhou Bay is one of China's most eutrophic waterbodies, yet water quality observations within the bay are few, and the estuary's nutrient dynamics are poorly understood. Five cruises (summer, autumn, winter, spring) were conducted in Hangzhou Bay and adjacent waters between July 2006 and November 2007 and in August 2018. A steady-state box model was also constructed to estimate summer and winter nutrient fluxes. The results show that the spatial distributions and temporal variations of nutrients within the bay are significantly influenced by not only direct inputs from rivers around the bay but also the Changjiang River plume to the north. Bay concentrations of nitrate (), dissolved inorganic phosphorus (DIP), and dissolved silicate (DSi) were quite high throughout the year, especially in the head of the bay. Relative to concentrations measured in 1981–1982, estuarine concentrations of and DIP had increased, whereas DSi had been stable. The model results indicate that riverine discharge is the major source of nutrients to Hangzhou Bay. In both summer and winter, nutrients were exported from the bay to the East China Sea. The fluxes of , dissolved inorganic nitrogen (DIN), DIP, and DSi were higher in summer than winter, but the flux of ammonium was higher in winter. Nutrient fluxes to Hangzhou Bay observed here during 2006–2007 are much higher than those observed in the 1980s. Additionally, nutrient abundances in Hangzhou Bay are significantly higher than those reported for other coastal embayments in China. The difference in algal blooms inside and outside the bay is possibly due to the difference in turbidity or the hydrological conditions. [ABSTRACT FROM AUTHOR]

Huge amount of trace metals emitted through manmade activities are carried by the Changjiang River into the East China Sea. Most of them deposit in the Changjiang River Estuary and threaten the regional aquatic environment. In this study, major and trace elements of 34 archive surface sediments and two cores are examined. Sequential extraction procedures were also performed on surface sediments from 12 sites. We found that Tl, Tm, Er show distinct accumulation in surface sediments in the order of Tm > Tl > Er. Particularly, abnormally elevated HREE are observed mainly in those sites near the mouth of the estuary. Most elements exhibit an obvious reduction in the upper 30 cm of core B8, reflecting a decrease of sediment discharge from Changjiang River runoff. The increase of some trace elements recorded in the upper 20 cm of core C3 demonstrates a distinct local anthropogenic input in recent years. • Most trace elements are sourced from land except Sr and Ba, related closely with their geochemical behavior. • Distribution characteristics of elements are dominantly controlled by complicated hydrodynamic and grain sorting procession. • HREE particularly Tm and Er combining with Tl are anthropogenic, indicating ecological risk. • The decrease of riverine sediments induces the decrease of metals in top core sediments of the Changjiang River. • Some metals show accumulation in the top of core sediment from mouth of Hangzhou Bay, indicating local anthropogenic input. [ABSTRACT FROM AUTHOR]

A wide variety of persistent organic pollutants (POPs) in the surface marine sediments and seafood from four geographic areas of the East China Sea were investigated. The POP concentrations were analyzed and their possible ecotoxicological risks assessed. The total concentrations of hexachlorocyclohexanes (HCHs), dichlorodiphenyltrichloroethanes (DDTs), polycyclic aromatic hydrocarbons (PAHs), and polychlorinated biphenyls (PCBs) in the sediments were found to be ND–22.40, ND–5.10, 32.10–171.70, and 0.60–63.00 ng/g dry weight (dw), respectively. Low-chlorinated biphenyl congeners and HCHs were predominantly found at the Hangzhou Bay and Yangtze River areas. The sediment ecotoxicological risk was assessed, indicating the toxic effect of PCBs and DDTs on benthic organisms. In marine organisms of economic importance, the concentration of total PAHs, PCBs, and organochlorine pesticides (OCPs) ranged from 43.20 to 291.20, 2.60 to 96.20, and 12.70 to 235.20 μg/kg dw, respectively. The bioaccumulation in marine organisms did not pose a significant health risk to consumers. As indicated by the POP residues in both marine sediments and organisms, POPs were persistent over time, posing a long-term risk to the local ecosystem and human health via the food chain. [ABSTRACT FROM AUTHOR]

Coastal estuaries are often heavily subject to riverine influences by the inputs of sediment from terrestrial sources. Hangzhou Bay (HZB) is threatened by the riverine derived trace metals from two large rivers of Qiantang River (QTR) and Yangtze River (YZR). However, previous studies mainly focused on the incidental transport from the largest river in China (YZR) and failed to simultaneously evaluate the contributions of these two rivers, especially the directly flowing river of QTR, by their trace elemental geochemical composition and distribution. Herein, a comprehensive study identified the river-derived sources of multiple trace metals in surface sediments which transported from both of the rivers. The sampling stations were separated into three regions of YZR, HZB, and QTR based on their spatial distributions of sediment grain size and components. The significant variations for most of the trace metals concentrations, except for Cd, Th, and U, were found among three regions (χ 2 ≥ 8.22, p ≤ 0.016). The highest concentrations in HZB were mainly resulted from the grain size effect (68.82% of the total variance), while the highest concentrations of Sr, Cd, and Ba in YZR and Zr and Hf in QTR were attributed to the anthropogenic source (11.90%) and mineral composition (6.21%) of river basins. After normalized the diversity of multiple trace metals concentrations and the influence of grain size by ratios of I geo and EF Li , three regions were effectively distinguished. It was indicated that As, Cd, and Sb were enriched in the sediments of rivers by anthropogenic source (EF Li > 1.5 and/or I geo > 1). The results evidenced that, after removing the influence of grain size, elemental geochemical composition of the surface sediments confidently identified the river-derived anthropogenic sources of the enriched trace metals from two major rivers, and largely from YZR. [Display omitted] • Regions of YZR, QTR, and HZB were separated by sediment grain size and components. • Most trace metals varied significantly in the surface sediments of three regions. • More enrichment of trace metals were found in two rivers after normalized by EF Li. • Anthropogenic trace metals in sediment of HZB were identified as riverine sources. • YZR was regarded as the main river-derived sources of trace metals in HZB. [ABSTRACT FROM AUTHOR]