Distribution characteristics and ecological risk assessment of nutrients in sediment particles in Hangzhou Bay, China

In April 2011, the contents of TC, TP, TN, NH4-N and the particle size and pH of surface sediment and suspended particulate matter at 18 stations in Hangzhou Bay were detected and analyzed. The content of nutrients in the bay features high values in the middle and mouth of the bay while low values at the top of the bay, and low values on the north side while high values on the south side of the bay. The contents of TC, TN and NH4-N in suspended particulate matter were significantly higher than those in surface sediments. To a certain extent, this feature reflected the effect of water and sediment transportation. Hydrodynamics in the studied area were active. The sediment differentiation caused by the repeated suspension-transport and sedimentation of the tidal current was one of the important reasons for the difference of the contents and dispersion of nutrients in suspended sediments and surface sediments. The contents of TP in the Hangzhou Bay were high and the contents of most of the sediment samples collected exceeded the class I, which indicated that the sediments in Hangzhou Bay had been contaminated. However, most areas were still within the range of benthic organisms. In terms of the distribution of pollution, the TP had the most obvious toxicity in front of the south shore of Hangzhou Bay.