| The Bohai Sea is a semi-enclosed bay with weak water exchange capacity and pollution levels that are increasing with the development of modern industry and agriculture. Heavy metal pollution has become an important factor, as it both directly and indirectly endangers human health. The release of heavy metals from sediments might significantly impact on the water environment and the ecological health of the sea. A survey of heavy metal content, distribution, enrichment, and pollution state of the sediments was conducted in August 2013 to determine the seas characteristics. The contents of Cu, Pb, Zn, and Cd in the surface sediment samples from 34 sites were measured, and the content and distribution characteristics of these heavy metals were studied. Single factor standard indices and potential ecological risk indices were used to evaluate the status of the heavy metal pollution and the degree of ecological risk. The results indicated that the average heavy metal content was low, and that all individual element contents were lower than the first class of GB 18668-2002. The spatial distribution of the heavy metals in the sediments showed that their contents decreased between the offshore and central regions. The Cu, Pb, and Zn surface sediment heavy metals, showed the most obvious changes with relation to their location; their coastal content was higher and was gradually reduced in samples moving towards the offshore region. The Cd content in the Yellow River estuary was high to the east and decreased along the western sides. The individual single-factors for each of the heavy metals in the surface sediments was less than 5, which indicated a low degree of pollution, and the descending order of the average single factors was Pb, Cu, Zn, As, Cd, and Hg. The single potential ecological risk factor of the six heavy metals, except for the Hg element at No. 1 (54.44) station, were less than 40 (0.9~38.80), which indicates a low level ecological risk. The descending order of the potential ecological risk factors was Hg, As, Cu, Zn, Pb, and Cd, and ranged from 0.58 to 10.50. The comprehensive potential ecological risk indices are all less than 150, and ranged from 16.39 to 79.57, which indicated low level of ecological risks. The descending order was Hg, Cd, As, Pb, Cu, and Zn. The Daqinghe River estuary had the highest risk values, and Hg was the main potential ecological risk factor in the surveyed area. |
