洋山深水港区海域秋、冬季沉积物中重金属来源分析及生态风险评价

摘要

通过测定洋山深水港区海域2010～2013年6个航次秋、冬季沉积物中重金属含量，分析其时空差异，结果表明该海域沉积物重金属总体含量较低，空间分布较为均匀，Hg、Zn、Pb、Cd 含量秋季明显高于冬季，As、Cu含量的季节性波动较小，用因子分析法研究该海域重金属来源，发现陆源工业、船舶航运排污以及有机质降解是研究海域 Pb、Cd、Zn 的主要来源；农业污染、码头货物装卸残留及建筑垃圾支配着Cu、As、Hg的来源。SQG-Q生态风险评价表明研究海域沉积物中重金属均存在中、低度的生态风险，秋季的生态风险高于冬季，Hg和Cu是主要生态风险因子；地累积指数法评价结果显示研究海域基本不受Hg、As、Zn、Pb的污染；Cd、Cu以轻度污染为主，部分站位属于偏中度污染，6种重金属污染程度依次为：Cd＞Cu＞Pb＞Zn＞Hg＞As。因子综合得分评价表明，重金属污染相对严重的站位依次为5号、4号及3号站位。但总体看来洋山深水港区附近海域沉积物中重金属污染状况属于轻度污染。%Temporal and spatial variations of concentrations of heavy metals including mercury (Hg), zinc (Zn), lead (Pb), arsenic (As), copper (Cu), and cadmium (Cd) in the sediments of the Yangshan Deepwater Harbor were determined based on 6 cruises in autumn and winter, respectively, from 2010 to 2013. The results demonstrated that the overal concentrations of heavy metals were low and distributed in uniform patterns. The concentrations of Hg, Zn, Pb, and Cd in autumn were significantly higher than those in winter with smal fluctuations for As and Cu in terms of seasonal variations. Results of factor analysis showed that Pb, Cd, and Zn were derived from inland industrial and shipping discharges as well as the degradation of organic pol utants in marine environment. While agricultural pollutions, cargo shifting and construction debris from reclamation projects contributed to the sources of Cu, As, and Hg. Ecological risk assessment by Mean Sediment Quality Guideline Quotient (SQG-Q) revealed that the degree for eco-risk of the sediments was low-and-moderate in autumn, higher than that in winter. Hg and Cu were the dominant eco-risk factors. The results of Index of geoaccumulation (Igeo) showed that the whole sites of the sea area were barely influenced by Hg, As, Zn, and Pb, and the extents of Cd and Cu contaminations were in low grade. Contamination degree of al the six heavy metals could be ranked as the fol owing: Cd>Pb>Zn>Hg>As. According to the results of integrated score of factor analysis, the contamination degree for heavy metals in sediments of the Yangshan Deepwater Harbor was low, despite sites No.5, No.4 and No.3, which were heavily contaminated compared with others.