长江口倾倒区海域水体与沉积物中重金属的分配与生态风险

Heavy Metals in Water and Sediment of Dumping Site in Yangtze River Estuary:Water-Sediment Partition and Ecological Risk

为研究长江口海域重金属的分布特征、水相-颗粒相分配规律及其潜在生态风险,于2014年8~9月对倾倒区海域水样和沉积物样进行了采集,并采用Hakanson潜在生态风险指数法对其生态风险进行了评价。研究结果显示,长江口海域表层海水中Cd、Hg和As的浓度分别为0.07±0.03、0.07±0.07和2.30±0.51μg/L,低于或接近海水一类标准值。表层沉积物中,Cd、Hg和As的浓度依次为0.18±0.09、0.05±0.03和8.02±2.14mg/kg。与国内外研究相比,长江口海域重金属浓度处于相对较低污染的水平。Cd、Hg和As的颗粒相-水相分配系数logKp与pH、无机氮和COD均呈负相关关系,即随pH、无机氮和COD值升高,Cd、Hg和As趋于从颗粒相中向水相中迁移。PO3-4对与Cd的分配系数呈正相关关系,表明PO3-4浓度的增加能够促进水相中Cd吸附或吸收到颗粒相中。长江口海域表层沉积物中Cd、Hg和As的潜在生态风险系数分别为14.59±7.12、7.94±3.49和5.34±1.43,表现为Cd>Hg>As,且均处于轻微污染的水平。

To learn the characteristics of spatial distribution,water-particle partition and potential ecological risks of heavy metals in Yangtze River Estuary （YRE）, water and sediment samples were collected from August to September 2012. Their potential ecological risks were evaluated by Hakanson potential ecological risk index method. Research results show that concentrations of Cd, Hg and As of surface water were 0.07±0.03,0. 07 ± 0. 07 and 2.30±0. 51 /,g/L respectively,which were lower than or close to the first class level of sea water. As to surface sediments, respectively the concentration of Cd, Hg and As were 0. 18±0.09 0.05 ±0. 03 and 8.02 ± 2. 14 mg/kg. Compared with research results worldwide, heavy metals：in YRE ranked a relatively slightly polluted level. The water-particle partition coefficients （logKp） of Cd, Hg and As,were all negatively correlated with pH,inorganic nitrogen and COD. With the increasing pH, inorganic nitrogen and COD,Cd, Hg and As trends to resolve to water phase from particle phase. However, the logKp value of Cd was positively correlated with PO4^3- , implying PO4^3- promote aqueous phase Cd to be adsorpted or absorpted into the particle phase. The potential ecological risk of Cd, Hg and As of the surface sediment in the Yangtze river estuary were 14. 59±7. 12,7. 94±3.49 and 5.34±1.43, exhibited the order of Cd〉 Hg）As, and stated in slightly polluted level.