莱州湾表层沉积物中重金属时空分布、污染来源及风险评价

Spatial and Temporal Distribution,Sources and Ecological Risk Assessment of Heavy Metals in the Surface Sediments of Laizhou Bay

运用污染风险评价标准和方法研究了2010年5月（春）、8月（夏）、10月（秋）和12月（冬）莱州湾表层沉积物中7种重金属污染物的时空分布特征、来源及生态风险。结果表明,表层沉积物中Cr、Zn和Pb含量均呈现春季低于其他季节特征,秋季Hg含量是其他季节的4倍,Cu、As和Pb含量无显著季节差异。表层沉积物中Cr、Cu、Zn、As和Cd最高值出现在莱州湾中部及小清河河口等西部水域,来源呈现受自然作用影响较大的特征;而Hg和Pb最高值出现在龙口和界河河口等东部水域,来源呈现受周边工业污染物的人为排放影响较大的特征。基于地理累积指数、生态效应浓度以及Hakanson潜在生态风险指数的综合评价表明,13%~29%的研究区域的表层沉积物受到轻微程度的Cd、Hg和Pb污染,Cd和Hg高值水域达到中等生态风险程度;Hg和As在65%~68%的研究区域的表层沉积物中达到可能对沉积物底质环境及生物群落产生不利生态影响水平。基于对重金属污染物的评价结果,莱州湾表层沉积物质量较好,局部区域存在Hg、Pb、Cd和As的潜在污染风险。

This study investigated the spatial and temporal distribution, sources and ecological risk of seven heavy metals in the surface sediments of Laizhou Bay, collected in May, August, October and December 2010, respectively. Results revealed that the concentrations of Cr, Zn and Pb in the sediments were all lower in May than in other sampling months and the concentrations of Hg in October were 4 times as high as other sampiing months. The concentrations of Cu, As and Pb did not significantly differ among sampling months. The highest concentrations of Cr, Cu, Zn, As and Cd in the sediments generally occurred in the central and western areas of the bay, which was probably affected to a large extend by natural sources such rock weathering. In contrast, Hg and Pb concentrations were found in the highest levels in the eastern areas of the bay such as the Jiehe River estuary and its adjacent areas. Hg and Pb could originate mainly from the emissions of anthropogenic pollutants of the industrial enterprises along the coastal waters. Results of geoaccumulation index, Hakanson potential ecological risk index and effect range indicated that 13% -29% of the sediments in the investigated areas were slightly polluted by Cd, Hg and Pb. The areas which exhibited high Hg and Cd concentrations were ranked middle-level ecological risk. Moreover, in 65% -68% of the investigated areas, Hg and As concentrations in the sediments reached the level at which heavy metals could exhibit adverse ecological impacts on the sediment environments and benthic bio-communities. With respect to heavy metals, the overall quality of the surface sediments in Laizhou Bay was good except in some specific sites in which Hg, Pb, Cd or As showed potential pollution risk.