摘要
本文对瑞典境内8个位点沉积物中各种来源的汞污染进行了研究,这些位点涵盖了广泛的气候、盐度和沉积物类型。各位点生物群(浮游生物、沉积物生物和鱼类)汞浓度高于附近参考位点的相应生物。决定位点汞污染风险率的主要过程是无机汞向毒性和生物可利用性更高的甲基汞(MeHg)的净转化。因此,河鲈(Percafluviatilis)体内汞浓度与沉积物中MeHg浓度(p<0.05)的相关性大于与无机汞浓度的相关性。除一个位点之外,沉积物中汞浓度(2～55μg/g)与MeHg(4～90ng/g)浓度显著正相关。各位点MeHg/Hg比值(表示MeHg除以汞浓度的净产量)具有很大差异。比值最大的位点是南部淡水松散纤维沉积物,比值最小的位点是半咸水沉积物和最北部淡水位点坚硬的成矿沉积物。这种分布模式的原因是随着温度、高能有机物(与初级生产力有关)和沉积物孔隙水中中性硫酸汞可获得性的增加,甲基化细菌产生的MeHg增加。因此,在评估沉积物汞污染风险时需要考虑这些因素的作用。
Sediments contaminated by various sources of mercury (Hg) were studied at 8 sites in Sweden covering wide ranges of climate,salinity,and sediment types. At all sites,biota (plankton,sediment living organisms,and fish) showed enhanced concentrations of Hg relative to corresponding organisms at nearby reference sites.The key process determining the risk at these sites is the net transformation of inorganic Hg to the highly toxic and bioavailable methylmercury (MeHg).Accordingly,Hg concentrations in Perca fluviatilis were more strongly correlated to MeHg than to inorganic Hg concentrations in the sediments.At all sites,except one,concentrations or inorganic Hg in sediments were significantly,positively correlated to the concentration of MeHg. The MeHg/Hg ratio (which is assumed to reflect the net production of MeHg normalized to the Hg concentration) varied widely among sites.The highest MeHg/Hg ratios were encountered in loose-fiber sediments situated in southern freshwaters,and the lowest ratios were found in brackish-water sediments and firm,minerogenic sediments at the northernmost freshwater site.This pattern may be explained by an increased MeHg production by methylating bacteria with increasing temperature,availability of energy-rich organic matter (which is correlated with primary production),and availability of neutral Hg sulfides in the sediment pore waters.These factors therefore need to be considered when the risk associated with Hgcontaminated sediments is assessed.
