Kress N, Herut B, Galil B S
Israel Oceanographic and Limnological Research, National Institute of Oceanography, Haifa 31080, Israel.
Mar Environ Res. 2004 Apr;57(3):213-33. doi: 10.1016/S0141-1136(03)00081-3.
The distributions of benthic assemblages, heavy metals and organic carbon (Corg) in sediments were examined during a long-term study at a sewage sludge disposal site off the Mediterranean coast of Israel. The disposal of sewage sludge has a marked but localized, seasonally dependent, impact on the benthic assemblages and sediment quality. Elevated concentrations of Corg, Hg, Cd, Cu, Zn, Pb, and to a lesser degree Ni in the sediments were detected mostly northward of the sewage outfall, in the direction of the prevalent longshore current. High concentrations of Corg and metals were reflected by elevated populations of tolerant and opportunistic polychaetes in spring and by an azoic zone in fall. The impacted area extended mainly towards the north (up to ca. 4 km) and to a lesser extent south of the outfall (up to ca. 2.5 km). No evidence of increased accumulation of sewage sludge with time was found, nor of pollutants associated with it. Principal component analysis (PCA) grouped the anthropogenic metals and Corg with infaunal abundance for the spring surveys, while biotic diversity was negatively correlated with the pollutants. In the PCA of fall surveys, abundance was negatively correlated with the pollutants, decreasing with increased concentration of Corg and anthropogenic metals. We suggest that the seasonal pattern shown by infaunal abundance, anthropogenic metals and Corg is due to the stratification of the water column from spring to fall on one-hand and winter storms on the other. Winter storms resuspend and disperse the fine organic particles, sweeping the site clean of sludge; accumulation of sludge takes place throughout the quiescent periods of the year, when stratification is reestablished. The disposal site is dispersive and the spatial extent of the impacted area varies seasonally and interannually. This monitoring study, in addition to addressing specific questions about sewage sludge impact, represents an unusually large and unique set of long-term measurements that will serve as a basis to evaluate the site recovery following the cessation of disposal.
在以色列地中海沿岸一个污水污泥处置场进行的长期研究中，对沉积物中的底栖生物群落、重金属和有机碳（Corg）分布进行了调查。污水污泥的处置对底栖生物群落和沉积物质量有显著但局部的、季节性相关的影响。沉积物中Corg、Hg、Cd、Cu、Zn、Pb浓度升高，Ni浓度在较小程度上升高，这些主要在污水排放口以北、沿盛行沿岸流方向被检测到。春季，耐污和机会主义多毛类动物数量增加，秋季出现无生物区，反映出Corg和金属的高浓度。受影响区域主要向北延伸（达约4公里），在较小程度上向排放口以南延伸（达约2.5公里）。未发现污水污泥随时间积累增加的证据，也未发现与之相关的污染物积累增加的证据。主成分分析（PCA）将人为金属和Corg与春季调查中的底内动物丰度归为一组，而生物多样性与污染物呈负相关。在秋季调查的PCA中，丰度与污染物呈负相关，随Corg和人为金属浓度增加而降低。我们认为，底内动物丰度、人为金属和Corg呈现的季节性模式一方面是由于从春季到秋季水柱分层，另一方面是由于冬季风暴。冬季风暴使细有机颗粒重新悬浮和扩散，将场地污泥清扫干净；污泥积累发生在一年中的静止期，此时分层重新建立。处置场具有分散性，受影响区域的空间范围随季节和年际变化。这项监测研究除了解决有关污水污泥影响的具体问题外，还代表了一组异常庞大且独特的长期测量数据，将作为评估处置停止后场地恢复情况的基础。
