Nutrient and heavy metal storage and mobility withinsediments in Kouris Reservoir, Cyprus

O. Tzoraki; G. Doerflinger; C. Demetriou

摘要

The objective of this study was to evaluate the risks associated with nutrient and heavy metal pollution in the water andsediments of Kouris Reservoir in Cyprus, and to recommend applicable measures to alleviate them. The reservoir drainagearea contains various historic abandoned copper mines existing in an ophiolite geological substrate. Kouris Reservoirwater is classified as oligotrophic to mesotrophic, with phosphorus being the limiting factor for algae growth. Thethermal stratification of the reservoir enhances anoxic conditions in the reservoir hypolimnion, initiating phosphorusrelease back into the water column from the lake bottom sediments. The increased phosphorus release, in combinationwith increased water temperatures during the summer months (i.e. reaching 27 °C in August), may be the key factorsenhancing the growth of microbial communities and cyanobacteria blooms. The sediment of Kouris Reservoir is classifiedas ‘low risk’ on the basis of the Ecological Risk Index scheme, in contrast to the Geoaccumulation Index, which indicatesa moderate degree of contamination for chromium (Cr), nickel (Ni) and copper (Cu), and a high degree for lead (Pb).Heavy metals are strongly bound to the sediment matrix at pH values between 7 and 9, but can be released back into thewater column at potential acid pH values. In addition, the sediments exhibit a high copper and chromium absorptionaffinity under current water quality conditions in the reservoir, as shown by batch absorption experiments. The experimentalresults suggest dredging of the reservoir sediment, and its subsequent dumping of the sediments near influentstreams, would have adverse effects on the environment in the event of acid rain or other environmental changes thatmight acidify the sediment.

机译：本研究的目的是评估塞浦路斯库里斯水库水和沉积物中与营养物质和重金属污染相关的风险，并建议采取适当的措施来缓解这些风险。水库排水区包含各种历史悠久的废弃铜矿，这些铜矿存在于蛇绿岩地质基质中。库里斯水库的水被归类为寡营养到中营养，磷是藻类生长的限制因素。储层的热分层增强了储层下层的缺氧条件，引发磷从湖底沉积物释放回水柱中。磷释放量增加，加上夏季水温升高（即8月达到27°C），可能是促进微生物群落生长和蓝藻大量繁殖的关键因素。根据生态风险指数方案，库里斯水库的沉积物被归类为“低风险”，而地质累积指数则表明铬（Cr）、镍（Ni）和铜（Cu）的污染程度为中等程度，铅（Pb）的污染程度很高。重金属在pH值在7至9之间时与沉积物基质紧密结合，但在潜在的酸性pH值下可以释放回水柱中。此外，沉积物在当前水质条件下表现出较高的铜和铬吸收亲和力，如批量吸收实验所示。实验结果表明，疏浚水库沉积物，随后将沉积物倾倒在进水溪流附近，如果发生酸雨或其他可能使沉积物酸化的环境变化，将对环境产生不利影响。

Nutrient and heavy metal storage and mobility withinsediments in Kouris Reservoir, Cyprus

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