浙江省温岭湖漫水库沉积物中营养盐分布及风险评价

Distribution and risk assessment of nutrients in sediments of Human Reservoir in Wenling City,Zhejiang Province

湖漫水库是温岭市最大的集中式饮用水源水库,水质富营养化状态逐年升高的趋势亟需系统调查该水库内源污染现状.以湖漫水库为研究对象,采集表、中、底层沉积物,根据TP、TN、TOC等影响水库富营养化因素,进行营养元素空间分布特征分析和生态风险评价,通过营养元素间的相互关系初步探究水库主要污染源.结果表明,湖漫水库表层沉积物中TP、TN、TOC均值分别为516.43 mg·kg^(−1)、1690 mg·kg^(−1)、1.28%.营养元素主要在大坝附近、库区中心、阮岙村和横溪村两个支流处富集;随着深度的增加,浓度逐渐降低,底层沉积物中TP含量为表层的77%,TN和TOC含量为表层的62%;水库中有64.3%的表层沉积物处于重度营养盐污染,主要为氮,尤其是有机氮污染,且存在可能释放的风险;该水库沉积物营养盐污染经解析主要由浮游动物、浮游植物和藻类等水生生物的排泄物及残骸逐渐在表层沉积物积累引起.

Human reservoir is the largest drinking water reservoirs in Wenling City.It was urgent to investigate systematically the internal pollution of the reservoir in view of the increasing trend of water eutrophication.The spatial distribution characteristics of nutrient elements and ecological risk evaluation were carried out by sampling the surface,middle and bottom sediments of the reservoir and exploring the influencing factors of eutrophication,such as the contents of TP,TN,TOC.The main eutrophication sources of the reservoir were primarily investigated through the correlation between nutrient elements.The results showed that the mean concentrations of TP,TN and TOC in surface sediment were 516.43 mg·kg^(−1),1690 mg·kg^(−1) and 1.28%,respectively.The nutrients were mainly enriched near the dam,in the center of the reservoir,and in the two tributaries of Ruanao village and Hengxi village.The nutrient concentration decreased gradually with the increase of depth.The TP content in bottom sediments was 77%of that in the surface layer,and TN and TOC contents were 62%of those in the surface sediments.Additionally,64.3%of the surface sediments in the reservoir were seriously polluted by nutrients(especially organic nitrogen),and there was a risk of possible release.According to the correlation and ratio between nutrients,it was speculated that the nutrient pollution of sediments in this reservoir was mainly caused by the gradual accumulation of excreta and debris from aquatic organisms such as zooplankton,phytoplankton and algae on the surface sediment.