清林径水库表层沉积物营养盐分布特征及污染评价

Pollution characteristics and evaluation of nutrients in surface sediments of Qinglinjing Reservoir

清林径引水调蓄工程是目前在建的深圳市三大储备调蓄水源系统之一,库区沉积物营养元素的污染特征直接关系到受水区的用水安全。本研究基于2019年7月的调查,分析了清林径水库表层沉积物中氮、磷和有机质的含量、分布特征及其主要来源,并采用有机指数与有机氮方法评价了沉积物污染状况。调查结果表明,清林径水库表层沉积物中有机碳(TOC)、总氮(TN)和总磷(TP)的含量分别为4330~23500 mg/kg、783~3080 mg/kg和29~532 mg/kg;从空间分布来看,库区下游沉积物中营养盐含量相对较低,上游料场附近表层沉积物污染相对严重。沉积物TOC/TN比值表明,藻类等水生生物是水库沉积物中有机质的主要来源。污染评价结果显示,有机指数平均值为0.19,整体处于较清洁状态(Ⅱ级);有机氮指数平均值为0.16,整体处于污染状态(Ⅳ级)。由此可见,清林径水库表层沉积物存在较为严重的氮污染问题,在后续水质保障工作中需引起高度重视。

As a regulation and storage reservoir for three important water diversion and storage projects in Shenzhen,the sediment pollution characteristics of Qinglinjing Reservoir directly affect water safety in water receiving areas.To illustrate the spatial distribution of nutrients in the surface sediments of Qinglinjing Reservoir,the total organic carbon(TOC),total nitrogen(TN),and total phosphorus(TP) were measured in July 2019.Canadian freshwater sediment quality guidelines for aquatic environments were used to assess the state of the nutrients in sediments.Results show that the TOC,TN,and TP contents of surface sediments in Qinglinjing Reservoir are 4330-23500 mg/kg,783-3080 mg/kg,and 29~532 mg/kg,respectively.The concentrations of these pollutants are relatively higher in the upper reaches than in the lower reaches.The value of ratio TOC/TN indicates that the organic matter within the surface sediment mainly originates from phytoplankton or other aquatic organisms.The average organic index is 0.19,which is ranked as Level Ⅱ(clean),while the average value of organic nitrogen is 0.16,ranked as Level Ⅳ(polluted by organic nitrogen).Overall,the surface sediments of Qinglinjing Reservoir have already been polluted by nitrogen,and thus more attention should be paid during ensuring the water quality.