清潩河许昌段表层沉积物中营养盐及重金属污染特征分析

为了解水污染治理后河道水生态环境改善情况,以许昌市清潩河为例,对治理前后河道5个点位表层沉积物中营养盐、重金属含量及沉积物氮释放量时空变化特征进行分析.结果表明:治理后,2017年5个点位的表层沉积物综合污染指数范围为7.69～15.25,均处于重污染状态,综合污染指数最低值为治理前2012年最高值4.87的1.6倍.各点位中重金属指标与2012年相比含量上升显著,Zn含量为2012年的12.44倍;而营养盐类指标含量下降明显,总氮及总磷平均含量仅分别为2012年的13.98%及5.68%.通过形态氮分析结果可知,离子可交换态氮的含量仅为2012年的6.73%,河道沉积物氮释放风险大大降低但沉积物中重金属污染更加严重.分析主要是清潩河上游长葛市涉及重金属排放的企业较多且在水污染治理中未得到有效控制.建议今后在对重污染河流实施综合治理时,应重视河道沉积物的污染状况评估.针对清潩河沉积物中重金属的污染状况,建议采取措施对重金属排放企业加强监管,并对河道沉积物中重金属污染进行治理和修复.

Temporal and spatial changes in sediment nutrients and heavy metals of Qingyi River of Xuchang city

To evaluate the improvement of water environment after the treatment of heavily polluted river, the temporal and spatial changes in sediment nutrients and heavy metals were analyzed by taking Qingyi River in Xuchang City as an example. The results indicated that the comprehensive pollution index of surface sediments in 5 sections ranged from 7.69 to 15.25, which all belonging to heavy pollution grade. The minimum value in 2017 is 1.6 times compared with the maximum value in 2012. The content of heavy metals in each section increased significantly compared with 2012, the content of Zn is 12.44 times compared with 2012 while the concentration of nutrient salts decreased obviously, and the average concentration of total nitrogen and total phosphorus was 13.98% and 5.68% respectively compared with 2012. According to the results of morphological nitrogen analysis, the content of ion exchangeable nitrogen is only 6.73% of 2012, and the risk of river sediment release is greatly reduced. Discharged by many enterprises but not controlled effectively, the heavy metals in Qingyi River upstream caused serious pollutions. According to heavy metal contamination in sediments, measures should be taken to regulate heavy metal emission, and the heavy metals in the channel sediment should be treated and repaired.