晋江市九十九溪流域河道底泥污染特征分析与风险评价

Risk assessment and contamination characteristics of river sediment in Jiushijiuxi River Basin,Jinjiang

以晋江市九十九溪流域4条主要河道23处典型河段作为研究对象,分上、中、下3层对底泥进行检测和分析,总结其污染特征,探讨时空分布特征,并对污染程度进行风险评价,为后续底泥污染综合防治和处置工程提供科学依据。研究结果表明:(1)重金属污染时空分布不均,位于下游河道的底泥重金属富集较严重;除九十九溪老河道因上游来水削减导致底泥中层重金属污染最严重之外,其余3条河道重金属含量均随底泥深度增加而降低;(2)营养盐均呈重度污染态势,上、中层底泥内梅罗综合污染指数接近且明显高于下层,同时九十九溪干流和潘湖支流的下层底泥污染程度显著偏高;(3)重金属主要源于周边工农业废水废气;(4)九十九溪老河道和潘湖支流底泥重金属综合生态风险总体为中风险,应重视底泥处理,同时针对底栖动物存在危害的重金属(Zn和Pb),应加强河道周边废水废气排放管控。

This study focused on 23 typical sites of 4 main rivers in Jiushijiuxi River Basin,Jinjiang.Through the analysis of three layers(upper,middle and lower layers)of river sediment,the contamination characteristics were summarized,temporal-spatial distribution characteristics were discussed and potential risk were assessed,which provided scientific suggestions for future comprehensive prevention and disposal treatment of sediment.Results showed that:(1)the heavy metals contents presented uneven for temporal-spatial distribution,and the heavy metal contents of rivers located in the lower reaches of Jiushijiuxi River Basin were higher;the heavy metal contents decreased with the increase of sediment depth,except for the Jiushijiuxi old river,which showed most serious pollution in middle layer due to the decrease of upstream inflow;(2)nutrients in sediments were seriously polluted and Nemerow comprehensive indexes of upper and middle layers were obviously higher than that in lower layer;besides,the Nemerow comprehensive pollution indexes of lower layer in Jiushijiuxi main stream and Panhu tributary were extremely higher;(3)the heavy metals in sediments were mainly from the waste water and gas produced by surrounding factories and farmland;(4)Jiushijiuxi old river and Panhu tributary presented moderate ecological risk in general.Therefore,attention should be paid to these sediments.Considering the negative impact of Zn and Pb towards zoobenthos,it was necessary to strengthen the control and treatment of waste water and gas.