资江疏浚底泥重金属赋存形态和生态风险评价

Existing Forms and Ecological Risk Assessment of Heavy Metals in Dredged Sediments of Zijiang River

为研究资江疏浚底泥重金属的赋存形态及其生态风险,对资江沿线18个底泥采样点的Cd、Zn、Cu、Pb、Ni、Cr、As的总含量及各赋存形态含量进行分析测定,同时进行重金属生态风险评价。结果表明,Cd的污染最严重,100%的点位风险筛选值超标,66.7%的点位风险管制值超标;其次是Zn、Cu和As,风险筛选值的点位超标率分别为55.6%、50.0%和22.2%;Pb、Ni、Cr的含量均未超过风险筛选值。Cd和Zn的可交换态和碳酸盐结合态占比较大,易被生物利用。As仅以铁锰氧化物结合态和残渣态存在,Pb和Cr可交换态和碳酸盐结合态含量低且总量未超标,因此风险较低。7种重金属地累积指数中偏重度、重度和严重污染与潜在生态风险指数中的强、很强、极强生态危害的比例相似。Cd、Cu、Zn为资江较典型的重金属污染物,建议疏浚过程中进行重点监测,实施污染监控和环保处置措施,预防疏浚底泥利用过程中重金属的危害和生态风险。

In order to study the existing forms and ecological risks of heavy metals in dredged sediments of Zijiang River,the total content of Cd,Zn,Cu,Pb,Ni,Cr and As in 18 sediment sampling points along the Zijiang River and the content of each existing forms were analyzed and determined,and the ecological risk assessment of heavy metals was carried out at the same time.The results showed that Cd was the most serious heavy metal contaminant,with 100%of the sampling sites exceeding the risk screening value and 66.7%exceeding the risk intervention value.Followed by Zn,Cu and As,the point-exceeding rate of the risk screening value was 55.6%,50.0%and 22.2%respectively;the contents of Pb,Ni and Cr didn’t exceed the risk screening value.Cd and Zn had a relatively high percentage of exchangeable state and carbonate combined state,which were easily used by creatures.As existed only in the iron-manganese oxide combined state and the residual state,the exchangeable state and carbonate combined state of Pb and Cr was low and the total amount didn’t exceed the standard,so the risk was low.The proportion of strongly,strongly to extremely and extremely contaminated in geo-accumulation index of the seven heavy metals was similar to that of strong,very strong and extremely strong ecological hazard in potential ecological risk coefficient.Cd,Cu,and Zn were typical heavy metal contaminants of Zijiang River,it was recommended to focus on monitoring the typical contaminants during dredging,and prevent ecological risks of heavy metals when utilize the dredged sediments.