山东南四湖底泥典型重金属的形态分布、稳定度与风险评价

Fraction distribution,stability and risk assessment of typical heavy metals in sediment of Nansi Lake,Shandong Province,China

为研究南四湖底泥重金属赋存形态与稳定度的空间差异,利用柱状底泥采样器分别在南阳湖、独山湖、昭阳湖和微山湖采集原位柱状样,在对典型重金属Pb、Cd、Hg、As形态分析的基础上,结合地积累指数法和潜在生态风险指数法,对表层底泥(0—4 cm)重金属污染程度进行评价,并对其稳定性进行分析。结果表明,南四湖的4个湖区采样点位表层底泥Pb、Cd、Hg、As均存在一定程度的富集,Hg、Cd富集最为明显,Pb、As次之;Cd和Hg的金属可交换态占比较高,约占总量的10%—15%,潜在风险较大。垂向分布上,4个湖区采样点各重金属形态差异较大,无明显规律。总体上,除南阳湖Hg污染外,其他湖区重金属污染均有降低趋势;地积累指数评价显示,4个湖区采样点表层底泥普遍受到Hg、Cd、As污染,Pb污染相对较轻,微山湖Cd污染和南阳湖Hg污染最为突出;潜在生态风险指数显示,南阳湖、微山湖为重污染生态风险强度,昭阳湖、独山湖为中等污染生态风险强度,污染风险顺序为:微山湖>南阳湖>昭阳湖>独山湖;各湖区采样点4种重金属元素稳定度差异较大,Hg、Cd、As稳定性较小,Pb比较稳定,四湖区各重金属稳定度顺序:Cd为独山湖>昭阳湖>微山湖>南阳湖,Hg为昭阳湖>微山湖>独山湖>南阳湖,As为昭阳湖>独山湖>南阳湖>微山湖。综合比较,南阳湖区底泥Hg污染应引起足够重视。

In order to study the space differences of heavy metal fraction and stability of sediments in Nansi Lake,columnar sediment sampler was used to collect the intact in situ sediment cores from Nanyang Lake,Dushan Lake,Zhaoyang Lake and Weishan Lake,respectively.On the basis of analyzing the fractions of typical heavy metal Pb,Cd,Hg,As,using geographical accumulation index method and potential ecological risk index method,the heavy metal pollution level of surface sediment(0—4 cm)was evaluated,and the stability of them was analyzed.Results showed that Pb,Cd,Hg,As in the surface sediments of four lakes were all enriched to a certain extent,and Hg,Cd enrichement was the most obvious,followed by Pb and As.The metal exchangeable state amounts of Cd and Hg,accounting for about 10—15%of the total amount,were very high with highly potential risk.The vertical distribution of heavy metal forms in four lakes was quite different with no obvious rules,and in general,the heavy metal pollution had the decreasing trend in Nansi Lake in recent years except for Hg in Nanyng Lake.According to the evaluation of geographical accumulation index,the surface sediments of four lakes were polluted by Hg,Cd and As,and the Cd pollution in Weishan Lake and Hg pollution in Nanyang Lake were the most serious.The potential ecological risk index showed that the sediments of Nanyang Lake and Weishan Lake had heavy ecological pollution risks,Zhaoyang Lake and Dushan Lake had moderate pollution risks,and the pollution risk order was Weishan Lake>Nanyang Lake>Zhaoyang Lake>Dushan Lake.The stability of sediment Hg,Cd and As was poor,the Pb was relatively stable,and the order of Cd stability in four lakes was Dushan Lake>Zhaoyang Lake>Weishan Lake>Nanyang Lake,the Hg was Zhaoyang Lake>Weishan Lake>Dushan Lake>Nanyang Lake,and the As was Zhaoyang Lake>Dushan Lake>Nanyang Lake>Weishan Lake,respectively.Comprehensive comparison,more attention should be paid to Hg pollution in sediment of Nanyang Lake.