曼谷湾河口区百年来沉积物重金属变化趋势及污染来源

Variation trend and contamination source of heavy metals in sediments from estuary area of Bangkok Bay in the past century

2015年7月在泰国曼谷湾邦巴功河河口采集了1根1.5m长的沉积物柱样,分析了样品中重金属元素(Cd、Pb、Co、Ni、Cu、Cr、Zn)含量,进行了粒度和^(210)Pb、^(137)Cs活度测试,使用地累积指数、元素污染指数和潜在生态风险参数对重金属污染情况进行评级,并结合实际情况对污染来源进行了推断。结果表明:沉积柱状样210 Pb、137 Cs活度测试结果计算获得的沉积速率约为2.3cm/a,沉积物柱状样记录了1948—2015年的沉积情况。7种重金属元素含量均值分别为0.11、29.60、19.78、44.18、28.99、80.93、99.01mg/kg。重金属含量较20世纪都有所增长,Cd、Zn、Pb、Cr在整段沉积时间框架内增长明显。元素富集程度顺序为Cd>Zn>Pb>Cr>Cu>Ni>Co,Cd元素污染程度最为严重,Pb、Cu和Zn为偏中度污染,Cr、Ni和Co为轻度污染。单一重金属生态风险系数Eir评级顺序为Cd>Pb>Cu>Ni>Co>Cr>Zn。其中Cd为很强至极强生态危害,Pb为轻微至中等生态危害。Cd、Zn、Cu和Pb元素没有超出泰国沉积物环境质量基准规定的效应区间低值,Ni超出效应区间低值,但没有超过效应区间中值。重金属元素与Al较差的相关性表明重金属元素主要是非自然来源,Cd、Cu、Zn可能源于金属冶炼和交通,此外,Cd还可能存在其他未知工业污染来源,受人类活动影响较大。Cr可能源于纺织业发展。1990年之后较1990年之前重金属元素之间的相关性更差,指示1990年之后相比1990年之前重金属污染来源更复杂。

A1.5-meter long sediment core was collected from the estuary of Bang Pakong River,Bangkok Bay,in July 2015.Calculated with 210Pb and 137Cs,the sedimentation rate is 2.3 cm/a.It means that the sediment has been deposited in the year from1948 to2015.Heavy metal element(Cd,Pb,Co,Ni,Cu,Cr and Zn)concentrations,measured by ICP-MS,are 0.11,29.60,19.78,44.18,28.99,80.93 and 99.01 mg/kg,respectively.Amounts of Cd,Zn,Pb and Cr increased significantly during the period.The degree of heavy metal pollution ranks in an order of Cd>Zn>Pb>Cr>Cu>Ni>Co.Calculated geoaccumulation indices demonstrate that the sediment are moderately polluted by Cd,and slightly by Pb,Co,Ni,Cu,Cr and Zn.The potential ecological risk indexes of single element(Eir)are ranked in an order of Cd>Pb>Cu>Ni>Co>Cr>Zn.Ecological risk evaluation of heavy metals suggests that Cd is high to very high in ecological risk,while Pb is low to moderate.The concentrations of Cd,Zn,Cu and Pb in the sediments are lower than the effects range low(ERL),and the concentrations of Ni have exceeded the effects range low(ERL),but below the effects range median(ERM).Cd,Cu and Zn mayderive from metallurgical industry and transportation.Cd has an unknown source of pollution,strongly influenced by human activities.The anomaly high Cr may be from textile industry.Inter-elemental correlation of heavy metals before the year of1990 was worse than that after 1990,indicating that there may be more complex sources of heavy metal pollution after the year of 1990.