北江中上游底泥重金属污染及其潜在生态危害评价

Evaluation of the Heavy Metals Contamination and Its Potential Ecological Risk of the Sediments in Beijiang River's Upper and Middle Reaches

为全面了解北江中上游底泥沉积物中重金属含量及其潜在生态危害程度,在北江干流及支流共采集了25个底泥样品,测试了Cu、Pb、Zn、Cd、Ni、Cr、As、Hg共8种重金属元素,采用地积累指数法和潜在生态危害指数法对北江中上游底泥重金属污染进行分析和评价.结果表明,北江中上游无论是干流还是支流其底泥受多种重金属污染而且污染程度相当严重,各种重金属的污染程度由强至弱依次为:Cd Hg>Zn>As>Pb≈Cu>Ni>Cr;金属污染物对北江中上游构成的潜在生态危害由强至弱依次为:Cd Hg>Pb≈As>Cu>Zn>Cr,其中Cd的影响占绝对主导地位.总体而言,北江干流由于纳污量最大,长期的积累使得北江干流段的重金属污染程度较支流严重;支流中马坝河的污染程度最高,其次是浈江和江.

In order to find out the heavy metals concentrations and their potential ecological risks of the sediments in Beijiang river＇ s upper and middle reaches, 25 sediments specimens were sampled from both the trunk stream and tributaries for analyzing Cu, Pb, Zn, Cd, Ni, Cr, As and Hg. The Index of Geoaccumulation and the Potential Ecological Risk Index were then employed to evaluate the pollution degree of heavy metals in the sediments. The results indicate that the sediments in Beijiang River have been severely contaminated by many heavy metals. The descending order of pollution degree of various metals is： Cd Hg〉Zn〉As〉Pb≈Cu〉Ni〉Cr; and similarly the potential ecological risk intensity caused by different metals is： Cd Hg〉Pb≈As〉Cu〉Zn〉Cr, and Cd is the predominant element among them. In general, because the trunk stream receives huge waste discharge, the pollution degree of heavy metals is stronger in the trunk stream than that in the tributaries due to long time accumulation. The Maba River is the worst polluted among the tributaries, and the Zhengshui River and Wongjiang River are next to it.