三亚河沉积物中重金属生态风险评价与污染历史

Eco-risk Assessment and Contamination History of Heavy Metals in the Sediments of Sanya River

主要研究了三亚河沉积物中重金属的分布、富集程度、生态风险以及污染历史,可为三亚河的污染治理和海洋环境保护提供参考信息。结果表明,三亚河表层沉积物中Cu、Zn、Pb、Cd、As、Cd、Hg、Ni等8种重金属元素的质量分数分别为(3.9±1.7)、(100.4±38.9)、(32.0±8.3)、(28.8±11.5)、(10.27±4.61)、(0.181±0.110)、(0.204±0.091)、(22.7±8.0)μg·g^(^(-1)),Al2O3、TOC的质量分数分别为10.34%±5.49%、1.29%±1.23%。210Pbex放射性比活度被用于确定研究区的平均沉积速率并建立沉积年代框架。应用210Pbex稳定初始浓度模型得出三亚河沉积物的平均沉积速率约为0.89 cm·a^(-1),所获取柱状样的沉积年代为1918─2014年。基于柱状样底部未受人类活动影响的子样得到的研究区8种重金属的背景值分别为7.5、38.7、14.3、31.9、4.95、0.027、0.015和6.4μg·g^(-1)。三亚河表层沉积物中Pb、Zn、Cu、Cd、Hg和TOC经Al元素标准化后的富集因子的算术平均值都大于1.5,说明这些重金属和有机质大部分来源于人类活动的输入。柱状沉积物中Cu、Zn、Pb、Cd和Hg的质量分数和富集因子在45 cm深度以上(即上世纪60年代以后)也存在明显的由人类活动的输入引起的上升和富集趋势。研究区沉积物中TOC与富集重金属Pb、Cr、Cd、Zn和Cu之间的Pearson相关系数r值为0.56~0.85,表明有机质降解所产生的腐殖酸吸附是导致沉积物中重金属质量分数变大的主要原因。对照美国NOAA沉积物生物效应数据标准,三亚河沉积物中Hg含量在多数站位介于ERL和ERM阈值之间,已对底栖生物产生负面影响。三亚河目前重金属的沉积通量约为2.26g·m-2·a^(-1),所沉积的重金属主要为Zn,约占总通量的50.6%,其次为Pb、Cr和Cu,它们的比例分别为16.1%,14.5%和11.5%,毒性较强的Hg和Cd分别仅占总通量的0.10%和0.09%。

The distribution, enrichment, eco-risk and contamination history of heavy metals in sediments of Sanya River were investigated in this study. It can provide helpful information on the pollution control and marine environmental protections of Sanya River. The results indicate that the concentrations of Cu, Zn, Pb, Cd, As, Cd, Hg, Ni, Al2O3 and TOC in the surface sediments are (3.9±1.7), (100.4±38.9), (32.0±8.3), (28.8±11.5), (10.27±4.61), (0.181±0.110), (0.204±0.091), (22.7±8.0)μg·g-1, 10.34%±5.49% and 1.29%±1.23%, respectively.210Pbex was utilized to determine the mean sedimentation rate and establish the deposition chronology. The mean sedimentation rate is about 0.89cm·a-1 in study area employing the constant concentration model of210Pbex and the deposition period of the retrieved sediment core is 1918─2014. The backgrounds of the eight heavy metals obtained from the core bottom unaffected by human activities are 7.5, 38.7, 14.3, 31.9, 4.95, 0.027, 0.015 and 6.4μg·g-1, respectively. The arithmetic mean values of Pb, Zn, Cu, Cd, Hg and TOC enrichment factors normalized by Al element all exceed 1.5 in surface sediment, implying most of these metals and organic matters are originated from human activities. The concentrations of Cu, Zn, Pb and Hg in the sediment core also demonstrate evident increasing and enrichment tendencies above 45 cm depth (after the year of ca. 1960), which are induced by the excessive input of anthropogenic pollution. The Pearson correlation coefficients between TOC and Pb, Cr, Cd, Zn and Cu are 0.56~0.85, suggesting the adsorption of humic acidproduced by organic matter degradation is the principle factor dominating the enrichments of heavy metals in sediments. According to the sediment quality guidelines of US NOAA screening quick reference, adverse biological effects have been induced by Hg in the sediments of study area since its concentrations at most stations fall between the ERL and ERM threshold. The annual sedimentation flux of heavy metals received by Sanya River in recent years is estimated at about2.26 g·m-2·a-1, in which Zn is dominated and accounts for a proportion of 50.6%. The proportions of Pb, Cr and Cu are 16.1%, 14.5% and 11.5%. The more toxic metals of Hg and Cd only occupy 0.10% and 0.09% in the flux.