青海湖流域东北部河流沉积物和土壤剖面记录的重金属污染特征

对青海湖流域东北部2个河流沉积物剖面和2个土壤剖面样品中As、Cd、Pb、V、Cr、Mn、Ni、Cu、Zn等9种重金属元素的含量进行了分析测定,采用污染系数、富集系数、地累积指数和潜在生态危害指数研究了其污染的时空变化特征。结果表明,河流沉积物剖面和土壤剖面记录的重金属元素的富集系数基本显示出深部低于1而近地表高于1,且在25cm深度内往上逐渐增加的特征;它们记录的重金属变化趋势大体一致但有量的差异;重金属元素的污染系数均小于2,且大多数样品的值低于1,高值者为近地表样品,包括河流沉积物样品中的As、Cd、Pb、Ni、Cu、Zn和土壤样品中的Cd;地累积指数大多为负值,大于1者出现在近地表,包括河流沉积物样品中的Cd、Cu、Zn和土壤样品中的Cd;Cd的潜在生态风险因子在表层样品中大于30,9种重金属潜在生态危害指数也在表层样品中大于70。以上结果暗示青海湖流域东北部存在重金属的人为排放,在近代更为显著,不同地理位置重金属排放源种类和排放强度等的不同、分散稀释作用等造成该地区重金属时空上的变化特征;该区域仅在地表出现Cd、Cu、Zn的局部轻度污染,达到中等生态风险级别。

Heavy Metal Contamination Characteristics of Fluvial Sediment Sections and Soil Sections in the Northeastern Qinghai Lake Watershed, China

Heavy metals(including As, Cd, Pb, V, Cr, Mn, Ni, Cu and Zn) concentration analysis and spatiotemporal contamination characteristics assessment for two fluvial sediment sections and two soil sections in the Northeastern Qinghai Lake watershed, China were carried out by using pollution coefficient(C_i), enrichment factor(EF), geoaccumulation index(I_geo) and potential ecological risk index(RI). The enrichment factors(EF) of heavy metals are lower than 1 for deep samples and exceeds 1 for samples near surface, and it gradually increases with increasing positions in 0-25 cm depth range. In addition, heavy metal enrichment factors show consistent variation characteristics. Heavy metals pollution coefficient(C_i) for these samples are lower than 2 and most of the value are lower than 1, and high values are for samples near surface(As, Cd, Pb, Ni, Cu, and Zn in fluvial sediment samples and Cd in soil samples); geoaccumulation index(I_geo) are mostly negative, and the values exceeded 1 are for samples near surface(Cd, Cu, Zn in fluvial sediment samples and Cd in soil samples); the potential ecological risk factor(E_i) of Cd in surface samples are higher than 30, and potential ecological risk index(RI) are also higher than 70 for samples near surface. These results suggest that anthropogenic emission of heavy metals in the Northeastern Qinghai Lake watershed does exist and it is more significant in modern times; different emission sources and emission intensity in different area, and dispersion dilution effect cause the spatiotemporal variation characteristics; in this region, only the surface sediment appear local pollution of Cd, Cu, and Zn, and reach moderate ecological risk level.