喀斯特山区水库底泥养分与重金属的含量特征——以阿哈水库为例

为摸清喀斯特山区阿哈水库底泥的养分情况和重金属污染状况,评价底泥农业资源化利用潜力,根据水库地形地貌、入库河流和出库口分布等特点,采集0~100 cm深度的底泥样品12个,分析和评价了阿哈水库底泥的养分状况及重金属污染水平。结果表明:底泥的有机质、总氮、总磷和总钾平均质量比分别为92.25 g/kg、3.35 g/kg、0.76 g/kg和14.18 g/kg,对照全国第二次土壤普查有关标准,有机质和总氮处于很高水平,总磷处于中上水平,而总钾处于中下水平,各养分指标的变异系数为25.49%~41.06%,空间差异较强;底泥Cr、Cd、Pb、As、Hg、Cu和Zn的平均质量比分别为104.86 mg/kg、1.12 mg/kg、75.87 mg/kg、26.68 mg/kg、0.27 mg/kg、59.53 mg/kg和164.65mg/kg,均高于贵州省土壤重金属背景值、贵州表生沉积物背景值和全国水系沉积物平均值,各重金属元素的变异系数为31.41%~132.34%,具有很强的空间变异性;以《食用农产品产地环境质量评价标准》为评价标准,底泥重金属內梅罗综合污染水平和潜在生态危害程度均为中等,且Cd的贡献最大。综上,阿哈水库底泥养分丰富,但污染较严重,不适于耕地利用,可考虑用于园林绿地。

Case study of the characteristic features of the nutritious and heavy metal contents in sediments of the Karst rock mountain reservoir in Guizhou

The aim of this paper is to investigate the characteristic features of the nutritious contents and heavy metal concentrations of the sediments in a Karst rock mountainous reservoir known as Aha in the central part of Guizhou Province.We have made an exploration of the water inflow and outflow of the reservoir while taking into a comprehensive consideration of the different thicknesses of the sediment at the bottom and the reservoir topography by using a gravity bar sampler and 12 samples collected in the 0-100 cm depth range of the sediment.And,next,we have also identified and analyzed the nutrient concentrations and the pollution degrees of the contaminants of the organic matters (OM),the total nitrogen (TN),the total phosphorus (TP),the total potassium (TK),Cr,Cd,Pb,As,Hg,Cu and Zn in the said 12 sediment samples in the reservoir based on the second national soil survey classification criteria as the nutrient evaluation criteria and the farmland environmental quality evaluation standards for edible agricultural products in reference to the Nemerow pollution index assessment and the risk index assessment.The finding results show that the average concentrations of OM,TN,TP and TK prove to be 92.25 g/kg,3.35 g/kg,0.76 g/kg and 14.18 g/kg,respectively,with OM and TN being at a remarkably high level,and TP-at the upper level,and TK-in the middle and lower levels,with the nutrient variation being in a range between 25.49％-41.06％ of strong spatial variability.The average concentrations of Cr,Cd,Pb,As,Hg,Cu and Zn account to the higher level than the background values of heavy metals in the soil and the surface sediment of the whole Province.In contrast,the average content rates of heavy metals in the sediments of the whole country are equal to 104.86 mg/kg,1.12 mg/kg,75.87 mg/kg,26.68 mg/kg,0.27 mg/kg,59.53 mg/kg and 164.65 mg/kg,correspondingly.This implies a great spatial heterogeneity in that the variation coefficient of the heavy metal contaminants is in a range between 31.41％-132.34％.According to the Nemerow pollution and risk index,the heavy metals in the sediments of Aha reservoir can be attributed to the moderately contaminated level and the secondary potential damage with its chief contributor being that of Cd.