贵阳市百花水库消落带土壤汞形态分布及风险评价

Distribution and Risk Assessment of Hg Species in Soil of the Water-level-fluctuating Zone in Baihua Reservoir

为了解百花水库消落带土壤汞污染风险,系统采集了该区的土壤样品,分析总汞(THg)、汞形态和甲基汞(MeHg)分布情况,探讨汞的生物有效性,并对比分析了土壤THg和汞形态的污染风险。结果表明,百花水库消落带土壤THg质量分数具有显著的空间差异性(n=45,P<0.05)。土壤THg质量分数范围为88.83-521.14μg·kg^(-1),平均为(226.08±129.62)μg·kg^(-1)。80%的采样点土壤THg质量分数超过了背景水平。土壤中不同形态汞占THg质量分数大小顺序为:强结合态(36.28%)>硫化物结合态(33.09%)>有机结合态(30.35%)>水溶态(0.19%)>胃酸溶态(0.08%),表明前3种形态汞为研究区土壤Hg的主要赋存形态。消落带土壤中生物有效态汞(BioavailableHg,Bio-Hg)质量分数为22.39-168.41μg·kg^(-1),占THg的比例为8.81%-58.68%。土壤MeHg平均质量分数为(3.70±4.49)μg·kg^(-1),S15采样点土壤MeHg质量分数显著高于其他采样点(n=45,P<0.05)。地积累指数、潜在生态危害指数和风险评估编码法(Riskassessmentcode,RAC)的评价结果均表明,百花水库消落带土壤汞污染生态较高,S5采样点土壤Bio-Hg质量分数已超过土壤汞背景水平。百花水库消落带土壤的汞污染风险不容忽视。

To analyze the environmental risk of Hg in soil of the water-level-fluctuating zone(WLFZ)in Baihua Reservoir,soil samples were collected systematically.The concentrations of total Hg(THg),Hg species and methylmercury(MeHg)were analyzed.Also the bioavailable of Hg in soil were discussed.Geoaccumulation index,Hakanson potential ecological risk index and risk assessment code were applied to assess the environmental risk of THg and Hg species,respectively.The results showed that significant differences(n=45,P<0.05)of THg mass fractions in different sites were observed in soil of WLFZ in Baihua Reservoir.The mass fractions of THg were in the range of 88.83.521.14μg·kg^-1,with an average of(226.08±129.62)μg·kg^-1.Approximately,80%of soil samples were higher than the soil background value of Guizhou Province.The percentage of five Hg species in soil followed the order:elemental mercury(36.28%)>mercuric sulfide(33.09%)>orgnao-chelated mercury(30.35%)>water soluble mercury(0.19%)>human stomach acid’soluble mercury(0.08%).This indicated that the former three of Hg species were in the domination of soil.The average mass fraction of bioavailable Hg was 22.39-168.41μg·kg^-1,and the percentage of bioavailable Hg to THg was in the range of 8.8%.58.9%.The average mass fraction of MeHg in soil was(3.70±4.49)μg·kg^-1.The greatest mass fraction of MeHg presented at S15 site which was significantly higher than that in the other sites(n=45,P<0.05).Based on the geoaccumulation index,Hakanson potential ecological risk index and risk assessment code,these three evaluation results showed Hg species had a high potential ecological risk.The mass fraction of bioavaiable Hg in soil at S15 site was greater than the background level of mercury in soil.As a summary,the real environmental level of Hg in soil of WLFZ in Baihua Reservoir should not be ingnore.