基于总量与形态的矿区周边土壤重金属生态风险与健康风险评估

Ecological and Health Risk Assessments Based on the Total Amount and Speciation of Heavy Metals in Soils Around Mining Areas

采集了龙岩市某矿区周边表层土壤及配套农作物样品,在分析土壤Pb、Cd和As等3种重金属总量和形态的基础上,采用Hakanson潜在生态风险评价法、基于地球化学统计学划分生态风险等级的方法以及符合我国人体暴露特征参数的健康风险评价法,开展了土壤重金属Pb、Cd和As的生态风险与人体健康风险评估.结果表明,研究区土壤重金属超出环境质量标准的元素为Pb和Cd,除残渣态外的4种生物可利用形态占比排序为:Pb>Cd>As,谷物籽粒重金属含量超出食品限量标准值的元素主要为Pb.基于重金属总量和生物可利用形态的生态风险评估结果均显示Cd是最主要的生态风险因子.相比基于总量,基于生物可利用形态的矿区土壤Cd的单一潜在生态风险以及Pb、Cd和As的综合生态风险显著降低,达到中等及以上级别样点占比分别由100%和50.0%降至17.2%和7.81%,且划分的风险区内基本包含了全部农作物超标的警示点.经口摄入是重金属主要的致癌和非致癌风险暴露途径.致癌风险中,无论是否考虑生物可利用性,Cd和As的人体致癌健康暴露风险均在可接受范围内.非致癌风险中,重金属Cd的非致癌风险可忽略.当仅考虑重金属总量时,Pb和As在3种暴露途径下的非致癌暴露风险指数范围分别为0.14~8.65和0.04~2.85.经考虑生物可利用性调整后,As不再具有非致癌风险.Pb的非致癌暴露风险指数虽然降低了84.7%,但最大值仍可达到1.69,会对人群产生非致癌性的危害,是矿区土壤修复的关键.

Topsoil and supporting crop samples around a mining area were collected in Longyan City,and the total amounts and speciation of Pb,Cd,and As in the samples were determined.The ecological risk and human health risk assessment of soil heavy metals Pb,Cd,and As were carried out using the Hakanson potential ecological risk assessment method,the ecological risk classification method based on the principle of geochemical statistics,and the health risk assessment method in accordance with the characteristics of human exposure parameters in China.The results indicated that the heavy metal elements in the soil in the study area exceeded the environmental quality standards for Pb and Cd,and the heavy metal contents in cereal grains exceeded the food limit value mainly for Pb.The proportion of the four bioavailable forms except the residue state followed the order of Pb>Cd>As.The ecological risk assessment results based on the total amount of heavy metals and bioavailable forms showed that Cd was the most important ecological risk factor.The single potential ecological risk of Cd and the comprehensive ecological risk of Pb,Cd,and As in the soil based on bioavailable forms were significantly reduced compared with that based on the total amount.The proportion of medium and superior samples decreased from 100%and 50.0%to 17.2%and 7.81%,respectively,and the divided risk zone basically contained all the warning points of exceeding the standard of crops.Oral ingestion was the main carcinogenic and non-carcinogenic exposure route of heavy metals.In terms of carcinogenic risk,the risk of human carcinogenic health exposure to Cd and As was within the acceptable range,regardless of whether bioavailability was considered.Among the non-carcinogenic risks,the non-carcinogenic risk of the heavy metal Cd was negligible.When only the total amount of heavy metals was considered,the non-carcinogenic risk index of Pb and As under the three exposure pathways ranged from 0.14 to 8.65 and from 0.04 to 2.85,respectively.After considering the adjustment of bioavailability,the non-carcinogenic risk of As was greatly reduced and could be considered to no longer have non-carcinogenic risk.Although the non-carcinogenic exposure risk index of Pb was reduced by 84.7%,the maximum value still reached 1.69,which would cause non-carcinogenic harm to the population and was the key to soil remediation in mining areas.