龙岩市适中镇一带土壤重金属异常成因与生态效应评价

本文采集了龙岩市适中镇一带不同层位土壤-土壤溶液配套样品,测试了其中重金属Pb、Cd、As含量,采用普通克里金插值法研究了土壤中3种重金属元素的空间分布特征,查明了异常成因。根据地球化学统计学分析原理,建立了一种基于土壤溶液重金属含量的风险评价方法,并利用该方法对3种重金属的生态效应进行了评价。结果表明,工作区土壤重金属主要来源于自然背景下的成土母质,人为叠加作用影响不显著,异常强度低。3种重金属在A、B、C层土壤的异常区域与零星分布的小规模工业企业叠合。在同一点位的垂向剖面上,重金属在表层土壤与深层土壤的相关度高,主要表现为无-弱-中等强度的表生富集,未出现大面积的强-极强程度的表生富集现象。工作区土壤总体上呈清洁-基本清洁水平,生态风险低。中等及以上风险水平的样点所占比例仅为8.24%、3.64%、1.81%,风险达到很强-极强水平的排序为CdAsPb。但从可能影响农作物安全性的角度看,仍需注意某些高的潜在风险点位产生的生态效应。

Genesis and Ecological Effect Assessment of Heavy Metal Anomaly in Soil of the Longyan City

The soil and soil solution samples from different soil profile layers were collected at the Shizhong Town, Longyan City, and the total amounts of Pb, Cd, and As in the samples were determined. Their spatial distributions were studied using the ordinary Kriging interpolation method to explore the genesis of heavy metal anomaly. Based on statistical analyses of in-situ heavy metal contents in soil solution, a method of soil ecological risk assessment was established and used to evaluate the ecological effect of these heavy metals. The results indicated that Pb, Cd, and As originated mainly from bedrocks of soils with little anomaly, and the artificially derived anomaly was also insignificant. Anomaly of Pb, Cd and As in soil was only found in scattered sites of small enterprises. For each sampling site, heavy metals contents in surface soil and in deep soil correlated significantly, there had no strong to extremely strong supergene enrichments were observed but no-weak-moderate supergene enrichments in the study area. In summary, there was no significant ecological risk associated with Pb, Cd, and As in the study area. The frequency of secondary or higher level risks were 8.24%, 3.64% and 1.81%, respectively, and the risk level of strong to extremely strong followed the order of Cd > As > Pb. From the perspective of crops safety, however, some sites still needs more attention on the ecological impacts.