某页岩气开发场地重金属污染风险分析

Risk analysis of heavy metal pollution in shale gas development site

为探究页岩气开发不同阶段对开发场地土壤中重金属含量的影响,以长宁区块某平台为例,监测开发过程中场地土壤重金属Cd、Hg、As、Pb、Cr、Cu、Ni、Zn的质量比变化,并对其分布特征评价。结果表明:页岩气开发各阶段场地土壤中重金属元素As的超标率最高达到了76.92%,页岩气开发对场地土壤中重金属Hg、Cd、As质量比变化影响程度相对较大;部分采样点土壤受重金属元素Cd与Hg影响存在中等生态危害风险,但场地内土壤重金属的综合生态风险指数RI平均值为70.357<150,仍有0.67%的比例存在中等生态危害风险;4.35%采样点土壤中因重金属元素As影响为中度污染风险,场地内土壤重金属的综合污染指数P的平均值为0.880,但1.35%采样点的土壤为中度污染风险。因此页岩气开发场地内土壤重金属存在一定的污染风险,为避免页岩气开发过程对场地土壤的污染,应加强重点区域防控与措施整改降低页岩气开发过程对场地土壤的污染风险,减少页岩气开采对资源地环境的影响。

To explore the influence of different stages of shale gas development on the content of heavy metals in the soil of the development site,a platform in the Changning block was taken as an example to monitor the content changes of Cd,Hg,As,Pb,Cr,Cu,Ni,and Zn in the soil of the site during the development process.Further,the distribution characteristics of heavy metals in the soil of shale gas development sites were evaluated by ecological risk assessment and comprehensive pollution index evaluation methods.The results show that the excess rate of As in the soil of each stage of shale gas development is as high as 76.92%.Shale gas development has a relatively large impact on the changes of Hg,Cd and As in site soil.The soil of some sampling sites is affected by Cd and Hg,and there is a moderate risk of ecological hazards.The average comprehensive ecological risk index RI of soil heavy metals in the site is 70.357<150,and 0.67%of the soil still has a moderate ecological hazard risk.4.35%of the soil sampling points have a moderate pollution risk due to the influence of the heavy metal element As.The average value of the comprehensive pollution index P of soil heavy metals in the site is 0.880,but 1.35%of the soil sampling points have a moderate pollution risk.Therefore,there is a certain risk of pollution by heavy metals in the soil of the shale gas development site.To avoid the pollution of the site soil during the shale gas development process,prevention and control measures in key areas should be strengthened to reduce the pollution risk of the site soil during the shale gas development process,thereby reducing the impact of shale gas exploitation on the environment of resource areas.