塌陷自修复区农田土壤重金属元素演变规律

Temporal Variations of Heavy Metals from Agricultural Soil in a Natural Restoration Region Affected by Coal Mining Subsidence

该研究以邯郸市峰峰矿区典型的塌陷自修复区为例,采集不同塌陷年限的农田表层土壤样品,分别测定农田土壤重金属元素(Cu、Zn、Ni、Cr、Cd、Pb、Hg和As)的含量,探讨重金属元素含量随塌陷年限的时空演变规律,并采用Hakanson潜在生态危害指数法评估了其潜在生态风险。结果表明:相比未塌陷区,各塌陷年限农田土壤的重金属含量Cu、Zn、Cd、Pb含量均偏高,元素Zn含量随塌陷年限的延长逐年递增,除塌陷6 a外元素As含量逐年降低,其余元素含量变化规律性不明显;对比《土壤环境质量农用地土壤污染风险管控标准(试行)》(GB 15618-2018),不同年限的农田土壤重金属元素Cd含量均超标,最大超标倍数为16.60;元素Pb和As仅在个别塌陷年限超标,其余元素均未超标。Hakanson生态风险评估结果表明,Cd是最主要潜在生态危害因子,其次是Hg、As;所有样点处土壤重金属的综合潜在生态危害指数均表现为较强生态风险水平。

Agricultural topsoils samples from different mining subsidence sites were collected around a coal mine-impacted natural restoration region in Fengfeng mining area,Handan City,China.The concentrations of the selected heavy metals(Cu,Zn,Ni,Cr,Cd,Pb,Hg and As)from agricultural soil were determined to analyze their temporal variations regularity with mining subsidence years,and evaluate potential risk level based on the potential ecological risk introduced by Hakanson.The results showed that the concentrations of Cu,Zn,Cd and Pb from subsidence sampling sites were higher than those from sites not suffering from coal mining.It was found that concentrations of Zn in studied years mainly presented an increasing trend year by year,concentrations of As presented a decreasing trend except for 6 years and the concentrations variations regularity of other heavy metals were insignificant.Using Soil Environmental Quality Risk Control Standard for Soil Contamination of Agricultural Land(Trial)(GB 15618-2018)as the reference assessment criteria,the concentrations of Cd for all studied years exceeded its risk screening values,and its largest over-standard times reached 16.60.Meanwhile,the concentrations of Pb and As only exceeded their own risk screening values in some years,while other heavy metal elements didn’t exceed the screening values specified by this standard.Hakanson potential ecological risk index suggested that Cd was the principal potential ecological hazard factor,followed by Hg and As.In addition,total potential ecological risk index(RI)of heavy metals for all studied years performed considerable risk level.