贵州玉屏县土壤Hg、Cd元素异常查证方法及其成因分析

Verification Method and Genesis Analysis of Soil Hg and Cd Anomalies in Yuping County,Guizhou Province

通过贵州省玉屏县耕地质量地球化学调查评价工作,发现该县部分区域耕地土壤中Hg、Cd元素含量超过国家土壤环境质量三级标准值,达到严格管控范围,出现高值异常,分别形成汞、镉两个异常区。进一步查清异常区特征及其异常源,对该区土壤质量的评价和农业种植结构调整具有实际指导意义。本文采用横向剖面法、垂向剖面法、地质剖面法等三种方法相结合开展异常查证及成因分析。经综合分析得知:汞异常区位于北东向新晃-玉屏深大断裂带上及其附近,异常源为区内的汞矿化点,其经强风化成土后残留原地或有较小的迁移而形成汞异常。镉异常区位于近东西向太阳山断层附近,其异常源为寒武系下统“黑色岩系”地层和区内铅锌矿化点,其“黑色岩系”地层中富含Cd元素和铅锌矿化点中伴生的镉矿物是引起镉异常的直接因素。

The geochemical investigation and evaluation of cultivated land quality in Yuping County,Guizhou Province found that the contents of elements Hg and Cd in soil of some areas exceed the third-class standard value of national soil environmental quality,reaching the strict control range,locally even beyond the control value by more than 10 times.They express high value anomalies,forming two anomaly areas of mercury and cadmium,respectively.It is necessary to further clarify the characteristics and sources of these anomaly areas,which has practical significance for the evaluation of soil quality and the adjustment of agricultural planting structure in this region.By combination of the transverse section,vertical section and geological section methods,this work undertook anomaly verification and genesis analysis in the research area.Comprehensive analysis shows that the mercury anomaly area is located on the NE-trending Xinhuang-Yuping deep fault zone and its vicinity.The source of the anomaly is the mercury mineralization site in the area,which remains in situ after strong weathering or has a small migration to form mercury anomalies.The Cd anomaly area is located near the East-West Taiyangshan fault.The source of the anomalies is the Lower Cambrian“black rock series”strata and the lead-zinc mineralization spots in the area.The Cd-rich“black rock series”strata and the associated Cd minerals at lead-zinc mineralization spots are the direct factors causing Cd anomalies.