Sources Of Heavy Metal Pollution In Farmland Soil In High Geological Background Area And Its Prevention And Control Zoning

At present,the pollution of heavy metals in soils with high geological background in the Pearl River Delta region is becoming more and more serious.It is of great significance to carry out the analysis of heavy metal pollution in high geological background area and the study of relevant prevention and control zoning.D District is located at the mouth of Xijiang River in the Pearl River Basin.It has a high concentration of heavy metals.D District is also a typical area with a high geological background and less human disturbance.Therefore,this paper takes the typical high-background heavy metal pollution areas in the Pearl River Basin and D District as the main research areas to identify the sources of heavy metal pollution in high-background soils.Based on the research results of the Pearl River Basin and D District,the prevention and control zoning of heavy metal pollution in soils is studied.The main conclusions are as follows:(1)The high geological background of the Pearl River Basin is mainly caused by the high content of heavy metals in the original parent rocks and the accumulation of heavy metals carried by the Xijiang and Beijiang rivers in the Pearl River Delta.As,Cd,Pb and Cu have the same distribution of heavy metals in surface and deep layers.As,Cd and Pb are the most abundant parent materials of sedimentary limestone,and the area is small,concentrated in the middle of the Pearl River Basin.Among them,the area of As element sedimentary shale is larger,widely distributed around the Pearl River Basin;the area of Cd element fluvial parent material is larger,concentrated in the central part of the Pearl River Basin;the area of the first three parent materials of Pb element is smaller,but the area of sedimentary shale is larger,widely distributed around the Pearl River Basin;the area of the highest abundance of Cu element is larger.Generally speaking,the area of parent material with high abundance of As and Cu is the largest,while that of Pb is the smallest.(2)The high-value areas of heavy metals in D District are mainly concentrated in the South and north of the study area,and human activities also have a certain impact on D District.Source analysis results show that as,Cu,Ni and Zn are the main heavy metals affected by natural factors such as parent materials.(3)The prevention and control zoning of heavy metals in soils of Pearl River Basin and D District were studied.The Pearl River Basin can be divided into five types: As-Cd-Pb-Cu control area of sedimentary limestone parent material,Cu control area of sedimentary sandstone,As control area of sedimentary shale,Cd-Cu control area of fluvial and marine parent material,and acid igneous rock risk-free area,and five control technologies that can be adopted in these areas are simply screened.D District is divided into four types,including Cu-Ni-Zn-As control zone,Cu-Ni-Zn control zone,Cu control zone and risk-free zone.