Research On Quality Evaluation And Zoning Management Of Heavy Metal Contaminated Farmland In High Geological Background Area

At present,the Pearl River Delta is a typical region with high geological background.Heavy metal pollution not only affects the quality of the regional soil,but also accumulates in agricultural products through the migration of plant roots,thereby endangering human health.Based on this,this article is based on the urgent needs of the prevention and control of heavy metal pollution in China.The study area selects the typical area D of the Pearl River Delta,and the comprehensive quality evaluation and human health risk assessment of the soil-rice system are carried out.Based on this,the high geological background area is carried out.Safe use of zoning,and put forward reasonable management and control suggestions.The main findings are as follows:(1)The soil in the study area is mainly polluted by Cd and Cu elements,there is a small amount of pollution by As element,and there is no pollution by Zn element.The areas with high content of heavy metals are concentrated in the middle and north of the study area,and the Xijiang estuary on the edge.Most rice does not exceed the standard,only a small amount of As and Cd elements are polluted.The order of bioconcentration factor(BCF)is: Cd>Zn>Cu>As,and the BCF value is less than 1,there is no obvious heavy metal enrichment in rice,which may be related to the strong stability of "endogenous" heavy metals.(2)Heavy metal pollution in the soil in the study area is affected by external input,and it is mostly in a polluted state.The soil in the lightly polluted and moderately polluted states occupies the largest area.The quality of rice is mostly in a clean state.In this area,91.88% of agricultural land is in a sub-healthy state,90.69%of agricultural land soil is contaminated,and rice meets the relevant limit standards.Under the oral intake route,these four heavy metals may not pose a threat to human health.As element contributes the most to health risks,and may have potential health risks to the human body.(3)The safe utilization zone of the high background area of geology is mainly the risk zone,that is,the low-risk monitoring zone,the medium-risk early warning zone,and the high-risk restricted zone.Priority protection strategy should be adopted for the soil in the safety zone;the pollution source should be controlled in the basic safety zone;the pollution source of the soil should be identified and cut off in the low-risk monitoring zone;for the medium-risk early warning zone,it is recommended to carry out heavy metal pollution risk assessment and implement Early warning,prevention and control management;for upstream high-risk restricted areas,the cultivation and utilization of agricultural products should be immediately restricted,and ecological interception zones can be established upstream to carry out land type conversion,such as agricultural land to non-agricultural land.At the same time,the farmland quality monitoring can be carried out from three aspects to ensure the quality and safety of soil and agricultural products: considering the correlation between spatial samples,the test samples should be arranged reasonably;select the indicators that reflect the status of soil pollution to build a monitoring indicator system,and properly carry out multi-target regional ecology Geochemical surveys;coordinated monitoring through multiple channels such as remote sensing images,field surveys,and construction of land health monitoring networks.