Classification Of Cadmium Pollution Risk Patterns Of Different Paddy Soils In Karst Area Of Guizhou

The rate of heavy metals in paddy soils in Guizhou is high,especially cadmium.In order to explore the cadmium pollution characteristics and pattern distribution of different paddy soils in Guizhou karst area,this paper takes four types of paddy soil formed by hydroponic ripening of red soil,yellow soil,lime soil and purple soil in Guizhou karst area as the research object,using single factor index method and space.Interpolation method was used to analyze the characteristics of cadmium content,pollution risk and related relationship of different types of paddy soil and their corresponding rice,and to classify the risk pattern of cadmium pollution in paddy soil in Guizhou karst area.The main conclusions are as follows:(1)The minimum and maximum cadmium content in the tested paddy soil were 0.06 mg/kg and 4.79 mg/kg,respectively,which were found in lime soil and yellow loam paddy soil,with an average value of 0.50 mg/kg,median value and The average content is ranked in lime soil paddy soil > purple soil paddy soil > yellow loam paddy soil > red soil paddy soil.18.5% of the samples exceeded the cadmium background value of Guizhou soil,and 63.5% of the samples were cadmiumfree.The pollution risk was ranked as yellow soil paddy soil > purple soil paddy soil > red soil paddy soil > lime soil paddy soil.(2)The minimum and maximum cadmium content in the tested rice were 0.009 mg/kg and 1.095 mg/kg,respectively.The minimum value appeared in the corresponding soil of red soil,lime soil and purple soil paddy soil,and the maximum appeared in yellow soil.The average paddy soil corresponds to rice,and the average value is 0.043 mg/kg.The order of the average and median content of cadmium in rice was all red paddy soil > yellow loam paddy soil > purple soil paddy soil = lime soil paddy soil.5.2% of rice samples were contaminated with cadmium,and the risk of cadmium contamination was ranked as lime soil paddy soil > red loam paddy soil > yellow loam paddy soil > purple soil paddy rice.(3)There was a significant positive correlation between the cadmium content of the tested paddy soil and rice(r=0.081**,n=2961),red paddy,yellow loam,lime soil,purple soil type 4 paddy soil and There is a certain correlation between the corresponding rice(r=0.092,n=199;r=0.127**,n=1694;r=0.106**,n=925;r=-0.041,n=145).At pH ? 5.5,the safety thresholds of cadmium in test paddy soil,red paddy paddy soil and yellow paddy paddy soil were 3.62,1.75 and 1.92 mg/kg,respectively.In the karst area of Guizhou,paddy soil is contaminated by cadmium,but the corresponding rice is not necessarily contaminated by cadmium.When the cadmium content of the tested paddy soil ? screening value,screening value < cadmium content ? control value,control value < cadmium content,that is,with the increase of soil cadmium content,the proportion of cadmium exceeding the standard of rice increased,but the increasing trend was limited.(4)The risk pattern of cadmium pollution in paddy soil is: the cadmium in paddy soil is mainly distributed without pollution,and the pollution risk area is scattered around the northern part of Guizhou,southern Guizhou,central Guizhou,southeast Guizhou,Guizhou.Northwest and other regions.The cadmium pollution in red soil paddy soil is scattered.The cadmium pollution area of yellow soil paddy soil is scattered and scattered in western Guizhou,northwest Guizhou,northeast Guizhou,etc.The cadmium pollution area of lime soil paddy is scattered in western Guizhou and northwest Guizhou.Areas;purple soil-soil cadmium-contaminated areas are scattered and scattered in northwest Guizhou and northern Guizhou.(5)The risk pattern of rice cadmium pollution is: the cadmium in rice is mainly distributed without pollution,and the central area of Guizhou is the center.The non-polluted areas are distributed in the whole province.The contaminated areas are scattered in southern Guizhou,western Guizhou and Guizhou.Eastern and other regions.The cadmium-contaminated area of rice in the red paddy soil is scattered in the eastern part of Guizhou.The cadmium-contaminated area of rice in the yellow paddy soil is scattered in eastern Guizhou,northern Guizhou and western Guizhou.The cadmium-contaminated areas of the paddy soil are scattered in the lime-soil paddy soil.In southern Guizhou,western Guizhou,northwest Guizhou,and eastern Guizhou,cadmium pollution in purple soily rice is scattered in southern Guizhou and western Guizhou.The cadmium pollution distribution area of rice and the soil cadmium pollution area do not completely coincide.