Geochemical Characteristics of Soil Se in Heavy Metal Geological High Background Area and Comprehensive Evaluation of Se-Rich Cultivated Land
In order to rationally protect and utilize Se-rich cultivated land resources and provide scientific basis for the safe development of Se-rich agricultural products in heavy metal geological high background area,74 sets of soil(0-20 cm)and rice seed samples were collected in Baitu Township,Qianjiang District,Chongqing.The contents of Se and heavy metals(Cd,Hg,Pb,As,Cr,Cu,Zn and Ni)in paddy and soil,as well as the contents of nutrient elements and oxides in soil were analyzed,the geochemical characteristics of various elements were study and the Se rich farmland was compre-hensively evaluation.The results show that the comprehensive quality of soil environment in the study area was mainly in grade 3(mild contamination)and grade 4(middle level pollution),with the area proportion of 41.65％and 50.71％,re-spectively,and the pollution factor was mainly the element Cd.The average content of soil Se was 0.91 mg·kg-1,and 97.29％of the sites with contents between 0.4 and 3.0 mg·kg-1,indicating Se resource is rich in the soil.The overall nutrient condition of cultivated soil in the study area is good,but there is a problem of single element deficiency in some areas,especially K deficiency.The contents of heavy metals and Se in cultivated soil are mainly related to the weathering of limestone and carbonaceous shale(coal line).In addition,agricultural activities can cause the input of Cd and As in cultivated soil.In the study area,the Se enrichment rate of brown rice was 100％,and the Cd excess rate of brown rice was 7.4％.Soil pH is the main factor affecting the absorption of Cd and Se by paddy,and the medium alkaline condition was conducive to the Se enrichment of rice and inhibited the absorption of Cd.The comprehensive grade of rich Se cultivat-ed land in the study area is mainly second class,and the area accounts for 95.68％,which is suitable for the development and utilization of rich Se resources.According to the scores of individual indexes of each cultivated land plot,the soil rich in Se resources can be used to seek advantages and avoid disadvantages through nutrient element supplement and soil pH adjustment,and the planting structure could be adjusted for those cultivated lands that are not suitable for the development and utilization of Se rich resources.
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