Risk evaluation of heavy metal pollution and correlation analysis in rice and its growing paddy soil in a certain city in northern Jiangsu from 2020 to 2022
Objective To understand the content of common heavy metals in rice and its growing paddy soil,evaluate the risk level of heavy metal pollution,and explore the correlation between heavy metal pollution in rice and its growing soil.Methods From 2020 to 2022,rice and its growing paddy soil samples were collected from various points in rural areas of a city in northern Jiangsu.The contents of lead(Pb),cadmium(Cd),mercury(Hg),chromium(Cr),arsenic(As)were detected by atomic absorption spectrophotometry or graphite furnace atomic absorption spectrometry,evaluate the risk level of heavy metal pollution with the methods of the single factor index and Nemerow comprehensive pollution index,and the correlation between the two was analyzed.Results The average content of Pb,Cd,Hg,Cr and As in paddy soil was 0.01,0.05,0.34,and 0.04 mg/kg,respectively,all of which did not exceed the standard.The evaluation result of single factor index showed that the soil was in a pollution-free state,while the comprehensive risk evaluation result of Nemero index showed that the soil in some points was in warning limit state(1.67％),and the others were in safe state(98.33％).Mercury was not detected in rice grown in soil.The average content of Pb,Cd,Cr and As in rice was 0.01,0.05,0.34 and 0.04 mg/kg,respectively.Lead in rice was below the limit by the official standards,while the exceed ratio of cadmium,arsenic and mercury in rice were 4.44％,3.89％and 0.006％,respectively.The results of safety evaluation of rice by single factor index showed that 8 sites had mild and severe cadmium exceedances,7 sites had mild arsenic exceedances,and 1 site had mild chromium exceedances.There were significant positive correlation between arsenic in paddy soil and arsenic in rice,lead in paddy soil and lead and arsenic in rice,mercury in paddy soil and mercury and chromium in rice(all P＜0.05).Conclusion The heavy metal environmental quality of paddy soil is generally clean or still clean,and the rice in some areas is polluted by cadmium,arsenic and chromium in varying degrees.The heavy metal contents such as As,Pb,Hg and Cr in rice were correlated with the As,Pb and Hg in the growth soil,so the safety of rice needs attention.
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