| In this study,six potato production areas in Guizhou were selected for sampling,and the contents of 7 heavy metals Cr,Ni,Cu,Zn,As,Cd and Pb in soil and potatoes were determined.The heavy metal pollution evaluation and health risk evaluation of soil and potatoes were conducted.Through pot experiment,the critical value of Cd effect on plants and microorganisms was obtained,and combined with field samples,the threshold value of Cd in soil for potato safety production was obtained.The main conclusions are as follows:（1）The average contents of heavy metals in soil from each production areas were compared with the background values in Guizhou Province soil.Libo and Chishui were relatively clean.Cu in Panxian was 5.84 times of the background value,Cu and Zn in Nayong were 3.75 and 1.52 times of the background value,respectively.All elements were higher than the background value in Weining.Cu and Pb in Huaxi were3.39 and 2.21 times of the background value,respectively.（2）The single factor index of heavy metals in soil showed that Libo and Chishui were slightly polluted by Cd,Panxian and Weining were polluted by Cu,As and Cd,Nayong and Huaxi were polluted by Cu,Zn and Cd,Nemeruo comprehensive pollution index showed that Libo and Chishui were slightly polluted,Panxian and Nayong were moderately polluted,and Weining and Huaxi were heavily polluted.（3）The assessment of soil heavy metal accumulation index showed that no heavy metals were accumulated in Libo and Chishui.Panxian,Nayong,Weining and Huaxi were moderately polluted by Cu,and some elements were slightly polluted.Panxian had no Pb accumulation,Nayong had no Ni,Cu,As,Cd and accumulation,and Weining and Huaxi had no As accumulation.（4）The assessment of pollution load index shows that the pollution degree is Weining（1.56）>Panxian（1.54）Huaxi（1.32）>Nayong（1.23）>Chishui（0.73）>Libo（0.72）.Libo and Chishui are generally minor polluted,while Panxian,Nayong,Weining and Huaxi are generally slightly polluted.（5）The assessment of potential ecological risk index shows that the comprehensive ecological risk index is Weining（143.29）>Panxian（128.67）>Huaxi（96.64）>Nayong（80.09）>Libo（50.36）>Chishui（42.48）.The potential risks of heavy metals in soil in each study area are mainly caused by Cd,which has the largest contribution rate to the comprehensive potential risk index.（6）Carcinogenic risk evaluation showed that under the hand mouth and skin exposure routes in all production areas,the R value was children>adults,which had a greater cancer risk for children,and the R value under the respiratory exposure routes was adults>children,which had a greater cancer risk for adults.The non-carcinogenic risk assessment showed that the HQ of Cr and As for adults and children under the hand mouth exposure route in each production areas were greater than 1,which might produce a non-carcinogenic risk for children>adults,and the HQ of heavy metals under the skin and respiratory exposure route was less than 1,which was not significant for adults and children.Children in each production areas might have a non-carcinogenic risk,and children with non-carcinogenic risk were greater than adults.（7）The evaluation of potato pollution shows that potatoes have a strong concentration of heavy metals in As,Ni,and Cd soils,and there are Cr and Cd pollution in potatoes in all production areas.The health risk assessment of heavy metals in potatoes shows that the THQ of Cu,Zn,and Pb in potatoes for adults and children in each production area is less than 1,and the risk to human health is not significant.Other heavy metals may pose certain health risks to adults and children,and TTHQ and THQ are children>adults,and TTHQ are Panxian>Weining>Huaxi>Libo>Nayong>Chishui.（8）Critical value of Cd effect on plants:With the increase of Cd concentration,the fresh weight of potato tubers showed a downward trend in calcareous soil and yellow soil.Based on the 10%reduction of fresh weight of tubers,the critical values of total and available Cd in the two soils were 14.042 mg·kg-1and 0.115 mg·kg-1,24.630 mg·kg-1and 0.214 mg·kg-1respectively by fitting the equation.Critical value of Cd’s effect on microorganisms:With the increase of Cd concentration,the activities of soil urease and alkaline phosphatase both showed a trend of first increasing and then decreasing in the two soils.Based on the 25%reduction of urease and alkaline phosphatase activities,the critical values of total and available Cd in the two soils were 37.283 mg·kg-1,0.237 mg·kg-1,47.532 mg·kg-1,0.373 mg·kg-1,62.118 mg·kg-1,0.476 mg·kg-1,55.186 mg·kg-1and 0.333 mg·kg-1respectively by fitting the equation.The available state of Cd in soil can better reflect the plant and microbial effects of Cd pollution than the total state.（9）The threshold of total Cd in the production area was 3.55 mg·kg-1,the threshold value of available Cd was 0.179 mg·kg-1;The threshold value of total and available Cd in soil of different production areas:0.503 mg·kg-1and 0.012 mg·kg-1in Libo,0.168 mg·kg-1and 0.015 mg·kg-1in Chishui,7.581 mg·kg-1and 0.105 mg·kg-1in Panxian,8.167 mg·kg-1and 0.010 mg·kg-1in Nayong,2.810 mg·kg-1and0.010 mg·kg-1in Weining,22.20 mg·kg-1and 0.041 mg·kg-1in Huaxi;When p H≤5.5,5.5<p H≤6.5,6.5<p H≤7.5,and p H>7.5,the threshold values of total and available Cd were 2.126 mg·kg-1and 0.016 mg·kg-1、2.452 mg·kg-1and 0.001 mg·kg-1、0.859 mg·kg-1and 0.056 mg·kg-1、6.789 mg·kg-1and 0.024 mg·kg-1respectively;In pot experiment,the total and available threshold of Cd in calcareous soil and yellow soil were 0.358 mg·kg-1and 0.031 mg·kg-1、1.586 mg·kg-1and0.054 mg·kg-1respectively。... |
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