| For a comprehensive understanding of the characteristics of heavy metal concentrations arable soils and crops in Salaxi demonstration area of Bijie,Guizhou,as well as the health risk of farmland soil under different exposure pathways,and preliminary explore the sources of heavy metals in the soil.In this study,samples of forestland soil,dryland soil and crops（maize,potato,rosa sterilis,pakchoi,walnut and garlic）collected,and the inductively coupled plasma mass spectrometer（ICP-MS）was used to analyze the Cr,Co,Cu,Cd,Pb,Zn,As and Ni content.Descriptive statistics,correlation analysis,principal component analysis and other multivariate statistical methods were used to reveal the characteristics,sources,influencing factors of heavy metal pollution.The pollution status of heavy metals in soil was studied by the methods of single factor index,Nemerow comprehensive index and potential ecological risk index,and the health risk assessment model evaluates the human health risks caused by soil exposure;The spatial distribution characteristics of heavy metals were studied by the semivariogram model and ordinary Kriging interpolation method.The results are as follows:（1）The average concentrations of Cr,Co,Cu,Cd,Pb,Zn,As and Ni were 91.5,4.35,15.2,0.682,33.3,74.8,21.2,22.0 mg·kg-1 respectively in forestland soil,and 131,33.4,79.9,1.71,32.6,146,26.6,64.4mg·kg-1,respectively,in dryland soil.The Cd and As content of forest soil are equivalent to the soil background value of Guizhou Province,and the content of other six heavy metals are lower than that of Guizhou Province Soil background value;except for Pb,the contents of other 7heavy metals in dryland soil are higher than the soil background value in Guizhou Province.Compared with the risk screening values for soil contamination of agricultural land,the Cd and Co content of forest soil and dry land soil exceed this value,and the others are lower than the corresponding risk screening value.Taking GB15618-2018 as the standard,The seven heavy metals including Cr,Co,Cu,Pb,Zn,As and Ni are all in the non-pollution level,while the pollution level of Cd is relatively high;the comprehensive pollution index is 3.00,which is moderate pollution and has the largest pollution contribution value.The evaluation results of Cd and enrichment factors also show that some samples of Cd and Cu are moderately polluted,which should be taken seriously.（2）Some of the crops in the demonstration area have heavy metals exceeding the standard.The average content of heavy metals Cu and Cd in vegetable crops,vegetables and garlic are 2.23,0.202 and 2.25,0.091mg·kg-1,which are higher than the standard limit,Cr,Cu,Zn,As and Ni are lower than the standard limit;The average concentrations of Pb,Zn and As in potato is 0.638,25.9 and 1.02 mg·kg-1,which are 3.19,1.29and 2.04 times of the standard limit;the maize Cr,Cd,Pb,As are higher than the standard limit,Cu,As and Ni are below the standard limit;The average concentrations of Cu,Cd,and Pb in walnut were 5.27,0.234,and 0.316 mg·kg-1,respectively,which were lower than the limit standards for contaminants in food;the concentrations of Cu,Pb,and Zn in rosa sterilis were 2.97,0.623,and 9.97 mg·kg-1,respectively,is lower than the corresponding standard,and Cd is equivalent to its standard.（3）The correlation analysis shows that the correlation coefficients of Cr and Co,Cu,Cd,Pb,Zn,As and Ni are 0.375,0.345,0.744,0.509,0.700,0.361 and 0.807,respectively,which are significantly correlated at the（P<0.05）level,indicating that They have the same origin,and may be mainly affected by the chemical weathering of the parent material;The correlation coefficient between Cd and Pb is 0.543,indicating that the two heavy metals have a high correlation,while the heavy metal Cd has a relatively low correlation with Co,Cu,As,and Pb with Co,Cu,and As,indicating that Pb and Cd have been artificially affected.The influence of the factors is obvious,mainly due to coal mining and lead-zinc smelting in the demonstration area.Two principal components were identified by principal component analysis.Cr,Co,Cu,Zn,As and Ni occupy a higher load on PC1,which are considered as natural sources and are mainly affected by the weathering of the parent rock.Cd and Pb have a higher loadon PC2 and are considered to be disturbed by human activities,mainly coal mining and agricultural activities.Cd and Pb occupies a certain load on PC1 and PC2,indicating that they are simultaneously affected by natural factors and Mixed-source influence of human activities.The results of ordinary kriging interpolation analysis show that the spatial distribution characteristics of heavy metals are related to the distribution of parent rocks,coal pits,zinc smelting sites and land use types in the demonstration area.（4）The results of potential ecological risk assessment showed that the average potential ecological risk indexes of soil Cr,Co,Cu,Cd,Pb,Zn,As,Ni were 1.23,4.67,3.39,69.16,1.36,0.53,8.54 and 2.83,respectively.Cd is medium ecological risk,and the others are mild ecological risks;the average value of the comprehensive potential ecological risk index of the 8 heavy metals is 91.7,which is in slight ecological risk.（5）The evaluation results of the health risk assessment model show that the non-carcinogenic risk index（HQ）of individual heavy metals Cr,Co,Cu,Cd,Pb,Zn,As,Ni is less than 1 for adults in the three non-carcinogenic exposure pathways.The health impact is not significant;For children,As exists a certain exposure risk.The non-carcinogenic health exposure risk index of the other 7 heavy metals is less than 1,which has a little impact on children’s health risks.Hand-mouth intake can lead to non-carcinogenic risks.The non-carcinogenic comprehensive health risk index（HI）is 2.21 in Children,which is approximately 4.6 times that of adults.Among the carcinogenic risks,the carcinogenic health risk indexes of Cr,Cd,As and Ni in the hand-to-mouth exposure route of adults and children are4.04E-05,1.49E-05,2.52E-05,3.11E-05 and 1.06E-04,3.90E-05,6.58E-05 and 8.13E-05,respectively,with low carcinogenic risk;The order of exposure levels of adults under different carcinogenic risk exposure routes:hand-mouth intake>oral-nasal inhalation>skin contact;children have the risk of carcinogenic exposure of Cr,hand-mouth intake is still the main exposure route,the contribution rate is 99.6%.The total carcinogenic exposure risks of adults and children are 1.18E-04 and2.96E-04,respectively,which are at the upper limit of carcinogenic health exposure. |
PDF Full Text Request