Enrichment Characteristics And Risk Assessment Of Heavy Metal Pollution In Gannan Navel Orange

The Gannan navel orange is the dominant industry in Ganzhou,Jiangxi Province.Gannan navel orange showed high quality from Ganzhou and was famous in China.With the rapid development of industry,human activities have caused soil environmental pollution.In southern Jiangxi,there is heavy metal pollution caused by mining industry,and heavy metals will be absorbed by plant roots and migrate into agricultural products,and enter the human body through food chain pollution,causing harm to human health.Characterizing the relationship between Gannan navel orange fruit quality and soil environment is of great significance for assessing navel orange fruit quality and soil safety in mining areas,promoting the healthy development of navel orange industry,and scientifically governing and safely utilizing cultivated land.In this study,the lead(Pb),cadmium(Cd),arsenic(As),and zinc(Zn)in navel orange pulp,peel,leaves and soil were detected by ICP-MS and ICP-OES.According to the national food safety standards and agricultural and soil pollution control standards,the safety judgment of navel orange pulp and soil were also carried out,and the correlation and principal components of heavy metal elements in various parts of navel orange were analyzed.The enrichment characteristics and potential ecological risk index method were used to evaluate the pollution degree and potential risk of heavy metal elements in soil in organge orchard.The main results were as following:(1)The detected heavy metal elements were far below the national food safety standards,which met the strict requirements of the national food safety standards;The national standard stipulates that the safety judgment of the peel and leaves is not carried out;soil pH in the navel orange control area is 5.29,and the soil is mainly strongly acidic.According to the soil control standards for agricultural land,the soil is mainly polluted by three heavy metals,e.g.Pb,Cd,and As.A small amount of copper(Cu)and Zn were polluted,but the pollution was serious,mainly concentrated in Liucun Village,Shexi Town,Shangyou County and Jiaoli Village,Yingqian Town,Shangyou County.Nickel(Ni)and Chromium(Cr)were low,and the soil is not polluted by Ni and Cr.(2)Cd and Pb in the navel orange peel showed a significant positive correlation(r=0.655).Principal component analysis showed that it was mainly composed of two principal components,and the cumulative contribution rate of the two principal components reached 64.5%.PC1 variance contribution rate was 41%,and Pb,Cd,and As had a large load on PC1;the correlation between Cd and Pb in leaves was 0.870,which was significantly positively correlated.The principal components reflect that the cumulative contribution rate of the three principal components of leaf heavy metals is 68.7%,of which the variance contribution rate of PC1 accounts for 33.9%of the total contribution rate,and Pb,Cd,and Cr have relatively large loads on PC1;Soil Cr was correlated with Ni(r=0.916);pH has a moderate correlation with As and Zn.Cd and As show a significant positive correlation,and a moderate positive correlation with Zn.It has a weak correlation with the rest of the elements,and As has a moderate positive correlation with Zn,Ni,and Cr.Two components with eigenvalues greater than 1 have been extracted.The contribution rate of the first principal component is 48.5%,and the cumulative contribution of the second principal component is up to 76.4%.The heavy metal elements with higher loads in the first principal component of the total variance are As,Ni,Cr,Zn and Cd,and the variance contribution rate is 48.46%.Among the second principal component,Pb and Zn have higher loads,and the variance contribution rate is 28%,and Ni and Cr are mainly negatively correlated.(3)The soil pollution elements were mainly composed of lead,cadmium and arsenic,and a small amount of zinc and copper were polluted.The single factor index method shows that Pb,Cd,As,Zn,and Cu were the second-class cleaners,respectively,with 10,1,4,1,and 3 plots;Cd,As,and Cu have 3,3,and 1 plots,respectively.It belongs to the third-class moderate pollution,Nemerow composite index method shows that Cd belongs to the fourth-class severe pollution.Seven plots were not polluted,5 plots are in a clean state,6 sample plots are generally in a second-class clean state,4 plots are in a third-class moderately polluted state,and 1 plot is in a heavily polluted state;potential risks.The evaluation method shows that the potential ecological risk coefficient of single factor is generally low,and the potential ecological risk of minor level is the main one.Among them,the pollution risk of cadmium element is the highest,and the pollution risks of heavy metals are ranked as follows:Cd>As>Pb>Cu>Ni>Cr>Zn,and the comprehensive evaluation of potential risks is extremely strong,strong,and medium ecological risk plots are 1,3,and 3,respectively.The average contribution of Cd in the comprehensive ecological risk assessment is as high as 70%,which largely affects the potential ecological risk level.