The Potential Ecological Risk Assessment Of Mainly Heavy Metals Pollution In Guanxi Pomelo Orchard

Total and available Cd,Pb,As,Hg contents in soils of 319 pomelo orchards in 10 villages and towns of Pinghe County were analyzed to assess heavy metal pollution and potential ecological risk.The correlation analysis of soil heavy metal contents with soil basic physicochemical properties and the heavy metal content of pomelo leaf as well as pomelo fruit was carried out.The main conclusions were as follows:1?The ranges of soil total Cd,Pb,As,Hg content in Guanxi pomelo orchards were 0.02-2.36 mg/kg?14.3-1213.7mg/kg?1.27-88.40mg/kg?0.03-0.74mg/kg,respectively,the average content were:0.09±0.18mg/kg,65.44±88.54mg/kg,9.80±12.03mg/kg,0.11±0.07mg/kg,respectively.According to the criteria of Grade ? in the "Environment Quality Standard for Soils"(soil pH<6.5,Cd?0.3mg/kg,Pb?250mg/kg,As?40mg/kg,Hg?0.3mg/kg),the content of soil Cd,Pb,As,Hg exceeded the rate of 1.88%,2.19%,4.08%,1.88%,respectively.According to the criteria of "green food producing area environment technical specifications"(pH<6.5,Cd ?0.3mg/kg,Pb?50 mg/kg,As ?25mg/kg,Hg?0.25mg/kg),the content of soil Cd,As,Hg exceeded the rate of 1.88%,8.46%,2.51%,respectively.Whereas,the soil Pb criteria of standard was not suitable for pomelo orchards.The results of single factor index evaluation showed that 90.6%of the soil samples was in the security level and soils were not polluted by heavy metals.The results of Integrated pollution indexes evaluation showed that 4.39%of the soil samples polluted lightly and the other soil samples was in the security level and soils were not polluted by heavy metals.The results of potential ecological risk assessment showed that soil heavy metals pollution was in a low risk.The results of health risk assessment showed that Pb,Hg had not significant adverse effects on human being,Cd,As can be ignored or acceptable.The distribution of As pollution in soil was relatively wider,the degree of Cd pollution was relatively higher in Guanxi pomelo orchards.Heavy metals pollution was mainly in Xiaoxi,Banzai and Xiazhai.2?The content of soil available Cd,Pb,As and Hg in Guanxi pomelo orchards ranged from undetectable to 1.940mg/kg,0.41-53.81mg/kg,0.01-2.24mg/kg and undetectable to 0.038mg/kg,respectively.the average content were:0.053 ± 0.176mg/kg,6.56 ± 6.28mg/kg,0.17± 0.24mg/kg and 0.008±0.008mg/kg,respectively.According to the criteria of Grade ? in "Standard for heavy-metal pollution classification for agricultural soils in Fujian Province"(available Cd?0.15mg/kg,available Pb?28mg/kg,available As ?2.5 mg/kg),soil available As content did not exceed the standard,but soil available Cd,Pb content exceeded the rate of 5.71%,1.88%,respectively.Correlation analysis showed that soil available Cd?Pb?As contents were very significantly positive correlated with soil total Cd?Pb?As content,respectively.There was no correlation between the soil available Hg content and soil total Hg content.Correlation analysis showed that Pb,As content in leaves and soil available Pb,As content were significantly positive correlation,respectively.There was no correlation between Cd?Hg content in leaves and soil available Cd?Hg content,respectively.Pb,As,Hg contents in fruits and Pb,As,Hg contents in leaves showed significant positive correlation,respectively.There is no correlation between Cd content in leaves and Cd content in fruits.In conclusion,soil Pb,As pollution caused soil available Pb,As content increase and then caused Pb,As contents in leaves and fruit exceed the standard.Cd,Hg content in leaves and Cd,Hg content in fruit had a poor correlation that may be related to the application of foliar fertilizer or fungicide with Cd,Hg.3?Correlation analysis between soil available Cd,Pb,As,Hg content and soil physical and chemical properties showed soil available Cd content was very significantly positive correlated with soil pH and 0.02-0.2mm particle content.Soil available Pb content was significantly negative correlated with soil available phosphorus content.Soil available Hg content was significantly negative correlated with soil pH,significantly or very significantly negative correlated with 0.2-2mm and 0.02-0.2mm particle content.Soil available As content was significantly negative correlated with soil organic matter content and soil available phosphorus content,very significantly negative correlated with soil 0.2-2mm particle content,but,significantly positive correlated with soil pH and 0.002-0.02mm particle content.