Accumulation And Risk Assessment Of Heavy Metals In Soil And Vegetables Under Different Application Rates Of Swine Manure Source Organic Fertilize

In order to study the accumulation and ecological risk of heavy metals in soil-vegetable system under different treatments of organic fertilizer,this paper collected samples of different kinds of vegetables in Chongming District of Shanghai and conducted field experiments in local production cooperatives.Using leaf vegetables,eggplant fruits and legumes as vegetable planting types,different dosage of pig manure source organic fertilizer was set up.And it included five treatments(CK,0 t?hm^-2;T1,20 t?hm^-2;T2,40 t?hm^-2;T3,60 t?hm^-2;T4,80 t?hm^-2),which were applied before planting,then soil and vegetable samples were collected simultaneously after harvest,and Cu,Pb,Cd,As contents were determined.In addition,the effects of different amounts of organic fertilizer application on heavy metal contents in soil and vegetables were evaluated by using pollution index and other evaluation methods,and the health risk of heavy metals in vegetables were also evaluated.The main conclusions were as follows:?1?In Chongming,Shanghai,the contents of Pb,Cd in real estate vegetables was lower than the limit standard of food pollutants.In leaf vegetables,rhizomes,eggplant fruits and melons,the highest contents of heavy metals were found in leaf vegetables and leaf vegetables,and Pb,in leaf vegetables was the highest in four kinds of vegetables:leaf vegetables,root vegetables,eggplant fruits and melons There were some differences in the content of Cd in different seasons and regions.The evaluation results of heavy metal pollution in vegetables were excellent in Chongming District.The health risk assessment of heavy metals in vegetables showed that the hazard quotient?HQ?values of Pb and Cd were less than 1 in adults and children,and there were not significant health risk.The HQ vegetable values of leaf vegetable,eggplant fruit and rhizome vegetable Cd were significantly higher than that of Pb,childrenundefineds HQ vegetable values of Pb and Cd were higher than those of adults.?2?The results showed that the contents of Cu,Pb,Cd and As in soil were in accordance with the quality standard of green food.The contents of Cu,Cd and As in the soil of the four-leaf vegetables was increased with different application rates of organic fertilizer after continuous application of multi-stubble.But the content of Pb was not increased significantly,and the total contents of Cu,Pb,Cd,As in soil of three-stubble eggplant vegetables had not obvious increasing trend.The content of Cu in soil under organic fertilizer treatment was significantly higher than that in blank treatment,but there was not significant difference in Pb,Cd,As contents between two crops of leguminous vegetables.?3?Under the field experiment of four stubble leaf vegetables,the contents of acetic acid exchangeable Cu,Pb,Cd,As in each stubble soil showed an increasing trend with the increase of planting stubble number and fertilizer application.The results of soil morphology analysis of the last stubble showed that the content of Cu is residue state,reducible state and oxidizable form,and the form of Pb was reducible state,residual state and oxidizable state in turn.The proportion of extracted acetic acid concentration of Cd was more than 50%of the total amount.The main form of As was residue,and acetic acid extraction accounted for less than 1%of the total amount.With the increase of fertilizer application,the concentration of acetic acid extractable state showed an increasing trend,which might increase the risk of vegetables to absorb As in soil.?4?The contents of Pb,Cd and As in leaf vegetables,eggplant fruits and legumes were all in accordance with the standard values of food contaminants under different organic fertilizer application rates.The content of Cu was higher in leafy vegetables treated with different organic fertilizer application in the fourth stubble,and showed the trend of synchronous accumulation.The Cu,Pb,Cd,As bioconcentration coefficients of three kinds of vegetables were all less than 1;The enrichment ability of vegetable species to heavy metals were higher than that of eggplant fruits and legumes,and that of leafy vegetables was significantly higher than that of green vegetables.?5?In the leafy vegetable-soil system,there was not significant correlation between total Cu and acetic acid extracted Cu in soil,but there was a significant positive correlation between Pb and Cu of leafy vegetables,and there was a significant positive correlation between Pb in vegetables and soil,and there was a significant positive correlation between Pb and Cu in leaf vegetables and soil,respectively.There was a significant negative correlation between the content of Cd in vegetables and the total amount of Cd in soil,and there was not significant correlation between As in the system.There was not significant correlation between Pb and As in the aubergine vegetable-soil system,but there was a very significant positive correlation between the content of Cd in the eggplant fruit vegetables and the soil.In legume vegetable-soil system,there was not significant correlation between Cu,Pb,Cd,As contents in soil and vegetable,but very significant positive correlation in vegetable.The migration and accumulation of Cu,Pb,Cd,As was complicated in soil-vegetable system,and the specific migration mechanism still needs to be further explored and analyzed.?6?According to the environmental quality standard of green food soil,the contents of Cu,Pb,Cd,As were within the safe range in soil under different application rates of organic fertilizer,after continuous cropping of 2-4-stubble vegetables.According to the environmental chemical background values of the farmland soil in Shanghai,the single factor pollution index in the field experiment soil was biggest of Cd on the partial accumulation phenomenon under the treatment of different organic fertilizer application.The results of geological accumulation index showed that the geological accumulation index of Cu,Pb,Cd,As in the three kinds of vegetable soils were all less than 0,and all of them were pollution-free.In addition,the potential ecological hazard of soil was evaluated,the comprehensive potential ecological risk was slight,and there were a slight potential ecological risk of Cu,Pb,As in soil of three kinds of vegetables under different organic fertilizer application.There was a moderate potential ecological risk of Cd in legume and leafy vegetables with the treatment high amount of organic fertilizer.In order to predict the potential ecological risk of Cd in vegetable soil,it is suggested to monitor the change of Cd content in soil during planting of vegetable.?7?According to the limit standard of contaminants in food,the content characteristics of Pb,Cd,As in 2-4-stubble leaf vegetables,eggplant fruits and leguminous vegetables under different organic fertilizer application rates showed that the single factor pollution index was less than 1,and the results were excellent.The exposure risk index of heavy metals in vegetables showed that the hazard quotient?HQ?values was less than 1 in the same amount of vegetables,and there were not significant health ecological risk.And The HQ vegetable values of heavy metals intake in children were higher than that in adults.