Study On The Risk Of Heavy Metal Pollution In Leafy Vegetables Planted With Sludge Compost In Xingyi Area

With the continuous improvement of my country’s urbanization rate,the scale of sewage treatment is getting larger and larger,and the sludge produced is difficult to dispose of,causing many environmental pollution problems.The land use after aerobic composting of sludge has good application prospects in relatively underdeveloped areas.In this study,the residual sludge of a domestic sewage treatment plant in Xingyi was used as compost raw material,and sawdust,bark and grain bran were used as conditioners,and aerobic composting was carried out to produce sludge compost products that met the standard.The sludge compost product is used as the base fertilizer according to the proportions of 0%,20%,40%,60% and80%(referred to as W0 treatment,W1 treatment,W2 treatment,W3 treatment,W4 treatment in the following and in the text)and farmland soil.Evenly mix and plant potted Shanghai Vegetable and Wawa Vegetable.By comparing and analyzing the changes of heavy metal content and form before and after sludge composting,the content and form of heavy metals in potted soil with different fertilization rates,the enrichment of heavy metals in Shanghai Vegetable and Wawa Vegetable,combined with potential ecological risk index,geoaccumulation index,comprehensive pollution The index method is used to study the harmless treatment effect of aerobic composting on heavy metals in sludge,the effect of applying sludge compost products on soil,the ability of Shanghai Vegetable and Wawa Vegetable to enrich and transport heavy metals,and the agricultural utilization of sludge after composting.Risk assessment of heavy metal pollution implemented in Xingyi area.The main findings show that:(1)The domestic sludge was treated by aerobic composting,and the decreasing rate of heavy metal content from high to low was:Cr(91.63%)>Zn(85.89%)>Cu(70.75%)>Pb(55.97%)>As(28.89 %)>Cd(23.30%)>Ni(-132.38%);the passivation effect of bioavailability of various heavy metals is Cd>Zn>Cu>Cr>Pb>As>Ni.The content of heavy metals in sludge compost products is lower than the limit requirements of "Standards for Pollutant Control of Agricultural Sludge(GB4284-2018)",in which the bioavailability of each heavy metal is Cd>Zn>As>Pb>Cu >Cr>Ni,the potential ecological risk mainly comes from Cd,which is at a moderate pollution level.(2)With the increase of the application amount of sludge compost products,the total amount of Pb,As,Cr,Ni,and Zn in Shanghai Vegetable soil showed a downward trend,Cd showed no obvious change,and Cu showed an upward trend.The content of Ni is getting lower and lower,and the total amount of As,Cr,Cu,and Zn all reach the maximum value during W1 treatment,and then show a downward trend.Among the treated soils,the bioavailability of Cd,Pb and Zn in Shanghai Vegetable soil was relatively strong,and the bioavailability of Cd,Pb and Zn in Chinese cabbage soil was relatively strong,and Cd was the main factor leading to soil pollution.(3)The content of Cd,Pb,As,Cr in W0,W1,W2,Pb,Cr,and W4 in edible parts of Shanghai Vegetable edible parts exceeded the "National Food Safety Standard for Contaminants in Food(GB 2762-2017)" ”;the content of Pb,As,W1 and W2 treated Cr in all treatments of Wawa vegetable exceeds the limit requirement of “National Food Safety Standard for Contaminants in Food(GB 2762-2017)”.The pollution degree of Wawa vegetable is higher than that of Shanghai Vegetable.Crops with excessive heavy metal content have non-carcinogenic health risks for the entire population,and the health risks of carcinogenic effects are unacceptable.The main pollution factors of Shanghai Vegetable are Cr and Cd.The main pollution factors are Pb and As.Appropriate fertilization can enhance the ability of crops to accumulate heavy metals,while excessive fertilization can inhibit the accumulation of Cd and Cr.