Screening And Cultivation Of Low-heavy Metal Absorption Crops Suitable For Acid Mining Drainage Contaminated Soil

As an important mineral resource,non-ferrous metals played a key role in the development of China's economy,but acid mining drainage generated during the mining process can causes heavy metal pollution in the surrounding soil,as a result,the soil in the contaminated area is largely deserted,and the utilization rate of farmland is low.In this study,in order to obtain low heavy metal absorption crops suitable for planting on this type of polluted farmland,taking red beans,konjac,yellow okra,lotus root,and zizania as research objects,and polluted farmland in Tongling City as a planting land,the heavy metal absorption characteristics of 5 crops have been studied.And the changes in heavy metal content and yield in crops under different soil improvement methods and different fertilization levels have been studied at the same time,in order to provide a scientific basis for the efficient and rational use of farmland soil in non-ferrous metal mining areas.The relevant research results are as follows:(1)Screening of low-heavy metal crops:The five selected crops can grow normally on farmland with low soil nutrients,low pH,and serious Cd pollution,and have certain tolerance to this type of polluted environment;There is a certain amount of Zn pollution in the edible part of red beans,and its Transfer Facter(TF)to Zn reaches 16.22%;the Cd content of the edible parts of konjac and okra is seriously exceeded,they all reach more than 3.5 times of the national food safety standard limit,the Cd Transfer Facter of them reaches 47.79%and 90.33%,respectively;Cu,Zn,As,Cd,and Pb in the edible parts of lotus root and zizania are far below the limits of national food safety standards,and the Transfer Facter for the five heavy metals were also less than 2%;Different crops have different heavy metal enrichment sites,red bean roots and leaves are higher than fruits,the concentration of Zn and Cd in konjac stems is more serious than other parts,and okra roots have a tendency to transport Cu,Zn,and Cd from bottom to top,the Cd content in lotus root gradually decreased from the first to the fourth section,the As,Cd,and Pb contents in the leaves of zizania were higher than fruits;The Target Hazard Quotient(THQ)of a single heavy metal and the Total Target Hazard Quotient(TTHQ)of the five elements for lotus root and zizania are the lowest among the five crops,and their values are less than 1,the health risks of eating them are small,and they are low-heavy metal absorption crops.(2)Effects of fertilization measures:The application of compound fertilizer increased the nitrogen and phosphorus content of low-heavy metal uptake crops(lotus root and zizania)soil,and the top dressing treatment(basic fertilizer 750 kg/hm~2,top dressing 375 kg/hm~2)increased at least 30%;Compound fertilizer can increase the biomass,yield,and economic benefits of lotus root and zizania grown on contaminated soil,and the topdressing treatment group has the best effect;Under three fertilization treatment conditions,starch,crude protein,reducing sugar,total nitrogen and total phosphorus content of the edible parts of lotus root and zizania are both in the order of top dressing>conventional fertilization(basic fertilizer 750 kg/hm~2)>non-fertilization;Different fertilization treatments have less effect on the content of heavy metals in edible parts of lotus root and zizania,and their heavy metal content are lower than the national food safety standard limits.(3)Effects of soil improvement:The application of modifiers can significantly affect the physical and chemical properties of heavy metal-contaminated soil and the contents of edible parts of konjac and okra;the pH value of unmodified konjac and okra is only 5.49-5.55,and there is serious Cd pollution in its edible part;After the improvement of C2(rice husk charcoal32g/kg soil)and P2(phosphite powder 8 g/kg soil),the soil pH value of konjac and okra was improved,the available Cd content in the soil was reduced by 29%-40%,and the content of Cd in edible parts was reduced by 33%-45%;After the improvement of C2P2(rice husk char 32g/kg soil+phosphate rock powder 8g/kg soil),the soil pH value is 5.90-6.01,the available Cd content in the soil was reduced by 50%-53%,and the content of Cd in edible parts was reduced by 41%-53%,the effect of mixed application of modifiers is better than single application;The edible parts of the modified konjac and okra have not decreased to less than the food safety standard limit(0.2mg/kg),therefore,it is temporarily not recommended to plant on this kind of polluted farmland.