Study On Trace Metals Migration In Soil-Vegetable System With Different Irrigation Methods

Long-term wastewater irrigation is one of the main reasons for the accumulation of trace metal elements in the soil surface of farmland.Soil trace metal pollution and agricultural product pollution caused by wastewater irrigation in China have been widely reported.Although the government and other relevant departments advocate the use of freshwater instead of wastewater to irrigate polluted farmland to reduce soil metal pollution and agricultural product pollution.But due to various reasons such as water shortage,many places still use wastewater to irrigate farmland.Baiyin City is located in the central region of Gansu Province.Copper,zinc,lead,manganese and gold are abundant in this area.It is a resource-based area with a long mining history of more than 60 years.In this area,the research work on chemical pollution behavior of trace metals in soil-vegetable system by different irrigation methods started relatively late,and systematic experimental research and research on compound pollution of trace metal elements are almost blank.In this paper,through field control experiments in the field,the soil with a history of 60 years of wastewater irrigation was selected as the test soil for the field control pot experiment.Four kinds of vegetables that are more common in the local area: cabbage,rape,carrot and potato were used as test materials.Irrigation method was used as a treatment method to study the migration and enrichment of trace metals As,Cd,Cr,Cu,Pb,Zn in the soil-vegetable system,and the effects of different irrigation methods on the absorption and accumulation of trace metals in vegetables.A series of results were obtained as follows:(1)We found that the effect of short-term freshwater irrigation on the concentration of trace metals in the soil and vegetables of vegetable cultivation was not significant.The average concentrations of trace metals(except Cr and Cu)measured in the soil of vegetable cultivation under different irrigation methods.All exceed the environmental quality evaluation standards for the origin of edible agricultural products.(2)There was no significant correlation between the morphological characteristics of vegetables and the content of trace metal elements in different parts of vegetables under different irrigation methods,and the content of trace metal elements in different parts showed a certain correlation.(3)The health risks of vegetables are high under different irrigation methods,and the risks of carrots are relatively low.Most of the risks are due to As,Cd and Pb.Freshwater irrigation can reduce As(5.85-43.8%),Cd(44-59.4%)risk.(4)The content of trace metals in different parts of vegetables are different,among which the trace metal concentration in the underground part of vegetables is lower,and the lowest value of trace metal concentration appears more frequently after the root of clean water is higher,which indicates that the irrigation of clean water root is beneficial to the growth of non-leaf vegetables.