Research On Heavy Metal Content And Migration Characteristics Of Crops In Linhuan Mining Area

Over the last decades,due to the rapid development of Chinese industry and economy,heavy metal pollution has increased rapidly,which has led to the accumulation of heavy metals in the environment,and therefore affects the accumulation of heavy metals in crops.Some mining areas,farmland and forests were more prone to high concentrations of at least two types of heavy metals.In addition,many types of heavy metals could accumulate in many plant species.The morphology and physiological properties of crops would be severely harmed by heavy metals,leading to a decline in the growth performance of various organs underground and above ground,an increase in nutrient and water absorption,cell division and other activities were disturbed,and plasma membrane permeability changes.This paper selected the Linhuan coal mining subsidence area in Huaibei as the research object,collects soil and crop samples,and analyzes the heavy metal pollution.Based on this,two types of heavy metals were selected for indoor simulation pot experiment,with vegetables and wheat as the test crops.The average concentration of Zn,Ni,and Pb in the stems and leaves of Chinese cabbage exceeded the national pollutant limit.The effects of single and compound heavy metals on the morphology and physiological properties of crops under the conditions of indoor simulated pot experiments,as well as the changes in the cumulative absorption of heavy metals by crops,were studied.The main results were as follows:(1)The content of Pb,As and Hg was the highest in corn leaves,while the content of Cu,Zn,Cd and Ni was the highest in corn roots.The average value of heavy metal content in each part of corn is Zn>Cu>Ni>Pb>As>Cd>Hg.Cu,Zn,Ni,Pb and Hg mainly accumulated in the roots of wheat.Cd and As mainly accumulated in the stems and leaves of wheat,indicated that different parts of wheat had different absorption capacities for heavy metals.Ingestion of corn,wheat and Chinese cabbage constituted a total health risk of more than 1,and local residented may have hidden health risks after eating.(2)Corn had a strong ability to absorb and enrich Zn,and had the least enrichment of As.The BCF values of Cu,Zn,Cd and Ni in maize were: root>stem>leaf>grain and Pb,As and Hg:leaf>root>stem>grain.The transport coefficients of Pb,As,and Hg from the stem to the leaf of maize were greater than 1.The TF root-stem leaf of As in wheat was higher.Except for As is mainly concentrated in the stem and leaf,other heavy metals are concentrated in the root.The enrichment and transport coefficients of heavy metals in pakchoi are all less than 1.(3)The biomass of pakchoi and wheat under heavy metal stress showed "low promotion and high suppression",and the combined effect of Cd and Zn was more significant than that of single stress.Single and compound heavy metal stress significantly inhibited the stem length and leaf size of Chinese cabbage,and also reduced the length,diameter and tiller number of wheat roots to varying degrees.The treatment with low concentration of heavy metals promoted the growth of wheat leaves and increased the length,width and area of wheat leaves;treatment with high concentrations of heavy metals inhibited the length,width and area of their leaves.(4)The heavy metal treatment caused the increase of CAT in pakchoi to varying degrees;the heavy metal treatment caused the wheat CAT activity to show "low promotion and high inhibition".With the increase of the concentration of heavy metal treatment,the POD activity in pakchoi and wheat first increased and then decreased,and the activity of compound heavy metals decreased compared with single heavy metal stress.Compound heavy metal treatment significantly reduced the MDA content of pakchoi.As the concentration of heavy metals increased,the MDA content in wheat showed an overall upward trend.Similar to the results of Chinese cabbage,the content of MDA decreased after adding Zn compared with single Cd treatment.(5)The content of Cd and Zn in cabbage and wheat increased with the increase of heavy metal content in the soil,and the content of heavy metals in different parts: root>stem>leaves.The addition of Zn promoted the absorption of Cd by the two crops.At this time,Zn had a synergistic effect on the absorption of heavy metal Cd;while the addition of Cd inhibits the absorption of Zn by wheat,at this time Cd had an antagonistic effect on the absorption of heavy metal Zn by wheat.The addition of Zn inhibited the two crops from transporting more Cd from underground to above ground,and the simultaneous action of Zn and Cd had an antagonistic effect on the transport of Cd.