Study On Soil Heavy Metal Pollution Characteristics And Oxidative Stress Effect Of Crops Under Tungsten Stress In Tungsten Ore Area

Gannan area of Jiangxi Province is known as the "tungsten capital of the world".In recent years,with the vigorous exploitation of tungsten ore,the mining area and the surrounding soil have serious heavy metal pollution.Based on the field research method,this paper took a tungsten mining area in Gannan as the research object,and carried out the evaluation of soil heavy metal pollution in the mining area,the analysis of the concentration of heavy metals in local crops and the correlation between the two.Through potting experiments,the oxidative stress response of crops under different tungsten concentrations was explored,so as to reveal the ecotoxic rational mechanism of tungsten in crops,in order to provide scientific basis for soil pollution prevention and control,crop safety production and tungsten risk value formulation in local mining areas.The main conclusions of this paper are as follows:(1)In the tungsten ore area and surrounding soils,the average concentrations of heavy metals Cr,Cu,Zn,Cd,Pb and W exceeded the background values of Jiangxi Province,and the contents of Cd and W were 16.82 times and 5.67 times of the background values of Jiangxi Province,respectively.The single-factor index method,land accumulation index method,potential ecological risk index method and grey hierarchy analysis method were used to evaluate the soil heavy metal pollution in the study area,and the results showed that the soil heavy metal pollution level was high within 3 km from the mine.The farther away from the mining area,the lower the level of heavy metal pollution.(2)Through the investigation and analysis of the heavy metal content of rape flower,garlic,cabbage,pea flower,green cabbage and oil wheat in the farmland around the tungsten mining area,the results showed that the Zn content was the highest in the aboveground part(edible part)of the six crops,and the average content of each heavy metal element was:Zn>Pb>Cu>Cr>W>Cd>As,and the heavy metal content in the aboveground part exceeded the limits of GB2762-2022 national food safety standard.The accumulation characteristics of heavy metals in the underground part(roots)and aboveground parts were as follows: the underground part > the aboveground part of most crops(the average value of heavy metal content in stems and leaves);The BCF(enrichment coefficient)of heavy metals Cd,Pb and Zn in the aboveground and underground parts of crops is the best,among which the BCF of heavy metals in the aboveground part is: Cd>Pb>Zn>Cr>Cu>W>As,and the BCF of heavy metals in the underground part is: Cd>Pb>Zn>Cu>As>W>Cr.Among the local crops,rape flower,garlic,pea flower and oil wheat have strong transport capacity for heavy metal Cr,among which garlic has the most extensive transport capacity for heavy metal,and its TF(transport coefficient)for Pb,Zn,Cr,W and As is greater than 1.Higher Pb and W elements in the soil in the study area can promote the absorption of As,W and Cr in the underground part of crops,higher Zn and Cu elements can promote the absorption of Cd in the aboveground part of crops,and the absorption of Zn,Cd and Cu in the underground part of crops can promote the accumulation of W,Cd and Cr in the aboveground part,and the transport mode of Cu elements in crops from underground to aboveground parts is an active absorption process.(3)The effects of different concentrations of tungsten(0,300,600,900,1200 mg/kg)on oxidative stress in crops were further explored through pot experiments,and the results showed that compared with CK(control group),the activities of CAT(catalase enzyme)were stimulated by tungsten when the tungsten concentrations were 600 mg/kg and 900 mg/kg,respectively,while the CAT activity was inhibited by tungsten at other tungsten concentrations.The POD(peroxidase)activity in the aboveground and underground parts was significantly different from that of CK(P<0.05),and the POD activity in the crop was stimulated by tungsten,and tungsten stimulated the SOD(superoxide dismutase)activity levels of WS1 and WS2 at different tungsten concentrations.Compared with CK,the CAT activity of CC1(Artemisia annua leaf)increased first and then decreased with the increase of tungsten concentration,and when the tungsten concentration was lower than 600 mg/kg,CAT activity was stimulated by tungsten,and then with the increase of tungsten concentration,CAT activity was inhibited by tungsten.The CAT activity of CC2(Artemisia stalk)was inhibited by tungsten;Compared with CK,the POD activity of the aboveground and underground parts was significantly different(P<0.05),and the POD activity of crops was stimulated by tungsten,and when the tungsten concentration was 900 mg/kg,the SOD activity of CC1 was inhibited by tungsten,and the SOD activity at other tungsten concentrations was stimulated.In CC2,tungsten inhibits SOD activity at 300 mg/kg and 900 mg/kg and tungsten concentration at 600 mg/kg and 1200 mg/kg.