| Mercury is a global heavy metal pollutant.To further understanding of the occurrence patterns and migration characteristics of mercury from different sources of pollution,this paper studies the soil mercury in Wanshan mine area and Dalong coal-fired power plant area in Tongren,Guizhou Province.The pollution-free soil in Huaxi,Guiyang,was used as a control.The main research aimed to investigate the morphological changes of mercury in the soil and the influencing mechanisms under different pollution sources and land use patterns.Conclusion as below:1.The total mercury content in Wanshan mercury mine ranged from 0.308 to 72.2 mg·kg-1,with an average of 22.7 mg·kg-1;The mercury content in Dalong coal-fired power plant ranged from 0.304 to 0.899 mg·kg-1,with an average of 0.648 mg·kg-1;while the mercury content in the unpolluted area ranged from 0.062 to 0.408 mg·kg-1,with an average value of 0.179 mg·kg-1.In the horizontal direction,the content of mercury in the soil near the pollution source in the Wanshan mercury mining area is relatively high,and it decreases significantly with the increase of the distance;In the Dalong coal-fired power plant area,the soil mercury first decreased and then increased within 2.5 km from the coal-fired power plant;there was no obvious change in soil mercury distribution in the control area.There are some differences in the distribution of mercury in soils in different polluted areas.The mercury in the Wanshan mercury mining area is mainly in the residue state,followed by the organically bound state,accounting for 66.6%and 30.0%of the total mercury,respectively;soil mercury in Dalong coal-fired power plant The organic bonding state dominates,accounting for 75.7%of the total mercury,residual mercury is only 17.5%of the total mercury.Soil pH affected the activity of mercury in soil to a certain extent.The percentage of dissolved mercury and exchangeable mercury in total mercury in Wanshan mercury mining area showed extremely significant negative correlation with pH,and the correlation coefficient was-0.640**.The percentage of oxidized mercury in the power plant area was significantly negatively correlated with pH,and the correlation coefficient was-0.641*.2.The total soil Hg content from high to low under different land use patterns in the Wanshan mercury mining area is as follows:wasteland(37.4mg·kg-1)>paddy field(18.2mg·kg-1)>dryland(12.6mg·kg-1),The concentration of mercury is mainly affected by the strength of the source.The results of the difference significance analysis showed that the differences in the distribution of soil mercury in different land use types did not reach a significant level,and land use patterns did not have a significant impact on the distribution of soil mercury.The results of correlation analysis showed that the soil pH under different land use patterns had a significant effect on the activity of mercury in the soil.The percentage of oxidized mercury and organic bound mercury in total mercury in the wasteland soil was negatively correlated with soil pH,and the correlation coefficients were-0.991**and-0.936*;There was a significant negative correlation between soil pH and the percentage of oxidized mercury in dry land,with a correlation coefficient of-0.933**;there was a significant positive correlation between soil pH in the paddy field and the percentage of residual mercury,with a correlation coefficient of 0.949.*.The percentage of oxidized mercury and organic bound mercury in the wasteland soil as a percentage of total mercury was positively correlated with organic matter,and the correlation coefficients were 0.896*and 0.948*.There was a significant positive correlation between organic matter in the paddy soil and the percentage of residual mercury,and the correlation coefficient was 0.891*,the effect of organic matter on the distribution of mercury in soil under different land use patterns remains to be further studied.3.In the vertical direction,the total soil mercury content under different land use patterns generally decreases through the soil depth.Mercury in the soil is mainly concentrated in the0-40cm soil layer,indicating that the source of soil Hg,is mainly from the input of exogenous substances.Different types of land use have certain differences in the vertical distribution of mercury in profile soils.The content of mercury in each form decreased with the increase of soil depth,but its percentage showed an irregular increase or decrease under different land use patterns.The percentage of oxidized mercury and organically bound mercury in paddy fields increased with the increase of soil depth,while the percentage of residual mercury showed a decreasing trend;oxidized mercury in the wasteland increased or decreased irregularly with the increase of soil depth,and the organic binding state The percentage of mercury decreases with the increase of soil depth,while the residual mercury shows an increasing trend;the percentage of oxidized mercury in dryland increases with depth,and the percentage of organically combined mercury decreases with depth,while the residual state Mercury shows an increasing trend. |
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