Tracing Mercury Contamination In The Environment Around A Coal-fired Power Plant And The Effects Of Mercury Contamination On Microbial Diversity

The coal-fired power plants are one of the most important sources of mercury emissions.Mercury in coal could discharge to the atmosphere with flue gas after high-temperature combustion and then leading to water and soil pollution.Therefore,it is particularly important to figure out the contribution rate and influence degree of mercury emissions from power plants to the surrounding areas.In this study,a large coal-fired power plant in the southeast coast was selected to determine the mercury isotope composition of different environmental samples and microbial composition in the surrounding area,try to analyze the contribution rate of the power plant to environment and impact on soil and air microorganisms.The main results are as follows:?1?The variation range of?²⁰²Hg in the power plant area is-1.26‰?-0.97‰,and the range of?¹⁹⁹Hg is 0.06‰?0.24‰;the range of?²⁰²Hg in soil is-1.19‰?-0.98‰,and the range of?¹⁹⁹Hg in soil is-0.01‰?0.05‰;the range of?²⁰²Hg in air particulate matter is-1.54‰?-0.76‰,the range of?¹⁹⁹Hg is-0.06‰?0.09‰;the range of?²⁰²Hg in lettuce leaves is-2.82‰?-1.34‰,the range of?¹⁹⁹Hg value is-0.29‰?-0.04‰.The isotopic composition of atmosphere,water and plant samples shows that there is obvious fractionation,and the isotopic fractionation in soil samples is less obvious.It is calculated that the coal-fired power plant contribute 9.4%to37.5%of mercury pollution in the study area,and the contribution rate will increase first and then decrease as the distance from the power plant increases.?2?The difference in total mercury concentration between paddy soil and dryland soil in the study area is not much different,while the concentration of methylmercury in paddy soil is significantly higher than that in dryland soil.The diversity and uniformity of the microbial community in the paddy soil are higher than those in the dryland soil;meanwhile,the dominant bacterial communities in the paddy soil and the dryland soil are very different in diversity and abundance.The correlation of mercury and methylmercury pollution in soil with microbial community abundance and microbial community diversity is relatively small.The concentrations of mercury and methylmercury in paddy soil were negatively correlated with the relative abundance of Nitrospira,but positively correlated with the relative abundance of Deltaproteobacteria,Actinobacteria,Bacteroides,and Firmicutes;In dryland soil,methylmercury concentration is only slightly positively correlated with the relative abundance of Bacteroidetes;total mercury concentration is positively correlated with Gammaproteobacteria,Betaproteobacteria,and Firmicutes,Negatively correlated with Acidobacteria and Chloroflexi.The abundance of potential mercury methylated microorganisms in paddy soil is higher than that in upland soil,and no functional gene for mercury methylation,hgcA gene,was detected in the microbial DNA of upland soil.The abundance of hgcA-Arc gene in paddy soil is higher than that of hgcA-Del gene,and the abundance of hgcA-Del gene is significantly positively correlated with the concentration of methylmercury.?3?The Alpha diversity index in the study area is less than the soil samples in the study area,indicating that the number and abundance of atmospheric microorganisms are small.The correlation analysis results of particulate matter and mercury and microbial diversity indicate that the number of airborne microorganisms will increase with the increase of particulate matter concentration,and will increase first and then decrease with the increase of mercury concentration;but there is no obvious correlation between diversity and particulate matter mercury concentration.The concentration of particulate matter was significantly positively correlated with Firmicutes,Proteobacteria,Gemmatimonadetes,Clostridia,and Negativicutes?p<0.05?,and negatively correlated with Cyanobacteria,Gammaproteobacteria,and Bacilli?p<0.05?;particulate mercury concentration was significantly positively correlated with Bacteroidetes,Gemmatimonadetes,Negativicutes?p<0.05?,and significantly negatively correlated with Gammaproteobacteria?p<0.05?.