| The mining and smelting of Wanshan mercury mine in Guizhou lead to different degrees of mercury pollution in the surrounding soil,and rice intake is the main way for local residents to expose total mercury and methylmercury.It is of great significance to carry out research on the remediation of mercury-contaminated soil to eliminate the environmental risks of mercury-contaminated soil and ensure the quality and safety of agricultural products and human health.In this study,the rice pot experiment was conducted to study the changes of total mercury and methylmercury content in soil at different growth stages of rice,and the soil microorganisms were detected by 16S r RNA high-throughput sequencing.The effects of cow dung（CD）,Pig manure（PM）,chemical fertilizer（CF）,cow dung combined with chemical fertilizer（CDCF）and Pig manure combined with chemical fertilizer（PMCF）on soil mercury methylation were explored,The absorption,transportation,and enrichment patterns of mercury and methylmercury in rice can provide a theoretical basis for the green remediation and safe utilization of mercury contaminated soil.（1）After pyrolysis remediation,the total mercury content of mercury-contaminated soil decreased from 496.49 to 62.15 mg?kg-1,and the removal rate was 87.48%.The two soil mercury forms are mainly oxidizable and residual mercury,accounting for 99%.During the rice growth period,the concentration of methylmercury in the two soils ranged from 3.13 to 26.73μg?kg-1.Compared with the non-fertilized treatment,HCD,HCDCF,HCF,HPM and HPMCF all increased the content of methylmercury in the soil by 55.89%,82.21%,34.45%,63.61%and 94.05%,respectively.Pig manure combined with chemical fertilizer had the greatest impact on soil mercury methylation.The content of methylmercury in soil after pyrolysis was positively correlated with organic matter and alkali-hydrolyzable nitrogen,and negatively correlated with p H,available phosphorus and available potassium.（2）The results of microbial detection showed that HCD,HCF and HPM increased the number of OTUs of soil bacteria by 69.8%,68.8%and 64.0%,respectively.Cow dung had the greatest influence on the number of OTUs of soil bacteria,and the number of OTUs was positively correlated with the content of total nitrogen and alkali-hydrolyzed nitrogen.In the two soils,Proteobacteria,Bacteroidetes and Actinobacteria were the dominant bacteria phylum,and Pedobacter,Sphingomonas and Flavobacterium were the dominant bacteria genus.（3）In the two soils,sulfate-reducing bacteria（10 families）and other bacteria（3 families）were mercury methylation functional microorganisms.The relative abundance of four families reached 0.2%,which were Geobacteraceae（0.31%～1.08%）,Bacillaceae（0.01%～0.61%）and Desulfobulbaceae（0.06%～0.22%）and Desulfuromonadaceae（0.02%～0.26%）.The main influencing factors of mercury methylation functional microbial community diversity in soil after pyrolysis and mercury contaminated soil in mining area were alkali-hydrolyzed nitrogen,p H,available phosphorus and alkali-hydrolyzed nitrogen,organic matter and available potassium,respectively.（4）The distribution of total mercury in rice organs was root>leaf>stem>husk>rice.The total mercury content of rice treated with HCD and HCF increased by 199.8%and 96.9%,respectively.The distribution of methylmercury in rice organs was root>rice>husk>stem>leaf.The content of methylmercury in rice treated with HCF and HPM increased by 17.5%and 46.6%.In summary,fertilizer application improved soil nutrient status,changed microbial diversity and community structure,and increased soil methylation rate.The methylation rate of pig manure alone was higher than that of chemical fertilizer and cow dung.The total amount of soil microorganisms and methylation rate of pig manure combined with chemical fertilizer were the highest.Attention should be paid to the management of fertilizer types after soil remediation by low temperature pyrolysis. |
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