Study On Methylation Ability Of Different Forms Of Mercury Selenide

In this study,paddy soils of Nantong,Suihua and Nanjing were used to study the methylation abilityof mercury selenides in different forms,mainly including the following contents:?1?Nanoparticles mercury selenide with particle size of 45.2±0.5 nm were synthesized by chemical synthesis in the laboratory,and bulkscaled mercury selenide was generated by natural agglomerationof nanoparticles.?2?There are five treatment groups?Blank,Inorganic mercury,Inorganic mercury+sodium selenite,NanoHgSe and BulkHgSe?,and methyl mercury,the total mercury,Fe²⁺,acid volatile sulfide?AVS?,total selenium in soil and pH,Eh,methyl mercury in overlying water were monitored during the experiment.The results showed that the methylation efficiency of inorganic mercury was the highest?1.00%in Nantong soil,3.35%inSuihua soil,0.99%in Nanjing soil?.Selenium application can significantly reduce the content of methyl mercury in soil?content of MeHg reduced by 70.9%in nantong soil,72.0%in Suihua soil and 63.0%in nanjing soil on average?.NanoHgSe has the ability of methylation,its methylation efficiency is 0.20%in Nantong soil,0.14%in Suihua and 0.28%in Nanjing soil on average.In Nantong and Nanjing paddy soils,the amount and methylation rate of methylmercury in the inorganic mercury and sodium selenite group and the nanoHgSe group were similar,indicating that the methylation ability of the nano-mercuric selenide particles in some soils was relatively strong,which was similar to the methylation ability of the inorganic mercury after selenium application.The methylation efficiency of BulkHgSe group was significantly lower than that of other treatment groups except the blank group.?3?A high-concentration of nanoHgSe was set up to study the changes of nanoHgSe during the experimental by using TEM-EDX.The results showed that before and after the experiment,nanoHgSe was agglomerated in the three types of paddy soils,which was consistent with the mineralization process of mercury selenide in the soil.?4?NanoHgSe methylation microorganisms were investigated by adding different microbial inhibitors?blank group,methanogenic bacteria inhibition group,sulfate reducing bacteria inhibition group,common eukaryotic microbial inhibition group?.The results showed that the sulfate-reducing bacteria in Nantong soil were the microorganisms of mercury selenide methylation,and the content of methyl mercury was significantly inhibited by the addition of molybdate?10.4%?.In Suihua and Nanjing paddy soils,there were sulfate reducing bacteria and methanogenic bacteria in the methylation of mercury selenide.The methylmercury content in the methanogenic inhibitory group was significantly reduced by 95.7%and 38.5%,respectively,in Suihua and Nanjing paddy soilsrespectively.The content of methyl mercury in the sulfate-reducing bacteria inhibition group was also significantly reduced,which was 90.6%and 69.2%in suihua and nanjing paddy soils,respectively.?5?Desulfovibrio desulfuricans subsp.Desulfuricans and iron reducing bacterium Shewanella oneidensis Mr-1 were used to explore the methylation of nano-mercury selenide in the pure bacteria system.However,the sulfate reducing bacterium Desulfovibrio desulfuricans subsp.Desulfuricans has a weak methylation ability,which is not suitable for being used as a strain to explore the methylation ability of nano-mercury selenide in the pure bacteria system,and the methylation of nano-mercury selenide in the pure bacteria system needs to be further explored.