AbstractWe studied the relationship between the change of methylmercury (MeHg) content and the number of sulfate-reducing bacteria (SRB) in Suaeda Heteroptera soil with different salinity at 20°C and 30°C. Salinity variation affects soil methylmercury content. We studied whether temperature variation is the dominant factor in SRB affecting mercury methylation. Our research shows that proper salinity favored the production of MeHg in soil; appropriate temperature increase could enhance SRB activity and MeHg output, and the mercury methylation effect of SRB was more significant at 30°C. SRB was present in the test soils at different salinities, and the amount of SRB did not vary regularly in the flooded salinity gradient. The SRB content in the culture soil was higher at 30°C than at 20°C. There was no significant correlation between SRB numbers and MeHg in the culture soil at 20°C. Soil MeHg content and SRB count had a significant positive correlation in the first 15 days of incubation at 30°C, whereas there was no correlation between the two in the later period.Practical ApplicationsSuaeda Heteroptera Kitag wetlands are a typical wetland type in the Liaohe estuary. Recently, with the development of paddy fields, freshwater resources in Liaohe estuary have decreased year by year, soil salinity has increased, and Suaeda Heteroptera Kitag wetland has degraded year by year, and increasing salinity is the main reason for alkali poncho degradation. With the global warming, high temperatures in Liaoning have increased. Sulfate-reducing bacteria are important influencing factors of mercury methylation, while salinity and temperature changes affect methylmercury (MeHg) and SRB content. Therefore, understanding the effects of different salinity gradients on methylmercury and SRB at a certain temperature will help to reduce mercury methylation. However, it is difficult to achieve the salinity gradient required in the actual environment, so indoor simulation experiments are used for research. Our results showed that proper salinity favors the production of MeHg in soil, proper elevated temperature increases the activity of SRB and MeHg production, and the methylation of Hg by SRB is more pronounced at 30°C. SRB was present in the soil under all salinity conditions, and the amount of SRB in the soil did not change regularly with increasing salinity of flooded water.

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