Effects of Spartina alterniflora Invasion on Soil Mercury and Methylmercury in Yellow River Delta Wetland
The invasion of Spartina alterniflora had became a serious problem for coastal wetlands in China.However,there was limited research on whether the invasion of Spartina alterniflora will alter the methylmercury process in estuarine wetlands.In July 2019,soil samples were collected from Phragmites australis wetlands,Suaeda glauca wetlands,Tamarix chinensis wetlands,bare flats,and Spartina alterniflora wetlands of different invasion durations(5 years,7 years,10 years,15 years,and 20 years)in the Yellow River Delta.A comparative analysis was conducted on the differences in total mercury and methylmercury content between Spartina alterniflora wetlands and other sampling sites'soils.The main influencing factors of methylmercury content changed under the influence of Spartina alterniflora invasion were investigated.The research results indicated that the average total mercury mass ratio in the soil of Spartina alterniflora wetlands was 75.74 μg/kg,significantly lower than those of other sampling sites.The average methylmercury mass ratio in the soil of Spartina alterniflora wetlands was 4.19 μg/kg,with an average methylmercury-to-total mercury ratio of 6.16％,which were higher than those of other sampling sites.Spartina alterniflora exhibited a higher potential for mercury methylation.As the duration of invasion increases,the total mercury content in the soil of Spartina alterniflora wetlands decreased,while the methylmercury content and the proportion of methylation rate generally increased.The total mercury content in all sampled soils was significantly positively correlated with iron element content.In Spartina alterniflora wetland soils,the methylmercury content was significantly positively correlated with total sulfur content,indicating that sulfur was an important factor influencing the proportion of methylmercury in Spartina alterniflora wetland soils.
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