互花米草入侵对黄河三角洲湿地土壤汞及甲基汞的影响

Effects of Spartina alterniflora Invasion on Soil Mercury and Methylmercury in Yellow River Delta Wetland

互花米草(Spartina alterniflora)入侵已成为中国滨海湿地面临的严重问题,但是互花米草入侵是否会改变河口湿地汞甲基化过程的研究较少。于2019年7月5日至7月11日,采集黄河三角洲芦苇湿地、碱蓬湿地、柽柳湿地、光滩及不同入侵年限互花米草湿地(入侵5 a、7 a、10 a、15 a和20 a)的土壤样品,对比分析互花米草湿地与其他采样地土壤中全汞和甲基汞的含量差异,探究互花米草入侵影响下甲基汞含量变化的主要影响因子。研究结果表明,互花米草湿地土壤中全汞质量比平均值为75.74μg/kg,显著小于其他采样地;互花米草湿地土壤中甲基汞质量比平均值为4.19μg/kg,甲基汞占全汞比例的平均值为6.16%,大于其他采样地,互花米草具有较高的汞甲基化潜力;随着入侵年限增加,互花米草湿地土壤中全汞含量减小,而甲基汞含量和甲基化率总体上增大;所有采样地土壤中全汞含量与铁元素含量显著正相关,互花米草湿地土壤中甲基汞含量与全硫含量显著正相关,硫元素含量是影响互花米草湿地土壤中甲基化的重要因子。

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 75.74μg/kg,significantly lower than those of other sampling sites.The average methylmercury mass ratio in the soil of Spartina alterniflora wetlands was 4.19μg/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.