• 关键词：水稻土  汞  甲基汞  水分条件  淹水  SRB

• 基金项目：国家自然科学基金（No.41203084，41371463）；国家水体污染控制与治理科技重大专项（No.2015zx07103-007）；国家重点研发计划（No.2016YFD0201306）

• 郑顺安
• 1. 农业部农业生态与资源保护总站, 北京 100125;2. 农业部环境保护科研监测所, 天津 300191

• 周玮
• 农业部农业生态与资源保护总站, 北京 100125

• 尹建锋
• 农业部农业生态与资源保护总站, 北京 100125

• 薛颖昊
• 农业部农业生态与资源保护总站, 北京 100125

• 黄宏坤
• 农业部农业生态与资源保护总站, 北京 100125

• 郑向群
• 农业部环境保护科研监测所, 天津 300191

• 摘要：通过培养实验，研究了70%田间持水量、干湿交替及淹水等3种水分管理方式对外源Hg在稻田土壤中甲基化的动态过程.外源添加浓度为5 mg·kg^-1 Hg²⁺，培养时间为42 d.结果表明，70%田间持水量下，土壤甲基汞（MeHg）含量基本保持稳定，平均为11.55 μg·kg^-1；淹水条件下，土壤MeHg含量呈上升趋势，平均为30.70 μg·kg^-1，约为70%田间持水量的2.7倍；干湿交替条件下，土壤MeHg呈现"涨-消"的波动趋势，平均含量为20.41 μg·kg^-1，约为70%田间持水量的1.7倍.培养结束后土壤MeHg含量和占总Hg比例依次为：淹水（37.42 μg·kg^-1，0.76%）>干湿交替（16.08 μg·kg^-1，0.33%）> 70%田间持水量（11.75 μg·kg^-1，0.25%），表明淹水条件有利于稻田土壤中汞的甲基化.Elovich方程可以拟合淹水条件下稻田土壤MeHg含量变化的动力学过程，表明土壤中MeHg含量在试验前期（7 d）快速升高，随后呈现缓慢增长的趋势.培养期间，各水分处理下稻田土壤中硫酸盐还原菌（SRB）数量均表现为上下波动式的周期性变化特征，均值分别为（533 ±31）cfu·g^-1（70%田间持水量）、（615 ±39）cfu·g^-1（淹水）和（509 ±43）cfu·g^-1（干湿交替）.相关分析表明，土壤MeHg含量与硫酸盐还原菌（SRB）数量、氧化还原电位（E_h）、土壤含水量之间的相关性达到了显著性水平（p < 0.05），与其他因素之间无显著相关性.可以推测，在稻田土壤淹水形成的厌氧环境中，SRB可能是生物汞甲基化的优势菌群.

• Abstract：The dynamic process of exogenous Hg in the paddy soil was studied by 3 water management methods, such as 70% field water holding capacity, dry/wet alternation and flooding. The exogenous Hg concentration was 5 mg·kg^-1, and the incubation time was 42 d. The results showed that soil methylmercury (MeHg) content was basically stable, with an average of 11.55 μg·kg^-1 under 70% field water holding capacity; showed an upward trend, with an average of 30.70 μg·kg^-1, about 2.7 times of 70% field water capacity under flooding; and showed a trend of "rising and eliminating", with an average content of 20.41 μg·kg^-1, about 1.7 times of 70% field water capacity under dry/wet alternation. After cultivation, MeHg content of soil and the total proportion of Hg was as follows:the flooding (37.42 μg·kg^-1, 0.76%) > dry/wet alternate (16.08 μg·kg^-1, 0.33%) > 70% field water holding capacity (11.75 μg·kg^-1, 0.25%), which showed that the flooding conditions are favorable to methylation of mercury in paddy soil. Elovich equation can fit the dynamic process of MeHg content change in paddy soil under flooding condition. It shows that the content of MeHg in soil increases rapidly at the beginning of experiment (7 d), and then presents a trend of slow increase. During the culture period, the quantity of sulfate reducing bacteria (SRB) in the soil of paddy soil under water treatment showed fluctuation characteristics, the mean values were (533+31) cfu·g^-1 (70% field water holding capacity), (615+39) cfu·g^-1 (flooding) and (509+43) cfu·g^-1 (dry/wet alternation). Correlation analysis showed that soil MeHg content and sulfate reducing bacteria (SRB), the number of oxidation reduction potential (E_h), the correlation between soil water content reached a significant level (p < 0.05), no significant correlation with other factors. It can be inferred that SRB may be the dominant group of mercury methylation in the anaerobic environment of paddy soil flooding.

• Key words：paddy soil  mercury  methymercury  moisture retime  flooding  SRB

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