Effect of moisture regime on the mercury methylation in paddy soil
ZHENG Shun'an;ZHOU Wei;YIN Jianfeng;XUE Yinghao;HUANG Hongkun;ZHENG Xiangqun;Rural Energy & Environment Agency,Ministry of Agriculture;Agro-Environmental Protection Institute,Ministry of Agriculture;
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(Me Hg)content was basically stable,with an average of 11.55μg·kg~(-1)under 70%field water holding capacity;showed an upward trend,with an average of 30.70μg·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 20.41μg·kg~(-1),about 1.7 times of 70%field water capacity under dry/wet alternation.After cultivation,Me Hg content of soil and the total proportion of Hg was as follows:the flooding(37.42μg·kg~(-1),0.76%)dry/wet alternate(16.08μg·kg~(-1),0.33%)70%field water holding capacity(11.75μg·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 Me Hg content change in paddy soil under flooding condition.It shows that the content of Me Hg 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 Me Hg content and sulfate reducing bacteria(SRB),the number of oxidation reduction potential(E_h),the correlation between soil water content reached a significant level(p0.05),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.
【Fund】： 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)~~
【CateGory Index】： X53
【CateGory Index】： X53