Methylmercury photodegradation in paddy water: An overlooked process mitigating methylmercury risks.

Autor: Zhong H; School of the Environment, Nanjing University, State Key Laboratory of Pollution Control and Resource Reuse, Nanjing, Jiangsu Province, PR China., Zhou H; School of the Environment, Nanjing University, State Key Laboratory of Pollution Control and Resource Reuse, Nanjing, Jiangsu Province, PR China., Li Y; Key Laboratory of Marine Chemistry Theory and Technology (Ministry of Education) and College of Chemistry and Chemical Engineering, Ocean University of China, Qingdao, Shandong Province, PR China. Electronic address: liyanbin@ouc.edu.cn., Li C; Institute of Environmental Research at Greater Bay Area, Guangzhou University, Guangzhou, Guangdong Province, PR China., Tsui MT; School of Life Sciences, Earth and Environmental Sciences Programme, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong SAR, PR China; State Key Laboratory of Marine Pollution, City University of Hong Kong, Kowloon Tong, Kowloon, Hong Kong SAR, PR China., Mitchell CPJ; Department of Physical and Environmental Sciences, University of Toronto Scarborough, 1265 Military Trail, Scarborough, Ontario M1C 1A4, Canada., Zhou Y; School of the Environment, Nanjing University, State Key Laboratory of Pollution Control and Resource Reuse, Nanjing, Jiangsu Province, PR China., Yang Y; School of the Environment, Nanjing University, State Key Laboratory of Pollution Control and Resource Reuse, Nanjing, Jiangsu Province, PR China., Chen L; Key Laboratory of Geographic Information Science (Ministry of Education), School of Geographic Sciences, East China Normal University, Shanghai, PR China., Ren H; School of the Environment, Nanjing University, State Key Laboratory of Pollution Control and Resource Reuse, Nanjing, Jiangsu Province, PR China., Tang W; School of the Environment, Nanjing University, State Key Laboratory of Pollution Control and Resource Reuse, Nanjing, Jiangsu Province, PR China. Electronic address: tangwenli@nju.edu.cn.
Jazyk: angličtina
Zdroj: Water research [Water Res] 2024 Apr 01; Vol. 253, pp. 121332. Date of Electronic Publication: 2024 Feb 17.
DOI: 10.1016/j.watres.2024.121332
Abstrakt: Photodegradation is critical to reduce the potent neurotoxic methylmercury (MeHg) in water and its subsequent accumulation along food chains. However, this process has been largely ignored in rice paddies, which are hotspots of MeHg production and receive about a quarter of the world's developed freshwater resources. Here, we reported that significant MeHg photodegradation, primarily mediated by hydroxyl radicals, occurs in the overlying water during rice growth. By incorporating field-measured light interception into a rice paddy biogeochemistry model, as well as photodegradation rates obtained from 42 paddy soils stretching ∼3500 km across China, we estimated that photodegradation reduced MeHg concentrations in paddy water and rice by 82 % and 11 %, respectively. Without photodegradation, paddy water could be a significant MeHg source for downstream ecosystems, with an annual export of 178 - 856 kg MeHg to downstream waters in China, the largest rice producer. These findings suggest that photodegradation in paddy water is critical for preventing greater quantities of MeHg entering human food webs.
Competing Interests: Declaration of competing interest None.
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Databáze: MEDLINE
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