Management strategies to reduce microbial mercury methylation in constructed wetlands: Potential routes and future challenges.

Constructed wetlands (CWs) are widely recognized as the potential hotspots for producing highly toxic methylmercury (MeHg). This presents an obstacle to the widespread application of CWs. A comprehensive discussion on strategies to control mercury methylation in CWs is currently lacking. This review highlighted the potential impacts of differences in oxygen supply and consumption in various CWs, the characteristics of influent quality, the interactions between different substrates and mercury (including mercury adsorption, reduction), and plants on microbial mercury methylation in CWs. We also proposed the potential strategies for human intervention in regulating or controlling microbial mercury methylation in CWs, including oxygenation, nitrate inhibition, selection of substrates with high adsorption capacity, weak reducibility and low organic matter release, and plant management. Knowledge summarized in this review would help achieve a comprehensive understanding of various research gaps in previous studies and point out future research directions by focusing on CWs types, influent quality, substrates selection and plants management, to reduce the mercury methylation in CWs.