Methane (CH4) as the second-highest contributor to global warming after CO2 occurs naturally in anaerobic environments such as wetlands. The global warming potential of CH4 is 25 times higher than that of carbon dioxide, implying that reducing methane emissions can effectively contribute to mitigating global warming. Nevertheless, there is no standard CH4 monitoring method, and only a few basic studies have been conducted on the measurements of CH4 emissions from wetlands. Our research team has focused on CH4 emissions from constructed wetlands with the goal of protecting watersheds affected by non-point source wastewater or mine drainage. The two-year monitoring results showed the ranges of CH4 flux in wetlands affected by mine drainage (–3.6 ~ 12.0 mg/m2/hr) and in constructed ecological wetlands (–0.6 ~ 20.5 mg/m2/hr). The factors that have the greatest influence on the amount of the CH4 flux are the water temperature and the amount of total organic carbon in the water. The sulfate concentration in the water was also found to be an influencing factor, and it was more prominent in mine wetlands. It was observed that as the sulfate concentration is higher in mine drainage, the methane flux is lower on the wetland water surface. Furthermore, laboratory experiments demonstrated that a sufficient amount of sulfate can suppress the activity of methanogens by activating sulfate-reducing bacteria. In addition, we are investigating the geochemical reactions of mercury and arsenic under simulated redox sensitive wetland conditions and developing biochar-based adsorbents as an arsenic treatment.
