광산배수 정화시설인 인공소택지 시스템 내의 메탄발생과정 및 제어요소들에 대한 연구

Abstract

Abstract

The adverse effects of global warming are becoming increasingly serious. As the second-highest contributor to global warming, methane’s global warming potential is 25 times higher than that of carbon dioxide. Therefore, it is critical to reduce methane emissions to mitigate global warming. Many countries have already committed to reduce methane emissions and have been making efforts to lower methane emissions to its promised level. As a first step to alleviate methane emissions, it is important to know how much methane comes from various sources. Atmospheric methane is mostly generated from anthropogenic sources, and the coal mining industry is known to account for 13% of the total, but there may be other methane emissions sources not included in the statistics. For example, methane emitted from mine drainage treatment facilities is one of the missing sources in statistics. Mine drainage, which is often contaminated with heavy metals, must be treated before discharge. Passive treatments, which are one of the most cost-effective methods, often include aerobic wetlands to treat residual heavy metals. However, these treatments can produce methane like other constructed wetlands that are responsible for 70 % of the methane emissions among natural sources. Studies on methane reduction in constructed wetlands have been reported in the literature, but there have been few studies on methane reduction from aerobic wetlands in mine drainage treatment systems.

This study investigated the characteristics of methane emissions from mine drainage treatment systems and determined the effect of the mine drainage’s water quality on the mitigation of methane emissions in wetlands. In order to estimate the methane flux in the field, changes in methane concentrations over time were measured using a closed gas chamber. Batch experiments were also carried out to estimate the methane production potential of sampled wetlands’ sediments and water. The amounts of methane emissions at mine sites(–3.6∼12.0 CH4 mg/m2/hr) were compared with those at constructed ecological wetlands(-0.6∼20.5 CH4 mg/m2/hr). Methane gas fluxes have been measured by multiplying the numbers of sites, but it is difficult to define the flux value by a certain amount due to the nature of gas flux that changes easily with time and space. The methane production characteristics were also investigated by the methane production potential test under a controlled anaerobic condition. The removal rates of carbon from the sediments collected at the mine area are higher than those at constructed ecological wetlands. The substrates of the mine site produced twice as much methane. By measuring the presence of microorganisms, it was confirmed that the decreasing carbon in the substrates was degraded by the microorganisms, and the methane produced was due to the activity of methanogen. In other batch experiments, the effect of sulfate concentrations on the methane emissions using the collected substrate of a mine wetland was investigated, and the results showed up to 1.5 lower methane emissions from the batches with a high sulfate dose. As a result, it was confirmed that the reduced carbon and hydrogen components in the substrate were due to the decomposition of microorganisms. Through the qPCR analysis, it was confirmed that sulfate reducing bacteria reduced the sulfate using substrates. In summary, the potential of methane emissions in mine wetlands is higher than those of general wetlands. The reduction of methane from mine wetlands may be possible through controlling the reduction ability of sulfate or the activities of sulfate reducing bacteria. The results of this study may contribute in studies on methane mitigation through biogeochemical processes in passive treatment systems of mine drainage.