Abstract
We propose a convenient method for monitoring hazardous gas based on the determination of ppm-level concentrations of CH4 in ambient air. The proposed method can be applied during the excavation of landfill or dumped waste at reclamation sites, and we investigated its usability in an actual field. A portable open-path type analyzer and a retroreflector were used to determine the CH4 concentration.
The hazardous gas in landfill gas emitted from final disposal and illegal-dumping sites always contains CH4 and H2S occurring together, with the latter considered to be the main hazardous component. The maximum concentration ratio (H2S/CH4) at final disposal and illegal-dumping sites was expected to be about 10−1. This study showed clearly that the ambient CH4 concentration could be useful as an indicator for the monitoring of hazardous gas for the evaluation of potential danger.
It was also shown that the proposed method could be useful for monitoring as a safety control at a reclamation site. This method works by comparing the measured ppm concentration levels of CH4 with a management value that is decided by considering the maximum concentration ratio (of the hazardous gas that was most harmful at the site, such as H2S/CH4), its acceptable concentration and a safety ratio.
