Evolution mechanism of high concentration of hydrogen sulfide from the least controlled landfill site

High concentration of gaseous hydrogen sulfide more than 10000 ppm has been observed in the least controlled landfill site. The waste had low organic content, and ignition loss was about 9%. It is considered that the sufficient input of rain water and aerobe activity promoted the reaction of organic matter with dissolved oxygen in the rain water, yielding water-soluble fatty acids that were readily consumed by anaerobes. The fatty acids were transported to deeper anaerobic region by entrainment infiltrating rain water. Accumulation of fatty acids is related to the evolution of high concentration of hydrogen sulfide. Lactic acid and pyruvic acid were not found in regions of high concentration of hydrogen sulfide, but existed in regions of low concentration of hydrogen sulfide. Evolution of high concentration of hydrogen sulfide requires a continuous supply of sulfate ion at this site. Sulfate ion mainly comes from gypsum plaster boards. Sulfide content at ground surface, which was the upper part of the region of high concentration of hydrogen sulfide, was 0.2 mg/g (dry earth), indicating that hydrogen sulfide did not ascend from the deeper anaerobic region to the surface.