Browsing by Author "Isobe, Y"

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item: Conference-Full-text
Flux measurements of greenhouse gases from an abandoned open dumping site of solid waste in Sri Lanka
(2013-11-13) Nagamori, M; Koide, T; Wijewardane, NK; Watanabe, Y; Isobe, Y; Mowjood, MIM; Ishigaki, T; Kawamoto, K
The investigation of greenhouse gas emission from a waste dumping site in Sri Lanka was conducted. The investigated site in this study is an abandoned waste dump site located at a hilly river bank in the Central Province of Sri Lanka (N 7º 09', E 80º 35'), consisting of two different sections with waste ages of around 0.5 year (New-section) and 7 years (Old-section). A simplified method for determination of methane gas flux using laser methane detector was considered to be effective to grasp the magnitude of methane flux. It was shown that the points those exhibited high value of methane gas flux also showed low EC-value compared with those of the other surround points. Furthermore, the low hardness of these points indicated that large amount of methane gas flux was caused by high permeability of surface as some stumps had been grown or as boundary between buried waste and ground line had been loosened. Measured fluxes for methane, carbon dioxide, and nitrous oxide in New-section ranged in <0.04-1800, 4.9-1800, and <0.0001-0.35 mL m-2 min-1, respectively. Little amount of methane gas was emitted from surface in Old-section. Relatively high fluxes of nitrous oxide were observed in some plots at middle and bottom for both sections, suggesting that nitrification was stimulated by aerobic condition due to the penetration of air from the slope of dumped waste.
item: Conference-Full-text
Landfill gases at an abandoned open dump: a case study at Udapalatha/Gampola site in the Central Province of Sri Lanka
(2013-11-13) Koide, T; Nagamori, M; Wijewardane, NK; Watababe, Y; Isobe, Y; Mowjood, MIM; Kawamoto, K
There are very limited studies on landfill gas on uncontrolled open dumps in developing countries. In this study, landfill gas samples at 1 m depth from an abandoned open dump (AOD) in the Central Province of Sri Lanka (N 7º 09', E 80º 35') were collected and the typical landfill gas composition such as O2, N2, CH4, CO2, H2, H2S, and N2O were measured. Buried waste samples at 1 m depth were also taken from the site and organic carbon and nitrogen contents in the residue (< 2 mm) were measured. The samples were taken from some marked plots inside the dump with waste ages of around 0.5 and 7 years (AOD0.5 and AOD7) and outside intact (AODint). Measured CH4 concentration for AOD0.5 and AOD7 ranged in 19–58 % and 0–12 %, respectively, suggesting that the dumped waste at 1 m depth was in the process to be the ‘stabilization phase’ at least 7 years after dumping. This is likely to be a much shorter time period to reach the phase after dumping than those in mid-latitude regions (typically in several decades). The carbon contents in the waste residue in AOD0.5 and AOD7 were 151±67 and 29±7 mg g-1, respectively, implying that high waste decomposition and leaching of organic compounds might have been enhanced due to high temperature and precipitation at the site. A further study for the landfill gas and waste quality in the deeper layer is required to judge whether whole of the dumpsite had reached the stabilization phase rapidly.
item: Conference-Full-text
Spatial variation in landfill gas composition under different precipitation condition and waste age in Sri Lanka
(2013-11-13) Koide, T; Nagamori, M; Watanabe, Y; Isobe, Y; Wijewardane, NK; Herath, GBB; Mowjood, MIM; Kawamoto, K
A study was conducted to assess the effect of precipitation and age of waste on the stabilization of the dumped waste. Landfill gas samples at 1-m depth were collected from 13 waste landfill sites in Sri Lanka with different annual precipitation ranging from 1,000 to 4,000 mm and waste age ranging from 1 to 120 months. Typical landfill gases O2, N2, CH4 and CO2 were measured quantitatively by a gas chromatograph. Buried waste samples at 1-m depth were also taken from all locations to determine organic carbon contents in the residue (< 2 mm). With the age of wastes, the measured O2 and N2 concentration (ranged in 1 - 20% and 2 - 80% respectively) in collected landfill gas samples were increased and the CH4 and CO2 concentration (ranged in 0-60% and 1-68%, respectively) decreased, implying the buried wastes are getting stabilized within 120 months after dumped (typically in several decades in mid-latitude regions). However, the correlations between measured gas concentrations and the annual precipitations at the sampling site show no definite results. Organic carbon contents in the waste residues (ranged in 24-236 mg g-1) were not fully related to the waste age and the precipitation amount, while significant time-dependent decreases of the organic carbon contents can be observed in some investigated landfill sites. Further studies are needed with continuous monitoring of rainfall with gas emission.