Environmental Isotope Characteristics of Landfill Leachates and Gases

Abstract

The isotopic characteristics of municipal landfill leachate and gases (carbon dioxide and methane) are unique relative to the aqueous and gaseous media in most other natural geologic environments. The δ13C of the CO2 in landfills is significantly enriched in 13C, with values as high as +20 ‰ reported. The δ13C and δD values of the methane fall within a range of values representative of microbial methane produced primarily by the acetate‐fermentation process. The δD of landfill leachate is strongly enriched in deuterium, by approximately 30 ‰ to nearly 60 ‰ relative to local average precipitation values. This deuterium enrichment is undoubtedly due to the extensive production of microbial methane within the limited reservoir of a landfill. The concentration of the radiogenic isotopes, 14C and 3H, are significantly elevated in both landfill leachate and methane. The 14C values range between approximately 120 and 170 pMC and can be explained by the input of organic material that was affected by the increased 14C content of atmospheric CO2 caused by atmospheric testing of nuclear devices. The tritium measured in leachate, however, is often too high to be explained by previous atmospheric levels and must come from material buried within the landfill. The unique isotopic characteristics observed in landfill leachates and gases provide a very useful technique for confirming whether contamination is from a municipal landfill or some other local source.

Application of Deuterium and Oxygen-18 to Trace Leachate Movement in Bantar Gebang Sanitary Landfill

“…Besides the effect of methanogenesis, it was possible that some deuterium enrichments observed in landfill leachate were due to isotopic exchange with H 2 S, which would be generated during SO 4 reduction in landfills. However, methanogenesis process was probably major effect producing deuterium enrichment in leachate relative to isotopic exchange reaction [5,13]. The highly enriched deuterium values of all leachate samples (including leachate ditches) in this investigation did not influenced significantly to those of Cibitung River water samples.…”

“…The later might be most important source of those major cations because clay was daily used as cover material of the trash. In this case, ionic exchange reaction occurred between major cations from clay and large amount of ammonium generated from refuse [13]. As mentioned above that deuterium and oxygen-18 were made to determine if constituents of dissolved leachate had a significant effect to the isotopic composition of groundwater and river water.…”

Geochemical Investigation of Aquifer Pollution From Waste Management. The Case of Komotini Landfill (Greece)

“…Light elements isotopic composition in particular, being affected by great relative mass differences among the isotopes of a same element, offers many possible applications in monitoring, also because of the sensible fractioning occurring at environmental temperatures (Clark and Fritz, 1997). This kind of analysis has become an integrating essential part in the study of environmental impact of landfills, being able to provide information and evaluation instruments not obtainable with other methods (see Hackley et al, 1996;Doveri et al, 2007).…”

Aerobic processes in landfill: an Australian field trial

“…The predicted values of δ 13 C-CO2,OX show that the CO2 produced from CH4 oxidation in these incubations was lighter than the heavy δ 13 C-CO2 in landfill, when compared against values observed by Coleman et al (1993) of -7 to -25‰. Hackley et al (1996) hypothesised for early phase landfill degradation activity when the highest rates of composting are most likely to occur, that the CO2 isotopic signature would reflect the δ 13 C-CO2 value of vegetation matter, which ranges from -10 to -35‰. Given that the incubations were conducted in batch mode, it is conceivable that the tendency of the bacteria to discriminate for 12 CH4, resulting in more isotopically CO2 light formation gas is more emphasised than in the landfill as there is no replenishment and mixing with production gas from the degradation of waste.…”

“…These Whiticar plots are utilised as an initial point of investigation to rapidly form qualitative indicators of ecosystems. Hackley et al (1996) later applied this method for characterising landfill gas using isotope data obtained from several sites from vent or extraction wells in the US.…”