The effect of atmospheric pressure on CH4 and CO2 emission from a closed landfill site in Manchester, UK
A time series study was conducted to ascertain the effect of barometric pressure on the variability of CH4 and CO2 concentrations in a closed landfill site. An in situ data of methane/carbon dioxide concentrations and environmental parameters were collected by means of an in-borehole gas monitor, the GasClam (Ion Science, UK). Linear regression analysis was used to determine the strength of the correlation between ground-gas concentrations and barometric pressure. The result shows CH4 and CO2 concentrations to be variable with weak negative correlations of 0.2691 and 0.2773, respectively, with barometric pressure over the entire monitoring period. Although the R(2) was slightly improved by considering their concentration over single periods of rising and falling pressure, single periods of rising pressure and single periods of falling pressure, their correlations remained insignificant at 95% confidence level. The result revealed that atmospheric pressure--the acclaimed major control on the variability of ground-gas concentration--is not always so. A case was made for the determination of other possible controls such as changes in temperature, soil permeability, landfill water depth, season, and geology of the borehole and also how much of control each factor would have on the variability/migration of CH4 and CO2 concentrations from the studied landfill.