Quantification of biodegradation rate of hydrocarbons in a contaminated aquifer by CO δC monitoring at ground surface.

Ground surface analysis of CO emissions with δC determination is experimentally demonstrated to be a potential methodology to monitor, on line, the dynamics of petroleum-hydrocarbon biodegradation in soil aquifers, thanks to the improvement of the Isotopic Ratio Infra Red Spectroscopy technique. Biodegradation rate of remaining hydrocarbon substrates in groundwater can be quantified using basic application of the Rayleigh equations, by δC analysis released at ground surface above the pollution plume instead of usual approaches based on groundwater hydrocarbons δC analysis, when physical and chemical properties for the contaminated site meet appropriate conditions. The validation approach for that gasoline contaminated specific site is discussed and verified by comparison of first order attenuation rate constant determined from δC analysis emitted at ground surface and from δC analysis in ground water.

A quantum cascade laser infrared spectrometer for CO2 stable isotope analysis: Field implementation at a hydrocarbon contaminated site under bio-remediation.

Real-time methods to monitor stable isotope ratios of CO2 are needed to identify biogeochemical origins of CO2 emissions from the soil-air interface. An isotope ratio infra-red spectrometer (IRIS) has been developed to measure CO2 mixing ratio with δ(13)C isotopic signature, in addition to mixing ratios of other greenhouse gases (CH4, N2O). The original aspects of the instrument as well as its precision and accuracy for the determination of the isotopic signature δ(13)C of CO2 are discussed.

Investigations of natural attenuation in groundwater near a landfill and implications for landfill post-closure.

The controlled landfill technology is now adopting passive attenuation techniques as an increasing number of landfill sites reach the post-closure phase. During the post-closure phase, landfill operators need to convince environmental authorities that landfills no longer pose a threat to health or the environment. The demonstration of acceptable risk should rely in particular on data collected during environmental monitoring in addition to modelling of possible future evolutions of environmental concentrations.