Quantification of biodegradation rate of hydrocarbons in a contaminated aquifer by CO2 δ13C monitoring at ground surface.

Ground surface analysis of CO2 emissions with δ13C 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 δ13CCO2 analysis released at ground surface above the pollution plume instead of usual approaches based on groundwater hydrocarbons δ13C 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 δ13CCO2 analysis emitted at ground surface and from δ13CTOLUENE analysis in ground water. A kinetic fractionation factor α of 0.9979 (or ε value of -2.1 ± 0.5‰) is estimated for the biodegradation of the most reactive hydrocarbon substrates (TEX). The treatment of this Rayleigh equations by linear regression of δ13CCO2 values along the predominant direction of groundwater flow leads to the following results and conclusions for that site: (i) first order biodegradation rate constants (and annual variation) are maximum after the activation of a Permeable Reactive Barrier (PRB) in May 2014: 0.92(+0.29-0.17) year-1, and during July and October: 0.46(+0.14-0.09) year-1 and minimum in mid-winter in February 2015: 0.17(+0.05-0.03) year-1, given by the estimation range for ε. These results are in the lower range with reported in literature for similar contaminated sites (1.6-18 year-1) considering natural attenuation under sulfate reducing conditions and (ii) the seasonal variation of the first order biodegradation rate constant is mainly correlated with the seasonal variation of the CO2 flux, where maximum values are in summers and minimum values in winters. Both seasonal variations are mainly due to the annual cycle of the natural biodegradation activity at the scale of the pollution plume, rather than the activation of the PRB. This work demonstrates that δ13CCO2 analysis released at ground surface from biodegradation of groundwater hydrocarbons could provide, under characterized and appropriate conditions, a non-intrusive (without soil samplings), fast, and low-cost online method to monitor and therefore to optimize soil remediation processes in real time. (Monitored Natural Attenuation or Enhanced Bioremediation).

Combination treatment of resveratrol and capsaicin radiosensitizes pancreatic tumor cells by unbalancing DNA repair response to radiotherapy towards cell death.

Pancreatic ductal adenocarcinoma (PDAC) remains one of the deadliest cancers because it is highly resistant to every available therapeutic strategy, in particular conventional chemotherapy or radiotherapy (RT). Sensitizing tumor cells to existing treatments remains a good option to obtain fast and applicable results. Considering that ionizing radiations induce radiolysis-derived reactive oxygen species (ROS), we hypothesized that ROS-inducing bioactive food components (BFCs) could exacerbate ROS-related cell damages, including DNA double stranded breaks (DSBs), leaving the cellular ROS scavenging systems overwhelmed, and precipitating tumor cell death. Combination of resveratrol and capsaicin radiosensitized radiosensitive tumor cells, but RT did not increase BFC combination toxicity in radioresistant tumor cells. BFC addition to RT increased ROS production and led to significant tumor volume reduction in xenografted mouse preclinical model. Strikingly, BFCs inhibited RT-induced DNA damage molecular response by strongly limiting the first steps of DSB repair, and by keeping cells in cell cycle, provoking exacerbated intrinsic apoptosis. This study positions BFCs as potent radiosensitizers when combined, and identifies an actionable molecular pathway by resveratrol and capsaicin combination.

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. A first application to biodegradation of hydrocarbons is presented, tested on a hydrocarbon contaminated site under aerobic bio-treatment. CO2 flux measurements using closed chamber method is combined with the determination of the isotopic signature δ(13)C of the CO2 emission to propose a non-intrusive method to monitor in situ biodegradation of hydrocarbons. In the contaminated area, high CO2 emissions have been measured with an isotopic signature δ(13)C suggesting that CO2 comes from petroleum hydrocarbon biodegradation. This first field implementation shows that rapid and accurate measurement of isotopic signature of CO2 emissions is particularly useful in assessing the contribution of contaminant degradation to the measured CO2 efflux and is promising as a monitoring tool for aerobic bio-treatment.