Nathalie Chiaramonti

Emission of biogenic volatile organic compounds involved in eruptive fire: implications for the safety of firefighters

Forest fires are can be fatal for firefighters owing to the phenomenon of eruptive fire. The hypothesis of this study is that biogenic volatile organic compounds (BVOCs) accumulate in the vicinity of the fire front. One of the factors required for an eruptive fire to take place is that BVOC concentrations must be between their lower flammable limit and upper flammable limit. When this accumulation of BVOCs is exacerbated by specific geographical zones (e.g. small valleys, thalwegs, canyons), the combination of these two factors can lead to situations with a very high flammability potential, representing a considerable risk for firefighters. In France, 16 firefighters have been fatally injured over the last 15 years. This work was carried out on three species of the Mediterranean basin: Pinus laricio Poir., Pinus pinaster Ait. and Cistus monspeliensis L. The maximum BVOCs emitted as a function of temperature (50–200°C) by these species were 147.9, 11.6 and 56.0 g m–3 respectively. The quantities of BOVCs emitted by P. laricio and C. monspeliensis were sufficiently high for eruptive fires to occur.

Variability of Polyphenol Compounds in Myrtus Communis L. (Myrtaceae) Berries from Corsica

Polyphenol compounds were extracted from Myrtus communis L. berries (Myrtaceae) by maceration in 70% ethanol and analysed by HPLC-DAD and electrospray mass spectrometry. The Myrtus berries were collected at maturity from seven localities on the island of Corsica (France) and the sampling was carried out during three years. The polyphenol composition of Corsican Myrtus berries was characterized by two phenolic acids, four flavanols, three flavonols and five flavonol glycosides. The major compounds were myricetin-3-O-arabinoside and myricetin-3-O-galactoside. Principal components analysis (PCA) is applied to study the chemical composition and variability of myrtle berries alcoholic extracts from the seven localities. Canonical analysis and PCA data distinguishes two groups of myrtle berries characterized by different concentrations of polyphenols according to soil and years of harvest. The variations in the polyphenol concentration were due to biotic and abiotic factors.

Volatile and semi-volatile organic compounds in smoke exposure of firefighters during prescribed burning in the Mediterranean region

Prescribed fires can be used as a forest management tool to reduce the severity of wildfires. Thus, over prolonged and repeated periods, firefighters are exposed to toxic air contaminants. This work consisted in collecting and analysing smoke released by typical Mediterranean vegetation during prescribed burning. Sampling was performed at five active zones on the island of Corsica. Seventy‐nine compounds were identified: volatile organic compounds and semi‐volatile organic compounds, including polycyclic aromatic hydrocarbons. Depending on exposure levels, the toxins present in smoke may cause short‐term or long‐term damage to firefighters’ health. The dangerous compounds emitted, benzene, toluene, ethylbenzene and xylenes, were quantified. Their concentrations varied as a function of the study site. These variations were due to the intrinsic and extrinsic characteristics of the fire site (e.g. plant species, fire intensity and wind). Our results show that benzene concentration is high during prescribed burning, close to the exposure limit value or short‐term exposure limit. Benzene can be considered as a toxicity tracer for prescribed burning because its concentration was above the exposure limit value at all the study sites. The authors suggest that respirators should be used to protect staff during prescribed burning operations.

The decomposition of hydrogen peroxide : A non-linear dynamic model

All thermal systems are subject to problems of thermal regulation. These can be understood through the use of thermochemical systems, in particular for those in the liquid phase. A dynamic linear model was earlier applied to obtain both the reaction enthalpy and the rate constant at constant temperature for the catalytic decomposition of hydrogen peroxide. This first model did not yield a good fitting between the calculated and experimental data. The hypothesis that the rate constant was independent of temperature was too strong.In the present study, a more elaborate, non-linear model was developed, which takes into account the rate constant variations as a function of temperature (Arrhenius law). This model allowed the activation energy to be determined. The calculated data then successfully fitted the experimental data. The literature indicates that the first-order rate law is not valid for a certain range of concentrations; the present model verified this.The results of dynamic modelling confirm and increase the precision of results obtained in different ways. The developed model is validated through these comparisons.

Scale effects on the heat release rate, smoke production rate, and species yields for a vegetation bed

The burning of a vegetation bed was investigated employing the cone calorimeter and the furniture calorimeter for testing on a small and a large scale. Heat release rate, smoke production rate, and species yields were measured at both scales and with two different setups at the full scale. The results show a clear influence of the scale on: the peak of heat release rate, the smoke extinction area, the soot yield, and the rate of smoke release. The species yields appear to depend not only on the burning scale but also on the experimental setup. This study clearly shows that even for litter with high packing ratio, the results obtained at bench scale cannot be extended directly to the full scale.

BTEX Emissions During Prescribed Burning in Function of Combustion Stage and Distance From Flame Front

The authors investigated the volatile organic compound group benzene, toluene, ethylbenzene, and xylenes (BTEXs) produced during the combustion of forest fuel. The analytes were chosen because they have been identified in other forest fires. As a result, firelighters and the general population can be exposed to hazardous concentrations of BTEXs during prescribed burning. Firefighters were equipped with Tenax adsorbent tubes and the BTEX concentrations analyzed by Automated Thermal Desorption–Gas Chromatography/Mass Spectrometry (ATDGC/MS). Total BTEX concentrations were measured in function of the distance from the flame front (between 1 and 10 m, 30 and 50 m, and 100 and 150 m) and the combustion phase (flaming and smoldering). The major compounds detected were benzene and toluene. Significant differences were observed between the data collected. BTEX concentrations were higher close to the flame front and during the smoldering phase. The benzene concentration (0.093–18 mg·m−3) exceeded the Short-Term Exposure Limit (STEL, 16 mg·m−3) in samples collected during the smoldering phase at a distance of 1–10 m from the flame front. Statistical analyses were carried out to summarize the results.

Sampling and Quantitative Analysis of Smoke during a Fire Spreading Through a Mediterranean Scrub

This work consists in sampling and analyzing volatiles and smoke released by a typical Mediterranean vegetation during a fire. On an experimental burning plot, we used two original devices to collect volatiles and smoke. Thanks to air sampling pumps, atmosphere samples were taken, into cartridges filled with an adsorbent and into tedlar bags. The test site was instrumented with different other sensors (thermocouples, fluxmeters, anemometers, IR and visible cameras) in order to get the maximum data [1]. Analyses were performed at the laboratory by gas chromatography one day after the field experiment. Samples were thermally desorbed from the cartridges in the GC column coupled to a MS detector. We aim to characterize the risks related to the toxicity of smoke in actual conditions. Benzene, Toluene and Xylene (BTX) are highly toxic compounds that we propose to quantify in the smoke sampled during the fire. Quantification of such compounds was done with an external calibration using commercial mixtures of BTX.

Analysis of smoke during prescribed fires

This work consist in sampling and analyzing smoke released by typical Mediterranean vegetation during a fire. To proceed we used an experimental apparatus made of an air sampling pump with a cartridge filled with Tenaxreg TA. The sampling device was situated in a fixed place corresponding to the position of a fireman for the four studied stations. Analyses were performed at the laboratory by gas chromatography one day after the field experiment. Samples were Thermally Desorbed from the cartridges in the Gas Chromatography column coupled to a detector by Mass Spectrometry. We aim to characterize the risks related to the toxicity of smoke in actual conditions. Benzene, Toluene and Xylene (BTX) are highly toxic compounds that we propose to quantify in the smoke sampled during the fire.

Fermentation alcoolique: Détermination des Grandeurs Thermocinétiques par Modélisation

The control of alcoholic fermentation is necessary to obtain a quality wine.The overall dynamic and phenomenological modelling already applied to the simulation of this type of reaction enables us to suggest, in this study, a simple model (of which two variants), are relatively satisfactory.The first variant does not take into account the variation of the ambient temperature; the model translates exactly the first phase of the experimental curve or the moment when highest temperatures are measured. The relaxation phase is less well described because of influence of variation of the ambient temperature is relatively important.The second one considers the system depending on the ambient temperature, the model is correct for the relaxation phase too (the reaction temperature decreases, it nears the ambient temperature).The advantage of this model: It permits one to determine the reaction enthalpy and the kinetic parameters.