Toussaint Barboni

Comparison of liquid-liquid extraction with headspace methods for the characterization of volatile fractions of commercial hydrolats from typically Mediterranean species

Chemical composition of volatile fractions of nine commercial hydrolats and corresponding essential oils obtained using an industrial process were studied. The hydrolat volatile fractions were reported for the first time. A comparative study of those obtained, on the one hand, by liquid-liquid extraction (LLE) and, on the other hand, using five solid-phase microextraction (SPME) fibers and also purge-and-trap-automatic thermal desorption (P&T-ATD) was conducted with analysis performed by GC and GC/MS. The use of various techniques has resulted in a change of chromatographic profile of the hydrolat volatile fractions. Quantitative differences were established between chemical compositions of headspace and those obtained by a conventional method (LLE). Statistical analyses were carried out to summarize the results.

Investigation on the Emission of Volatile Organic Compounds from Heated Vegetation and Their Potential to Cause an Accelerating Forest Fire

An experimental study is conducted on the emission of volatile organic compounds (VOCs) emitted by Rosmarinus officinalis plants when exposed to an external radiant flux. The thermal radiation heats the plant and causes the emission of VOCs. The thermal radiation simulates the radiant flux received by vegetation in a forest fire. The results of the experiments are used in a simplified analysis to determine if the emissions of VOCs in an actual forest fire situation could produce a flammable gas mixture and potentially lead to the onset of an accelerating forest fire. The experiments consist of placing a plant in a hermetic enclosure and heating it with a radiant panel. The VOCs produced are collected and analyzed with an automatic thermal desorber coupled with a gas chromatograph/mass spectrometer (ATD-GC/MS). The effects of the fire intensity (radiant panel heat flux) and the fire retardant on the VOCs emission are then investigated. Two thresholds of the VOCs emission are observed. The first is for plant temperatures of around 120°C and appears to be caused by the evaporation of the water in the plant, which carries with it a certain amount of VOCs. The second one is around 175°C, which is due to the vaporization of the major parts of VOCs. The application of a fire retardant increases the emission of VOCs due to the presence of the water (80%) in the fire retardant. However, the use of the retardant results in a lower production of VOCs than using water alone. The measurements are used to estimate the concentration of VOCs potentially produced during the propagation of a specific fire and compared to the flammability limits of α-pinene. It is concluded that the quantities of VOCs emitted by Rosmarinus officinalis shrubs under certain fire conditions are capable of creating an accelerating forest fire.

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.

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.

Relationships between the leaf and fruit mineral compositions of Actinidia deliciosa var. Hayward according to nitrogen and potassium fertilization.

The variations of the elements that are examined most frequently during foliar analysis were determined for kiwi as a function of different nitrogen and potassium fertilizer loads. The values recorded demonstrated the existence of a relation between the leaves and the fruit. Two groups of elements were identified that exhibited different responses. The first group comprised elements that, in leaves and fruits, presented a different evolution as a function of at least one of the fertilizers. This group included B, Cu, Fe, Na, and Zn. The second group comprised elements that, in both leaves and fruits, exhibited a comparable evolution as a function of both fertilizer types. This group included N, Ca, Mg, Mn, P, and K.

Steady and Unsteady Fireline Intensity of Spreading Fires at Laboratory Scale

Fireline intensity is the rate of heat release per unit time and per unit length of a fire front. With rate of spread, it is one of the most relevant quantities used in forest fire science. It allows to evaluate the effects of fuel treatment on fire behavior, to establish limits for prescribed burning or to support fire suppression activities. Although it is widely used, conversely its measurement is often coarse and has received very little attention. Furthermore, literature only refers to steady state when dealing with this quantity. In the present paper, we measure directly the fireline intensity at laboratory scale by using the oxygen consumption calorimetry principle. This methodology allows us to provide this quantity not only for steady fires but also for unsteady spreading fires for the first time. We show that the current approach used to as- sess fireline intensity can lead to overestimation from about 20%. As the experiments were conducted under well- ventilated conditions, the heat release rate calculated by calorimetry was compared to mass loss rate and heat of combus- tion taking into account the combustion efficiency.

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.

Phenolic compounds of Pinus laricio needles: a bioindicator of the effects of prescribed burning in function of season.

Fire is a dominant ecological factor in Mediterranean-type ecosystems. Forest management includes many preventive tools, in particular for fire prevention, such as mechanical treatments and prescribed burning. Prescribed burning is a commonly used method for treating fuel loads, but fuel reduction targets for reducing wildfire hazards must be balanced against fuel retention targets in order to maintain habitat and other forest functions. This approach was used on Pinus nigra ssp laricio var. Corsicana, a pine endemic to Corsica of great ecological and economic importance. Many studies of plant phenolic compounds have been carried out concerning responses to various stresses. The aim of this study was to understand i) the effects of prescribed burning 1 to 16 months later and ii) the effects of the seasonality of burning, spring or fall, on the production of phenolic compounds in Pinus laricio. After prescribed burning conducted in spring, Pinus laricio increases the synthesis of total phenolic compounds for a period of 7 months. The increase is greater after spring-burning than fall-burning. With regard to simple phenols, only dihydroferulic acid responds about 1 year after both types of prescribed burning. The causes of these increases are discussed in this paper. Total phenolic compounds could be used as a bioindicator for the short-term response of Pinus laricio needles to prescribed burning. Simple phenols may be useful for revealing the medium-term effects of prescribed burning. The results of this study include recommending forest managers to use prescribed burning in the fall rather than spring to reduce fuel loads and have less impact on the trees.