Temperature dependence of emission of volatile organic compounds (VOC) from litters collected in two Mediterranean ecosystems determined before the flaming phase of biomass burning.

Fire represents a major threat to Mediterranean terrestrial ecosystems because of the high temperatures reached during summer. While massive loads of organic, inorganic compounds and particulate matter are known to be emitted into the atmosphere from forest wildfires, less is known about the emission from vegetation surrounding fires where air temperatures higher than 100 °C can be reached. Little information exists on the emission from dead vegetation accumulated as litter over forest soils, from which fires often starts. In this study, the response of litter to heatwaves generated by nearby fires was investigated under controlled conditions. Litter samples collected in a Mediterranean maquis and a Holm oak stand during summer were placed in an enclosure flushed with a continuous flow of air, the temperature of the enclosure was progressively risen to 125 °C, until some smog developed but no flaming occurred. The gas from the enclosure was analysed for the content of CO2, H2O, and volatile organic compounds (VOC) to assess the dependence of emission from the air temperature. VOC emission was continuously determined by Proton-Transfer-Reaction mass spectrometry with time of flight (PTR-TOF-MS). Data obtained were complemented with those obtained by collecting VOC on traps that were later analysed by Gas chromatography-mass spectrometry (GC-MS). Results provided useful information to understand the emission mechanism of VOC and other gases from dead vegetation present in the litter of two Mediterranean ecosystems, both dominated by evergreen vegetation species. The study demonstrated that low molecular weight VOC and aromatic hydrocarbons (arenes) produced mostly by thermal oxidation of the wood biopolymers are emitted in addition to isoprenoids typically associated to storage organs and photosynthetic pathway. Moreover, our results support parameterization of litter VOC emission processes in air quality models.

Real-time air concentrations and turbulent fluxes of volatile organic compounds (VOCs) over historic closed landfills to assess their potential environmental impact.

For the first time, emission/deposition fluxes of volatile organic compounds (VOCs) and H2S from a historic closed landfill site in Southern Italy were determined by Eddy Covariance (EC) using Proton Transfer Reaction Time-of-Flight Mass Spectrometry (PTR-TOF-MS). This was done in two field campaigns of one week performed in July and October 2016, where fluxes of CO2 and CH4 were also measured. Many compounds not previously identified in the biogas were detected by PTR-TOF-MS, but only in July some of them produced positive fluxes exceeding the flux limit of detection. Methanol was the most emitted compound with an average flux of 44.20 ± 4.28 µg m-2 h-1, followed by toluene with a mean flux of 18.97 ± 2.47 µg m-2 h-1. Toluene fluxes were 10 times higher than those of benzene, fitting rather well with values previously measured in the biogas. VOCs emission fluxes of monoterpenes and highly reactive arenes did not reflect, however, the biogas composition. This, combined with tiny emissions of VOC oxidation products, suggests that landfill emissions underwent some photochemical degradation before being dispersed in the atmospheric boundary layer (ABL). Deposition fluxes of some VOCs emitted from the sea was also observed in July. No relevant VOC fluxes were instead measured in October, suggesting that temperature was the variable controlling most landfill emission. Albeit small, summer landfill emissions from the investigated site can have an impact on the population living nearby, because they contain or still generate compounds that causing nuisance.

New formaldehyde-free adhesives for wood manufacturing: In vitro evaluation of potential toxicity of fine dust collected during wood sawing using a new experimental model to simulate occupational inhalation exposure.

Formaldehyde mainly emitted from wood adhesives, finishing materials, paint for furniture represents, together with wood dust, a potential carcinogenic risk for wood workers. Aims of this multidisciplinary study are to investigate the possibility of replacing urea-formaldehyde (UF) adhesives in the wood industry with organic and/or inorganic-based glues to obtain a final less toxic product and to evaluate the potential toxicity of wood glued with such new adhesives. For this purpose we selected poplar wood to test an organic new adhesive HBP (Hemp Based Protein), a mixture of hemp flour and cross-linker PAE (polyaminoamide epichlorohydrin), and spruce wood to test an inorganic adhesive geopolymer K-PSS (potassium-polysiloxosialate) plus polyvinyl acetate. For the poplar wood, we also used a commercial panel glued with UF for comparison. We reproduced occupational inhalation exposure during sawing activities of mentioned woods, collected and characterized the wood dusts emitted during sawing and evaluated in vitro their potential cyto-genotoxic and inflammatory effects. We used human lung cells (A549) exposed for 24 h to 20 and 100 µg/mL of collected PM2.5 wood dust. We found that both the new adhesives wood dusts induced a slightly higher apoptotic effect than untreated natural wood dusts particularly in spruce wood. Only geopolymer K-PSS wood dust induced membrane damage at the highest concentration and direct and oxidative DNA damage that could be explained by the different chemical composition and the lower particle sizes in respect to organic HBP adhesive wood dust. We found slight induction of IL-6 release, not influenced by K-PSS treatment, at the highest concentration in spruce wood. For poplar wood, IL-6 and IL-8 induction was found particularly for untreated and UF-treated wood at the highest concentration, where hemp adhesive treatment induced lower inflammation while at lower concentration similar slight cytokine induction was found for all tested wood dusts. This preliminary study shows that natural adhesives used to replace UF adhesives represent an interesting alternative, particularly the organic hemp-based adhesive showing very low toxicity.

Assessment of carbon recovery from solid organic wastes by supercritical water oxidation for a regenerative life support system.

The carbon recovery from organic space waste by supercritical water oxidation (SCWO) was studied to support resource recovery in a regenerative life support system. Resource recovery is of utmost importance in such systems which only have a limited total amount of mass. However, the practical waste treatment strategies for solid space wastes employed today are only storing and disposal without further recovery. This work assesses the performance of SCWO at recovering organic wastes as CO2 and water, to discuss the superiority of SCWO over most present strategies, and to evaluate the different SCWO reactor systems for space application. Experiments were carried out with a batch and a continuous reactor at different reaction conditions. The liquid and gas products distribution were analyzed to understand the conversion of organics in SCWO. Up to 97% and 93% of the feed carbon were recovered as CO2 in the continuous and the batch reactor, respectively. Residual carbon was mostly found as soluble organics in the effluent. Compared with the batch reactor, the continuous reactor system demonstrated a ten times higher capacity within the same reactor volume, while the batch reactor system was capable of handling feeds that contained particulate matter though suffering from poor heat integration (hence low-energy efficiency) and inter-batch variability. It was concluded that SCWO could be a promising technology to treat solid wastes for space applications. A continuous reactor would be more suitable for a regenerative life support system.

Composition and emission of VOC from biogas produced by illegally managed waste landfills in Giugliano (Campania, Italy) and potential impact on the local population.

The composition in Volatile Organic Compounds (VOC) of the biogas produced by seven landfills of Giugliano (Naples, Campania, Italy) was determined and VOC emission rates assessed to verify if these compounds represent a potential threat to the population living nearby. VOC composition in the biogas could not be predicted, as heterogeneous waste was dumped from the late 1980s to the early 2000s and then underwent biological degradation. No data are available on the amount and composition of VOC in the biogas before the landfills closure as no operational biogas collection system was present. In this study, VOC composition was determined by gas chromatography-mass spectrometry (GC-MS), after collecting samples from collection pipes and from soil fractures in cover soil or capping. Individual VOC were quantified and data compared with those collected at two landfills in Latium, when they were still in operation. Relevant differences were observed, mainly due to waste aging, but no specific VOC revealing toxic waste dumping was found, although the concurrent presence of certain compounds suggested that dumping of industrial wastes might have occurred. The average VOC emission was assessed and a dispersion model was run to find out if the emitted plume could affect the health of population. The results suggested that fugitive emissions did not represent a serious danger, since the concentrations simulated at the neighboring cities were below the threshold limits for acute and chronic diseases. However, VOC plume could cause annoyance at night when the steady state conditions of the atmosphere enhance pollutants accumulation in the lower layers. In addition, some of the emitted VOC, such as alkylbenzenes and monoterpenes, can contribute to tropospheric ozone formation.

Differences between a deciduous and a conifer tree species in gaseous and particulate emissions from biomass burning.

In the Mediterranean ecosystem, wildfires are very frequent and the predicted future with a probable increase of fires could drastically modify the vegetation scenarios. Vegetation fires are an important source of gases and primary emissions of fine carbonaceous particles in the atmosphere. In this paper, we present gaseous and particulate emissions data from the combustion of different plant tissues (needles/leaves, branches and needle/leaf litter), obtained from one conifer (Pinus halepensis) and one deciduous broadleaf tree (Quercus pubescens). Both species are commonly found throughout the Mediterranean area, often subject to wildfires. Experiments were carried out in a combustion chamber continuously sampling emissions throughout the different phases of a fire (pre-ignition, flaming and smoldering). We identified and quantified 83 volatile organic compounds including important carcinogens that can affect human health. CO and CO2 were the main gaseous species emitted, benzene and toluene were the dominant aromatic hydrocarbons, methyl-vinyl-ketone and methyl-ethyl-ketone were the most abundant measured oxygenated volatile organic compounds. CO2 and methane emissions peaked during the flaming phase, while the peak of CO emissions occurred during the smoldering phase. Overall, needle/leaf combustion released a greater amount of volatile organic compounds into the atmosphere than the combustion of branches and litter. There were few differences between emissions from the combustion of the two tree species, except for some compounds. The combustion of P. halepensis released a great amount of monoterpenes as α-pinene, ß-pinene, p-cymene, sabinene, 3-carene, terpinolene and camphene that are not emitted from the combustion of Q. pubescens. The combustion of branches showed the longest duration of flaming and peak of temperature. Data presented appear crucial for modeling with the intent of understanding the loss of C during different phases of fire and how different typologies of biomass can affect wildfires and their speciation emissions profile.

Biogenic volatile organic compound emissions from vegetation fires.

The aim of this paper was to provide an overview of the current state of the art on research into the emission of biogenic volatile organic compounds (BVOCs) from vegetation fires. Significant amounts of VOCs are emitted from vegetation fires, including several reactive compounds, the majority belonging to the isoprenoid family, which rapidly disappear in the plume to yield pollutants such as secondary organic aerosol and ozone. This makes determination of fire-induced BVOC emission difficult, particularly in areas where the ratio between VOCs and anthropogenic NOx is favourable to the production of ozone, such as Mediterranean areas and highly anthropic temperate (and fire-prone) regions of the Earth. Fire emissions affecting relatively pristine areas, such as the Amazon and the African savannah, are representative of emissions of undisturbed plant communities. We also examined expected BVOC emissions at different stages of fire development and combustion, from drying to flaming, and from heatwaves coming into contact with unburned vegetation at the edge of fires. We conclude that forest fires may dramatically change emission factors and the profile of emitted BVOCs, thereby influencing the chemistry and physics of the atmosphere, the physiology of plants and the evolution of plant communities within the ecosystem.

Constitutive and herbivore-induced monoterpenes emitted by Populus x euroamericana leaves are key volatiles that orient Chrysomela populi beetles.

Chrysomela populi beetles feed on poplar leaves and extensively damage plantations. We investigated whether olfactory cues orientate landing and feeding. Young, unexpanded leaves of hybrid poplar emit constitutively a blend of monoterpenes, primarily (E)-beta-ocimene and linalool. This blend attracts inexperienced adults of C. populi that were not previously fed with poplar leaves. In mature leaves constitutively emitting isoprene, insect attack induces biosynthesis and emission of the same blend of monoterpenes, but in larger amount than in young leaves. The olfactometric test indicates that inexperienced beetles are more attracted by adult than by young attacked leaves, suggesting that attraction by induced monoterpenes is dose dependent. The blend does not attract adults that previously fed on poplar leaves. Insect-induced emission of monoterpenes peaks 4 d after the attack, and is also detected in non-attacked leaves. Induced monoterpene emission is associated in mature leaves with a larger decrease of isoprene emission. The reduction of isoprene emission is faster than photosynthesis reduction in attacked leaves, and also occurs in non-attacked leaves. Insect-induced monoterpenes are quickly and completely labelled by 13C. It is speculated that photosynthetic carbon preferentially allocated to constitutive isoprene in healthy leaves is in part diverted to induced monoterpenes after the insect attack.

Earth's degassing: a missing ethane and propane source.

Current emission inventories require an additional "unknown" source to balance the global atmospheric budgets of ethane (C2H6). Here, we provide evidence that a substantial part of the missing source can be attributed to natural gas seepage from petroliferous, geothermal, and volcanic areas. Such geologic sources also inject propane (C3H8) into the atmosphere. The analysis of a large data set of methane (CH4), ethane, and propane concentrations in surface gas emissions of 238 sites from different geographic and geologic areas, coupled with published estimates of geomethane emissions, suggests that Earth's degassing accounts for at least 17% and 10% of total ethane and propane emissions, respectively.

The methane sink associated to soils of natural and agricultural ecosystems in Italy.

In the present work, the CH4 sink associated to Italian soils was calculated by using a process-based model controlled by gas diffusivity and microbial activity, which was run by using a raster-based geographical information system. Georeferenced data included land cover CLC2000, soil properties from the European Soil Database, climatic data from the MARS-STAT database, plus several derived soils properties based on published algorithms applied to the above mentioned databases. Overall CH4 consumption from natural and agricultural sources accounted for a total of 43.3 Gg CH4 yr(-1), with 28.1 Gg CH4 yr(-1) removed in natural ecosystems and 15.1 Gg CH4 yr(-1) in agricultural ecosystems. The highest CH4 uptake rates were obtained for natural areas of Southern Apennines and islands of Sardinia and Sicily, and were mainly associated to areas covered by sclerophyllous vegetation (259.7+/-30.2 mg CH4 m(-2) yr(-1)) and broad-leaved forest (237.5 mg CH4 m(-2) yr(-1)). In terms of total sink strength broad-leaved forests were the dominant ecosystem. The overall contribution of each ecosystem type to the whole CH4 sink depended on the total area covered by the specific ecosystem and on its exact geographic distribution. The latter determines the type of climate present in the area and the dominant soil type, both factors which showed to have a strong influence on CH4 uptake rates. The aggregated CH4 sink, calculated for natural ecosystems present in the Italian region, is significantly higher than previously reported estimates, which were extrapolated from fluxes measured in other temperate ecosystems.

Isomeric analysis of BTEXs in the atmosphere using beta-cyclodextrin capillary chromatography coupled with thermal desorption and mass spectrometry.

An analytical method capable of determining trace levels of BTEX-aromatics (benzene, toluene, ethylbenzene, m-, p- and o-xylenes) in the atmosphere with as high resolution as possible has been developed. The method is based on the preconcentration of air samples using a multibed tube (Carbopack C, Carbograph 1) at ambient temperature, followed by thermal desorption, and analysis of aromatic species by a beta-cyclodextrin capillary chromatography coupled with mass spectrometry. The resolution achieved was sufficient for individual separation of BTEXs as well as m- and p-xylenes. The BTEX-ratios have been determined in an air tunnel and in on-road, suburban and rural forest atmosphere. The ethylbenzene/m-xylene ratios could provide a deep insight into anthropogenic related NMHC patterns at different locations and under different meteorological conditions and may reflect photochemical processes in the best way.

Quantitative determination of volatile organic compounds (VOC) in milk by multiple dynamic headspace extraction and GC-MS.

A method for the accurate determination of volatile organic compounds (VOC) in milk samples has been developed and tested. It combines multiple dynamic headspace extraction with GC-MS. Absolute amounts of VOC in the liquid phase are obtained by determining the first order kinetic dependence of the stepwise extraction of the analytes and internal standards from the liquid matrix. Compounds released from milk were collected on a train of traps filled with different solid sorbents to cover all components having a number of carbon atoms ranging from 4 to 15. They were analysed by GC-MS after thermal desorption of VOC from the collecting traps. Quantification of VOC in milk was performed using deuterated compounds as internal standards. The method was used to follow seasonal variations of monoterpenes in goat milk and to detect the impact of air pollution on the quality of milk.

13C labeling reveals chloroplastic and extrachloroplastic pools of dimethylallyl pyrophosphate and their contribution to isoprene formation.

Isoprene emitted from plants is made in chloroplasts from dimethylallyl pyrophosphate (DMAPP). Leaves of Populus nigra and Phragmites australis exposed to (13)CO(2) for 15 min emitted isoprene that was about 90% (13)C, but DMAPP isolated from those leaves was only 28% and 36% (13)C, respectively. The labeled DMAPP is likely to represent chloroplastic DMAPP contributing to isoprene emission. A substantial (13)C labeling was also found in both emission and DMAPP pool of low-emitting, young leaves of Phragmites. This confirms that low emission of young leaves is not caused by absence of chloroplastic DMAPP but rather by enzyme characteristics. A very low (13)C labeling was found in the DMAPP pool and in the residual isoprene emission of leaves previously fed with fosmidomycin to inhibit isoprene formation. This shows that fosmidomycin is a very effective inhibitor of the chloroplastic biosynthetic pathway of isoprene synthesis, that the residual isoprene is formed from extra-chloroplastic sources, and that chloroplastic and extrachloroplastic pathways are not cross-linked, at least following inhibition of the chloroplastic pathway. Refixation of unlabeled respiratory CO(2) in the light may explain incomplete labeling of isoprene emission, as we found a good association between these two parameters.

Characterisation of different clones of Picea abies (L.) Karst using head-space sampling of cortical tissues combined with enantioselective capillary gas chromatography for the separation of chiral and non-chiral monoterpenes.

Head-space sampling (HS) has been combined with enantioselective gas chromatography (GC) for the analysis of chiral and non-chiral monoterpenes present in the cortical tissues of five different Norway spruce clones. (1S)-(-)-alpha-Pinene, (1S,5S)-(-)sabinene, (1S)-(-)-beta-pinene, and (4S)-(-)limonene dominated over (1R)-(+)-alpha-pinene, (1R,5R)-(+)-sabinene, (1R)-(+)-beta-pinene, and (4R)-(+)-limonene. Results showed a large variation in the enantiomeric composition of cortical tissues between different clones. The development of HS-GC greatly increased the speed of precise analyses of chiral monoterpenes in small samples and therefore offer excellent opportunities in studies on the ecophysiological and chemotaxomic roles of these chiral components.

A hypothesis on the evolution of isoprenoid emission by oaks based on the correlation between emission type and Quercus taxonomy.

We show that Mediterranean oaks that emit isoprene, monoterpenes or no isoprenoids belong to different subgenera as indicated by morpho-taxonomy and molecular genetics. On the other hand, oaks from North America and Asia that are taxonomically similar to the Mediterranean monoterpene emitter Q. ilex emit isoprene only. We surmise that isoprene emission is a genetic character which evolved ancestrally in the oak genus since this is the prevalent emission type in oaks widespread around the world and adapted to different environments. This ancestral character may have been either lost or modified in more recent clades such as those originating the Mediterranean oaks. If our hypothesis is correct then the taxonomy of European oaks is validated by this independent trait. Isoprenoid emission could serve as a chemo-taxonomical marker and could be used to reconstruct the phylogeny of oaks in association with molecular markers.