Volatile Organic Compounds Families Research Articles

Feasibility of using volatile urine fingerprints for the differentiation of sexually transmitted infections

Sexually transmitted infections (STIs) are a public health problem worldwide, and current diagnostic methods have certain limitations. In recent years, volatile organic compounds (VOCs) have been studied as an alternative diagnostic method. Due to this, this study aimed to detect, in vaginal swabs and urine samples, VOCs emitted by highly prevalent STIs-causing bacteria (Chlamydia trachomatis, Mycoplasma genitalium, and Neisseria gonorrhoeae) to identify potential biomarkers that allow the detection of these STIs. VOCs detected in urine samples showed a better differentiation of patients with STIs due to C. trachomatis from those not infected, with 2,6-dimethyl-4-heptanone as the volatile compound most related to the presence of this bacterium. Among the VOCs most related to M. genitalium in urine, 4-methyltetradecane and 2-methylpentadecane stood out, while 3,4,4-trimethyl-2-cyclohexen-1-one was the VOC most closely related to N. gonorrhoeae infection. Moreover, C12 alcohols were the main VOC family associated with positive samples in all three bacteria, which could indicate the presence of aldehyde reductases in their metabolism. In contrast, alcohols such as 3-methyl-1-heptanol and 1-octanol, as well as dimethyl esters, were more associated with negative samples and may be useful in ruling out an STI caused by one of these three bacteria. In short, the VOCs identified as potential biomarkers in patients with infection by C. trachomatis, M. genitalium, or N. gonorrhoeae could be used in the early diagnosis of these STIs, quickly interrupting the chain of transmission, especially interesting in asymptomatic patients.Key points• Sexually transmitted infections are a serious public health problem worldwide.• The study of VOCs in multiple infections is increasing in recent years.• The identification of volatile biomarkers could allow new diagnostic methods.Graphical abstract

Local atomic structure order and electrochemical properties of NiO based nano-catalysts for ethanol sensing at room temperature

The increased emission of volatile organic compounds (VOCs) and their adverse effects on environment led to the development of more economical and sustainable sensing technologies. Ethanol is a member of VOC family and has harmful effect on human health and environment. Therefore, an efficient electrocatalyst for ethanol detection at ambient temperature is highly desirable. Here we present the successful synthesis of NiO based sensing material where modification of NiO was carried out by transition metals doping (8% Cu and 8% Zn) and codoping (4% Cu + 4% Zn). The synthesized catalysts were characterized by several techniques like powder X ray diffraction, Raman spectroscopy, scanning electron microscopy, X-ray absorption fine structure, Brunauer–Emmett–Teller and diffuse reflectance spectroscopy. The electrochemical responses showed that the codoped NiO has a better catalytic performance towards ethanol detection with a wide linear range from 3 mM to 12 mM, and a low detection limit (LOD) of 2.2 mM. The striking analytical performance and facile preparation technique make this catalyst effective for efficient enzyme-free electrochemical ethanol sensing.

Prediction of heel build-up on activated carbon using machine learning

Determining the long-term performance of adsorbents is crucial for the design of air treatment systems. Heel buildup i.e., the accumulation of non-desorbed/ non-desorbable adsorbates and their reaction byproducts, on the surface/pores of the adsorbent is a primary cause of adsorption performance deterioration. However, due to the complexity of heel buildup mechanisms, theoretical models have yet to be developed to map the extent of heel buildup to the adsorption/desorption parameters. In this work, two machine learning (ML) algorithms (XGBoost and neural network (NN)) were applied to predict volatile organic compounds (VOCs) cyclic heel buildup on activated carbons (ACs) by considering the adsorbent characteristics, adsorbate properties and regeneration conditions. The NN algorithm showed better performance in prediction of cyclic heel buildup (R2 = 0.94) than XGBoost (R2 = 0.81). To analyze interaction between heel buildup and adsorbent characteristics, adsorbate properties, and regeneration conditions, partial dependency plots were generated. The proposed ML-based heel prediction methods can be ultimately used to: (i) optimize adsorption/desorption operating conditions to minimize heel buildup on activated carbon in cyclic adsorption/desorption processes and (ii) quickly screen various adsorbents for efficient adsorption/desorption of a particular family of VOCs by excluding adsorbents prone to high heel formation.

Vacuum ultraviolet free-electron laser photoionization mass spectrometry of alpha-pinene ozonolysis

α-pinene is the most abundant monoterpene that represents an important family of volatile organic compounds. Molecular identification of key transient compounds during the α-pinene ozonolysis has been proven to be a challenging experimental target because of a large number of intermediates and products involved. Here we exploit the recently developed hybrid instruments that integrate aerosol mass spectrometry with a vacuum ultraviolet free-electron laser to study the α-pinene ozonolysis. The experiments of α-pinene ozonolysis are performed in an indoor smog chamber, with reactor having a volume of 2 m3 which is made of fluorinated ethylene propylene film. Distinct mass spectral peaks provide direct experimental signatures of previously unseen compounds produced from the reaction of α-pinene with O3. With the aid of quantum chemical calculations, plausible mechanisms for the formation of these new compounds are proposed. These findings provide crucial information on fundamental understanding of the initial steps of α-pinene oxidation and the subsequent processes of new particle formation.

Gaseous Emissions from the Composting Process: Controlling Parameters and Strategies of Mitigation

Organic waste generation, collection, and management have become a crucial problem in modern and developing societies. Among the technologies proposed in a circular economy and sustainability framework, composting has reached a strong relevance in terms of clean technology that permits reintroducing organic matter to the systems. However, composting has also negative environmental impacts, some of them of social concern. This is the case of composting atmospheric emissions, especially in the case of greenhouse gases (GHG) and certain families of volatile organic compounds (VOC). They should be taken into account in any environmental assessment of composting as organic waste management technology. This review presents the relationship between composting operation and composting gaseous emissions, in addition to typical emission values for the main organic wastes that are being composted. Some novel mitigation technologies to reduce gaseous emissions from composting are also presented (use of biochar), although it is evident that a unique solution does not exist, given the variability of exhaust gases from composting.

Quality and volatile organic compounds emission alterations in ‘August Flame’ peaches due to low dose methyl bromide fumigation

As all perishable fruit, peaches must be stored in cold temperature during transportation for maintenance of fruit quality. Australian peaches exported to China must undergo fumigation quarantine treatments prior to shipment for biosecurity reasons. ‘August Flame’ peaches were fumigated with methyl bromide (MB) at the low dosage of 18 g/m3 for 5.5 h at flesh temperature of 18 °C, as a biosecurity disinfestation treatment, with a subsequent cold storage period at 2 °C and 4 °C for 5 and 9 d to simulate air freight transportation. Fruit quality parameters measured during shelf life (SL) were: firmness, index of delta absorbance (IAD), ethylene production and respiration. Four families of volatile organic compounds (VOCs) from samples of fruit flesh and skin were analysed along SL: aldehydes, alcohols, esters and lactones. Overall trends in the evolution of quality parameters and VOCs emissions were identified. Fumigation, under our experimental conditions, anticipated the climacteric ethylene peak, but did not affect fruit quality enough to be detrimental for consumption and did not cause skin or internal disorders. During SL aldehydes decreased, lactones increased, alcohols were higher in skin than in flesh, but none of these general trends were clearly affected by the fumigation.

Evolution of volatile compounds during dry‐cured deer loin processing

SummaryDuring dry‐cured meat processing, several reactions leads to the development of volatile organic compounds (VOCs) responsible for a typical flavour and aroma. Hence, this study aimed to access the evolution of VOCs profile in dry‐cured deer loin during its manufacture at day 0, 30 and 60. For the sake of characterising the changes of VOCs, 8 chemical families (95 compounds) were identified, with the hydrocarbons (terpenes), ketones, acids and aldehydes as the most powerful descriptors for ripening period. Meanwhile, the most abundant compounds were acetoin and o‐cymene. Except for ‘others’, all VOCs families steadily increased (P < 0.001) along processing and reached their content at 60 days. The main VOCs found in the present research, which derived mainly from the degradation of lipids and amino acids/proteins during ripening stage, contributed to the VOCs profile evolution. This fact agrees with the results obtained in a previous study about the lipolytic, proteolytic and oxidative changes of dry‐cured deer loin during processing. Additionally to the general increase of volatiles, other specific VOCs play a vital role in the dry‐cured deer loin aroma, such as 2‐ketones, acetoin, alcohols (1‐octanol, 1‐hexanol, 1‐octen‐3‐ol), aliphatic (pentanal, hexanal, heptanal) and branched aldehydes (butanal, 2‐methyl and butanal, 3‐methyl), furans, acids and esters. The content of these compounds showed a dramatic increase, which produce the typical odour of cured meat, while the terpenoids provide the VOCs derived from spices. Within these compounds, the results indicated that the ketones, aldehydes and acids chemical family could play an important role on the aroma and flavour of dry‐cured deer loin. However, it is important to note that further studies should be performed evaluating the sensory characteristics and acceptability of dry‐cured deer loin.

Characteristics of wintertime VOCs in urban Beijing: Composition and source apportionment

Abstract Characteristics and sources of volatile organic compounds (VOCs) were investigated with highly time-resolved measurements by a proton-transfer-reaction time-of-flight mass spectrometer (PTR-ToF-MS) at an urban site in Beijing in winter 2017. During the measurement period, high mixing ratios of VOCs (48.9 ppbv) and trace gases were observed, with alternating episodes of strong haze pollution and clean air. Ten VOC families showed clear dependence on the VOC concentration. Aromatics increased the most during haze, with significantly elevated benzene concentration at high VOC concentration, while CxHyO3 and CxHy increased the least. The positive matrix factorization (PMF) receptor model was applied to the VOC mass spectra, yielding four major VOC factors: traffic emissions (21.0%), solid fuel combustion (SFC, 24.4%), and two oxygenated VOC (OVOC) factors (32.3% and 22.3%). Traffic and solid fuel combustion were dominant during the periods of high total VOC concentration, while the OVOC1 fraction was reduced. Comparisons with organic aerosol (OA) sources showed increased oxygenated organic aerosol (OOA) concentration during high VOC concentration periods, indicating the importance of OVOCs to secondary organic aerosol formation. Furthermore, trajectory analysis showed that most of the clean days were associated with northerly winds with high ratios of OVOC1. In contrast, the haze periods were not only due to high primary emissions under stagnant conditions, but also influenced by air masses from a more regional scale.

Indoor volatile organic compounds exposures and risk of childhood acute leukemia: a case-control study in shanghai

A case-control study was conducted to investigate the relationship between indoor air pollution and childhood acute leukemia (AL) in Shanghai. 97 cases and 148 gender-, age-, and residence-matched controls were included. Indoor air pollution was evaluated by questionnaires and quantitative measurement including 14 volatile organic compounds (VOCs) and nitrogen dioxide (NO2) in the homes of the two groups. The levels of individual VOCs, VOC families, TVOC (sum of the concentrations of the individual VOCs) and NO2 were compared between the two groups. Exposure to styrene and butyl alcohol were associated with an increased risk of childhood AL (styrene: odds ratio (OR)=2.33, 95% confidence interval (CI): 1.07-5.07; butyl alcohol: OR = 2.51, 95%CI: 1.19-5.28); 4th quartile of chlorinated hydrocarbons (OR = 2.52, 95%CI: 1.02-6.26) and 3rd quartile of TVOC (OR = 4.03, 95%CI: 1.06-6.81) had significant higher ORs for childhood AL compared with that in the lowest quartiles. Elevated levels of individual VOCs, VOC families and TVOC were also associated with self-reported risk factors. Our findings suggest that VOCs exposure was associated with an elevated risk of childhood AL, underscore that more attention should be paid to indoor air pollution as a risk factor of childhood AL.

Towards the Establishment of Baseline Scientific Information Based on the Volatile Organic Compounds (VOCs) of Philippine Traditional Alcoholic Beverages

Investigations on four Philippine traditional alcoholic beverages – namely, lambanog, tapuy, basi, and tuba – were carried out by determining volatile organic compounds (VOCs) in these beverages. Headspace gas chromatography with flame ionization detection (HS-GC-FID) is employed in this study to quantify four compounds – namely, ethanol, ethyl acetate, isoamyl alcohol, and isobutyl alcohol. Mean concentration values for the these VOCs within each beverage type were found to be as follows: 35.69% (v/v) ethanol, 329.67 mg/L ethyl acetate, 145.03 mg/L isoamyl alcohol, and 51.86 mg/L isobutyl alcohol for lambanog; 10.86% (v/v) ethanol, 212.87 mg/L ethyl acetate, 175.82 mg/L isoamyl alcohol, and 37.98 mg/L isobutyl alcohol for tapuy; 11.06% (v/v) ethanol, 114.18 mg/L ethyl acetate, 247.45 mg/L isoamyl alcohol, and 66.54 mg/L isobutyl alcohol for basi; and 8.79% (v/v) ethanol, 351.77 mg/L ethyl acetate, 68.74 mg/L isoamyl alcohol, and 16.23 mg/L isobutyl alcohol for tuba. Results showed that there is wide variability in the VOCs quantified in the four beverages, possibly on account of the sampling site, raw material used, and manufacturing process. Preliminary gas chromatography – mass spectrometry (GC-MS) studies qualitatively confirm the presence of other families of VOCs. The results from this study are envisioned to serve as new baseline information on Philippine traditional beverages.

Environmental performance of an industrial biofilter: Relationship between photochemical oxidation and odorous impacts

Biological techniques are widely used to treat gaseous streams derived from waste treatment plants. The generation of volatile organic compounds (VOCs) is one of the principal pollution sources in composting facilities from which nuisance odours are released. In addition, the generation of photochemical smog with other gases such as NOX can produce ozone at ground level due to their photochemical ozone creation potential (POCP). In this work, the performance of an industrial biofilter was evaluated from an environmental point of view. Specifically, this study evaluated the potential impact in terms of photochemical oxidation and odour emission derived from composting in a vessel under four different aeration conditions. Gas chromatography–time-of-flight mass spectrometry (GC-TOFMS) was used to perform the chemical characterisation of the gaseous streams, while dynamic olfactometry was used to carry out the sensorial analysis. A total of 95 compounds belonging to 12 different families of VOCs were selected. Principal component analysis revealed the influence of each VOC family on each impact category and explained 88% of the total variance. Multivariate regression was used to study the correlation between photochemical oxidation and odour impact, which has never been reported before. The correlations obtained (r ≥ 0.97) evidenced the direct relationship between these two impacts. Photochemical oxidation and odour emission were proven to be important environmental impacts derived from composting facilities, whose abatement might be carried out by biofiltration systems.

Indoor exposure to particulate matter and volatile organic compounds in dwellings and workplaces and respiratory health in French farmers

IntroductionFew investigations have related objective assessments of indoor air pollutants to respiratory health in farmers, in spite of the many rural environmental hazards to which they are exposed. Chemical air pollution has been particularly neglected.ObjectiveWe investigated the relationships of indoor exposure to particulate matter (PM) and volatile organic compounds (VOCs) to respiratory health in farmers.MethodsNineteen VOCs (5 families) and PM (from ultrafine to total suspended particles (TSP)) were objectively assessed in dwellings and workplaces in 109 French farmers during a week. To take into account multiple exposures, scores of exposure were computed for total VOCs and VOCs families. Individuals filled a standardized questionnaire and underwent spirometry with bronchodilation test.ResultsOn average, VOCs concentrations were higher in dwellings than in workplaces. The reverse was observed for PM. When considering the mean concentrations of air pollutants for the whole farm (dwellings + workplaces), asthma (9.3%) was positively associated with elevated exposure to benzene (adjusted odds-ratio (ORa) = 6.64, 95%CI: 1.56–28.27), trichloroethylene (4.80, 1.00–23.30) and halogenated hydrocarbons score (2.9, 95% 1.3–6.8). Early airway obstruction (FEF25–75 < 80%, with normal FEV1 and FVC and FEV/FVC ≥ 70%) (29.8%) was related to elevated exposure to 2-butoxyetylacetate (11.49, 1.55–85.37) and glycol ethers score (2.0; 1.0–4.1) in the whole farm and to PM2.5 (ORa = 5.26, 95% CI: 1.09–25.28) in the granary/stable. The risk of Chronic Obstructive Pulmonary Diseases (FEV/FVC < 70%) (COPD) (4.26%) was found to be larger with elevated exposure to aldehydes (OR = 3.95, 1.09–14.26).ConclusionIndoor chemical air pollution is detrimental to farmers’ respiratory health. More epidemiological investigations with detailed exposure assessments and clinical measures of respiratory effects are needed in rural settings to corroborate these findings.

Indoor exposure to particulate matter and volatile organic compounds in dwellings and workplaces and respiratory health in French farmers

Introduction: Few investigations have related objective assessments of indoor air pollutants to respiratory health in farmers, in spite of the many rural environmental hazards to which they are exposed. Chemical air pollution has been particularly neglected. Objective: We investigated the relationships of indoor exposure to particulate matter (PM) and volatile organic compounds (VOCs) to respiratory health in farmers. Methods: Nineteen VOCs (5 families) and PM (from ultrafine to total suspended particles (TSP)) were objectively assessed in dwellings and workplaces in 109 French farmers during a week. To take into account multiple exposures, scores of exposure were computed for total VOCs and VOCs families. Individuals filled a standardized questionnaire and underwent spirometry with bronchodilation test. Results: On average, VOCs concentrations were higher in dwellings than in workplaces. The reverse was observed for PM. When considering the mean concentrations of air pollutants for the whole farm (dwellings + workplaces), asthma (9.3%) was positively associated with elevated exposure to benzene (adjusted odds-ratio (ORa) = 6.64, 95%CI: 1.56–28.27), trichloroethylene (4.80, 1.00–23.30) and halogenated hydrocarbons score (2.9, 95% 1.3–6.8). Early airway obstruction (FEF25–75 &lt; 80%, with normal FEV1 and FVC and FEV/FVC ≥ 70%) (29.8%) was related to elevated exposure to 2-butoxyetylacetate (11.49, 1.55–85.37) and glycol ethers score (2.0; 1.0–4.1) in the whole farm and to PM2.5 (ORa = 5.26, 95% CI: 1.09–25.28) in the granary/stable. The risk of Chronic Obstructive Pulmonary Diseases (FEV/FVC &lt; 70%) (COPD) (4.26%) was found to be larger with elevated exposure to aldehydes (OR = 3.95, 1.09–14.26). Conclusion: Indoor chemical air pollution is detrimental to farmers’ respiratory health. More epidemiological investigations with detailed exposure assessments and clinical measures of respiratory effects are needed in rural settings to corroborate these findings.

Biochar reduces volatile organic compounds generated during chicken manure composting

The efficiency of biochar for reducing the levels of volatile organic compounds (VOC) was investigated in a composting mixture containing 90% poultry manure and 10% straw (with and without 3% biochar addition) at three different stages of the process. The use of a low application rate of biochar reduced the concentration of VOC during the thermophilic phase. Biochar significantly reduced the levels of nitrogen volatile compounds, which are the most abundant VOC family, originated from microbial transformation of the N-compounds originally present in manure. The most efficient VOC reduction was observed in oxygenated volatile compounds (ketones, phenols and organic acids), which are intermediates of organic matter degradation, whereas there was no effect on other VOC families (aliphatic, aromatic and terpenes). These results suggest the importance of not only the sorption capacity of biochar but also its impact in the composting progress as main drivers for VOC reduction.

Emission characteristics of VOCs and potential ozone formation from a full-scale sewage sludge composting plant

Volatile organic compounds (VOCs) are the major components of the odor emitted from sewage sludge composting plants and are generally associated with odorous nuisances and health risks. However, few studies have considered the potential ozone generation caused by VOCs emitted from sewage sludge composting plants. This study investigated the VOC emissions from a full-scale composting plant. Five major treatment units of the composting plant were chosen as the monitoring locations, including the dewatered room, dewatered sludge, blender room, fermentation workshop, and product units. The fermentation workshop units displayed the highest concentration of VOC emissions at 2595.7 ± 1367.3 μg.m−3, followed by the blender room, product, dewatered sludge, and dewatered room units, whose emissions ranged from 142.2 ± 86.8 μg.m−3 to 2107.6 ± 1045.6 μg.m−3. The detected VOC families included oxygenated compounds, alkanes, alkenes, sulfide compounds, halogenated compounds, and aromatic compounds. Oxygenated compounds, particularly acetone, were the most abundant compounds in all samples. Principal component analysis revealed that the dewatered room and dewatered sludge units clustered closely, as indicated by their similar component emissions. The product units differed from the other sampling units, as their typical compounds were methanethiol, styrene, carbon disulfide, and hexane, all of which were the products of the latter stages of composting. Among the treatment units, the fermentation workshop units had the highest propylene equivalent (propy-equiv) concentration. Dimethyl disulfide and limonene were the major contributors. Limonene had the highest propy-equiv concentration, which contributed to the increased atmospheric reactivity and ozone formation potential in the surrounding air. To control the secondary environmental pollution caused by the VOC emissions during sewage sludge composting, the emission of limonene and dimethyl disulfide must be controlled from the blender room and fermentation workshop units.

Adsorption and Quantification of Volatile Organic Compounds (VOCs) by using Hybrid Magnetic Nanoparticles.

The ability of Fe3 O4 magnetic nanoparticles decorated with perylene bisimides to adsorb aromatic volatile organic compounds (VOCs) is reported. We have used DFT-D3 calculations to anticipate the strong ability of the electron-poor perylene bisimide to form noncovalent complexes with electron-rich aromatic rings belonging to the VOC family. Subsequently, we synthesized a hybrid magnetic nanomaterial based on bisimide perylene dopamine and iron oxide nanoparticles. This material was used to fill a sorbent tube to study its ability to adsorb aromatic VOCs. We connected two tubes in series filled with the hybrid nanoparticles. The analysis of the front and back tubes was performed by thermal desorption (TD) coupled with capillary gas chromatography (GC)/flame ionization detector (FID). Adsorption values (defined as %VOCs found in the back tube) were determined for a series of aromatic VOCs and compared with the DFT binding energies. The tubes can be desorbed and reutilized more than 200 times without losing their properties.

Relationships between emitted volatile organic compounds and their concentration in the pile during municipal solid waste composting

Composting operations taking place at municipal solid waste (MSW) treatment plants represent a source of volatile organic compounds (VOC) to the atmosphere. Understanding the variables governing the release of VOC at these facilities is crucial to assess potential health risks for site workers and local residents. In this work the changes in the VOC composition of a composting pile were monitored and compared to the VOC emmited from the same pile in order to understand the impact of composting operations on the release of VOC. More than one hundred VOC were indentified in the solid phase of the composting piles, which were dominated by terpenes (about 50% of the total amount of VOC) and in a lower quantity alcohols, volatile fatty acids and aromatic compounds. There was a reduction in the total concentration of VOC in the pile during composting, from 45 to 35 mg/kg, but the compostion and distribution of VOC families remained stable in the pile even in the mature compost. However, there was no correlation between the emitted VOC and their concentration in the composting pile. The VOC emission pattern was affected by the biological activity in the pile (measured by temperature, CO2 evolution and the presence of CH4 emissions). The highest VOC emissions were detected at early stages of the process, alongside with the generation of CH4 in the pile, and then decreased sharply in the mature compost as a consequence of biodegradation and volatilisation. These results pointed to the importance of composting operation rather than the composition of the raw materials on the release of VOC in composting plants.

Characterization of odorous compounds and odor load in indoor air of modern complex MBT facilities

Gaseous emissions and chemical compounds responsible for odor nuisance are the most common social concerns arising from modern municipal mechanical-biological waste treatment (MBT) facilities. Regarding to this, an inventory of indoor concentrations of hydrogen sulfide and volatile organic compounds (VOCs) along with odor analyses were carried out at three different full-scale MBT facilities. 48-h profiles of total volatile organic compounds (tVOCs) and hydrogen sulfide were performed in selected areas (reception warehouse, pretreatment, anaerobic digestion and composting areas) and a complete gases and odor characterization were performed at two selected moments of the day according to maximum and minimum tVOCs concentrations, which corresponded to day/night variations. Terpenoids, aromatic hydrocarbons and aliphatic hydrocarbons were the families of VOCs more often detected. The average percentage of contribution of these three VOCs families was 32, 21 and 24%, respectively, while the average percentage of contribution of other VOCs families ranged from 0.2 to 5.5%. A multiple regression method was developed as a simple tool for odor modeling and prediction, showing that 98.5% (p<0.001) of the variance in odor concentration could be explained by the concentrations of hydrogen sulfide and tVOCs. Results obtained suggested that optimization of indoor ventilation systems and, concomitantly, operational costs of MBT facilities was possible in certain locations where ventilation could be reduced up to 20–25% during night hours.

Adsorption of Volatile Organic Compounds on Zeolite L

The adsorption properties of commercial zeolite L for various types of probe molecules selected from different families of volatile organic compounds were studied. The probe molecules had various sizes and polarities and included hexane isomers (n-hexane and cyclohexane), aromatic molecules (benzene and toluene), oxygenated molecules (ethanol, acetone, and methyl ethyl ketone), and a chlorinated molecule (trichloroethane). The adsorption isotherms were determined at two temperatures and modeled by the Dubinin–Astakhov (DA) and Toth equations. The DA equation was applicable for a broader range of experimental conditions.

Remote sensing estimation of isoprene and monoterpene emissions generated by natural vegetation in Monterrey, Mexico.

In addition to oxygen, hydrocarbons are the most reactive chemical compounds produced by plants into the atmosphere. These compounds are part of the family of volatile organic compounds (VOCs) and are discharged in a great variety of forms. Among the VOCs produced by natural sources such as vegetation, the most studied until today are the isoprene and monoterpene. These substances can play an important role in the chemical balance of the atmosphere of a region. In this project, we develop a methodology to estimate the natural (vegetation) emission of isoprene and monoterpenes and applied it to the Monterrey Metropolitan Area, Mexico and its surrounding areas. Landsat-TM data was used to identify the dominant vegetation communities and field work to determine the foliage biomass density of key species. The studied communities were submontane scrub, oak, and pine forests and a combination of both. We carried out the estimation of emissions for isoprene and monoterpenes compounds in the different plant communities, with two different criteria: (1) taking into account the average foliage biomass density obtained from the various sample point in each vegetation community, and (2) using the foliage biomass density obtained for each transect, associated to an individual spectral class within a particular vegetation type. With this information, we obtained emission maps for each case. The results show that the main producers of isoprene are the communities that include species of the genus Quercus, located mainly on the Sierra Madre Oriental and Sierra de Picachos, with average isoprene emissions of 314.6 ton/day and 207.3 ton/day for the two methods utilized. The higher estimates of monoterpenes were found in the submontane scrub areas distributed along the valley of the metropolitan zone, with an estimated average emissions of 47.1 ton/day and 181.4 tons for the two methods respectively.