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PubMed2005

Distribution of volatile organic compounds over a semiconductor Industrial Park in Taiwan.

This study examined volatile organic compounds (VOC) concentration in ambient air collected during the years 2000--2003 at several different locations of Hsinchu Science-based Industrial Park (HSIP) in Taiwan. A canister automated GC-MS system analyzed the volatile organics in ambient air grasp samples according to T0-15 method. Oxygenated volatiles were the most abundant VOC detected in HSIP followed by aromatics that are commonly used as solvents in the semiconductor industries. The major components measured in the ambient air are 2-propanol (29-135 ppbv), acetone (12-164 ppbv), benzene (0.7-1.7 ppbv), and toluene (13-20 ppbv). At some of the sampling locations, odorous compounds such as carbon disulfide and dimethyl sulfide levels exceed threshold values. The estimated toluene/benzene ratio is very high at most of the sites. However, the total amount of VOC is reduced over the years from 2000 to 2003 due to strict implementation on use and discharge of solvents in industries. There exists no definite seasonal pattern for sporadic occurrence of high levels of some of the volatile organics. Stagnant weather conditions with low wind speeds aid accumulation of toxic species at ground level. The results entail that hi-tech semiconductor industries are still a potential source for harmful organic substances to surrounding microenvironment.

2-Propanol↗

PubMed2003

Volatile organic compounds in rural atmospheres of central Portugal.

Atmospheric concentrations of volatile organic compounds were measured at two rural sites in central Portugal. The sites were chosen to be in line with the summer northwesterly sea breezes in order to study the evolution of the chemical composition of air masses during transport to inland areas. The most abundant non-oxygenated hydrocarbon in the ambient air was isoprene and the monoterpenes alpha-pinene, beta-pinene and 1,8 cineol. The maximum isoprene levels (6-7 ppb) were recorded at the most inland site, suggesting an enrichment of coastal air masses with biogenic emissions during transport over eucalyptus forests. Formaldehyde was the most prominent carbonyl compound in the atmosphere but acetaldehyde and acrolein were also abundant. Concentrations of carbonyl compounds had a tendency to be higher inland, particularly for glyoxal, methyl glyoxal, methyl vinyl ketone, metacrolein and pentanal. The observed increases indicate that carbonyls were produced by photochemical oxidation of biogenic hydrocarbons in aged air masses with coastal origin. Isoprene, monoterpenes and various carbonyls exhibited pronounced diurnal variations, which are explained on the basis of emissions from vegetation, oxidation pathways of biogenic hydrocarbons and meteorological conditions.

Agriculture↗

PubMed2001

Volatile organic compound measurements in the California/Mexico border region during SCOS97.

Measurements of volatile organic compounds (VOC) were carried out in the California/Mexico border region during the Southern California Ozone Study in the summer of 1997 (SCOS97). Integrated 3-h samples were collected in Rosarito (south of Tijuana, Mexico) and in Mexicali during intensive operational periods (IOP), twice per IOP day. VOC were collected using stainless-steel 6-1 canisters; carbonyl compounds were collected using 2,4-dinitrophenyl-hydrazine (DNPH) impregnated C18 SepPak cartridges. The canister samples were analyzed for speciated volatile hydrocarbons (C2-C12), CO, CO2, CH4, methyl t-butyl ether (MTBE), and halogenated hydrocarbons. DNPH-impregnated cartridges were analyzed for 14 C1-C7 carbonyl compounds. The concentrations of all species were higher at Mexicali than in Rosarito. A good correlation between total non-methane hydrocarbons (TNMHC), CO, and other pollutants associated with motor vehicle emissions observed for Mexicali indicates that the main source of TNMHC at this site is vehicular traffic.

Air Pollution↗

PubMed2002

A model to predict the adsorber thermal behavior during treatment of volatile organic compounds onto wet activated carbon.

A model for adsorption of volatile organic compounds (VOCs) onto a wet activated carbon bed was proposed in this study. This model accounts for temperature changes induced by the reversed and coupled mass-transfer processes of both organic species adsorption and water desorption. Indeed, it was experimentally pointed out that temperature rises, which result from the exothermal nature of the energetic interactions between the organic molecule and the activated carbon surface, are notably reduced when the adsorbent contains an initial moisture of approximately 10% in weight. Moreover, it was shown that water rate desorption was enhanced in the presence of organic vapor. This phenomenon may be explained by the displacement of sorbed water bythe organic molecules, owing to more intensive interactions with the activated carbon surface. The model proposed was elaborated from a previous comprehensive analysis of the diffusion mechanisms governing VOC adsorption at high concentrations onto a dry activated carbon bed. In a similar way, a theoretical approach was developed to model water desorption during drying of a wet activated carbon bed under pure flowing air. At last, a theoretical depiction of both competitive and reverse processes was outlined. The final model fits reasonably with experimental data relative to both breakthrough curves and thermal wave shape along the bed, even if local temperature change calculation may require some further improvement.

Adsorption↗

PubMedDate not supplied

Correlation of human olfactory responses to airborne concentrations of malodorous volatile organic compounds emitted from swine effluent.

Direct multicomponent analysis of malodorous volatile organic compounds (VOCs) present in ambient air samples from 29 swine (Sus scrofa) production facilities was used to develop a 19-component artificial swine odor solution that simulated olfactory properties of swine effluent. Analyses employing either a human panel consisting of 14 subjects or gas chromatography were performed on the air stream from an emission chamber to assess human olfactory responses or odorant concentration, respectively. Analysis of the olfactory responses using Fisher's LSD statistics showed that the subjects were sensitive to changes in air concentration of the VOC standard across dilutions differing by approximately 16%. The effect of chemical synergisms and antagonisms on human olfactory response magnitudes was assessed by altering the individual concentration of nine compounds in artificial swine odor over a twofold concentration range while maintaining the other 18 components at a constant concentration. A synergistic olfactory response was observed when the air concentration of acetic acid was increased relative to the concentration of other VOC odorants in the standard. An antagonistic olfactory response was observed when the air concentration of 4-ethyl phenol was increased relative to the other VOC odorants in the standard. The collective odorant responses for nine major VOCs associated with swine odor were used to develop an olfactory prediction model to estimate human odor response magnitudes to swine manure odorants through measured air concentrations of indicator VOCs. The results of this study show that direct multicomponent analysis of VOCs emitted from swine effluent can be applied toward estimating perceived odor intensity.

Animals↗

PubMed2006

Air to brain, blood to brain and plasma to brain distribution of volatile organic compounds: linear free energy analyses.

Partition coefficients, K(brain), for volatile organic compounds, VOCs, from air to brain have been collected for 81 compounds (air to human brain and air to rat brain). For the 81 VOCs a linear free energy equation (LFER) correlates log K(brain) with R(2) = 0.923 and S.D. = 0.346 log units. Use of training and test sets gives a predictive assessment of 0.35-0.40 log units. Combination of log K(brain) with our previously listed values of log K(blood) enables blood to brain partition, as log P(b-brain), to be obtained for 78 VOCs. These values can be correlated with R(2) = 0.725 and S.D. = 0.203 log units; use of training and test sets allows a predictive assessment for log P(b-brain) of 0.16-0.20 log units. Values for air to plasma were available for 21 VOCs. When these data were combined with the data on air to blood and air to brain, values for partition between (blood or plasma) to brain, P(bp-brain), were available for 99 VOCs. A LFER correlates this data with R(2) = 0.703 and S.D.=0.197 log units; use of training and test sets allows a predictive assessment for log P(bp-brain) of 0.15-0.20 log units.

Algorithms↗

PubMed1999

[Passive personal sampler for exposure to low concentration of volatile organic compounds].

A passive personal sampler has been developed for monitoring volatile organic compounds(VOCs) in ambient air and nonoccupational exposure. The sampler collecting target VOCs is based upon the mechanism of molecular diffusion and absorption onto a single layer of active carbon fibre (ACF) absorbent. After exposure, the ACF is transferred from the sampler into stainless steel tubes for thermal desorption. The desorbed target VOCs is analyzed by capillary GC. Under the condition of facing velocity of 10-260 cm/s, relative humidity of 30%-80%, and temperature of 10-30 C, the sampling rate for benzene, toluene, tetrachloroethylene, p-xylene and styrene is 25.74, 25.16, 25.85, 8.16 and 6.47 ml/min respectively. The analysis on the new passive sampler demonstrated that its relative overall uncertainty for target VOCs was in the range of +/- 25% compared with the active ACF tube sampling method.

Air Pollutants↗

PubMed2002

Solid phase microextraction: measurement of volatile organic compounds (VOCs) in Dhaka City air pollution.

A solid phase microextraction (SPME) technique was applied for the sampling of volatile organic compounds (VOCs) in ambient air polluted by two stroke autorickshaw engines and automobile exhausts in Dhaka city, Bangladesh. Analysis was carried out by capillary gas chromatography (GC) and GC-mass spectrometry (MS). The methodology was tested by insitu sampling of an aromatic hydrocarbon mixture gas standard with a precision of +/-5% and an average accuracy of 1-20%. The accuracy for total VOCs concentration measurement was about 7%. VOC's in ambient air were collected by exposing the SPME fiber at four locations in Dhaka city. The chromatograms showed signature similar to that of unburned gasoline (petrol) and weathered diesel containing more than 200 organic compounds; some of these compounds were positively identified. These are normal hydrocarbons pentane (n-C5H2) through nonacosane (n-C29H60), aromatic hydrocarbons: benzene, toluene, ethylbenzene, n-propylbenzene, n-butylbenzene, 1,3,5-trimethylbenzene, xylenes, and 1-isocyanato-3-methoxybenzene. Two samples collected near an autorickshaw station contained 783000 and 1479000 microg/m3 of VOCs. In particular, the concentration of toluene was 50-100 times higher than the threshold limiting value of 2000 microg/m3. Two other samples collected on street median showed 135000 microg/m3 and 180000 microg/m3 of total VOCs. The method detection limit of the technique for most semi-volatile organic compounds was 1 microg/m3.

Air Pollutants↗

PubMed2006

Development of a multibed sorption trap, comprehensive two-dimensional gas chromatography, and time-of-flight mass spectrometry system for the analysis of volatile organic compounds in human breath.

A method for the determination of volatile organic compounds (VOCs) at sub-trace levels in breath samples based on a multibed sorption trap for the collection and concentration of VOCs, a comprehensive multidimensional gas chromatograph (GCxGC) for the separation of complex mixtures, and a time-of-flight mass spectrometer detector is designed and developed. The good performance of the trap tube device developed for the concentration together with the high sensitivity and separation power of the GCxGC results in a powerful system. In the analysis of samples, more than 100 different compounds are detected of which between 65 and 85 are clearly identified. A total of approximately 250 different compounds are observed in all the samples evaluated of which 142 are identified. A preliminary study to evaluate breath biomarkers for active smoking is performed. The levels of previously described biomarkers are found to be strongly time-dependent with amounts found approximately 1 h after smoking returning to the levels found in nonsmoking volunteers. However, 2,5-dimethylfuran, 2-methylfuran, and furan are found to be effective biomarkers given that they were only found in samples taken from smokers and could still be detected more than 2 h after smoking.

Adsorption↗

PubMed2000

Cryogen free automated gas chromatography for the measurement of ambient volatile organic compounds.

An automated gas chromatographic system was constructed for measuring ambient volatile organic compounds (VOCs). Preconcentration of the VOCs was performed by using two separated sorbent traps of different combinations with each designated for either low or high boiling VOCs. Both traps and their associated valve systems were integrated as a complete system sharing a common sample inlet. Precise temperature controls for desorption relied on the use of a process controller with proportional-integral-derivative algorithm to throttle the current supply. No additional cryo-focusing stage prior to the column was needed owing to the flash heating capability for desorption. Other than the cryogen free preconcentration and focusing, the separation of VOCs of large volatility difference was also performed without cryogen. The system employed an Al2O3/KCl porous-layer open tubular column for separating C3-C7 compounds; and a DB-1 column for C6-C12. This automated GC system has been deployed in a Taiwan Environmental Protection Agency urban air quality monitoring station of Taiwan for continuous measuring C3-C7 ozone precursors. Excellent correlation between the car exhaust type of compounds measured by our GC system and carbon monoxide measured by a non-dispersive infrared spectrometer was observed, suggesting the automated GC system was robust and reliable.

Automation↗

PubMed2004

Estimating the biogenic emissions of non-methane volatile organic compounds from the North Western Mediterranean vegetation of Catalonia, Spain.

An estimation of the magnitude of non-methane volatile organic compounds (NMVOCs) emitted by vegetation in Catalonia (NE of the Iberian Peninsula, Spain), in addition to their superficial and temporal distribution, is presented for policy and scientific (photochemical modelling) purposes. It was developed for the year 2000, for different time resolutions (hourly, daily, monthly and annual) and using a high-resolution land-use map (1-km2 squared cells). Several meteorological surface stations provided air temperature and solar radiation data. An adjusted mathematical emission model taking account of Catalonia's conditions was built into a geographic information system (GIS) software. This estimation uses the latest information, mainly relating to: (1) emission factors; (2) better knowledge of the composition of Catalonia's forest cover; and (3) better knowledge of the particular emission behaviour of some Mediterranean vegetal species. Results depict an annual cycle with increasing values in the March-April period with the highest emissions in July-August, followed by a decrease in October-November. Annual biogenic NMVOCs emissions reach 46.9 kt, with monoterpenes the most abundant species (24.7 kt), followed by other biogenic volatile organic compounds (e.g. alcohols, aldehydes and acetone) (16.3 kt), and isoprene (5.9 kt). These compounds signify 52%, 35% and 13%, respectively, of total emission estimates. Peak hourly total emission for a winter day could be less than 10% of the corresponding value for a summer day.

Environmental Monitoring↗

PubMed1995

Marine Vibrio species produce the volatile organic compound acetone.

While screening aerobic, heterotrophic marine bacteria for production of volatile organic compounds, we found that a group of isolates produced substantial amounts of acetone. Acetone production was confirmed by gas chromatography, gas chromatography-mass spectrometry, and high-performance liquid chromatography. The major acetone producers were identified as nonclinical Vibrio species. Acetone production was maximal in the stationary phase of growth and was stimulated by addition of l-leucine but not the other common amino acids, suggesting that leucine degradation leads to acetone formation. Acetone production by marine vibrios may contribute to the dissolved organic carbon associated with phytoplankton, and some of the acetone produced may be volatilized to the atmosphere.

Journal Article↗

PubMed2005

Volatile organic compounds in selected micro-environments.

A program of sampling for volatile organic compounds (VOCs) in ambient air was undertaken in selected locations and micro-environments in Perth, Western Australia to characterise concentrations of target VOCs and to determine the relative strength of the contributing sources to ambient air in different micro-environments in a major Australian city. Twenty-seven locations were sampled and, of the forty-one target compounds, 26 VOCs were detected in the samples collected. The highest concentrations were recorded for benzene, toluene, ethylbenzene, xylenes (BTEX), chloroform and styrene. The maximum 12-h toluene and benzene concentrations observed were from a basement carpark and were 24.7 parts per billion (ppb) and 5.6 ppb, respectively. The maximum xylenes concentration was 29.4 ppb and occurred in a nightclub where styrene was also detected. A factor analysis of the data was undertaken. Two key factors emerge that appear to be associated with petroleum and motor vehicles and environmental tobacco smoke. A third significant occurrence was a high concentration of chloroform that was observed at a sports centre complex with a swimming pool text and was uncorrelated with other compounds in the data set. This study indicates that locations associated with motor vehicles and petrol fuel, tobacco and wood smoke and chlorinated water represent the major risks for personal exposure to VOCs in Perth.

Air Pollutants↗

PubMed2006

Volatile organic compounds released by the entomopathogenic fungus Beauveria bassiana.

The composition of volatile organic compounds (VOC) released by the entomopathogenic fungus Beauveria bassiana (Hyphomycete: Deuteromycotina) utilizing two different carbon sources was investigated. Analyses were performed by solid-phase microextraction (SPME) coupled to capillary gas chromatography (CGC) and CGC-mass spectrometry (MS). Major components in glucose-grown cultures were diisopropyl naphthalenes, ethanol, and sesquiterpenes. Alkane-grown fungal VOC switched to a fingerprint with prevalence of n-decane. This is the first report on the volatiles released by entomopathogenic fungi.

Alkanes↗

PubMedDate not supplied

Attenuation of methane and volatile organic compounds in landfill soil covers.

The potential for natural attenuation of volatile organic compounds (VOCs) in landfill covers was investigated in soil microcosms incubated with methane and air, simulating the gas composition in landfill soil covers. Soil was sampled at Skellingsted Landfill at a location emitting methane. In total, 26 VOCs were investigated, including chlorinated methanes, ethanes, ethenes, fluorinated hydrocarbons, and aromatic hydrocarbons. The soil showed a high capacity for methane oxidation resulting in very high oxidation rates of between 24 and 112 microg CH4 g(-1) h(-1). All lower chlorinated compounds were shown degradable, and the degradation occurred in parallel with the oxidation of methane. In general, the degradation rates of the chlorinated aliphatics were inversely related to the chlorine to carbon ratios. For example, in batch experiments with chlorinated ethylenes, the highest rates were observed for vinyl chloride (VC) and lowest rates for trichloroethylene (TCE), while tetrachloroethylene (PCE) was not degraded. Maximal oxidation rates for the halogenated aliphatic compounds varied between 0.03 and 1.7 microg g(-1) h(-1). Fully halogenated hydrocarbons (PCE, tetrachloromethane [TeCM], chlorofluorocarbon [CFC]-11, CFC-12, and CFC-113) were not degraded in the presence of methane and oxygen. Aromatic hydrocarbons were rapidly degraded giving high maximal oxidation rates (0.17-1.4 microg g(-1) h(-1)). The capacity for methane oxidation was related to the depth of oxygen penetration. The methane oxidizers were very active in oxidizing methane and the selected trace components down to a depth of 50 cm below the surface. Maximal oxidation activity occurred in a zone between 15 and 20 cm below the surface, as this depth allowed sufficient supply of both methane and oxygen. Mass balance calculations using the maximal oxidation rates obtained demonstrated that landfill soil covers have a significant potential for not only methane oxidation but also cometabolic degradation of selected volatile organics, thereby reducing emissions to the atmosphere.

Bacteria↗

PubMed1996

Microbial volatile organic compounds--what substances can be found in sick buildings?

There is a relationship between damp buildings and health complaints. Damp conditions in building constructions also favour the growth of micro-organisms. Growth of micro-organisms results in the production of volatile organic compounds, which has been shown to have an impact on Indoor-air monitored via a microbial volatile organic compound (MVOC) analysis. In order to widen the applicability of MVOC analysis, it is necessary to increase this analysis by including more volatiles. By active sampling on Anasorb 747 and selected ion monitoring on a mass spectrometer equipped with a quadropole detector, it is possible to determine these volatiles with sufficient accuracy in indoor air of non-industrial buildings.

Air Microbiology↗

PubMed2005

Air to blood distribution of volatile organic compounds: a linear free energy analysis.

Partition coefficients, K(blood), for volatile organic compounds from air to blood have been collected for 155 compounds (air to human blood) and 127 compounds (air to rat blood). For 86 common compounds, the average error, AE, between the two sets of log K(blood) values is 0.12 log units, somewhat smaller than our estimated interlaboratory average SD value of around 0.16 log units. We conclude that with regard to experimental errors, there is no significant difference between K(blood) values in human blood and in rat blood. There are 196 compounds for which either or both K(blood) (human) and K(blood) (rat) are available. A training set of 98 compounds could be fitted with the Abraham solvation parameters with R(2) = 0.933 and SD = 0.34 log units. The training equation was then used to predict the test set of values with AE = 0.04 log units, SD = 0.33 log units, and an average absolute error, AAE, of 0.25 log units. A second training and test set yielded similar values: AE = 0.01, SD = 0.39, and AAE = 0.29 log units. It is concluded that it is possible to construct an equation capable of predicting further values of log K(blood) to around 0.30 log units. Because the descriptors used in the correlation equations can be predicted from structure, it is now possible to predict log K(blood) for any chemical structure.

Air↗

PubMed2003

Source profiles and ozone formation potentials of volatile organic compounds in three traffic tunnels in Kaohsiung, Taiwan.

Twenty-five volatile organic compounds (VOCs) up to C10 were measured using Carbotrap multibed thermal adsorption tubes during the morning and afternoon rush hours on four different days in all three traffic tunnels in Kaohsiung, Taiwan. A gas chromatograph (GC) equipped with a flame-ionization detector (FID) was then used to analyze the VOCs. The analytical results show that VOC concentrations increase with traffic flow rate, and emission profiles in the three tunnels are mostly in the range C2-C6. In addition to the traffic conditions and vehicle type, the pattern of emissions in each tunnel was also influenced by other factors, such as vehicle age, nearby pollution sources, and the spatial or temporal variation of VOCs in the urban atmosphere. The ozone formation potential (OFP) in each tunnel was assessed based on the maximum incremental reactivities of the organic species, demonstrating that OFP increases with traffic flow rate. Vehicle distribution influences the contributions of organic group to OFP in a tunnel. Meanwhile, when ranked in descending order of contribution to OFP in all tunnels, the organic groups followed the sequence olefins, aromatics, and paraffins.

Air Pollutants↗