Trends Of Volatile Organic Compounds Research Articles

Evaluation of Typical Volatile Organic Compounds Levels in New Vehicles under Static and Driving Conditions.

In modern societies, the air quality in vehicles has received extensive attention because a lot of time is spent within the indoor air compartment of vehicles. In order to further understand the level of air quality under different conditions in new vehicles, the vehicle interior air quality (VIAQ) in new vehicles with three different brands was investigated under static and driving conditions, respectively. Air sampling and analysis are conducted under the requirement of HJ/T 400-2007. Static vehicle tests demonstrate that with the increasing of vehicle interior air temperature in sunshine conditions, a higher concentration and different types of volatile organic compounds (VOCs) release from the interior materials than that in the environment test chamber, including alkanes, alcohols, ketones, benzenes, alkenes, aldehydes, esters and naphthalene. Driving vehicle tests demonstrate that the concentration of VOCs and total VOCs (TVOC) inside vehicles exposed to high temperatures will be reduced to the same level as that in the environment test chamber after a period of driving. The air pollutants mainly include alkanes and aromatic hydrocarbons. However, the change trends of VOCs and TVOC vary under different conditions according to various kinds of factors, such as vehicle model, driving speed, air exchange rate, temperature, and types of substance with different boiling points inside the vehicles.

Traffic, transport, and vegetation drive VOC concentrations in a major urban area in Texas

The population of Texas has increased rapidly in the past decade. The San Antonio Field Study (SAFS) was designed to investigate ozone (O3) production and precursors in this rapidly changing, sprawling metropolitan area. There are still many questions regarding the sources and chemistry of volatile organic compounds (VOCs) in urban areas like San Antonio which are affected by a complex mixture of industry, traffic, biogenic sources and transported pollutants. The goal of the SAFS campaign in May 2017 was to measure inorganic trace gases, VOCs, methane (CH4), and ethane (C2H6). The SAFS field design included two sites to better assess air quality across the metro area: an urban site (Traveler's World; TW) and a downwind/suburban site (University of Texas at San Antonio; UTSA). The results indicated that acetone (2.52 ± 1.17 and 2.39 ± 1.27 ppbv), acetaldehyde (1.45 ± 1.02 and 0.93 ± 0.45 ppbv) and isoprene (0.64 ± 0.49 and 1.21 ± 0.85 ppbv; TW and UTSA, respectively) were the VOCs with the highest concentrations. Additionally, positive matrix factorization showed three dominant factors of VOC emissions: biogenic, aged urban mixed source, and acetone. Methyl vinyl ketone and methacrolein (MVK + MACR) exhibited contributions from both secondary photooxidation of isoprene and direct emissions from traffic. The C2H6:CH4 demonstrated potential influence of oil and gas activities in San Antonio. Moreover, the high O3 days during the campaign were in the NOx-limited O3 formation regime and were preceded by evening peaks in select VOCs, NOx and CO. Overall, quantification of the concentration and trends of VOCs and trace gases in a major city in Texas offers vital information for general air quality management and supports strategies for reducing O3 pollution. The SAFS campaign VOC results will also add to the growing body of literature on urban sources and concentrations of VOCs in major urban areas.

Long-term Trends of Volatile Organic Compounds over the Texas, USA in the Past Two Decades

Volatile organic compounds (VOCs) are organic compounds in the air that have low vapor pressure. VOCs can be emitted from a variety of sources including biogenic, anthropogenic and pyrogenic processes. VOCs are precursors of aerosols and tropospheric 03. which harm human health. However, the potential of VOCs forming secondary air pollutants varies by species. Here, we analyze the long-term trends of soiu'ce. concentration and reactivity of six classes of VOCs from 1995 to 2018 over Texas. USA. VOCs emission from petroleum and related companies in Texas kept increasing these years. Among the VOCs tracers of oil and gas companies, the concentration of ethane kept increasing until 2015. Despite the increase of oil and gas related VOCs. the concentration of total VOCs and reactivity-weighted VOCs have decreased in the past two decades. We further investigate the seasonality of VOC reactivities, which depend on both temperature and VOC concentration. We find that VOC reactivity generally is highest in fall and lowest in spring, and such seasonality does not change over the two decades.

Spatial and temporal characteristics of ambient atmospheric hydrocarbons in an active shale gas region in North Texas

Over the past decade, significant development in shale gas extraction technologies has led to a massive increase in oil and gas production within the Barnett Shale region in North Texas. This region abuts a fast-growing Dallas-Fort Worth urban area with increasing air quality concerns. Air quality information for 2011–2015 from two urban and three non-urban monitoring sites within the Barnett Shale region were analyzed to identify the spatial and temporal trends of volatile organic compounds (VOC) concentrations. The non-urban sites had higher mean concentrations of total non-methane organic compounds (TNMOC) at 123.6 ppb-C than 77.06 ppb-C at the urban sites. Alkanes, which includes ethane, propane and n-butane, were the dominant VOC group at all five monitoring sites, with 88% of TNMOC at urban sites and 95% at the non-urban sites. Alkenes, alkynes and aromatics composition at urban sites accounted for 3.96%, 0.72% and 4.72% of TNMOC, and at the non-urban sites these were 1.55%, 0.43% and 1.94%, respectively. Seasonal variations were noted in the VOC profiles with high concentrations during the winter months and low during summer months. The alkane/TNMOC ratio also showed a similar seasonal pattern, with a median value of 0.8 at the urban sites and 0.9 at non-urban sites. Alkene/TNMOC ratios were highest during the summer months, while alkyne/TNMOC ratios were highest during spring and low in winter, due to the influence of localized urban emissions. Higher concentrations of isoprene were measured at one of the urban sites as a result of biogenic emissions from nearby urban forests. Spatial and temporal analysis of measured VOC concentrations at ambient air monitoring stations in North Texas revealed strong influence of source regions with high oil and gas activities in close proximity.

Spatial distribution and temporal trends of VOCs in a highly industrialized town in Turkey.

An extensive monitoring study of volatile organic compounds (VOCs) was conducted at sites across the highly industrialized town of Dilovasi, northern Turkey to determine temporal and spatial trends in pollutant concentrations and relate to the effects of source locations, meteorology, and topography. Two-week passive samplers (Tenax tubes) were deployed at twelve sites from February to December 2012 and analysed using thermal desorption and gas chromatography with mass spectrometric detection (TD-GC-MS). Sampled total VOC (TVOC) levels were highest in the July through October period and were highest at low-altitude sites near industry facilities and vehicle traffic sources (148.3 µg/m(3) at site 11, 154.1 µg/m(3) at site 10) and lowest at high-altitude sites located furthest upwind from industry and traffic sources (78.4 µg/m(3) at site 5 and 78.5 µg/m(3) at site 6). Analysis of "T/B" ratios suggested that contributions to ambient VOC in Dilovasi are dominated by the town's industrial sources. Meteorological conditions and the town's basin topography were also found to significantly influence the city's air quality, with strong winds from the NE observed to correlate with periods of higher sampled TVOC. Compared with other industrialized urban centers, the study revealed that there is significant toluene pollution in Dilovasi and recommended enhanced continuous monitoring at the city's industrial and residential zones.

大気中の揮発性有機化合物(VOC)の動態に関する地球化学的研究

大気中の揮発性有機化合物(VOC)の動態に関する地球化学的研究

Occurrence, Distribution, and Trends of Volatile Organic Compounds in Urban Rivers and Their Estuaries in Osaka, Japan, 1993–2006

Fifty-five volatile organic compounds (VOCs) in 738 water samples collected from 33 monitoring sites in the rivers of highly industrialized urban area in Osaka, Japan, 1993-2006 were analyzed. VOCs could be classified into three groups by the detection frequency and levels of mean concentrations detected. Firstly, for 30 compounds, almost all data were non detection or were around the detection limits. Secondly, for 11 compounds, higher values were occasionally observed at some sites. Thirdly, VOCs were ubiquitously found at relatively high or high levels. Spatial distributions of mean concentrations of the most ubiquitous VOCs throughout 13 years have shown exponentially decreasing trends towards the downstream direction of the rivers. Time series of mean concentrations of all sites of five solvents have shown monotonically downward trends. In contrast, three disinfection by-products and six gasoline compounds were not decreasing.

A Mass Transfer Model to Predict the Performance of Tube-type Passive Samplers for Exposure Determination of Volatile Organic Compounds

In past decades, due to its cost-effectiveness and convenience, passive samplers have been frequently employed to investigate spatial and long-term temporal trends of volatile organic compounds (VOCs) at local, regional scales and to assess people’s exposure to VOCs (Raw et al., 2004; Vardoulakis et al., 2011). Uptake rates (URs) of passive samplers have been verified to be the main source of the uncertainty of measurement (Plaisance et al., 2008; Martin et al., 2010; Walgraeve et al., 2011). Thus it is necessary to determinate the uptake behaviors of passive samplers and keep the URs stable for accurate exposure measurement. Some models have been developed to predict the URs of passive samplers. However, these models have been limited either by neglecting parts of the mass transfer processes of passive uptake or by considering only a small subset of VOCs, which are not sufficient for the design and sorbent selection of passive samplers for different VOCs (Palmes et al., 1973; Coutant et al., 1985; Tolnai et al., 2001). The objective of this study is to build a general model based on the mass transfer processes of tube-type passive samplers which are popular in environmental monitoring. By using the finite difference method, the model can be solved coupling with mass conservation equations applied at the boundaries. The model could be used to calculate the effective URs of tube-type passive samplers under various conditions and to select the proper sorbents which can be effective for different VOCs. The kinetic resistance within the sorbents results in two distinct uptake processes for passive sampling; diffusion coefficients D and partition coefficients K of VOCs between the sorbents and the air phase are the main influencing factors. Temperature dependence of URs may be described by the model once the temperature dependence of D and K is available.

Trends in ozone, its precursors, and related secondary oxidation products in Los Angeles, California: A synthesis of measurements from 1960 to 2010

AbstractDecreases in ozone (O3) observed in California's South Coast Air Basin (SoCAB) over the past five decades have resulted from decreases in local emissions of its precursors, nitrogen oxides (NOx = NO + NO2) and volatile organic compounds (VOCs). Ozone precursors have been characterized in the SoCAB with measurements dating back to 1960. Here we compile an extensive historical data set using measurements in the SoCAB between 1960 and 2010. Faster rates of decrease have occurred in abundances of VOCs (−7.3 ± 0.7% yr−1) than in NOx (−2.6 ± 0.3% yr−1), which have resulted in a decrease in VOC/NOx ratio (−4.8 ± 0.9% yr−1) over time. Trends in the NOx oxidation products peroxyacetyl nitrate (PAN) and nitric acid (HNO3), measured in the SoCAB since 1973, show changes in ozone production chemistry resulting from changes in precursor emissions. Decreases in abundances of PAN (−9.3 ± 1.1% yr−1) and HNO3 (−3.0 ± 0.8% yr−1) reflect trends in VOC and NOx precursors. Enhancement ratios of O3 to (PAN + HNO3) show no detectable trend in ozone production efficiency, while a positive trend in the oxidized fraction of total reactive nitrogen (+2.2 ± 0.5% yr−1) suggests that atmospheric oxidation rates of NOx have increased over time as a result of the emissions changes. Changes in NOx oxidation pathways have increasingly favored production of HNO3, a radical termination product associated with quenching the ozone formation cycle.

Multiyear trends in volatile organic compounds in Los Angeles, California: Five decades of decreasing emissions

Airborne measurements of volatile organic compounds (VOCs) were performed during CalNex 2010 (California Research at the Nexus of Air Quality and Climate Change) in the Los Angeles (LA) basin in May–June 2010 and during ITCT2k2 (Intercontinental Transport and Chemical Transformation) in May 2002. While CO2 enhancements in the basin were similar between the two years, the ΔCO/ΔCO2 ratio had decreased by about a factor of two. The ΔVOC/ΔCO emission ratios stayed relatively constant between the two years. This indicates that, relative to CO2, VOCs in the LA basin also decreased by about a factor of two since 2002. These data are compared with the results from various previous field campaigns dating back as early as 1960 and from the extensive air quality monitoring system in the LA basin going back to 1980. The results show that the mixing ratios of VOCs and CO have decreased by almost two orders of magnitude during the past five decades at an average annual rate of about 7.5%. Exceptions to this trend are the small alkanes ethane and propane, which have decreased slower due to the use and production of natural gas. A comparison with trends in London, UK shows that, due to stricter regulations at the time, VOC mixing ratios in LA decreased earlier than in London, albeit at a slower rate, such that typical mixing ratios in both cities in 2008 were at about the same level.

Introduction to the European Monitoring and Evaluation Programme (EMEP) and observed atmospheric composition change during 1972–2009

Abstract. European scale harmonized monitoring of atmospheric composition was initiated in the early 1970s, and the activity has generated a comprehensive dataset (available at http://www.emep.int) which allows the evaluation of regional and spatial trends of air pollution during a period of nearly 40 yr. Results from the monitoring made within EMEP, the European Monitoring and Evaluation Programme, show large reductions in ambient concentrations and deposition of sulphur species during the last decades. Reductions are in the order of 70–90% since the year 1980, and correspond well with reported emission changes. Also reduction in emissions of nitrogen oxides (NOx) are reflected in the measurements, with an average decrease of nitrogen dioxide and nitrate in precipitation by about 23% and 25% respectively since 1990. Only minor reductions are however seen since the late 1990s. The concentrations of total nitrate in air have decreased on average only by 8% since 1990, and fewer sites show a significant trend. A majority of the EMEP sites show a decreasing trend in reduced nitrogen both in air and precipitation on the order of 25% since 1990. Deposition of base cations has decreased during the past 30 yr, and the pH in precipitation has increased across Europe. Large inter annual variations in the particulate matter mass concentrations reflect meteorological variability, but still there is a relatively clear overall decrease at several sites during the last decade. With few observations going back to the 1990s, the observed chemical composition is applied to document a change in particulate matter (PM) mass even since 1980. These data indicate an overall reduction of about 5 μg m−3 from sulphate alone. Despite the significant reductions in sulphur emissions, sulphate still remains one of the single most important compounds contributing to regional scale aerosol mass concentration. Long-term ozone trends at EMEP sites show a mixed pattern. The year-to-year variability in ozone due to varying meteorological conditions is substantial, making it hard to separate the trends caused by emission change from other effects. For the Nordic countries the data indicate a reduced occurrence of very low concentrations. The most pronounced change in the frequency distribution is seen at sites in the UK and the Netherlands, showing a reduction in the higher values. Smaller changes are seen in Germany, while in Switzerland and Austria, no change is seen in the frequency distribution of ozone. The lack of long-term data series is a major obstacle for studying trends in volatile organic compounds (VOC). The scatter in the data is large, and significant changes are only found for certain components and stations. Concentrations of the heavy metals lead and cadmium have decreased in both air and precipitation during the last 20 yr, with reductions in the order of 80–90% for Pb and 64–84% for Cd (precipitation and air respectively). The measurements of total gaseous mercury indicate a dramatic decrease in concentrations during 1980 to about 1993. Trends in hexachlorocyclohexanes (HCHs) show a significant decrease in annual average air concentrations. For other persistent organic pollutants (POPs) the patterns is mixed, and differs between sites and between measurements in air versus precipitation.

The use of passive sampling to monitor spatial trends of volatile organic compounds (VOCs) at an industrial city of Turkey

Ambient concentrations of volatile organic compounds (VOCs) were measured using passive sampling technique at 49 sampling points in Kocaeli, an important industrial city in Turkey. Air samples were analyzed using thermal desorption (TD) and gas chromatography/flame ionization detectors (FID). Concentrations of benzene, toluene, ethylbenzene, m/p-xylenes, and o-xylene (BTEX), 1,3,5-trimethylbenzene, n-propylbenzene, 3-ethyltoluene, and 4-ethyltoluene were investigated to determine their spatial distribution and source apportionment. Concentrations of ΣBTEX ranged from 3.7 to 335.5 μg/m 3. Among all the VOC species, m/p-xylene and toluene have the highest concentration. The spatial distributions for BTEX concentrations showed characteristic patterns: high concentrations were typically found along major roads, city centres, and near industrial plants. Pollution sources potentially affecting concentrations were identified using statistical analyses. The results of factor analysis indicated that vehicle exhaust and industrial activity were the predominant emission sources of the VOCs.

Spatial and temporal trends of volatile organic compounds (VOC) in a rural area of northern Spain

Ambient concentrations of volatile organic compounds (VOCs) were measured at 40 rural sampling points in Navarre (northern Spain). Air samples were collected by means of sorbent passive sampling and analyzed by thermal desorption (TD) and gas chromatography/mass-selective detector (GC/MSD). A total of 140 VOCs were identified during the study, which was carried out between May to October 2004 for a total of a 10 biweekly sampling campaigns. Concentrations of benzene, toluene, ethylbenzene, m/p-xylenes, o-xylene (BTEX) and 1,3,5-trimethylbenzene were determined in order to investigate their temporal and spatial distributions. Geostatistical analysis pointed to traffic as the main emission source of these compounds. Supporting this idea, BTEX and nitrogen oxides concentrations were found to be highly significantly correlated (r=0.495, P=0.001), whereas a strong negative correlation between BTEX and ozone was also observed (r=−0.355, P=0.025). The concentrations for the BTEX group were similar to the values that have been previously reported for other rural areas.

Seasonal variability and trends of volatile organic compounds in the lower polar troposphere

Measurements of the atmospheric mixing ratios of 10 nonmethane hydrocarbons (NMHC) and four halocarbons (methyl chloride, dichloromethane, trichloroethene, and tetrachloroethene) were conducted between January 1989 and July 1996 at Alert (Canadian Arctic, 82°27′N, 62°31′W). About 270 canister samples were analyzed covering the 7‐year period with an average frequency of about one sample every 9 days. The mixing ratios of these volatile organic compounds (VOC) exhibit considerable variability, which can partly be described by systematic seasonal dependencies. The highest mixing ratios were always observed during winter. During spring, the mixing ratios decrease for some compounds to values near the detection limit. The amplitudes of the seasonal variability, the time of the occurrence of the maxima, and the relative steepness of the temporal gradients show a systematic dependence on OH reactivity. The steepest relative decrease is less than 1% d−1 for methyl chloride, increasing to about 4% d−1 for highly reactive VOC. Similarly, the highest relative increase rates vary between 0.5% d−1 for VOC with low reactivity to 4% d−1 for reactive VOC. With the exception of ethyne, toluene, and methyl chloride the concentrations of all measured VOC decrease during the studied period, although this decrease is not always statistically significant. In general, the largest changes were found for the most reactive VOC, although the seemingly random overall variability observed for these compounds results in substantial uncertainties. For the less reactive VOC (ethane, benzene, and propane) the average relative annual decrease rate is in the range of a few percent per year. Dichloromethane and tetrachloroethene showed a decrease of 4 and 14% yr−1, respectively. The average decrease rate for the other alkanes is in the range of some 10% yr−1, indicating a substantial change of emission rates during this period. A likely explanation is a reduction in VOC emissions in the area of the former Soviet Union, most likely Siberia, as a consequence of the recent major economic changes in this region. The measurements were compared with the results of chemical transport models' simulations using the Emission Database for Global Atmospheric Research NMHC emission inventory. Although the model captures most of the main features of the shapes of the seasonal cycles of the NMHC, the results clearly show that model estimates are consistently too low compared to the observations. Most likely this is the consequence of an underestimate of the NMHC emission rates in the emission inventory.

Comparison of Temporal Trends in VOCs as Measured with PDB Samplers and Low‐Flow Sampling Methods

AbstractThe effectiveness of passive diffusion bag (pdb) samplers in the measurement of selected volatile organic compounds (VOCs) is dependent on a number of factors. At some sites and wells, pdb sampling methods provide an attractive alternative to other sampling methods. In this discussion, I provide two examples of comparisons of temporal trends in tetrachloroethylene (PCE) concentrations from passive and low‐flow sampling methods. At the example field site, large changes in PCE concentrations occurred over the deployment period(s) of the pdb samplers, yet the concentrations from the pdb samples are similar to the low‐flow samples and the overall trends are the same.