Organic Compounds In Ambient Air Research Articles

Measurements of volatile organic compounds in ambient air by gas-chromatography and real-time Vocus PTR-TOF-MS: calibrations, instrument background corrections, and introducing a PTR Data Toolkit

Abstract. Volatile organic compound (VOC) emissions and subsequent oxidation contribute to the formation of secondary pollutants and poor air quality in general. As more VOCs at lower mixing ratios have become the target of air quality investigations, their quantification has been aided by technological advancements in proton-transfer-reaction time-of-flight mass spectrometry (PTR-TOF-MS). However, such quantification requires appropriate instrument background measurements and calibrations, particularly for VOCs without calibration standards. This study utilized a Vocus PTR-TOF-MS coupled with a gas chromatograph for real-time and speciated measurements of ambient VOCs in Boulder, Colorado, during spring 2021. The aim of these measurements was to understand and characterize instrument response and temporal variability as to inform the quantification of a broader range of detected VOCs. Fast, frequent calibrations were made every 2 h in addition to daily multipoint calibrations. Sensitivities derived from the fast calibrations were 5 ± 6 % (average and 1 standard deviation) lower than those derived from the multipoint calibrations due to an offset between the calibrations and instrument background measurement. This offset was caused, in part, by incomplete mixing of the standard with diluent. These fast calibrations were used in place of a normalization correction to account for variability in instrument response and accounted for non-constant reactor conditions caused by a gradual obstruction of the sample inlet. One symptom of these non-constant conditions was a trend in fragmentation, although the greatest observed variability was 6 % (1 relative standard deviation) for isoprene. A PTR Data Toolkit (PTR-DT) was developed to assess instrument performance and rapidly estimate the sensitivities of VOCs which could not be directly calibrated on the timescale of the fast calibrations using the measured sensitivities of standards, molecular properties, and simple reaction kinetics. Through this toolkit, the standards' sensitivities were recreated within 1 ± 8 % of the measured values. Three clean-air sources were compared: a hydrocarbon trap, zero-grade air and ultra-high purity nitrogen, and a catalytic zero-air generator. The catalytic zero-air generator yielded the lowest instrument background signals for the majority of ions, followed by the hydrocarbon trap. Depending on the ionization efficiency, product ion fragmentation, ion transmission, and instrument background, standards' limits of detection (5 s measurement integration) derived from the catalytic zero-air generator and the fast calibration sensitivities ranged from 2 ppbv (methanol) to 1 pptv (decamethylcyclopentasiloxane; D5 siloxane) with most standards having detection limits below 20 pptv. Finally, applications of measurements with low detection limits are considered for a few low-signal species including sub-parts-per-trillion by volume (pptv) enhancements of icosanal (and isomers; 1 min average) in a plume of cooking emissions, and sub-parts-per-trillion by volume enhancements in dimethyl disulfide in plumes containing other organosulfur compounds. Additionally, chromatograms of hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane, and decamethylcyclopentasiloxane (D3, D4, and D5 siloxanes, respectively), combined with high sensitivity, suggest that online measurements can reasonably be associated with the individual isomers.

Effective Monitoring of Volatile Organic Compounds in Ambient Air

Effective Monitoring of Volatile Organic Compounds in Ambient Air

Volatile organic compounds in ambient air of a major Asian port: spatiotemporal variation and source apportionment.

This study investigated the spatiotemporal variation and source characteristics of volatile organic compounds (VOCs) in Kaohsiung Harbor, one of the busiest ports in the world. The VOCs' potential to form ozone (O3) and secondary organic aerosols (SOAs) was also examined. The temporal variation was studied in February, May, July, and November of 2020, while the spatial distribution was investigated in the export processing zone (KEPZ) and at the two port entrances (E1 and E2). The most polluted month in the harbor was November (37.7 ± 12.6ppbv), while the most polluted site was the industrial area (KEPZ). A significant positive correlation was found between VOCs and O3 (r = 0.985). Meanwhile, a moderate positive correlation (r = 0.449) was observed between VOCs and secondary organic aerosol formation potential (SOAFP), mainly affected by the concentration of toluene in the study area. The diagnostic ratios indicated that the air parcels in the site were "fresh," and three possible ambient sources of VOC were identified by the positive matrix factorization (PMF): industrial emissions (53.6%), freight transport emissions (29.6%), and others (17.7%). The study highlights the current state of VOCs and their potential sources in the port city of Kaohsiung, which can be used to enhance the strategies for regulating and controlling industrial activities and improving air pollution control measures to reduce VOC emissions.

Volatile Organic Compounds in Ambient Air: Potential Sources, Distribution and Impact

Volatile Organic Compounds in Ambient Air: Potential Sources, Distribution and Impact

Methodical peculiarities of air sampling for detecting contents of low molecular weight organic compounds on the example of furan and methylfuran

Introduction. Variable analytical control methodologies are applied in monitoring over contents of low molecular weight organic compounds in ambient air. Their unification is a vital and serious challenge requiring valid substantiation and selection of optimal air sampling techniques. Our research goal was to substantiate and select an air sampling technique for chemical analysis of furan and methylfuran. Materials and methods. Our research concentrated on developing and optimizing the process of air samples preparation for chemical analysis of furan and methylfuran; examining effectiveness of furan and methylfuran sorption-desorption using various sorbents. Standard furan and methylfuran samples (≥99.0% Sigma-Aldrich), heptane solvents, sorbent tubes with Tenax, Sylochrom C-120, and coal as sorbents were used in the research. All experimental studies were aimed at testing effective procedures for taking and preparing air samples for further furan and methylfuran analysis in them. They were performed on “Kristall-5000” gas chromatographer with mass-selective detection (MSD) and 25-meter long PoraPlotQ-capillary column. Results. We comparatively analyzed the results produced by taking air samples for further detection of furan and methylfuran in them using different techniques. They included low temperature concentration; sorption on filters made of quartz microfiber and a sorbent tube with Nenax TA; sorption on a tube with Tenax TA at t=20-25 °C. The analysis enabled us to reveal an effective procedure for taking ambient air samples for further detection of furan and methylfuran in them. This procedure was low temperature concentration of low molecular weight organic compounds on a sorbent tube with Tenax TA. Limitations. The accomplished study had no limitations. Conclusion. The accomplished study allows us to recommend taking air samples during 10 minutes with consumption being 0.1 l/min for further detection of furan and methylfuran in them using low temperature concentration on a sorbent tube with Tenax TA. The achieved effectiveness is 99.2% for furan and 100% for methylfuran.

Field Test of Mini Photoionization Detector-Based Sensors—Monitoring of Volatile Organic Pollutants in Ambient Air

The determination of the concentrations of the organic compounds in ambient air using reference methods is a time-consuming process. The samples must be collected on a specific sorbent material and analyzed. In the best-case scenario, the analysis may be performed on site by portable chromatography techniques; otherwise, transport and laboratory analysis is necessary. Continuous sensory measurement is advantageous, especially concerning speed, resolution, price and ease of use. On the other hand, questions are raised, especially on the subject of the quality of data obtained by sensory measurements. The authors tested several types of volatile organic compound (VOC) sensors. The chosen type was deployed in a 25-unit sensor network for further testing by parallel measurements with the reference technique within the CLAIRO project.

Seasonal and Spatial Variation of Volatile Organic Compounds in Ambient Air of Almaty City, Kazakhstan

Air pollution is one of the primary sources of risk to human health in the world. In this study, seasonal and spatial variations of multiple volatile organic compounds (VOCs) were measured at six sampling sites in Almaty, Kazakhstan. The seasonal and spatial variations of 19 VOCs were evaluated in 2020, including the periods before and after COVID-19 lockdown. The concentrations of 9 out of 19 VOCs had been changed significantly (p < 0.01) during 2020. The maximum concentrations of total VOCs (TVOCs) were observed on 15, 17, and 19 January and ranged from 233 to 420 µg m−3. The spatial distribution of TVOCs concentrations in the air during sampling seasons correlated with the elevation and increased from southern to northern part of Almaty, where Combined Heat and Power Plants are located. The sources of air pollution by VOCs were studied by correlations analysis and BTEX ratios. The ranges of toluene to benzene ratio and benzene, toluene, and ethylbenzene demonstrated two primary sources of BTEX in 2020: traffic emissions and biomass/biofuel/coal burning. Most of m-, p-xylenes to ethylbenzene ratios in this study were lower than 3 in all sampling periods, evidencing the presence of aged air masses at studied sampling sites from remote sources.

Atmospheric Photoionization Detector with Improved Photon Efficiency: A Proof of Concept for Application of a Nanolayer Thin-Film Electrode.

Atmospheric photoionization is a widely applied soft ionization mechanism in gas sensing devices for the detection of volatile organic compounds in ambient air. Photoionization is typically induced by low-pressure Vacuum Ultraviolet (VUV) lamps with MgF2 or LiF lamp surface windows depending on the gas fill and the required wavelength transmission window. These lamps are known to exhibit gradually reduced VUV transmission due to hydrocarbon contamination. LiF surface windows are known to be especially problematic due to their hygroscopic nature, reducing VUV lamp lifetime to a mere 100 h, approximately. Here, we present a new design for the electrode of a photoionization detector based on thin-film technology. By replacing the commonplace metal grid electrode’s VUV lamp surface window with a chromium/gold thin film we obtain a doubling of photon efficiency for photoionization. Replacing the hygroscopic LiF lamp window surface with a metallic layer additionally offers the possibility to vastly increase operational lifetime of low-pressure Argon VUV lamps.

Novel Graphene Wool Gas Adsorbent for Volatile and Semivolatile Organic Compounds.

Volatile and semivolatile organic compounds in ambient air and occupational settings are of great concern due to their associated adverse human health and environmental impacts. Novel graphene wool samplers have been developed and tested to overcome limitations of commercially available sorbents that can only be used once and typically require solvent extraction. Graphene wool (GW) was synthesized by non-catalytic chemical vapor deposition with optimized conditions, resulting in a novel fibrous graphene wool that is very easy to manage and less rigid than other forms of graphene, lending itself to a wide range of potential applications. Here, the air pollutant sampling capabilities of the GW were of interest. The optimal packing weight of GW inside a glass tube (length 178 mm, i.d. 4 mm, o.d. 6 mm) was investigated by the adsorption of vaporized alkane standards on the GW, using a condensation aerosol generator in a temperature-controlled chamber and subsequent detection using a flame ionization detector. The optimized GW packing density was found to be 0.19 mg mm–3 at a flow rate of 500 mL min–1, which provided a gas collection efficiency of >90% for octane, decane, and hexadecane. The humidity uptake of the sampler is less than 1% (m/m) for ambient humidities <70%. Breakthrough studies showed the favorable adsorption of polar molecules, which is attributed to the defective nature of the graphene and the inhomogeneous coating of the graphene layers on the quartz wool, suggesting that the polar versus non-polar uptake potential of the GW can be tuned by varying the graphene layering on the quartz wool substrate during synthesis. Oxidized domains at the irregular edges of the graphene layers, due to a broken, non-pristine sp2 carbon network, allow for adsorption of polar molecules. The GW was applied and used in a combustion sampling campaign where the samplers proved to be comparable to frequently used polydimethylsiloxane sorbents in terms of sampling and thermal desorption of non-polar semivolatile organic compounds. The total alkane concentrations detected after thermal desorption of GW and PDMS samplers were found to be 17.96 ± 13.27 and 18.30 ± 16.42 μg m–3, respectively; thus, the difference in the alkane sampling concentration between the two sorbent systems was negligible. GW provides a new, exciting possibility for the monitoring of organic air pollutants with numerous advantages, including high sampling efficiencies, simple and cost-effective synthesis of the thermally stable GW, solvent-free and environmentally friendly analysis, and, importantly, the reusability of samplers.

Improvement of Sensor Technology for Monitoring Vocs in Harbour and Maritime Areas: Use Case and first Findings

Fugitive emissions of Volatile Organic Compounds (VOCs) resulting from industrial sources (e.g. storage tanks, gas pipelines or exhausted areas) are often sources of great concerns due to the release of unpleasant odors, irrespective if there is, or is not, a potential health impact (Manes et al., 2011). In this regard, trends of total VOCs are useful to detect the release of organic substances into the atmosphere for correlating them with potential odor harassments.Sensors based on photoionization principle have been successfully tested for continuous monitoring of the volatile organic compounds in ambient air: at the fence of productive plants; close to industrial factories or urban settlements (Locke et al., 1965). PID sensor is already proofed (University of Bari) for providing accurate data with detectable levels in the order of ppb, even in presence of high humidity conditions (Di Gilio et al., 2018). The aim of this study was the test of an innovative sensor technology (NetPID, Lab Service Analytica) capable of operating in hard weather conditions such as maritime environment, where equipment is exposed to high levels of moisture and condensate marine aerosols (droplet, not solubilized particles) (ref. MiniPID manual). The experimental design required the implementation of several PID detectors, placed on boats for dynamic monitoring of volatile organic compounds in an industrial harbour (Tsow et al., 2009). Electronic compensation for suppressing the non-specific contribution of moisture has been improved on these sensors: this led to a sensitivity below the ppb. In addition, flow chambers have been engineered and developed. Sensors have been also integrated on the dedicated smart network platform for collecting real-time data and trends with high resolution. Thanks to the data given by NetPID by the IoT platform, managers were so able to compare them with periodic information on port activities (storage, unloading, handling of raw and refined products). The setting of specific routines, based on the matching of multiple information levels (Port activities, total VOCs concentrations, weather conditions) (Choi et al., 2009), allowed to adopt the necessary corrective procedures for the mitigation of the impact of fugitive emissions in surrounded areas. Long-term tests have shown a high stability of instrumental responses, high robustness and reliability (Amodio et al., 2013).

Working out a procedure for determining potentially hazardous volatile organic compounds (trichloroethylene and tetrachloroethylene) in ambient air

The article dwells on results obtained via experimental research on working out a gas chromatography procedure for determining trichloroethylene and tetrachloroethylene in ambient air. Experiments were performed on substances which had low limits of detection with gas-liquid chromatography with electron capture detection (GLC/ECD) when examined substances were absorbed from ambient air on Tenax TA sorbent. Optimal gas chromatography parameters were established with a hardware-software complex based on «Crystal-5000» gas chromatographer and use of a column from IDBPX-VOL series, 60m⋅0.32mm⋅1.8µm, under the following temperatures: column, 50–230о С; evaporator, 250о С; detector, 250о С. The developed capillary gas chromatography procedure allows determining trichloroethylene in concentrations ranging from 0.000146 to 0.00146 mg/m3, and tetrachloroethylene, from 0.000081 to 0.00081 mg/m3 with inaccuracy not exceeding 25.0%. We performed metrological assessment of the procedure and it allowed determining quality of analysis results for trichloroethylene and tetrachloroethylene; they were as follows: precision, 21.97% and 14.3%: repeatability, 4.22% and 3.38%; reproducibility, 5.66% and 4.9%. Limit of detection (LOD) for trichloroethylene and tetrachloroethylene was =0.0000038 mg/dm3 and =0.00000083 mg/dm3 accordingly. Limit of quantitative determination (LOQ) was =0.000013 mg/m3 for trichloroethylene, and = 0.0000028 mg/m3 for tetrachloroethylene. The developed procedure allowed detecting contents of the examined substances in ambient air near a construction site and a dry-cleaner’s, trichloroethylene in a range from 0.00001 mg/m3 to 0.0009 mg/m3, tetrachloroethylene, from 0.000011 mg/m3 to 0.00039 mg/m3. This unified high-sensitive and selective procedure is recommended for systemic control over potentially hazardous volatile organic compounds in ambient air as it allows providing objective and reliable hygienic assessment of chemical safety and quality of the environment and health risk assessment.

Разработка методики определения потенциально опасных летучих органических соединений (трихлорэтилен и тетрахлорэтилен) в атмосферном воздухе

The article dwells on results obtained via experimental research on working out a gas chromatography procedure for determining trichloroethylene and tetrachloroethylene in ambient air. Experiments were performed on substances which had low limits of detection with gas-liquid chromatography with electron capture detection (GLC/ECD) when examined substances were absorbed from ambient air on Tenax TA sorbent. Optimal gas chromatography parameters were established with a hardware-software complex based on «Crystal-5000» gas chromatographer and use of a column from IDBPX-VOL series, 60m⋅0.32mm⋅1.8µm, under the following temperatures: column, 50–230о С; evaporator, 250о С; detector, 250о С. The developed capillary gas chromatography procedure allows determining trichloroethylene in concentrations ranging from 0.000146 to 0.00146 mg/m3, and tetrachloroethylene, from 0.000081 to 0.00081 mg/m3 with inaccuracy not exceeding 25.0%. We performed metrological assessment of the procedure and it allowed determining quality of analysis results for trichloroethylene and tetrachloroethylene; they were as follows: precision, 21.97% and 14.3%: repeatability, 4.22% and 3.38%; reproducibility, 5.66% and 4.9%. Limit of detection (LOD) for trichloroethylene and tetrachloroethylene was =0.0000038 mg/dm3 and =0.00000083 mg/dm3 accordingly. Limit of quantitative determination (LOQ) was =0.000013 mg/m3 for trichloroethylene, and = 0.0000028 mg/m3 for tetrachloroethylene. The developed procedure allowed detecting contents of the examined substances in ambient air near a construction site and a dry-cleaner’s, trichloroethylene in a range from 0.00001 mg/m3 to 0.0009 mg/m3, tetrachloroethylene, from 0.000011 mg/m3 to 0.00039 mg/m3. This unified high-sensitive and selective procedure is recommended for systemic control over potentially hazardous volatile organic compounds in ambient air as it allows providing objective and reliable hygienic assessment of chemical safety and quality of the environment and health risk assessment.

Evaluating the effectiveness of multiple emission control measures on reducing volatile organic compounds in ambient air based on observational data: A case study during the 2010 Guangzhou Asian Games

Volatile organic compounds (VOCs) play a crucial role in modulating air pollution by ozone and fine particles, particularly in urban areas. While in recent years short-term intervention actions for better air quality during big events in China did present good opportunities to examine the effectiveness of control measures in reducing anthropogenic VOCs emission, it is highly challenging to interpret the real effect of a specific control measure based on field monitoring data when a cocktail of control measures were adopted. Here we took the air quality intervention actions during the 16th Asian Games (AG) in Guangzhou as a case study to explore the impact of short-term multiple measures on VOCs reduction. The average mass concentrations of VOCs decreased by 52–68% during the AG. These percentages could not reflect emission reduction rates as the concentration might be also heavily impacted by dispersion conditions. Diagnostic ratios, such as methyl tert-butyl ether to carbon monoxide (MTBE/CO) and i-pentane/CO, decreased by over 60% during the AG, suggesting a substantial reduction in gasoline related emissions. A method linking emission reduction rates of two sources with their contribution percentages before and during the AG by using a receptor model was further formulated. With the available reduction rate of 34% for vehicular exhaust obtained during the traffic restriction drill in our previous study, VOCs emissions from gasoline evaporation and solvent use reduced by 45.7% and 13.6% during the AG, respectively. Total VOCs emissions decreased by 25.3% on average during the AG, and the emission control of vehicular exhaust, oil evaporation, and solvent use accounted for 17.0%, 6.3% and 2.0% of total VOCs emission reduction, respectively. This study presented an observed-based method with diagnostic/quantitative approaches to single out the effectiveness of each control measures in reducing VOCs emissions.

Real time analysis of trace volatile organic compounds in ambient air: a comparison between membrane inlet single photon ionization mass spectrometry and proton transfer reaction mass spectrometry.

Real-time monitoring of volatile organic compounds (VOCs) is critical for a better understanding of chemical processes in ambient air or making minute-by-minute decisions in emergency situations. Proton transfer reaction mass spectrometry (PTR-MS) is nowadays the most commonly used technique for real-time monitoring of VOCs while membrane single photon ionization mass spectrometry (MI-SPI-MS) is a promising MS technique for online detection of trace VOCs. Here, to evaluate the potential of MI-SPI-MS as a complementary tool to PTR-MS, a comprehensive comparison has been performed between MI-SPI-MS and PTR-MS. By using two sets of standard gas mixtures TO15 and PAMS, SPI-MS shows advantages in the detection of ≥C5 alkanes, aromatics and halogens; especially for aromatics, the LODs can reach the ppt level. PTR-MS has performed better in the detection of alkenes, ketones and aldehydes. For outdoor measurements, a number of VOCs have been detected while using MI-SPI-MS and PTR-MS in parallel. Consistent temporal variations have been observed for toluene, C8-aromatics and C9-aromatics by the two instruments, with a more sensitive response from the MI-SPI-MS. Thus by measuring both standard gas mixture and complex ambient air samples, we have successfully demonstrated that MI-SPI-MS will be a helpful tool to provide important complementary information on aromatics and alkanes in air, and proper application of MI-SPI-MS will benefit the real-time monitoring of trace VOCs in relative fields.

Monitoring of volatile organic compounds in ambient air of Taldykorgan, Kazakhstan

The pollution of ambient air is one of the main sources of risk to human health in the world. There is a direct relationship between the level of air pollution and risk of the development of cancer, cardiovascular, respiratory and other diseases. Benzene, toluene, ethylbenzene and o-xylene (BTEX) are one of the most toxic volatile organic compounds. The aim of this study was to quantify BTEX in air of Taldykorgan, Kazakhstan using solid-phase microextraction followed by gas chromatography with mass-spectrometric detection. In different sampling seasons, average concentrations of four BTEX analytes varied from 7.5 to 27 µg/m3, from 15 to 250 µg/m3, from 2.4 to 12.8 µg/m3 and from 2.6 to 21 µg/m3, respectively. The highest concentrations of TEX were detected in autumn, while the highest concentrations of benzene were observed in winter. Toluene-to-benzene ratios in almost all measurements were above 1 indicating that the traffic emissions are the main source of air pollution with BTEX.

Hazardous volatile organic compounds in ambient air of China.

Volatile organic compounds (VOCs) are ubiquitous in the atmosphere and the majority of them have been proved to be detrimental to human health. The hazardous VOCs were studied very insufficiently in China, despite the enormous emissions of VOCs. In this study, the concentrations and sources of 17 hazardous VOCs reported in literature were reviewed, based on which the health effects were assessed. In-depth survey indicated that benzene and toluene had the highest concentrations in eastern China (confined to the study regions reviewed, same for the other geographic generalization), which however showed significant declines. The southern China featured high levels of trichloroethylene. Dichloromethane and chloroform were observed to be concentrated in northern China. The distributions of 1,2-dichloropropane and tetrachloroethylene were homogeneous across the country. Basically consistent with the spatial patterns of ozone, the summertime formaldehyde exhibited higher levels in eastern and northern China, and increased continuously. While transportation served as the largest source of benzene and toluene, industrial emissions and secondary formation were the predominant contributors of halogenated hydrocarbons and aldehydes (formaldehyde and acetaldehyde), respectively. The chronic non-cancer effects of inhalation exposure to the hazardous VOCs were insignificant, however the probabilities of developing cancers by inhaling the hazardous VOCs in ambient air of China were quite high. Formaldehyde was identified as the primary carcinogenic VOC in the atmosphere of most regions. The striking results, especially the high inhalation cancer risks, alerted us that the emission controls of hazardous VOCs were urgent in China, which must be grounded upon full understanding of their occurrence, presence and health effects.

Optimization of a gas chromatographic unit for measuring biogenic volatile organic compounds in ambient air

Abstract. A new online gas chromatographic method dedicated to biogenic volatile organic compound (BVOC) analysis was developed for the measurement of a 20 BVOC gaseous mixture (isoprene; β-pinene; α-pinene; limonene; ocimene; myrcene; sabinene; Δ3-carene; camphene; 1,8 cineole; terpinolene; linalool; α-phellandrene; nopinone; citral; α-terpinene; β-caryophyllene; p-cymene; γ-terpinene; and 2-carene) at a time resolution of 90 min. The optimized method includes an online Peltier-cooled thermodesorption system sample trap made of Carbopack B coupled to a gas chromatographic system equipped with a 60 m, 0.25 mm internal diameter (i.d.) BPX5 column. Eluent was analysed using flame ionization detection (FID). Potassium iodide was identified as the best ozone scrubber for the 20 BVOC mixture. In order to obtain an accurate quantification of BVOC concentrations, the development of a reliable standard mixture was also required. Quantification of BVOCs was reported with a detection limit ranging from 4 ppt for α-pinene to 19 ppt for sabinene. The main source of uncertainty was the calibration step, stressing the need for certified gaseous standards for a wider panel of BVOCs. This new method was applied for the first time to measure BVOCs in a pine forest during the LANDEX episode 1 field campaign (summer 2017). All target BVOCs were detected at least once during the campaign. The two major monoterpenes observed were β-pinene and α-pinene, representing 60 % of the measured terpenoid concentration on average, while isoprene represented only 17 %. The uncertainties determined were always below 13 % for the six major terpenes.

Influence of rice straw open burning on levels and profiles of semi-volatile organic compounds in ambient air.

Semi-volatile organic compounds (SVOCs) of polycyclic aromatic hydrocarbons (PAHs) and organo-chlorinated pesticides (OCPs) were sampled (24h, Hi-Vol XAD-2) in dry and wet season, and separately analyzed for particulate and gaseous phases. To reveal the influence of rice straw open burning (RSOB), SVOC levels and profiles were comparatively analyzed between two areas, rice plantation area (KL) with intensive RSOB activities and remote national park (KY), and with fresh RSOB smoke. PAHs were significantly higher in KL than KY in both seasons. PAHs levels in KL during burning season were ∼10 times above the wet season indicating RSOB influence. In KY, however, PAHs levels in wet season were 2 times above dry season suggesting impacts of local emission transport. OCPs levels were not statistically different between 2 seasons and between 2 sites in each season. RSOB smoke contained 5880ng/m3 of 14 PAHs and 13.5ng/m3 of 16 OCPs which were respectively 14 and 7 times above those in KL during burning period. The 4-ring compounds, most remarkably fluoranthene, and 5-ring (BbF and BaP) were dominant PAHs species in RSOB smoke. Similarity in PAH profiles and diagnostic ratios between KL dry season and RSOB smoke suggested its strong influence on the local air quality. Elevated OCPs levels in RSOB smoke may be associated with re-emission of the compounds accumulated in the paddy soil during the burning. RSOB in Southeast Asia has a serious implication on exposure to the toxic air pollutants hence should be eliminated with priority.

Real Time Analysis of Total Volatile Organic Compounds in Ambient Air at Different Areas Kalasin, Thailand

Real Time Analysis of Total Volatile Organic Compounds in Ambient Air at Different Areas Kalasin, Thailand

Electrostatic Switching and Selection of H3O+, NO+, and O2+• Reagent Ions for Selected Ion Flow-Drift Tube Mass Spectrometric Analyses of Air and Breath.

Soft chemical ionization mass spectrometry techniques, particularly the well-established proton transfer reactionmass spectrometry, PTR-MS, and selected ion flow tube mass spectrometry, SIFT-MS, are widely used for real-time quantification of volatile organic compounds in ambient air and exhaled breath with applications ranging from environmental science to medicine. The most common reagent ions H3O+, NO+, or O2+• can be selected either by quadrupole mass filtering from a discharge ion source, which is relatively inefficient, or by switching the gas/vapor in the ion source, which is relatively slow. The chosen reagent ions are introduced into a flow tube or flow-drift tube reactor where they react with analyte molecules in sample gas. This article describes a new electrostatic reagent ion switching, ERIS, technique by which H3O+, NO+, and O2+• reagent ions, produced simultaneously in three separate gas discharges, can be purified in post-discharge source drift tubes, switched rapidly, and selected for transport into a flow-drift tube reactor. The construction of the device and the ion-molecule chemistry exploited to purify the individual reagent ions are described. The speed and sensitivity of ERIS coupled to a selected ion flow-drift tube mass spectrometry, SIFDT-MS, is demonstrated by the simultaneous quantification of methanol with H3O+, acetone with NO+, and dimethyl sulfide with O2+• reagent ions in single breath exhalations. The present ERIS approach is shown to be preferable to the previously used quadrupole filtering, as it increases analytical sensitivity of the SIFDT-MS instrument while reducing its size and the required number of vacuum pumps.