Personal exposure of graduate students attending the college of natural sciences or social sciences to volatile organic compounds on campus

The present study measured the levels of 24 selected volatile organic compounds (VOCs) in the personal air samples obtained from graduate students attending the college of natural sciences (GSNSs) or social science (GSSSs) during their daily activities on campus along with associated indoor and outdoor air samples. In addition, the sources of their personal exposure were characterized using multivariate statistical models. In the personal samples of GSNSs and GSSSs, 16 and 15 different VOCs were always detected, respectively. The personal exposure of five chlorinated hydrocarbons and six aromatics was significantly higher for GSNSs than for GSSSs. Consistently, the indoor levels of these compounds were higher for GSNSs (in research and laboratory rooms) than for GSSSs (in research rooms). However, the personal exposure of two aromatic VOCs (1,2,4- and 1,3,5-trimethylbenzene) was higher for GSSSs. Moreover, the personal exposure of the five chlorinated and six aromatic compounds was significantly correlated with VOC concentrations both in the research and laboratory rooms of GSNSs and with those in the research rooms of GSSSs. For certain VOCs, outdoor sources were also a major contributor to the personal exposure of both GSNSs and GSSSs. The multivariate models identified five factors that accounted for 81% of the total variance and four factors that explained 76% of the total variance. It was further suggested that multiple indoor sources in research rooms such as office equipment, building finishing materials, and air fresheners were the main source for the personal exposure to VOCs for GSNSs, whereas building finishing materials were the main source for GSSSs.     

Priority volatile organic compounds in surface waters of the southern North Sea

The occurrence of 25 volatile organic compounds (VOCs) was studied from April 1998 to October 2000 in the southern North Sea. Target VOCs were selected from lists of priority pollutants for the marine environment and included, e.g., chlorinated short-chain hydrocarbons (CHCs), monocyclic aromatic hydrocarbons (MAHs), and chlorinated monocyclic aromatic hydrocarbons (CMAHs). Water samples were taken from the Channel, the Belgian Continental Shelf, the mouth of the Scheldt estuary and the Southern Bight, and were analysed by purge-and-trap and high-resolution gas chromatography-mass spectrometry. All data were produced by analyses deemed 'in control' by a rigorous quality assurance/quality control program provided by QUASIMEME (Quality Assurance of Information for Marine Environmental Monitoring in Europe). Chloroform and trichloroethene were commonly detected at concentrations up to 1900 and 270 ng l(-1), respectively. The other CHCs were generally found below 5 ng l(-1), and rarely exceeded 10 ng l(-1). Concentrations of MAHs were at least one order of magnitude higher than those of the CHCs. The higher levels were attributed to anthropogenic emissions from oil-related activities in coastal areas. CMAHs, except chlorobenzene and 1,4-dichlorobenzene, were hardly detected in North Sea waters. The levels of several CHCs and MAHs were shown to decrease compared to previous investigations in 1994-1995, probably as a result of on-going emission reduction efforts. The occurrence of 1,1,1-trichloroethane, for instance, was substantially reduced since the Montreal Protocol was implemented in 1995.     

Wet scrubber analysis of volatile organic compound removal in the rendering industry

The promulgation of odor control rules, increasing public concerns, and U.S. Environmental Protection Agency (EPA) air regulations in nonattainment zones necessitates the remediation of a wide range of volatile organic compounds (VOCs) generated by the rendering industry. Currently, wet scrubbers with oxidizing chemicals are used to treat VOCs; however, little information is available on scrubber efficiency for many of the VOCs generated within the rendering process. Portable gas chromatography/mass spectrometry (GC/MS) units were used to rapidly identify key VOCs on-site in process streams at two poultry byproduct rendering plants. On-site analysis was found to be important, given the significant reduction in peak areas if samples were held for 24 hr before analysis. Major compounds consistently identified in the emissions from the plant included dimethyl disulfide, methanethiol, octane, hexanal, 2-methylbutanal, and 3-methylbutanal. The two branched aldehydes, 2-methylbutanal and 3-methylbutanal, were by far the most consistent, appearing in every sample and typically the largest fraction of the VOC mixture. A chlorinated hydrocarbon, methanesulfonyl chloride, was identified in the outlet of a high-intensity wet scrubber, and several VOCs and chlorinated compounds were identified in the scrubbing solution, but not on a consistent basis. Total VOC concentrations in noncondensable gas streams ranged from 4 to 91 ppmv. At the two plants, the odor-causing compound methanethiol ranged from 25 to 33% and 9.6% of the total VOCs (v/v). In one plant, wet scrubber analysis using chlorine dioxide (ClO2) as the oxidizing agent indicated that close to 100% of the methanethiol was removed from the gas phase, but removal efficiencies ranged from 20 to 80% for the aldehydes and hydrocarbons and from 23 to 64% for total VOCs. In the second plant, conversion efficiencies were much lower in a packed-bed wet scrubber, with a measurable removal of only dimethyl sulfide (20-100%).     

Wet Scrubber Analysis of Volatile Organic Compound Removal in the Rendering Industry

Abstract

The promulgation of odor control rules, increasing public concerns, and U.S. Environmental Protection Agency (EPA) air regulations in nonattainment zones necessitates the remediation of a wide range of volatile organic compounds (VOCs) generated by the rendering industry. Currently, wet scrubbers with oxidizing chemicals are used to treat VOCs; however, little information is available on scrubber efficiency for many of the VOCs generated within the rendering process. Portable gas chromatography/mass spectrometry (GC/MS) units were used to rapidly identify key VOCs on-site in process streams at two poultry byproduct rendering plants. On-site analysis was found to be important, given the significant reduction in peak areas if samples were held for 24 hr before analysis. Major compounds consistently identified in the emissions from the plant included dimethyl disulfide, methanethiol, octane, hexanal, 2-methylbutanal, and 3-methylbutanal. The two branched aldehydes, 2-methylbutanal and 3-methylbutanal, were by far the most consistent, appearing in every sample and typically the largest fraction of the VOC mixture.

A chlorinated hydrocarbon, methanesulfonyl chloride, was identified in the outlet of a high-intensity wet scrubber, and several VOCs and chlorinated compounds were identified in the scrubbing solution, but not on a consistent basis. Total VOC concentrations in noncondensable gas streams ranged from 4 to 91 ppmv. At the two plants, the odor-causing compound methanethiol ranged from 25 to 33% and 9.6% of the total VOCs (v/v). In one plant, wet scrubber analysis using chlorine dioxide (ClO2) as the oxidizing agent indicated that close to 100% of the methanethiol was removed from the gas phase, but removal efficiencies ranged from 20 to 80% for the aldehydes and hydrocarbons and from 23 to 64% for total VOCs. In the second plant, conversion efficiencies were much lower in a packed-bed wet scrubber, with a measurable removal of only dimethyl sulfide (20–100%).     

Determination of Volatile Organic Compounds in the Atmosphere Using Two Complementary Analysis Techniques

ABSTRACT

During a preliminary field campaign of volatile organic compound (VOC) measurements carried out in an urban area, two complementary analysis techniques were applied to establish the technical and scientific bases for a strategy to monitor and control VOCs and photochemical oxidants in the Autonomous Community of the Basque Country. Integrated sampling was conducted using Tenax sorbent tubes and laboratory analysis by gas chromatography, and grab sampling and in situ analysis also were conducted using a portable gas chromatograph. With the first technique, monocyclic aromatic hydrocarbons appeared as the compounds with the higher mean concentrations. The second technique allowed the systematic analysis of eight chlorinated and aromatic hydrocarbons. Results of comparing both techniques, as well as the additional information obtained with the second technique, are included.     

Prediction of the adsorption capacity for volatile organic compounds onto activated carbons by the Dubinin-Radushkevich-Langmuir model

Prediction of the adsorption capacity for volatile organic compounds (VOCs) onto activated carbons is elucidated in this study. The Dubinin-Radushkevich (D-R) equation was first used to predict the adsorption capacity of nine aromatic and chlorinated VOCs onto two different activated carbons. The two key parameters of the D-R equation were estimated simply from the properties of the VOCs using quantitative structure-activity relationship and from the pore size distribution of the adsorbent. The approach based on the D-R equation predicted well the adsorption capacity at high relative pressures. However, at the relative pressures lower than -1.5 x 10(-3), the D-R approach may significantly overestimate adsorption capacity. To extrapolate the approach to lower relative pressures, the integration of the D-R equation and the Langmuir isotherm, called the D-R-L model, was proposed to predict adsorption capacity over a wide range of relative pressures of VOCs. In this model, the Langmuir isotherm parameters were extracted from the predicted D-R isotherm at high relative pressures. Therefore, no experimental effort was needed to obtain the parameters of the D-R-L model. The model successfully predicted the adsorption capacity of aromatic and chlorinated hydrocarbons tested onto BPL and Sorbonorit B carbons over relative pressures ranging from 7.4 x 10(-5) to 0.03, suggesting that the model is applicable at the low relative pressures of VOCs often observed in many environmental systems. In addition, the molecular size of organic compounds may be an important factor affecting the adsorption capacity of activated carbons. For BPL carbon, an ultramicroporous adsorbent, the limiting pore volume Wo of the D-R equation decreased when the kinetic diameter of the adsorbate was larger than 6 angstroms. However, for Sorbonorit B carbon, no reduction of Wo was found, suggesting that the Wo may be related to the pore size distribution of the adsorbents, as well as to their molecular size. This size exclusion effect may play an important role in predicting the adsorption capacity of VOCs onto microporous adsorbents in the D-R-L model and in the corresponding D-R equation.     

Residue levels of chlorinated hydrocarbon compounds in water and sediment samples from Nile branches in the Delta, Egypt.

Water and sediment samples were collected from eight different locations along the River Nile and its branches. Residues of hexachlorocyclohexane (HCH's), hexachlorobenzene (HCB), DDT's, cyclodienes and polychlorinated biphenyls (PCB's) were analyzed by GLC. Data on Grand Total (GT) concentration values pointed out that Rosetta Branch was more polluted with all components than Demietta Branch. Kafr El-Ziate was the most polluted location showing 1355.8 ng/L for water and 7396.9 ng/g for sediments, while Delta Barrage was the least polluted site. The concentrations of gamma-HCH were higher than the other isomers (alpha- and beta-HCH) in all studied sites. The results showed that HCB was the smallest pollutant at all locations on comparison with other chlorinated hydrocarbons. El-Mansoura, Rosetta and Kafr El-Ziate sites contained the highest concentrations of DDT's in both water and sediment samples. P,P'-DDE was dominate in all locations of water samples, but P,P'-DDT was in sediment samples. Also, the results showed the prominent presence of cyclodienes when compared with the other OC's compounds in sediment samples, especially Aldrin. Kafr El-Ziate was the most polluted location by PCB's, particularly the Ar1242. However, there were increasing levels of chlorinated hydrocarbons in the sediment samples parallel to percentage extractable organic matter (% EOM). Sediment/water ratios were calculated for all locations.     

Thermal degradation of polychlorinated alkanes

Thermal degradation products of two polychlorinated alkanes (PCA) containing 59 % and 70 % chlorine, respectively, and also a commercial chlorinated paraffin (CP) containing 70 % chlorine were determined by gas chromatography and mass spectrometry. Thermolyses were performed in both inert atmosphere and air at different temperatures and times. Aliphatic and aromatic hydrocarbons and minor amounts of chlorinated substances were identified products of the medium chlorinated PCA. The highly chlorinated PCA and the commercial CP in addition gave products such as polychlorinated benzenes, toluenes, biphenyls and naphthalenes.     

Effect of solid waste landfill organic pollutants on groundwater in three areas of Sicily (Italy) characterized by different vulnerability

The aim of this study was to obtain information on the presence and levels of hazardous organic pollutants in groundwater located close to solid waste landfills. Eighty-two environmental contaminants, including 16 polycyclic aromatic hydrocarbons (PAHs), 20 volatile organic compounds (VOCs), 29 polychlorinated biphenyls (PCBs), 7 dioxins (polychlorinated dibenzo-p-dioxins, PCDDs) and 10 furans (polychlorinated dibenzofurans, PCDFs) were monitored in areas characterised by different geological environments surrounding three municipal solid waste landfills (Palermo, Siculiana and Ragusa) in Sicily (Italy) in three sampling campaigns. The total concentrations of the 16 PAHs were always below the legal threshold. Overall, the Fl/Fl + Py diagnostic ratio revealed that PAHs had a petrogenic origin. VOC levels, except for two notable exceptions near Palermo landfill, were always below the legal limit. As concerns PCB levels, several samples were found positive with levels exceeding the legal limits. It is worth noting that the % PCB distribution differs from that of commercial compositions. In parallel, some samples of groundwater containing PCDDs and PCDFs exceeding the legal threshold were also found. Among the 17 congeners monitored, the most abundant were the highest molecular weight ones.

     

Volatile organic compounds in some urban locations in United States

Volatile organic compounds (VOCs) have been determined to be human risk factors in urban environments, as well as primary contributors to the formation of photochemical oxidants. Ambient air quality measurements of 54 VOCs including hydrocarbons, halogenated hydrocarbons and carbonyls were conducted in or near 13 urban locations in the United States during September 1996 to August 1997. Air samples were collected and analyzed in accordance with US Environmental Protection Agency-approved methods. The target compounds most commonly found were benzene, toluene, xylene and ethylbenzene. These aromatic compounds were highly correlated and proportionally related in a manner suggesting that the primary contributors were mobile sources in all the urban locations studied. Concentrations of total hydrocarbons ranged between 1.39 and 11.93 parts per billion, by volume (ppbv). Ambient air levels of halogenated hydrocarbons appeared to exhibit unique spatial variations, and no single factor seemed to explain trends for this group of compounds. The highest halogenated hydrocarbon concentrations ranged from 0.24 ppbv for methylene chloride to 1.22 ppbv for chloromethane. At participating urban locations for the year of data considered, levels of carbonyls were higher than the level of the other organic compound groups, suggesting that emissions from motor vehicles and photochemical reactions strongly influence ambient air concentrations of carbonyls. Of the most prevalent carbonyls, formaldehyde and acetaldehyde were the dominant compounds, ranging from 1.5-7.4 ppbv for formaldehyde, to 0.8-2.7 ppbv for acetaldehyde.     

Analysis of halogenated polycyclic aromatic hydrocarbons in urban air, snow and automobile exhaust

Urban air, snow and automobile exhaust samples were extensively cleaned up by open column liquid chromatography. The appropriate fractions were analysed for halogenated polycyclic aromatic hydrocarbons (XPAH) by gas chromatography/negative chemical ionization mass spectrometry (GC/NCIMS). XPAH were found in all three sample types. A urban air sample was found to contain chlorinated pyrenes, fluoranthenes and benzopyrene and brominated pyrenes and fluoranthenes. Furthermore, the concentration of 1-chloropyrene in that air sample was estimated to be 10 pg/m³. XPAH were also found in snow samples taken in the vicinity of a motor-way. Ethylene dibromide and ethylene dichloride, are probably the source of the halogen atoms in the XPAH detected in car exhaust.     

Chlorinated and polycyclic aromatic hydrocarbons in riverine and estuarine sediments from Pearl River Delta, China

Spatial distribution of chlorinated hydrocarbons [chlorinated pesticides (CPs) and polychlorinated biphenyls (PCBs)] and polycyclic aromatic hydrocarbons (PAHs) was measured in riverine and estuarine sediment samples from Pearl River Delta, China, collected in 1997. Concentrations of CPs of the riverine sediment samples range from 12 to 158 ng/g, dry weight, while those of PCBs range from 11 to 486 ng/g. The CPs concentrations of the estuarine sediment samples are in the range 6-1658 ng/g, while concentrations of PCBs are in the range 10-339 ng/g. Total PAH concentration ranges from 1168 to 21,329 ng/g in the riverine sediment samples, whereas the PAH concentration ranges from 323 to 14,812 ng/g in the sediment samples of the Estuary. Sediment samples of the Zhujiang River and Macao harbor around the Estuary show the highest concentrations of CPs, PCBs, and PAHs. Possible factors affecting the distribution patterns are also discussed based on the usage history of the chemicals, hydrologic condition, and land erosion due to urbanization processes. The composition of PAHs is investigated and used to assess petrogenic, combustion and naturally derived PAHs of the sediment samples of the Pearl River Delta. In addition, the concentrations of a number of organic compounds of the Pearl River Delta samples indicate that sediments of the Zhujiang river and Macao harbor are most likely to pose biological impairment.     

Contaminated site remedial investigation and feasibility removal of chlorinated volatile organic compounds from groundwater by activated carbon fiber adsorption

Groundwater contaminated by dense, non-aqueous phase liquids (DNAPLs) such as chlorinated solvents has become a serious problem in some regions of Taiwan. The sources of these contaminants are due to industrial discharges. These chlorinated volatile organic compounds (VOCs) have been proven to be carcinogenic to humans. The groundwater is used for domestic drinking water supply in some cities of Taiwan and the severely contaminated groundwater has to be treated in order to meet the requirement of drinking water standards. This study covers two areas of work. In the first part, polluted groundwater samples were collected from the contaminated site and analytical results indicated measurable concentrations of 12 representative chlorinated VOCs in water samples. The primary VOCs detected included trichloroethene (TCE), tetrachloroethene (PCE), 1,1,2-trichloroethane (1,1,2-TCA), and 1,1-dichloroethene (1,1-DCE). Second, to remove VOCs groundwater was treated using adsorption on activated carbon fiber (ACF). This involved pumping groundwater through vessels containing ACF. Most VOCs, including TCE, PCE, 1,1,2-TCA, and DCE, were readily adsorbed onto ACF and are removed from the water stream. Our study showed that the technology was able to significantly reduce chlorinated VOCs concentrations in groundwater.     

Biodegradation of trace gases in simulated landfill soil cover systems

The attenuation of methane and seven volatile organic compounds (VOCs) was investigated in a dynamic methane and oxygen counter gradient system simulating a landfill soil cover. The VOCs investigated were: Tetrachloromethane (TeCM), trichloromethane (TCM), dichloromethane (DCM), trichloroethylene (TCE), vinyl chloride (VC), benzene, and toluene. Soil was sampled at Skellingsted landfill, Denmark. The soil columns showed a high capacity for methane oxidation, with oxidation rates up to 184 g/m2/d corresponding to a 77% reduction of inlet methane. Maximal methane oxidation occurred at 15-20 cm depth, in the upper part of the column where there were overlapping gradients of methane and oxygen. All the chlorinated hydrocarbons were degraded in the active soil columns with removal efficiencies higher than 57%. Soil gas concentration profiles indicated that the removal of the fully chlorinated compound TeCM was because of anaerobic degradation, whereas the degradation of lower chlorinated compounds like VC and DCM was located in the upper oxic part of the column. Benzene and toluene were also removed in the active column. This study demonstrates the complexity of landfill soil cover systems and shows that both anaerobic and aerobic bacteria may play an important role in reducing the emission of trace components into the atmosphere.     

High concern chemicals in top layer sediments of the northern Adriatic seabed as markers of old waste dumpings

The results are presented of a survey planned to assess the presence of high concern chemicals in sediments collected in a northern sector of the Adriatic sea neighboring the Venice lagoon. For the assessment, persistent marker chemicals were selected from the families of polycyclic aromatic hydrocarbons, polychlorobiphenyls, polychlorodibenzo-p-dioxins (PCDDs), polychlorodibenzofurans (PCDFs), and chlorinated pesticides. Based on the chemical-specific concentrations and PCDD+PCDF profiles determined in the sediments analyzed, dumping zones appear to have existed approximately 5-6km away from lagoon shoreline. Contamination levels exceed the quality criteria established by the pertinent Italian national regulation at many sampling sites, eventually reflecting ("fingerprinting") industrial activities once performed in the industrial settlement of Porto Marghera within the Venice lagoon. In coastal samples, concentration levels appear to be lower than those determined at offshore sampling sites.     

Biodegradation of Trace Gases in Simulated Landfill Soil

Abstract

The attenuation of methane and seven volatile organic compounds (VOCs) was investigated in a dynamic methane and oxygen counter gradient system simulating a landfill soil cover. The VOCs investigated were: Tetrachloromethane (TeCM), trichloromethane (TCM), dichloromethane (DCM), trichloroethylene (TCE), vinyl chlo-ride (VC), benzene, and toluene. Soil was sampled at Skellingsted landfill, Denmark. The soil columns showed a high capacity for methane oxidation, with oxidation rates up to 184 g/m²/d corresponding to a 77% reduction of inlet methane. Maximal methane oxidation occurred at 15–20 cm depth, in the upper part of the column where there were overlapping gradients of methane and oxygen. All the chlorinated hydrocarbons were degraded in the active soil columns with removal efficiencies higher than 57%. Soil gas concentration profiles indicated that the removal of the fully chlorinated compound TeCM was because of anaerobic degradation, whereas the degradation of lower chlorinated compounds like VC and DCM was located in the upper oxic part of the column. Benzene and toluene were also removed in the active column. This study demonstrates the complexity of landfill soil cover systems and shows that both anaerobic and aerobic bacteria may play an important role in reducing the emission of trace components into the atmosphere.     

Online hourly determination of 62 VOCs in ambient air: system evaluation and comparison with another two analytical techniques

This paper presents results of the processing and validation of data collected by an automatic gas chromatograph (AGC). This system was used to monitor 62 volatile organic compounds (VOCs) in urban air in the Basque Country, Spain. The nonpolar compounds (C2-C10) identified-paraffins, olefins, aromatics, and chlorinated compounds-accounted for 88% of the mass of total non-methane hydrocarbons (TNMHCs) in ambient air. The evaluation of linearity, precision, detection limits (DLs), and stability of retention times (RTs) indicates that the equipment is suitable for measuring ambient air automatically for prolonged periods (6 months). The calibration of the equipment using response factors calculated on the basis of the effective carbon number (ECN) showed variations of over 10% for acetylene, isoprene, and n-hexane. The results provided by the automatic chromatograph correlated significantly with simultaneous results from other widely used techniques for determining VOCs in ambient air: (1) portable GC, equipped with photoionization detector (PID), and (2) active adsorption on Tenax-TA followed by thermal desorption and chromatographic analysis.     

Organic Compounds in Cloud Water and their Deposition at a Remote Continental Site

Some organic compounds (alkylbenzene, chlorinated hydrocarbons and poiycyclic aromatic hydrocarbons) in clouds have been determined from samples collected above the canopy of a coniferous forest. The cloud samples were collected during 1987 and 1988 at Mt. Mitchell State Park, North Carolina, a remote high elevation (～2006 m MSL) continental site. Concentrations of the organic chemicals in clouds were in the range of 0.2 to ～200 ng mL^-1; and their estimated deposition rates via clouds were found to range from 1.58 * 10⁴ to 4.67 * 10⁶ ng m^-2 yr^-1. Great variations in concentrations were found which can best be explained, based on 72 hour back trajectory analysis, by different source locales and moving air masses. The concentration of these chemicals exceeded their water solubility as predicted by Henry's Law, suggesting that clouds are an excellent scavenger of organic chemicals in the ambient environment.     

机动车尾气VOCs排放特征及减排措施研究

分析了机动车尾气挥发性有机物(VOCs)的排放特征,发现尾气VOCs排放具有明显的日变化和季节变化特征。不同区域不同车型机动车尾气VOCs成分谱略有差异,轻型汽油车尾气VOCs中芳香烃和烷烃含量较高,柴油车烷烃含量较高。尾气排放受机动车保有量、行驶里程、维护保养水平、行驶速度和燃油标准、排放标准等因素影响。从优先控制汽油车、加快机动车更新、采取本地化减排措施、加强多元管理措施、提高科研水平等方面提出了针对性的减排措施。     

A modeling evaluation of the effect of chlorine on the formation of particulate matter in combustion

The effect of chlorine on the fuel-rich oxidation of hydrocarbons and on the molecular weight growth of aromatics is analyzed by simulating experiments featuring a model chlorinated additive CH3Cl in a jet-stirred/plug-flow reactor and premixed flames. The kinetic model used in this work emphasizes the role of resonantly stabilized radicals in the formation and growth of aromatics, and considers soot inception as the net effect of molecular weight growth and graphitization of aromatic structures. Chlorinated hydrocarbons decompose at temperatures significantly lower than hydrocarbons, producing reactive Cl-atoms, which have a strong tendency to go to HCl. The HCI, tying up the H-atoms, inhibits hydrocarbon oxidation. The model is able to predict not only the levels but the shape of the experiments quite well and also the surprising finding of an increased soot formation associated with lower PAH levels found in rich flames with significant levels of chlorine. Based on reaction kinetic analysis, chlorine addition to the fuel enhances soot formation by promoting the formation of aromatic-ring compounds and accelerating the abstraction of aromatic H-atoms from stable PAH molecules. This process activates the transformation of aromatics to soot.