Gasoline Evaporation Research Articles

Source Identification of VOCs In METU Campus Through Factor Analysis

In this study, 55 ozone precursor VOCs, which are routinely measured in PAMS (Photochemical Assessment Monitoring Station) were measured in a suburban station located at Middle East Technical University, Environmental Engineering Department in, Ankara. Daily air samples were collected in evacuated canisters between January – December, 2014. Collected samples were analyzed with GC-FID system and concentrations of 51 VOCs were determined. Mean VOC concentrations ranged between 0.048±0.061 µg m-3 (cis-2-penten) and 10±13 µg m-3 (toluene). Average benzene concentration was 1.49 ± 1.74 μg m-3. Factor Analysis (FA) was applied to determine the major sources of VOCs that contribute to the measured concentrations in the university campus. FA application revealed nine factors that can be grouped under four major components, including (1) transportation: gasoline vehicle exhaust emissions, evaporative losses from gasoline vehicles, gasoline evaporation in gas stations and diesel emissions, (2) industrial emissions: industrial evaporation and industrial application, (3) solvent emissions: surface coatings and solvent use and (4) asphalt application.

Idle performance of a hydrogen rotary engine at different excess air ratios

Rotary engine has flat chamber and longs for fuel with high flame speed and small quenching distance. Hydrogen has many excellent characteristics that are suitable for the rotary engine. In this paper, the performance of a rotary engine fueled with pure hydrogen at different excess air ratios was experimentally investigated. The investigation was carried out on a single-rotor hydrogen-fueled rotary engine equipped with port fuel injection system. An online electronic control module was used to govern the hydrogen injection duration and excess air ratio. In this study, the engine was operating at the idle speed of 3000 rpm and different excess air ratios varied from 0.993 to 1.283. The test results demonstrated that the fuel energy flow rate of the hydrogen rotary engine and engine stability were reduced with the increase of excess air ratio. When the excess air ratio increased from 0.993 to 1.283, the hydrogen energy flow rate was decreased from 14.91 to 11.55 MJ/h. Both the flame development and propagation periods were increased with excess air ratio. CO emission was negligible, but HC, CO2 and NOx emissions were still detected due to the evaporation and possible burning of the lubrication-used gasoline, and oxidation reaction of nitrogen of the intake air.

DESIGNING OF AUTOMOTIVE PRE-START HEAT SOURCES WITH THERMOELECTRIC GENERATOR

Under reduced ambient temperatures, a low rotational frequency of a cranked shaft of a carburettor engine during its start-up stipulates the decrease in the parameters of the compression stroke end (pressure and temperature), which has a significant impact on the conditions of preparation of fuel and air mixture for ignition in cylinders. The decrease in pressure of gasoline saturated vapours together with low velocities of passage in an intake manifold significantly deteriorate the conditions for gasoline evaporation and combustible mixture formation with required combustion limits. In addition, the reduction in the rotational frequency of the cranked shaft of the engine affects the operation of the ignition system, which leads to the decrease in the reliability of spark formation. Therefore, the engine should be warmed-up before its starting.Preheating of the cooling fluid is one of the most common and most effective individual methods of engine warming-up at reduced temperatures. Such heaters are suitable for almost all types of vehicles; therefore, they are used in cars, trucks, buses, aircrafts, yachts and boats.However, in spite of broad possibilities, pre-heaters have not yet found mass application. The main reason that reduces the advantages of pre-heating is non-autonomous operation of the heater components: a fuel pump, a fan for supplying air to the combustion chamber, a circulating pump for pumping a liquid heating medium, which often results in “deep” discharge of a rechargeable battery and prevents the vehicle from starting, in general.In order to avoid the battery discharge during preheating, it is reasonable to use the thermoelectric generator as a source of electricity for the heater components.The design of a gasoline-operated thermoelectric heater for vehicle pre-heating with the engine capacity of 4-10 litres has been developed in this paper. The conditions ensuring the maximum electric power and efficiency of the device have been determined using computer design methods.Based on the results of computer simulation, it is shown that the use of the thermoelectric generator ensures an autonomous operation of the components of the heaters and allows solving the problem of car battery discharging during pre-start equipment operation

Decadal changes in emissions of volatile organic compounds (VOCs) from on-road vehicles with intensified automobile pollution control: Case study in a busy urban tunnel in south China.

In the efforts at controlling automobile emissions, it is important to know in what extent air pollutants from on-road vehicles could be truly reduced. In 2014 we conducted tests in a heavily trafficked tunnel in south China to characterize emissions of volatile organic compounds (VOC) from on-road vehicle fleet and compared our results with those obtained in the same tunnel in 2004. Alkanes, aromatics, and alkenes had average emission factors (EFs) of 338, 63, and 42mgkm-1 in 2014 against that of 194, 129, and 160mgkm-1 in 2004, respectively. In 2014, LPG-related propane, n-butane and i-butane were the top three non-methane hydrocarbons (NMHCs) with EFs of 184±21, 53±6 and 31±3mgkm-1; the gasoline evaporation marker i-pentane had an average EF of 17±3mgkm-1; ethylene and propene were the top two alkenes with average EFs of 16±1 and 9.7±0.9mgkm-1, respectively; isoprene had no direct emission from vehicles; toluene showed the highest EF of 11±2mgkm-1 among the aromatics; and acetylene had an average EF of 7±1mgkm-1. While EFs of total NMHCs decreased only 9% from 493±120mgkm-1 in 2004 to 449±40mgkm-1 in 2014, their total ozone formation potential (OFP) decreased by 57% from 2.50×103mgkm-1 in 2004 to 1.10×103mgkm-1 in 2014, and their total secondary organic aerosol formation potential (SOAFP) decreased by 50% from 50mgkm-1 in 2004 to 25mgkm-1 in 2014. The large drop in ozone and SOA formation potentials could be explained by reduced emissions of reactive alkenes and aromatics, due largely to fuel transition from gasoline/diesel to LPG for taxis/buses and upgraded vehicle emission standards.

Numerical simulation of gasoline evaporation in refueling process

A numerical model of multiphase flow was developed to investigate the heat and mass transfer mechanisms in refueling process. The two-dimensional model takes into account the effects of surface ten...

Pollution Characteristics and Source Apportionment of VOCs at City Centre of Kunming in Summer and Autumn

Based on the data of volatile organic compounds (VOCs) collected from July to October, 2014 in the centre of Kunming, characteristic of their variability and source identification by principal component analysis (PCA) were analyzed. In summer, 40.60% of the total VOC concentrations were attributed to biogenic emissions and industrial process, 19.33% to vehicle emissions, 19.19% to solvent usage, 10.02% to fuel evaporation(including LPG/NG leakage and gasoline evaporation), and 8.34% to industrial production. In autumn, 39.73% of the total VOC concentrations were attributed to industrial production, 27.67% to solvent usage, 21.26% to vehicle emissions, 8.12% to fuel evaporation.

Characterizations of volatile organic compounds (VOCs) from vehicular emissions at roadside environment: The first comprehensive study in Northwestern China

Vehicular emission (VE) is one of the important anthropogenic sources for ground-level volatile organic compounds (VOCs) in both urban and suburban areas. A first comprehensive campaign was conducted at an urban roadside in Xi'an, China in summer, 2016. A total of 57 VOCs, as known as critical surface ozone (O3) precursors, and other trace gases were measured simultaneously during the sampling period. Iso-pentane, a tracer of gasoline evaporation, was the most abundant VOC in the roadside samples, followed by isobutane and benzene, attributed to the largest composition (∼70%) of gasoline-fueled vehicles on the road. The molar ratio of toluene/benzene (T/B) in our study (0.36) is far lower than the range reported in other cities, indicating the stronger contributions from diesel emissions. The results of source apportionment achieved with positive matrix factorization (PMF) receptor model were highly consistent with the vehicles compositions, strongly evidenced that the precise characterization of the VE sources from those marker species. The degrees of individual compound contributed to O3 production were weighed by ozone formation potential (OFP). Propylene (20%), 1-butene (11%) and iso-pentane(10%) were the top three contributors at the roadside. The information of this study complements the VOCs database regarding to the VE sources in Northwestern China.

Quantitative cancer risk assessment and local mortality burden for ambient air pollution in an eastern Mediterranean City.

Health risks posed by ambient air pollutants to the urban Lebanese population have not been well characterized. The aim of this study is to assess cancer risk and mortality burden of non-methane hydrocarbons (NMHCs) and particulates (PM) based on two field-sampling campaigns conducted during summer and winter seasons in Beirut. Seventy NMHCs were analyzed by TD-GC-FID. PM2.5 elemental carbon (EC) components were examined using a Lab OC-EC aerosol Analyzer, and polycyclic aromatic hydrocarbons were analyzed by GC-MS. The US EPA fraction-based approach was used to assess non-cancer hazard and cancer risk for the hydrocarbon mixture, and the UK Committee on Medical Effects of Air Pollutants (COMEAP) guidelines were followed to determine the PM2.5 attributable mortality burden. The average cumulative cancer risk exceeded the US EPA acceptable level (10-6) by 40-fold in the summer and 30-fold in the winter. Benzene was found to be the highest contributor to cancer risk (39-43%), followed by 1,3-butadiene (25-29%), both originating from traffic gasoline evaporation and combustion. The EC attributable average mortality fraction was 7.8-10%, while the average attributable number of deaths (AD) and years of life lost (YLL) were found to be 257-327 and 3086-3923, respectively. Our findings provide a baseline for future air monitoring programs, and for interventions aiming at reducing cancer risk in this population.

Exposure to hazardous air pollutants in underground car parks in Guangzhou, China

Volatile organic compounds (VOCs), carbon monoxide (CO), and PM10 were studied by field sampling in six underground car parks beneath multi-level buildings in Guangzhou, China. CO and PM10 in the car parks range from 3.0 to 69.0 ppm and 0.087 to 0.698 mg m−3, with mean concentrations of 10.8 ppm and 0.228 mg m−3, respectively. Overall mean concentrations of methyl tertiary-butyl ether (MTBE), benzene, toluene, ethyl-benzene, and xylene (BTEX) are 90.5, 54.8, 239.9, 47.7, and 189.3 μg m−3, respectively. Indoor air pollutants in the car parks show an obvious seasonal variation and are higher in winter than in summer. The total estimated cancer risks of occupational exposure for car park staff and casual exposure for parking users are 3.73 × 10−4 and 5.60 × 10−6, indicating definite and possible risks, respectively. The hazard quotient of target VOCs is 4.33, implying a definite risk for people using underground car parks. Indoor/outdoor (I/O) ratios for MTBE and BTEX are significantly higher than one, reflecting strong emission sources in underground car parks. The BTEX to MTBE ratios in the car parks are almost the same as those in tunnel air, indicating that indoor aromatic hydrocarbons were mainly from engine emissions and gasoline evaporation. With increasing urbanization in China, more attention should be paid to the exposure of staff and users to hazardous air pollutants in underground car parks.

Concentration and source apportionment of volatile organic compounds (VOCs) in the ambient air of Kuala Lumpur, Malaysia

The accumulation of volatile organic compounds (VOCs) in ambient air affects air quality through the generation of surface level ozone and secondary organic aerosol. A study of the distribution and source apportionment of VOCs was conducted at two stations to investigate the air quality status of Kuala Lumpur. Samples of ambient air were collected into Tedlar sampling bags using an air sampling pump and then pre-concentrated with solid-phase micro-extraction fibre. Gas chromatography–mass spectrometry (GC–MS) was employed to measure the VOC species. An absolute principal component score–multiple linear regression (APCS–MLR) model was then applied to identify the possible source contributions of VOCs. Seventeen VOCs were detected, and methylene chloride (243 ± 241 ppbv) was the most abundant species at both stations. Within the benzene, toluene, ethyl benzene and xylene group of VOCs, toluene was dominant with an average of 135 ± 202 ppbv, followed by p-xylene (41.3 ± 24.7 ppbv), ethyl benzene (34.0 ± 32.6 ppbv) and benzene (18.2 ± 12.9 ppbv). A strong correlation between benzene and toluene (p < 0.01, r = 0.65) indicated the influence of motor vehicle emissions during the sampling period. The APCS–MLR results indicated that the source contributors for VOCs at the sampling stations were gasoline evaporation (31 %), motor vehicle exhaust/solvent (22 %), motor vehicle emissions (21 %), petrol pump/solvent usage (15 %) and industrial emissions (10 %).

Characterization and source apportionment of volatile organic compounds based on 1-year of observational data in Tianjin, China

From November 2014 to October 2015, the concentrations of volatile organic compounds (VOCs), O3 and NOx were simultaneously monitored by using online instruments at the air monitoring station belonged to Tianjin Environmental Protection Bureau (TEPB). The results indicated that VOCs concentrations were higher in autumn and lower in spring, while O3 concentrations were higher in summer, and lower in winter. The diurnal variations of VOCs and NOx (NO2 plus NO) showed opposite tendency comparing to that of O3. The concentrations of alkanes were higher (the average of 18.2 ppbv) than that of aromatics (5.3 ppbv) and alkenes (5.2 ppbv), however, the alkenes and aromatics made larger contributions to ozone because of their high reactivity. Tianjin belonged to the VOC-limited region during most of seasons (except summer) according to the VOC/NOx ratios (the 8:1 threshold). The automobile exhaust, industrial emission, liquefied petroleum gas/natural gas (LPG/NG), combustion, gasoline evaporation, internal combustion engine emission and solvent usage were identified as major sources of VOCs by Positive Matrix Factorization (PMF) model in Tianjin, and the contributions to VOCs for the entire year were 23.1%, 19.9%, 18.6%, 10.6%, 8.7%, 5.4% and 4.7%, respectively. The conditional probability function (CPF) analysis indicated that the contributing directions of automobile exhaust and industrial emission were mainly affected by source distributions, and that of other sources might be mainly affected by wind direction. The backward trajectory analysis indicated that the trajectory of air mass originated from Mongolia, which reflected the features of large-scale and long-distance air transport, and that of beginning in Jiangsu, Shandong and Tianjin, which showed the features of small-scale and short-distance. Tianjin, Beijing, Hebei and Northwest of Shandong were identified as major potential source-areas of VOCs by using potential source contribution function (PSCF) and concentration-weighted trajectory (CWT) models.

Improving the environmental and performance characteristics of vehicles by introducing the surfactant additive into gasoline.

The operation of modern vehicles requires the introduction of package of fuel additives to ensure the required level of operating characteristics, some of which cannot be achieved by current oil refining methods. The use of additives allows flexibility of impact on the properties of the fuel at minimal cost, increasing the efficiency and environmental safety of vehicles. Among the wide assortment of additives available on the world market, many are surfactants. It has been shown that the introduction of some surfactants into gasoline concurrently reduces losses from gasoline evaporation, improves the mixture formation during injection of gasoline into the engine and improves detergent and anticorrosive properties. The surfactant gasoline additive that provides significant improvement in the quality of gasoline used and environmental and operating characteristics of vehicles has been developed and thoroughly investigated. The results of studies confirming the efficiency of the gasoline additive application are herein presented.

Source apportionment vs. emission inventories of non-methane hydrocarbons (NMHC) in an urban area of the Middle East: local and global perspectives

Abstract. We applied the positive matrix factorization model to two large data sets collected during two intensive measurement campaigns (summer 2011 and winter 2012) at a sub-urban site in Beirut, Lebanon, in order to identify NMHC (non-methane hydrocarbons) sources and quantify their contribution to ambient levels. Six factors were identified in winter and five factors in summer. PMF-resolved source profiles were consistent with source profiles established by near-field measurements. The major sources were traffic-related emissions (combustion and gasoline evaporation) in winter and in summer accounting for 51 and 74 wt %, respectively, in agreement with the national emission inventory. The gasoline evaporation related to traffic source had a significant contribution regardless of the season (22 wt % in winter and 30 wt % in summer). The NMHC emissions from road transport are estimated from observations and PMF results, and compared to local and global emission inventories. The PMF analysis finds reasonable differences on emission rates, of 20–39 % higher than the national road transport inventory. However, global inventories (ACCMIP, EDGAR, MACCity) underestimate the emissions up to a factor of 10 for the transportation sector. When combining emission inventory to our results, there is strong evidence that control measures in Lebanon should be targeted on mitigating the NMHC emissions from the traffic-related sources. From a global perspective, an assessment of VOC (volatile organic compounds) anthropogenic emission inventories for the Middle East region as a whole seems necessary as these emissions could be much higher than expected at least from the road transport sector.

Heating and evaporation of a new gasoline surrogate fuel: A discrete multicomponent modeling study

In Gasoline Direct Injection (GDI) engines, a fuel spray is injected directly into the cylinder during the compression stroke, creating a fuel–air mixture with an ignitable composition at the spark gap at the time of ignition. Spraying droplet breakup, heating and evaporation is essential for the mixture preparation and the ignition/combustion. For numerical modeling of spray evaporation and combustion, it is impractical to include all real components. In this study, a new 6-component surrogate mixture composed of i-pentane/n-heptane/toluene/iso-octane/n-propyl cyclohexane/iso-undecane is developed to match the targeted gasoline in terms of thermo-physical properties and experimental distillation curve. This new surrogate also covers TRF (toluene reference fuel) components, which are the three basic components for ignition modeling. This allows both physical and chemical modeling of gasoline using only one surrogate. This new surrogate fuel is implemented into an existing modeling methodology which simultaneously accounts for finite conductivity, finite mass diffusivity and turbulence effects within atomizing multicomponent liquid fuel sprays. The main purpose of this study is to perform analysis of heating and evaporation of the new surrogate gasoline. Both normal evaporation and flash boiling evaporating processes are investigated.

A surrogate mixture and kinetic mechanism for emulating the evaporation and autoignition characteristics of gasoline fuel

Gasoline direct-injection spark-ignition engines and gasoline direct-injection compression-ignition engines have received attention due to their higher fuel economy with respect to conventional port fuel injected internal combustion spark-ignition engines. Combustion modeling of these types of engines requires a fuel surrogate that mimics both physical (e.g., evaporation) and chemical (e.g., combustion) characteristics of the gasoline fuel. In this work, we propose a novel methodology for the formulation of a gasoline surrogate based on the essential physical and chemical properties of the target gasoline fuel. Using the proposed procedure, a surrogate with seven components has been identified to emulate the physical and chemical characteristics of a real non-oxygenated gasoline fuel, RD387. A surrogate kinetic mechanism was developed by combining available detailed kinetic mechanisms from the Lawrence Livermore National Laboratory library. The modeling results for distillation curve, ignition delay and laminar flame speed were validated against available experimental data in the literature. The surrogate and gasoline fuels display similar physical/chemical properties, including distillation curve, H/C ratio, density, heating value, and ignition behavior and flame propagation over a wide range of pressures, temperatures, and equivalence ratios.

Modelling of gasoline fuel droplets heating and evaporation

Abstract The paper presents a new approach to modelling of the heating and evaporation of gasoline fuel droplets with a specific application to conditions representative of internal combustion engines. A number of the components of gasoline with identical chemical formulae and close thermodynamic and transport properties are replaced with characteristic components leading to reducing the original composition of gasoline fuel (83 components) to 20 components only. Furthermore, the approximation to the composition of gasoline with these components is replaced with a smaller number of hypothetical quasi-components/components as previously suggested in the multi-dimensional quasi-discrete (MDQD) model. The transient diffusion of quasi-components and single components in the liquid phase as well as the temperature gradient and recirculation inside the droplets, due to the relative velocities between the droplets and the ambient air, are accounted for in the model. In the original MDQD model, n-alkanes and iso-alkanes are considered as one group of alkanes. In this new approach, the contributions of these two groups are taken into account separately. The values for the initial model parameters were selected from experimental data measured in a research engine prior to combustion. The results are compared with the predictions of the single-component model in which the transport and thermodynamic properties of components are averaged, diffusion of species is ignored and liquid thermal conductivity is assumed to be infinitely large, or approximated by those of iso-octane. It is shown that the application of the latter models leads to an under-prediction of the droplet evaporation time by approximately 67% (averaged) and 47% (iso-octane), respectively, compared to those obtained using the discrete component model, taking into account the contributions of 20 components. It is shown that the approximation of the actual composition of gasoline fuel by 6 quasi-components/components, using the MDQD model, leads to an under-prediction of the estimated droplet surface temperatures and evaporation times by approximately 0.9% and 6.6% respectively, for the same engine conditions. The application of the latter model has resulted in an approximately 70% reduction in CPU processor time compared to the model taking into account all 20 components of gasoline fuel.

Missing in total OH reactivity of VOCs from gasoline evaporation

Abstract Gasoline evaporation is an important anthropogenic source of atmospheric volatile organic compounds (VOCs). Total OH reactivity for gasoline vapor was measured from 4 kinds of gasoline for the first time by comparative reactivity method (CRM) using proton transfer reaction mass spectrometer (PTR-MS). Compositions of 56 PAMS (photochemical assessment monitoring station) nonmethane hydrocarbons (NMHCs) were measured for both liquid and headspace of gasoline. We found high abundance of alkenes and aromatics in gasoline. The calculated OH reactivity derived from quantified NMHCs speciation accounted for only 57 ± 4% of total reactivity obtained from CRM method. N-Alkenes, only 6 wt% in liquid gasoline, contributed to 70% of calculated reactivity. We assume that the undetected branched alkenes are the possible reason for the missing reactivity. We suggest that the priority of gasoline quality improvement is to reduce alkenes content in gasoline in term of reactivity-based control.

Investigation of gasoline distributions within petrol stations: spatial and seasonal concentrations, sources, mitigation measures, and occupationally exposed symptoms.

We measured levels of VOCs and determined the distributions of benzene concentrations over the area of two petrol stations in all three seasons. Using the concentrations and sampling positions, we created isoconcentration contour maps. The average concentrations ranged 18-1288 μg m(-3) for benzene and 12-81 μg m(-3) for toluene. The contour maps indicate that high-level contours of benzene were found not only at the fuel dispenser areas but also at the storage tank refilling points, open drainage areas where gasoline-polluted wastewater was flowing, and the auto service center located within the station area. An assessment of the benzene to toluene ratio contour plots implicates that airborne benzene and toluene near the fuel dispenser area were attributed to gasoline evaporation although one of the studied stations may be influenced by other VOC sources besides gasoline evaporation. Additionally, during the routine refilling of the underground fuel storage tanks by a tank truck, the ambient levels of benzene and toluene increased tremendously. The implementation of source control by replacing old dispensers with new fuel dispensers that have an efficient cutoff feature and increased delivery speed can reduce spatial benzene concentrations by 77%. Furthermore, a questionnaire survey among 63 service attendants in ten stations revealed that headache was the most reported health complaint with a response rate of 32%, followed by fatigue with 20%. These prominent symptoms could be related to an exposure to high benzene concentrations.

Trends of non-methane hydrocarbons (NMHC) emissions in Beijing during 2002–2013

Abstract. Non-methane hydrocarbons (NMHCs) play a critical role in the photochemical production of ozone (O3) and organic aerosols. Obtaining an accurate understanding on temporal trends of NMHC emissions is essential for predicting air quality changes and evaluating the effectiveness of current control measures. In this study, we evaluated temporal trends of anthropogenic NMHC emissions during August in Beijing based on ambient measurements during selected summer periods at an urban site in Beijing from 2002 to 2013. In the contrast to the results from the most recent inventory (Multi-resolution Emission Inventory for China, MEIC), which reported that anthropogenic NMHC emissions during August increased by 28% from 2004 to 2012, whereas mixing ratios of NMHCs measured at this urban site decreased by 37% during the same time period. A positive matrix factorization (PMF) model was applied to these NMHC measurements for source apportionment. The results showed that the relative contributions of vehicular exhaust and gasoline evaporation to measured NMHC concentrations decreased by 66% during August from 2004 to 2012, comparable to the relative decline of 67% for transportation-related NMHC emissions reported by the MEIC inventory. This finding indicates that the implementation of stricter emissions standards for new vehicles and specific control measures for in-use vehicles has been effective for reducing transportation-related NMHC emissions. In addition, the PMF results suggested that there were no significant temporal changes in NMHC concentrations from solvent use and industry during August from 2004 to 2012, in contrast with the rapid rate of increase (8.8% yr−1) reported by the MEIC inventory. To re-evaluate the NMHC emissions trends for solvent use and industry, annual variations in NMHC / NOx ratios were compared between ambient measurements at the PKU site and the MEIC inventory. In contrast to the significant rise in NMHC / NOx ratios from the MEIC inventory, the measured NMHC / NOx ratios declined by 14% during August from 2005 to 2012. The inferred NMHC / NOx ratios based on PMF results exhibited a comparable decline of 11% to measured ratios. These results indicate that the increase rate for NMHC emissions from solvent use and industry in Beijing might be overestimated in the current inventory; therefore, additional research is necessary to verify the NMHC emission trends for this source.

Multi-year evaluation of ambient volatile organic compounds: temporal variation, ozone formation, meteorological parameters, and sources.

The multi-year characteristics of ambient volatile organic compounds (VOCs) and their source contribution in a selected metropolitan (Seoul) and rural (Seokmolee) areas in Korea were investigated to provide the framework for development and implementation of ambient VOC control strategies. For Seoul, none of the three VOC groups exhibited any significant trend in their ambient concentrations, whereas for Seokmolee, they all showed a generally decreasing trend between 2005 and 2008 and an increasing trend after 2008. Two paraffinic (ethane and propane) and two olefin (ethylene and propylene) hydrocarbons displayed higher concentrations during the cold season than warm season, while the other target VOCs did not exhibit any significant trends. Ethylene and toluene were the first and second largest contributors to ozone formation, respectively, whereas several other VOCs displayed photochemical ozone formation potential values less than 0.01 ppb. For both areas, there was a significant negative correlation between ambient temperature and the selected VOC group concentrations. In contrast, a significant positive correlation was observed between relative humidity and the three VOC group concentrations, while no significant correlation was observed between wind speed and VOC group concentrations. For Seoul, the combination of vehicle exhaust and gasoline/solvent evaporation was the greatest source of VOCs, followed by liquid natural gas (LNG) and liquid petroleum gas (LPG). However, combination of LNG and LPG was the greatest source of VOCs at Seokmolee, followed by the combination of vehicle exhaust and gasoline evaporation, and then biogenic sources.