Spatial and temporal variations of volatile organic compounds using passive air samplers in the multi-industrial city of Ulsan, Korea

Effects of ground transport on the presence of heavy metals in selected honeybee products

Honeybees are insects very sensitive to environmental pollution and at the same time very good indicators of the pollution levels for certain types of pollutants. The morphology and ethology of these insects make them perfect vectors for dust and substances, including heavy metals produced by anthropic activities or naturally generated and deposited on foraged flora. When bees are raised to produce foods such as honey and pollen, they can easily transfer pollutants collected from contaminated flower affecting the quality of these products. However, depending on geographical location of the apiaries and their distance from pollution sources, the risk to contaminate bee products can be higher or lower requiring deep investigations. In this study, two apiaries were built near ground transport infrastructures and used as monitoring stations for investigating heavy metal presence in beehive products such as bee wax, pollen, and honey. Another apiary was placed between these two locations at a distance of 500 m from each one and used as central node to asses possible diffusion trends. Parallel, air quality was monitored in the proximity of each apiary to verify the air pollution of the environments close to these sites. The results of the study suggest that the presence of the highway and the train station affected the levels of heavy metal presence in the apiary products. Air quality near apiaries was also negatively affected by ground transport, especially in proximity of the highway. Wax resulted significantly more polluted in the apiary close to train station with elements such as Al, Zn, and Ni, while honey and pollen were significantly more polluted in the proximity of the highway with elements such as Al, Fe, Cu, and Zn. Honey was the product suffering less the contamination by heavy metals while pollen was the worse. In conclusion, the presence of transportation nodes determined a higher accumulation of heavy metals in beehive products respect the apiary placed in between, suggesting to pay particular attention in the site selection for the placement of apiaries to protect both bees and human health.

Primary and oxidative source analyses of consumed VOCs in the atmosphere

Consumed VOCs are the compounds that have reacted to form ozone and secondary organic aerosol (SOA) in the atmosphere. An approach that can apportion the contributions of primary sources and reactions to the consumed VOCs was developed in this study and applied to hourly VOCs data from June to August 2022 measured in Shijiazhuang, China. The results showed that petrochemical industries (36.9 % and 51.7 %) and oxidation formation (20.6 % and 35.6 %) provided the largest contributions to consumed VOCs and OVOCs during the study period, whereas natural gas (5.0 % and 7.6 %) and the mixed source of liquefied petroleum gas and solvent use (3.1 % and 4.2 %) had the relatively low contributions. Compared to the non-O3 pollution (NOP) period, the contributions of oxidation formation, petrochemical industries, and the mixed source of gas evaporation and vehicle emissions to the consumed VOCs during the O3 pollution (OP) period increased by 2.8, 3.8, and 9.3 times, respectively. The differences in contributions of liquified petroleum gas and solvent use, natural gas, and combustion sources to consumed VOCs between OP and NOP periods were relatively small. Transport of petrochemical industries emissions from the southeast to the study site was the primary consumed pathway for VOCs emitted from petrochemical industries.

Geographic information system-based determination of priority monitoring areas for hazardous air pollutants in an industrial city

Industrial cities are hotspots for many hazardous air pollutants (HAPs), which are detrimental to human health. We devised an identification method to determine priority HAP monitoring areas using a comprehensive approach involving monitoring, modeling, and demographics. The methodology to identify the priority HAP monitoring area consists of two parts: (1) mapping the spatial distribution of selected categories relevant to the target pollutant and (2) integrating the distribution maps of various categories and subsequent scoring. The identification method was applied in Ulsan, the largest industrial city in South Korea, to identify priority HAP monitoring areas. Four categories related to HAPs were used in the method: (1) concentrations of HAPs, (2) amount of HAP emissions, (3) the contribution of industrial activities, and (4) population density in the city. This method can be used to select priority HAP monitoring areas for intensive monitoring campaigns, cohort studies, and epidemiological studies.

Mapping the spatial distribution of primary and secondary PM2.5 in a multi-industrial city by combining monitoring and modeling results

Industrial cities are strongly influenced by primary emissions of PM2.5 from local industries. In addition, gaseous precursors, such as sulfur oxides (SOX), nitrogen oxides (NOX), and volatile organic compounds (VOCs), emitted from industrial sources, undergo conversion into secondary inorganic and organic aerosols (SIAs and SOAs). In this study, the spatial distributions of primary and secondary PM2.5 in Ulsan, the largest industrial city in South Korea, were visualized. PM2.5 components (ions, carbons, and metals) and PM2.5 precursors (SO2, NO2, NH3, and VOCs) were measured to estimate the concentrations of secondary inorganic ions (SO42-, NO3-, and NH4+) and secondary organic aerosol formation potential (SOAFP). The spatial distributions of SIAs and SOAs were then plotted by combining atmospheric dispersion modeling, receptor modeling, and monitoring data. Spatial distribution maps of primary and secondary PM2.5 provide fundamental insights for formulating management policies in different districts of Ulsan. For instance, among the five districts in Ulsan, Nam-gu exhibited the highest levels of primary PM2.5 and secondary nitrate. Consequently, controlling both PM2.5 and NO2 emissions becomes essential in this district. The methodology developed in this study successfully identified areas with dominant contributions from both primary emissions and secondary formation. This approach can be further applied to prioritize control measures during periods of elevated PM levels in other industrial cities.

Passive air sampling of VOCs, O3, NO2, and SO2 in the large industrial city of Ulsan, South Korea: spatial-temporal variations, source identification, and ozone formation potential

Concerns about volatile organic compounds (VOCs) have increased due to their toxicity and secondary reaction with nitrogen oxides (NOX) to form ozone (O3). In this study, passive air sampling of VOCs, O3, NO2, and SO2 was conducted in summer, fall, winter, and spring from 2019 to 2020 at six industrial and ten urban sites in Ulsan, the largest industrial city in South Korea. Over the entire sampling period, the concentration of toluene (mean: 8.75 μg/m3) was the highest of the 50 target VOCs, followed by m,p-xylenes (4.52 μg/m3), ethylbenzene (4.48 μg/m3), 3-methylpentane (4.40 μg/m3), and n-octane (4.26 μg/m3). Total (Σ50) VOC levels did not statistically differ between seasons, indicating that large amounts of VOCs are emitted into the atmosphere throughout the year. On the other hand, O3, NO2, and SO2 exhibited strong seasonal variation depending on the meteorological conditions and emission sources. The spatial distribution of Σ50 VOCs, NO2, and SO2 indicated that industrial complexes were major sources in Ulsan, while O3 had the opposite spatial distribution. Using a positive matrix factorization model, five major sources were identified, with industrial effects dominant. Aromatic compounds, such as m,p,o-xylenes, toluene, and 1,2,4-trimethylbenzene, significantly contributed to O3 formation. The VOC/NO2 ratio and O3 concentrations suggested that reducing VOC emissions is more effective than reducing NO2 emissions in terms of preventing the secondary formation of O3. The findings of this study allow for a better understanding of the relationship between VOCs, O3, NO2, and SO2 in industrial cities.

Changes in source apportioned VOCs during high O3 periods using initial VOC-concentration-dispersion normalized PMF

Ambient volatile organic compounds (VOCs) concentrations are affected by emissions, dispersion, and chemistry. This work developed an initial concentration-dispersion normalized PMF (ICDN-PMF) to reflect the changes in source emissions. The effects of photochemical losses for VOC species were corrected by estimating the initial data, and then applying dispersion normalization to reduce the impacts of atmospheric dispersion. Hourly speciated VOC data measured in Qingdao from March to May 2020 were utilized to test the method and had assessed its effectiveness. Underestimated solvent use and biogenic emissions contributions due to photochemical losses during the O3 pollution (OP) period reached 4.4 and 3.8 times the non-O3 pollution (NOP) period values, respectively. Increased solvent use contribution due to air dispersion during the OP period was 4.6 times the change in the NOP period. The influence of chemical conversion and air dispersion on the gasoline and diesel vehicle emissions was not apparent during either period. The ICDN-PMF results suggested that biogenic emissions (23.1 %), solvent use (23.0 %), motor-vehicle emissions (17.1 %), and natural gas and diesel evaporation (15.8 %) contributed most to ambient VOCs during the OP period. Biogenic emissions and solvent use contributions during the OP period increased by 187 % and 135 % compared with the NOP period, respectively, whereas that of liquefied petroleum gas substantially decreased during the OP period. Controlling solvent use and motor-vehicles could be effective in controlling VOCs in the OP period.

Characteristics of volatile organic compounds in the metropolitan city of Seoul, South Korea: Diurnal variation, source identification, secondary formation of organic aerosol, and health risk

Atmospheric volatile organic compounds (VOCs) in Seoul, the capital of South Korea, have attracted increased attention owing to their emission, secondary formation, and human health risk. In this study, we collected 24 hourly samples once a month at an urban site in Seoul for a year (a total of 288 samples) using a sequential tube sampler. Analysis results revealed that toluene (9.08 ± 8.99 μg/m³) exhibited the highest annual mean concentration, followed by ethyl acetate (5.55 ± 9.09 μg/m³), m,p-xylenes (2.79 ± 4.57 μg/m³), benzene (2.37 ± 1.55 μg/m³), ethylbenzene (1.81 ± 2.27 μg/m³), and o-xylene (0.91 ± 1.47 μg/m³), indicating that these compounds accounted for 77.8-85.6% of the seasonal mean concentrations of the total (Σ₅₉) VOCs. The concentrations of the Σ₅₉ VOCs were statistically higher in spring and winter than in summer and fall because of meteorological conditions, and the concentrations of individual VOCs were higher during the daytime than nighttime owing to higher human activities during the daytime. The conditional bivariate probability function and concentration weighted trajectory analysis results suggested that domestic effects (e.g., vehicular exhaust and solvents) exhibited a dominant effect on the presence of VOCs in Seoul, as well as long-range atmospheric transport of VOCs. Further, the most important secondary organic aerosol formation potential (SOAFP) compounds included benzene, toluene, ethylbenzene, and m,p,o-xylenes, and the total SOAFP of nine VOCs accounted for 5-29% of the seasonal mean PM_2.5 concentrations. The cancer and non-cancer risks of the selected VOCs were below the tolerable (1 × 10^-4) and acceptable (Hazard quotient: HQ < 1) levels, respectively. Overall, this study highlighted the feasibility of the sequential sampling of VOCs and hybrid receptor modeling to further understand the source-receptor relationship of VOCs.

Volatile organic compounds in an e-waste dismantling region: From spatial-seasonal variation to human health impact

The dismantling of electrical and electronic waste (e-waste) can release various Volatile organic compounds (VOCs), impacting the surrounding ambient environment. We investigated the spatio-temporal characteristics and health risks of the ambient VOCs emitted in a typical e-waste dismantling region by conducting multi-site sampling campaigns in four seasons. The pollution of benzene, toluene, ethylbenzene, and xylenes (BTEX) in the e-waste dismantling park has relation to e-waste dismantling by seasonal trend analysis. The highest concentrations of most VOCs occurred in winter and autumn, while the lowest levels were observed in summer and spring. The spatial distribution map revealed the e-waste dismantling park to be a hotspot of BTEX, 1,2-dichloropropane (1,2-DCP), and 1,2-dichloroethane (1,2-DCA), while two major residential areas were also the hotspots of BTEX. The e-waste emission source contributed 20.14% to the total VOCs in the e-waste dismantling park, while it was absent in the major residential and rural areas. The cancer risk assessment showed that six VOCs exceeded 1.0 × 10^-6 in the e-waste dismantling park, while only three or four compounds exceeded this risk in other areas. The noncancer risks of all compounds were below the safety threshold. This study supplements the existing knowledge on VOC pollution from e-waste dismantling and expands the research scope of chemical pollution caused by e-waste.

Occurrence, Potential Sources, and Risk Assessment of Volatile Organic Compounds in the Han River Basin, South Korea

Increasing public awareness about the aesthetics and safety of water sources has shifted researchers’ attention to the adverse effects of volatile organic compounds (VOCs) on humans and aquatic organisms. A total of 17 VOCs, including 10 volatile halogenated hydrocarbons and seven volatile non-halogenated hydrocarbons, were investigated at 36 sites of the Han River Basin, which is the largest and most important drinking water source for residents of the Seoul metropolitan area and Gyeonggi province in South Korea. The VOC concentrations ranged from below detection limits to 1.813 µg L⁻¹. The most frequently detected VOC was 1,2-dichloropropane, with a detection frequency of 80.56%, as it is used as a soil fumigant, chemical intermediate, and industrial solvent. In terms of geographical trends, the sampling sites that were under the influence of sewage and industrial wastewater treatment plants were more polluted with VOCs than other areas. This observation was also supported by the results of the principal component analysis. In the present study, the detected concentrations of VOCs were much lower than that of the predicted no-effect concentrations, suggesting low ecological risk in the Han River. However, a lack of available ecotoxicity data and limited comparable studies warrants further studies on these compounds.

Source apportionment of biogenic and anthropogenic VOCs in Bolu plateau

Total of 69 volatile organic compounds (VOCs) including both biogenic (isoprene, monoterpenes and oxygenated compounds) and anthropogenic ones were investigated in Bolu plateau by passive sampling technique. The main objective of this study was to determine spatial distributions, seasonal variations and possible sources for a wide variety of VOCs. Two-week passive sampling campaigns were performed in the winter and summer of 2017. Anthropogenic VOCs were predominant with a high percentage of contribution, 91% and 69% for winter and summer, respectively. Relatively higher concentrations of biogenic VOCs during the summer campaign were found to be related to higher solar intensity, temperature and amount of broad-leaved tree species. Benzaldehyde, toluene, phenol, benzene, hexane, decanal, benzothiazole, dodecane and acetophenone were anthropogenic VOCs with higher concentrations. Among biogenic VOCs, hexanal, alpha-pinene and limonene were found to be in higher concentrations. Spatial distribution maps were drawn for each VOC. Elevated concentrations of VOCs around the city center and major roads indicate that emissions from domestic heating activities and vehicular emissions can be significant sources of VOCs. The results were also supported by Positive Matrix Factorization (PMF) analyses and G-score distribution maps. Solvent evaporation, wood-coal combustion, biogenic emissions (pine, grain, grass), city atmosphere (styrene emissions from plastic production), biogenic (hornbeam, pine, juniper) and vehicle emissions were the identified as the primary VOC sources in Bolu plateau, contributing 31%, 22%, 8.0%, 8.0%, 13%, and 18%, respectively to the total VOC concentrations.

Spatiotemporal Variations and Health Implications of Hazardous Air Pollutants in Ulsan, a Multi-Industrial City in Korea

We measured a wide range of hazardous air pollutants (HAPs) simultaneously at five sites over four seasons in 2009–2010 in Ulsan, the largest industrial city in Korea. Target analytes included volatile organic compounds (VOCs), carbonyls, polycyclic aromatic hydrocarbons (PAHs), phthalates, and heavy metals (HMs). The objectives of this study were to evaluate the occurrence and spatiotemporal distributions of HAPs, and to identify important HAPs based on health risk assessment. Industrial emissions affected ambient levels of VOCs and HMs, as demonstrated by spatial distribution analysis. However, concentrations of PAHs and phthalates were relatively uniform at all sites. VOCs and HMs exhibited little seasonal variation, while formaldehyde increased in the summer due to its secondary formation. PAHs exhibited notable seasonal variation; higher in cold seasons and lower in warm seasons. Cumulative cancer risks imposed by 35 HAPs were 4.7 × 10−4 and 1.7 × 10−4 in industrial and residential areas, respectively. The top five major cancer risk drivers appeared to be formaldehyde, benzene, benzo[a]pyrene, As, and Co. The sums of hazard quotients (HQ) derived by 47 HAPs were 10.0 (industrial) and 2.4 (residential). As the individual species, only two HAPs exceeded the HQ of 1, which are As (3.1) and Pb (2.1) in the industrial area. This study demonstrated the importance of a comprehensive monitoring and health risk assessment to prioritize potentially toxic pollutants in the ambient air of a large industrial city.

Observations of BTEX in the ambient air of Kuala Lumpur by passive sampling

Benzene, toluene, ethylbenzene and xylenes (BTEX) are well known hazardous volatile organic compounds (VOCs) due to their human health risks and photochemical effects. The main objective of this study was to estimate BTEX levels and evaluate interspecies ratios and ozone formation potentials (OFP) in the ambient air of urban Kuala Lumpur (KL) based on a passive sampling method with a Tenax® GR adsorbent tube. Analysis of BTEX was performed using a thermal desorption (TD)-gas chromatography mass spectrometer (GCMS). OFP was calculated based on the Maximum Incremental Reactivity (MIR). Results from this study showed that the average total BTEX during the sampling period was 66.06 ± 2.39 μg/m³. Toluene (27.70 ± 0.97 μg/m³) was the highest, followed by m,p-xylene (13.87 ± 0.36 μg/m³), o-xylene (11.49 ± 0.39 μg/m³), ethylbenzene (8.46 ± 0.34 μg/m³) and benzene (3.86 ± 0.31 μg/m³). The ratio of toluene to benzene (T:B) is > 7, suggesting that VOCs in the Kuala Lumpur urban environment are influenced by vehicle emissions and other anthropogenic sources. The average of ozone formation potential (OFP) value from BTEX was 278.42 ± 74.64 μg/m³ with toluene and xylenes being the major contributors to OFP. This study also indicated that the average of benzene concentration in KL was slightly lower than the European Union (EU)-recommended health limit value for benzene of 5 μg/m³ annual exposure.

Application of spatial analysis to investigate contribution of VOCs to photochemical ozone creation

This study was concerned with the temporal analysis of benzene, toluene, ethylbenzene, xylenes (BTEXs), and ozone in Rochester, New York, between 2012 and 2018. Additionally, the influence of ozone precursors (e.g., BTEXs and NO₂) and meteorological variables (e.g., relative humidity (RH), temperature along with wind speed) on ozone dispersion was investigated in the eastern half of the USA using the integrated nested Laplace approximation and stochastic partial differential equation (INLA-SPDE). The benzene variability at seasonal scale was characterized by higher values during the cold seasons. On the contrary, the long-term temporal trend of ozone depicted a repetitive cyclic behavior while an episode, with values exceeding 5 μg/m³, was detected associated with benzene in 2015. The spatial analysis by INLA-SPDE indicated that 1,3,5-trimethylbenzene and benzene were the key ozone precursors influencing ozone formation. It was demonstrated that increase of temperature had a considerable impact on ozone build-up whereas the increment of RH leads to decrease in ambient values of ozone. The amounts of root mean squared error (RMSE), mean absolute error (MAE), and bias for the validation data (e.g., 32 samples) were 0.005, 0.004, and 0.0008, exhibiting a reasonable out-of-sample forecasting by the INLA-SPDE model. The distribution map of ozone highlighted a hot spot in the state of Florida.