Chemical characteristics and sources apportionment of volatile organic compounds in the primary urban area of Shijiazhuang, North China Plain.

VOCs (Volatile organic compounds) exert a vital role in ozone and secondary organic aerosol production, necessitating investigations into their concentration, chemical characteristics, and source apportionment for the effective implementation of measures aimed at preventing and controlling atmospheric pollution. From July to October 2020, online monitoring was conducted in the main urban area of Shijiazhuang to collect data on VOCs and analyze their concentrations and reactivity. Additionally, the PMF (positive matrix factorization) method was utilized to identify the VOCs sources. Results indicated that the TVOCs (total VOCs) concentration was (96.7 ± 63.4 µg/m3), with alkanes exhibiting the highest concentration of (36.1 ± 26.4 µg/m3), followed by OVOCs (16.4 ± 14.4 µg/m3). The key active components were alkenes and aromatics, among which xylene, propylene, toluene, propionaldehyde, acetaldehyde, ethylene, and styrene played crucial roles as reactive species. The sources derived from PMF analysis encompassed vehicle emissions, solvent and coating sources, combustion sources, industrial emissions sources, as well as plant sources, the contribution of which were 37.80%, 27.93%, 16.57%, 15.24%, and 2.46%, respectively. Hence, reducing vehicular exhaust emissions and encouraging neighboring industries to adopt low-volatile organic solvents and coatings should be prioritized to mitigate VOCs levels.

[Characteristics and Source Apportionment of Atmospheric Volatile Organic Compounds in Zhengzhou During O3 Campaign Period].

An online gas chromatograph （GC5000） was used to monitor the volatile organic compounds （VOCs） in the atmospheric environment of Zhengzhou City during the ozone campaign period from May to September of 2022. The relationship between O3 and its precursors as well as meteorology was analyzed and the pollution characteristics of VOCs during the O3 exceeding and non-exceeding the standard days were compared and explored. Different VOC activity evaluation methods of OFP and L·OH were utilized to compare and analyze the key active components and species and the ratio analysis （RA） and positive matrix factorization （PMF） analysis models were used to study the apportionment contribution of VOCs. The results showed that the O3 pollution in June and September in Zhengzhou was mainly due to the adverse meteorological conditions of high temperature and low humidity, strong radiation, and low wind speed, superimposed by the prominent concentrations of local VOCs and NO2, resulting in frequently high and excessive O3 occurrences. The VOCs concentration in Zhengzhou during the campaign period was an average of （68.3 ± 18.4） µg·m-3, whereas it was 75.7 µg·m-3 during O3 exceeding standard days and 13.4 µg·m-3 during O3 non-exceeding days, respectively. Among the VOC species, the OVOCs was 31.6%, accounting for the highest mass fraction, followed by halogenated hydrocarbon, alkane, and aromatic hydrocarbon, and the major species were ethane, n-butane, dichloromethane, propane, isopentane, toluene, chloromethane, 1,2-dichloroethane, and acetylene. VOC diurnal variation indicated that the emission of VOC pollution sources in the morning, evening peak, and at night should be paid more attention. The contribution of VOCs to OFP during the campaign period was （130.5 ± 46.4） µg·m-3, and the L·OH was （6.5 ± 2.9） s-1, among which the top 15 species with high activity were primarily acetaldehyde, isoprene, ethylene, m/p-xylene, toluene, hexal, isopentane, propanal, propylene, trans-2-butene, etc. In particular, the contributions of acetaldehyde, isoprene, ethylene, and hexal species were prominent during the O3 exceeding days. Ratio analysis showed that the B/T ratio in Zhengzhou from May to September ranged from 0.05 to 5.3, with an average value of 1.1 ± 0.6, and the regional VOCs was mainly controlled by the aging air mass with possible long-distance transports. The analysis of the PMF model showed that the major pollution sources to VOC concentration in Zhengzhou were motor vehicle exhaust emission sources and industrial solvent and secondary conversion sources, contributing 25.6% and 25.8%, respectively. The contribution rates of solvent coating sources, oil and gas volatile sources, plant emission sources, industrial solvents, and secondary conversion sources during O3 exceeding days were 5.4%, 4.7%, 3.3%, and 0.7% higher than those during O3 non-exceeding days, respectively. The research showed that the management of VOCs and NOx pollution sources should be strengthened to reduce their contribution to the O3 generation when O3 exceeds the standard.

VOC species emissions from gasoline direct injection (GDI) and port fuel injection (PFI) vehicles combusting different gasoline.

Reducing VOCs can effectively reduce the concentration of PM2.5 and O3. Different gasoline compositions can impact the VOC species emitted by GDI and PFI vehicles. In this study, VOC species emitted from GDI and PFI vehicles combusting gasoline with different compositions (i.e., G1-market #92 gasoline, G2-high alkane gasoline, and G3-high heavy aromatic gasoline) were tested, and the influence of VOC species on O3 formation were investigated. The results indicated that the GDI vehicle consistently exhibited higher VOC emissions than the PFI vehicle in combusting three types of gasolines. The presence of short-chain alkanes and alkenes in the exhaust of combusting G2 and ethyne among the aromatics of combusting G3 resulted in higher VOC emissions from combusting G2 and G3 than from combusting G1 in the GDI vehicle. High alkane gasoline exhibited larger reductions of VOC emissions in the PFI vehicle but increased the proportions of propene, 1-butene, and ethyne emissions. High heavy aromatic gasoline increased the proportion of ethyne emissions in the GDI vehicle and increased the proportion of toluene, formaldehyde, and propane emissions in the PFI vehicle. The overall emission variation of ozone formation potential (OFP) was similar to those of VOC emissions. Alkene (C2-C6), monocyclic aromatic hydrocarbons (MAHs) and aldehydes had high contribution to O3 formation. Further research is needed to optimize fuel upgrading for GDI vehicles to ensure effective emission reduction. The results would help reduce vehicle emissions and provide support for achieving synergistic prevention and control of PM2.5 and O3 pollution.

[Source Profiles and Impact of Volatile Organic Compounds in Typical Industries in Luohe City].

Ten typical industries in Luohe City were selected for the sampling of organized emissions of volatile organic compounds （VOCs）, and 114 VOCs components of each sample were detected to analyze their source characteristics and effects. The results showed that VOCs emissions of packaging and printing were mainly composed of OVOC （60.9%）. In terms of the industrial coating, aromatic hydrocarbons （42.4%） and OVOC （38.9%） were the main VOCs species. The emissions of the footwear, furniture manufacturing, and paper industries were mainly composed of OVOC （32.3% - 42.6%） and aromatic hydrocarbons （20.7% - 33.7%）, with noticeable halogenated hydrocarbons. Chemical and pharmaceutical industries mainly emitted halogenated hydrocarbons, with the proportions of 59.3% and 46.6%, respectively. The emissions of the brick industry were primarily composed of alkane （62.7%）, and OVOC （48.5%）, and halogenated hydrocarbons （19.7%） were the main contributors to VOCs emissions of the thermal industry. OVOC （48.1%） and alkane （29.4%） were the dominant species for the food manufacturing industry. In the packaging and printing industry, acetone （14.8%）, isopropanol （14.0%）, ethylacetate （11.1%）, and toluene （10.2%） were the characteristic VOCs species. The emissions of industrial coating were dominated by isopropanol （25.6%）, toluene （15.0%）, m/p-xylene （12.4%）, and acetone （7.1%）. In the furniture manufacturing industry, m/p-xylene （15.8%）, followed by hexanal （15.1%）, 1,2-dichloroethane （9.6%）, and acetone （8.4%） were the characteristic VOCs species. The emissions of the footwear industry were dominated by acetone （18.9%）, toluene （18.1%）, methylene chloride （8.0%）, and acetaldehyde （6.8%）. The characteristic species of the chemical industry were methylene chloride （23.9%）, 1,2-dichloroethane （14.7%）, acetone （12.7%）, and trichloromethane （11.1%）, and those for the pharmaceutical industry were bromoethane （36.7%）, acetone （19.2%）, benzene （5.0%）, and vinyl acetate （3.0%）. The emissions of the brick industry were mainly ethane, propane, ethylene, and benzene. Acetone, toluene, acetylene, and acetaldehyde were the primary VOCs species in the paper industry. The emissions of the food manufacturing industry were dominated by acetaldehyde, n-pentane, acrolein, and n-heptane. The emissions of the thermal industry were characterized by acetone, acetaldehyde , benzene, and toluene. Although different industries emitted various characteristic VOCs species, in general, acetone, isopropanol, benzene, toluene, m/p-xylene, ethane, acetaldehyde, and methylene chloride were the main characteristic species in most industries in Luohe. OVOC and aromatic hydrocarbons had higher contributions to ozone generation potential （OFP）, and aromatic hydrocarbons contributed over 80.0% to secondary organic aerosol formation potential （SOAP）. The source reactivity of ozone [SR（O3）] of the food and furniture manufacturing industries were higher, with values of 3.7 g·g-1 and 3.5 g·g-1, respectively, whereas the source reactivity of secondary organic aerosol SR（SOA） of the industrial coating, furniture manufacturing, and footwear industries were higher, with the values of 0.021, 0.017, and 0.014 g·g-1. Hence, the food manufacturing, industrial coating, and furniture manufacturing industries should be the primary industries for the collaborative control of PM2.5 and ozone in Luohe City, of which the furniture manufacturing industry was the top priority.

[Pollution Characteristics and Source Apportionment of VOCs in Urban Areas of Shijiazhuang in Spring].

Samples of ambient volatile organic compounds （VOCs） were collected using SUMMA canisters at three Country Control Sites in Shijiazhuang during the spring of 2019, 2021, and 2022, which were detected using gas chromatography/mass spectrometry （GC/MS）. To investigate the characteristics and temporal variations of VOCs mass concentration levels, the online monitoring data of ozone （O3） and PM2.5 at the same site were also collected. Subsequently, the ozone formation potential （OFP） and secondary organic aerosol formation potential （SOAFP） were utilized to assess the chemical activity of VOCs. Additionally, the potential source areas of VOCs in spring in Shijiazhuang were further identified using the potential source contribution factor （PSCF） method and concentration weight trajectory analysis （CWT）. Hence, the major VOCs sources were evaluated with the VOCs initial mixing ratio. The results demonstrated that the averaged concentration of VOCs during the polluted period and clean period of spring in Shijiazhuang were 191.17 µg·m-3 and 122.18 µg·m-3, respectively. Meanwhile, the OFP was 361.23 µg·m-3 during the polluted period and 266.96 µg·m-3 during the clean period, whereas the SOAFP was 1.98 µg·m-3 and 1.61 µg·m-3, respectively. Therefore, effective control of benzene, toluene, ethylbenzene, and xylene （BTEX） is crucial for reducing PM2.5 and O3 pollution. Based on the results obtained from weight PSCF and CWT, the potential source areas of VOCs were further identified to be primarily located in the eastern Yuhua District, the high-tech district, and the northern Luancheng District of Shijiazhuang. These areas were influenced not only by local emissions but also by transport from neighboring regions, in which consistency between the CWT and PSCF results further supported these findings. Furthermore, the results obtained from the benzene/toluene/ethylbenzene （B/T/E） and xylene/benzene （X/B） ratios indicated that the main sources of VOCs in Shijiazhuang in spring were vehicle exhaust sources and burning sources, leading to a more serious air mass aging phenomenon. Hence, controlling vehicle emissions and implementing regional cooperative measures are the effective strategies for optimizing the air quality of Shijiazhuang.

Characteristics and Source Apportionment of Volatile Organic Compounds in a Coastal Industrial Area: A Case Study in the Yangtze River Delta of China.

In recent years, the coastal area in East China has experienced elevated volatile organic compounds (VOCs) levels during specific periods. VOCs have become one of the major atmospheric pollutants in these areas. In this study, 64 compounds including alkanes, alkenes, halohydrocarbons, aromatics, and oxygenated VOCs (OVOCs) were obtained by the TO-15 method through a 12-month campaign in industrial, urban and suburban areas in the Yangtze River Delta of China. The overall trends of total VOC (TVOC) concentrations at eight sampling sites were as follows: winter > autumn > spring > summer. The proportion of VOC categories was various at industrial sites, while OVOCs and halohydrocarbons had high proportions at urban sites and suburban sites, respectively. Coating, vehicle emission, petrochemical source, industrial source, and gasoline volatilization were identified as the major VOC emission sources by the positive matrix factorization model. Petrochemical and coating sources were the prime VOC sources at industrial sites. Aromatics contributed the most ozone formation potential at industrial sites, while OVOCs provided the main contributions at both urban and suburban sites during four seasons. According to the health risk assessment, a high probability of non-carcinogenic risk existed at three industrial sites. Special attention should be given to certain VOCs, such as acrolein and 1,2-dibromoethane in industrial areas.

Disinfection by-product formation potential in response to variability in dissolved organic matter and nutrient inputs: Insights from a mesocosm study.

Changes in rainfall patterns driven by climate change affect the transport of dissolved organic matter (DOM) and nutrients through runoff to freshwater systems. This presents challenges for drinking water providers. DOM, which is a heterogeneous mix of organic molecules, serves as a critical precursor for disinfection by-products (DBPs) which are associated with adverse health effects. Predicting DBP formation is complex due to changes in DOM concentration and composition in source waters, intensified by altered rainfall frequency and intensity. We employed a novel mesocosm approach to investigate the response of DBP precursors to variability in DOM composition and inorganic nutrients, such as nitrogen and phosphorus, export to lakes. Three distinct pulse event scenarios, mimicking extreme, intermittent, and continuous runoff were studied. Simultaneous experiments were conducted at two boreal lakes with distinct DOM composition, as reflected in their color (brown and clear lakes), and bromide content, using standardized methods. Results showed primarily site-specific changes in DBP precursors, some heavily influenced by runoff variability. Intermittent and daily pulse events in the clear-water mesocosms exhibited higher haloacetonitriles (HANs) formation potential linked to freshly produced protein-like DOM enhanced by light availability. In contrast, trihalomethanes (THMs), associated with humic-like DOM, showed no significant differences between pulse events in the brown-water mesocosms. Elevated bromide concentration in the clear mesocosms critically influenced THMs speciation and concentrations. These findings contribute to understanding how changing precipitation patterns impact the dynamics of DBP formation, thereby offering insights for monitoring the mobilization and alterations of DBP precursors within catchment areas and lake ecosystems.

Seasonal and height dynamics of volatile organic compounds in rubber plantation: Impacts on ozone and secondary organic aerosol formation.

Rubber trees emit a range of volatile organic compounds (VOCs), including isoprene, monoterpenes, and sesquiterpenes, as part of their natural metabolism. These VOCs can significantly influence air quality through photochemical reactions that produce ozone and secondary organic aerosols (SOAs). This study examines the impact of VOCs detected in a rubber tree plantation in Northeastern Thailand on air quality, highlighting their role in atmospheric reactions that lead to the formation of ozone and SOAs. VOCs were collected at varying heights and seasons using Tenax-TA tubes paired with an atmospheric sampler pump and identified by gas chromatography-mass spectrometry. In total, 100 VOCs were identified, including alkanes, alkenes, terpenes, aromatics, and oxygenated VOCs. Principal Coordinate Analysis (PCoA) revealed distinct seasonal VOC profiles, with hydrocarbons, peaking in summer and terpenes in the rainy season. The Linear Mixed-Effects (LME) model indicates that VOC concentrations are more influenced by seasonal changes than by sampling heights. Secondary organic aerosol potential (SOAP) and ozone formation potential (OFP) of selected VOC species were also determined. The total SOAP ranged from 67.24 µg/m3 in summer to 17.87 µg/m3 in winter, while the total OFP ranged from 377.87 µg/m3 in summer to 139.39 µg/m3 in winter. Additionally, positive matrix factorization (PMF) analysis identified four main VOC sources: gasoline combustion (18.3 %), microbial activity (38.6 %), monoterpene emissions during latex production (15.0 %), and industrial sources (28.1 %). These findings provide essential information for managing air pollution in rubber tree plantations. By adopting focused air quality management strategies, plantation operators can mitigate the adverse effects of VOCs, promoting a healthier and more sustainable future.

Temporal evolution of speciated volatile organic compound (VOC) emissions from solvent use sources in the Pearl River Delta Region, China (2006-2019).

Volatile organic compounds (VOCs) emitted from solvent use sources constitute an important part of ozone (O3) and secondary organic aerosols (SOA) in the Pearl River Delta (PRD) region, China. While stringent control measures targeting VOCs have been implemented in recent years, an assessment of historical trends is imperative to evaluate their effectiveness. In this study, trends of VOC emissions, compositions, and reactivity from solvent use sources in the PRD region from 2006 to 2019 were estimated using a developed methodology, which considered the improvement of manufacturing equipment and removal efficiency. Results showed that total VOC emissions from solvent use sources displayed an overall increase from 277 kt in 2006 to 400 kt in 2019 despites some fluctuations, with metal products contributing more than 20 % each year. Aromatics and oxygenated VOCs (OVOCs) accounted for over 70 % of total VOC emissions, increasing by 21 kt and 52 kt respectively. OFP and SOAFP increased by 40 % and 23 % respectively from 2006 to 2019. Specific aromatic species, including m/p-xylene, toluene, 1,2,3,5-tetramethylbenzene, o-xylene and ethylbenzene were identified as key species in both VOC emission amount and reactivity. This study aims to facilitate the understanding of VOC emission evolution from solvent use sources in the region and provide insights into the impact of enacted measures, aiding in the future development of more targeted and efficient strategies in the PRD region.

The ideal model for determination the formation potential of priority DBPs during chlorination of free amino acids.

Amino acids (AAs) account for about 15-35% of dissolved organic nitrogen (DON), and are known as the important precursors of nitrogenous disinfection by-products (N-DBPs). Determining the formation potential (FP) of AAs to DBPs is used to reveal the key precursors of DBPs for further control, while the ideal method for N-DBPs FP of AAs during chlorination is not revealed. In this study, the ideal FP test models for five classes of priority DBPs during chlorination of four representative AAs (accounted for about 35% of total AAs) were analyzed. For haloaldehydes (HALs), haloketones (HKs), haloacetonitriles (HANs), haloacetamides (HAMs), and halonitromethanes (HNMs), their FPs during chlorination of four AAs were 0.1-13.0, 0.01-1.1, 0.1-104, not detectable (nd)-173, and nd-0.4 µg/mg, respectively. The FPs of priority DBPs had significant deviations between different FP test models and different tested AAs. For HALs, the model, whose chlorine dosage was determined by 15 × molar concentration of AAs [Cl (mM) = 15 × M](named: model II), was the ideal model. For HKs, model II was also the ideal FP test model for AAs with ≤3 carbons, while for AAs with 4 carbons, the model, whose chlorine dosage was determined by keeping the residual chlorine at 1 ± 0.2 mg/L after 24 h of reaction (named: model 4), was the ideal model. For HANs and HNMs, model 4 was the ideal FP test model for most of the studied AAs. The performance of HAMs during chlorination of amino acids was totally different from other P-DBPs, and model 3 was recommended to be the ideal model, in which chlorine dosage was determined by 3 × mass concentration of AAs [Cl (mg/L) = X × DOC]. This study is a reference that helps researchers select an ideal model for N-DBPs FP study of AAs.

Characteristics of Volatile Organic Compounds Emitted from Airport Sources and Their Effects on Ozone Production.

In recent years, commercial air transport has increased considerably. However, the compositions and source profiles of volatile organic compounds (VOCs) emitted from aircraft are still not clear. In this study, the characteristics of VOCs (including oxygenated VOCs (OVOCs)) emitted from airport sources were measured at Shenzhen Bao'an International Airport. The results showed that the compositions and proportions of VOC species showed significant differences as the aircraft operating state changed. OVOCs were the dominant species and accounted for 63.17%, 58.44%, and 51.60% of the total VOC mass concentration during the taxiing, approach, and take-off stages. Propionaldehyde and acetone were the main OVOCs, and dichloromethane and 1,2-dichloroethane were the main halohydrocarbons. Propane had the highest proportion among all alkanes, while toluene and benzene were the predominant aromatic hydrocarbons. Compared with the source profiles of VOCs from construction machinery, the proportions of halogenated hydrocarbons and alkanes emitted from aircraft were significantly higher, as were those of propionaldehyde and acetone. OVOCs were still the dominant VOC species in aircraft emissions, and their calculated ozone formation potential (OFP) was much higher than that of other VOC species at all stages of aircraft operations. Acetone, propionaldehyde, formaldehyde, acetaldehyde, and ethylene were the greatest contributors to ozone production. This study comprehensively measured the distribution characteristics of VOCs, and its results will aid in the construction of a source profile inventory of VOCs emitted from aircraft sources in real atmospheric environments.

Characterization of VOC emissions and health risk assessment in the plastic manufacturing industry.

Volatile organic compounds (VOCs) significantly contribute to ozone pollution formation, and many VOCs are known to be harmful to human health. Plastic has become an indispensable material in various industries and daily use scenarios, yet the VOC emissions and associated health risks in the plastic manufacturing industry have received limited attention. In this study, we conducted sampling in three typical plastic manufacturing factories to analyze the emission characteristics of VOCs, ozone formation potential (OFP), and health risks for workers. Isopropanol was detected at relatively high concentrations in all three factories, with concentrations in organized emissions reaching 322.3 µg/m3, 344.8 µg/m3, and 22.6 µg/m3, respectively. Alkanes are the most emitted category of VOCs in plastic factories. However, alkenes and oxygenated volatile organic compounds (OVOCs) exhibit higher OFP. In organized emissions of different types of VOCs in the three factories, alkenes and OVOCs contributed 22.8%, 67%, and 37.8% to the OFP, respectively, highlighting the necessity of controlling them. The hazard index (HI) for all three factories was less than 1, indicating a low non-carcinogenic toxic risk; however, there is still a possibility of non-cancerous health risks in two of the factories, and a potential lifetime cancer risk in all of the three factories. For workers with job tenures exceeding 5 years, there may be potential health risks, hence wearing masks with protective capabilities is necessary. This study provides evidence for reducing VOC emissions and improving management measures to ensure the health protection of workers in the plastic manufacturing industry.

[Characteristics of VOCs Emissions and Ozone Formation Potential for Typical Chemicals Industry Sources in China].

This study selected five typical types of chemical industry volatile organic compounds (VOCs) emission characteristics in China for analysis. The results from 70 source samples showed that alkanes were the dominant VOCs category from synthetic material industry sources, petrochemical industry sources, and coating industry sources (accounting for 43%, 63%, and 68%, respectively); olefins were the main VOCs category from the daily supplies chemical industry (46%); and halogenated hydrocarbons were the dominate VOCs category from specialty chemicals industry account source emissions (43%). Additionally, the machine learning method was applied in this study to analyze the marker components of the above industries. The results showed that decane and tetrahydrofuran were the source markers of the synthetic material industry; n-butanol and toluene were the markers of the daily supplies industry source; 1,2,3-trimethylbenzene and 1,3,5-trimethylbenzene were the markers of the petrochemical industry source; propylene and 3-methyl pentane were the source markers of the coating industry; and P-Xylene and cumene were the markers of the specialty chemicals industry source. The maximum incremental reactivity method (MIR) was used to estimate the ozone formation potential (OFP) of different VOCs-sources. The calculation results showed that when considering per unit TVOCs concentration emissions, the contribution to the ozone generation potential was in the order of the daily supplies chemical industry, specialty chemical industry, petrochemical industry, synthetic material industry, and coating industry. Therefore, we suggest that more attention should be paid to the key active species emitted by various industry sources rather than only the total amount of VOCs emissions in future ozone prevention and control efforts.

[Formation Potential of Secondary Organic Aerosols and Sources of Volatile Organic Compounds During an Air Pollution Episode in Autumn, Langfang].

A typical particulate matter pollution process occurred from October 9 to 17,2018,in Langfang,and 99 types of volatile organic compounds (VOCs) were monitored by using ZF-KU-1007. The characteristics of VOCs,formation potential of secondary organic aerosol (SOA),and source of VOCs were systematically analyzed. The results showed that the maximum concentration of PM2.5 was 198 µg·m-3 during the pollution process and was 2.64 times the National Ambient Air Quality Standard (GB 3095-2012). The average concentration of VOCs was 56.8×10-9,127.8×10-9,and 72.5×10-9 in the early,middle,and late stages of the pollution process,respectively,and the concentration of VOCs increased significantly in the middle stage. The formation potential of SOA was significantly positively correlated with PM2.5,and the contribution of aromatic hydrocarbon for SOA was larger and significantly correlated with the concentration of PM2.5. In the middle pollution stage,SOA increased,and the contribution ratio of aromatic hydrocarbon increased significantly. Conversely,the contribution of alkanes and olefin decreased significantly,which showed that aromatic hydrocarbons,namely benzene series,were the dominant species of SOA generation and had a great influence on the pollution process. Benzene,toluene,m-/p-xylene,o-xylene,and ethylbenzene and nonane,n-undecane,and methylcyclohexane were the priority control species in this pollution process. Solvent use source and motor vehicle emission source (gasoline and diesel vehicles) were the main sources affecting the concentration of VOCs during the autumn pollution process of Langfang,among which the contribution of gasoline vehicle emissions increased significantly in the middle pollution contribution and was the key control source.

Elucidating the unexpected importance of intermediate-volatility organic compounds (IVOCs) from refueling procedure.

Evaporative emissions release organic compounds comparable to gasoline exhaust in China. However, the measurement of intermediate volatility organic compounds (IVOCs) is lacking in studies focusing on gasoline evaporation. This study sampled organics from a real-world refueling procedure and analyzed the organic compounds using comprehensive two-dimensional gas chromatography coupled with a mass spectrometer (GC×GC-MS). The non-target analysis detected and quantified 279 organics containing 93 volatile organic compounds (VOCs, 64.9 ± 7.4 % in mass concentration), 182 IVOCs (34.9 ± 7.4 %), and 4 semivolatile organic compounds (SVOCs, 0.2 %). The refueling emission profile was distinct from that of gasoline exhaust. The b-alkanes in the B12 volatility bin are the most abundant IVOC species (1.9 ± 1.4 µg m-3) in refueling. A non-negligible contribution of 17.5 % to the ozone formation potential (OFP) from IVOCs was found. Although IVOCs are less in concentration, secondary organic aerosol potential (SOAP) from IVOCs (58.1 %) even exceeds SOAP from VOCs (41.6 %), mainly from b-alkane in the IVOC range. At the molecular level, the proportion of cyclic compounds in SOAP (12.1 %) indeed goes above its mass concentration (3.1 %), mainly contributed by cyclohexanes and cycloheptanes. As a result, the concentrations and SOAP of cyclic compounds (>50 %) could be overestimated in previous studies. Our study found an unexpected contribution of IVOCs from refueling procedures to both ozone and SOA formation, providing new insights into secondary pollution control policy.

Ambient volatile organic compounds in the Seoul metropolitan area of South Korea: Chemical reactivity, risks and source apportionment.

The chemical reactivity, contribution of emission sources, and risk assessment of volatile organic compounds (VOCs) in the atmosphere of the Seoul metropolitan area (SMA) were analyzed. Datasets collected from 6 photochemical assessment monitoring stations (PAMS) of SMA from 2018 to 2021 were used. Alkenes and aromatics contributed significantly to ozone formation relative to the emission concentrations, and aromatics accounted for most of the secondary organic aerosols (SOA) formation in the SMA. The contributions of ozone and SOA formation were found to be notably higher at measurement stations in residential areas such as Guwol (GW) and Sosabon (SS) compared to other measurement stations. From the results of an emission source analysis, it was confirmed that anthropogenic sources such as combustion sources, vehicle exhaust, fuel evaporation, and solvent use had a significant effect at all measurement stations. Assessing the health risk, non-carcinogenic compounds were at acceptable level at all measurement stations. On the other hand, carcinogenic compounds were approaching risk level (10-4), thereby demanding immediate attention. The level of exposure to carcinogenic compounds increased by age group, and male was more vulnerable than female. It was found that SS had the highest level of exposure to carcinogens in the atmosphere of the population ages 60 or older. The health threat of the SMA population is expected due to direct exposure from inhalation of ambient toxic compounds and indirect exposure from ozone and PM2.5 formations through oxidation of VOCs. This study emphasizes the importance of addressing specific emission sources within the metropolitan area and developing comprehensive regional strategies to mitigate VOCs.

Spatiotemporal variations, sources, and atmospheric transformation potential of volatile organic compounds in an industrial zone based on high-resolution measurements in three plants.

Industrial emissions are significant sources of volatile organic compounds (VOCs). This study conducted a field campaign at high temporal and spatial resolution to monitor VOCs within three plants in an industrial park in southern China. VOC concentrations showed significant spatial variability in this industrial zone, with median concentrations of 75.22, 40.53, and 29.41 µg/m3 for the total VOCs in the three plants, respectively, with oxygenated VOCs (OVOCs) or aromatics being the major VOCs. Spatial variability within each plant was also significant but VOC-dependent. Seasonal variations in the VOC levels were governed by their industrial emissions, meteorological conditions, and photochemical losses, and they were different for the four groups of VOCs. The temporal and spatial variations in the VOC compositions suggest similar sources of each class of VOCs during different periods of the year in each plant. The diurnal patterns of VOCs (unimodal or bimodal) clearly differed from those at most industrial/urban locations previously, reflecting a dependence on industrial activities. The secondary transformation potential of VOCs also varied temporally and spatially, and aromatics generally made the predominant contributions in this industrial park. The loss rate of OH radicals and ozone formation potential were highly correlated, but the linear relationship substantially changed in summer and autumn due to the intensive emissions of an OVOC species. The lifetime cancer and non-cancer risks via occupational inhalation of the VOCs in the plants were acceptable but merit attention. Taking the secondary transformation potential and health risks into consideration, styrene, xylene, toluene, trichloroethylene, and benzene were proposed to be the priority VOCs regulated in the plants.

Changes of characteristics and disinfection by-products formation potential of intracellular organic matter with different molecular weight in metalimnetic oxygen minimum.

Metalimnetic oxygen minimum (MOM) occurs in reservoirs or lakes due to stratification and algal blooms, which has low dissolved oxygen (DO) levels and leads to the deterioration of water quality. The transformation mechanism and the impact on the water quality of intracellular organic matter (IOM) derived from algae are poorly understood under MOM conditions. In this study, IOM extracted by Microcystis aeruginosa was divided into five components according to molecular weight (MW), and the changes of characteristics and correlated disinfection by-products formation potential (DBPFP) were analyzed and compared under MOM conditions. The removal efficiency of dissolved organic carbon (DOC) in the <5 kDa fraction (66.6%) was higher than that in the >100 kDa fraction (41.8%) after a 14-day incubation under MOM conditions. The same tendency also occurred in Fmax and DBPFP. The decrease in Fmax was mainly due to the decline in tryptophan-like and tyrosine-like for all IOM fractions. The diversity of microorganisms degrading the MW > 100 kDa fraction was lower than others. Besides low MW fractions, these findings indicated that more attention should be paid to high MW fractions which were resistant to biodegradation under MOM conditions during water treatment.

Differentiated emissions and secondary organic aerosol formation potential of organic vapor from industrial coatings in China.

Organic vapors emitted during solvent use are important precursors of secondary organic aerosols (SOAs). Industrial coatings are a major class of solvents that emit volatile and intermediate volatile organic compounds (VOCs and IVOCs, respectively). However, the emission factors and source profiles of VOCs and IVOCs from industrial coatings remain unclear. In this study, representative solvent- and water-based industrial paints were evaporated, sampled and tested using online and offline instruments. The VOC and IVOC emission factors for solvent-based paints are 129-254 and 25-80 g/kg, while for water-based paint are 13 and 32 g/kg, respectively. In solvent-based paints, the VOCs are mainly aromatics, while the IVOCs are composed of long-chain alkanes, alkenes, carbonyls and halocarbons. The VOCs and IVOCs in water-based paint are mostly oxygenates, such as ethanol, acetone, ethylene glycol, and Texanol. During the evaporation of solvent-based paints, the fraction of IVOCs increases along with those of alkenes and aldehydes, while the proportion of aromatics decreases. For water-based paint, the fraction of IVOCs slightly decreases with evaporation. The SOA formation potentials of solvent-based paints are 8.6-28.0 g/kg, much higher than that of water-based paint (0.65 g/kg); thus, substituting solvent-based paints with water-based paints may significantly decrease SOA formation.

Impact of changes in biofilm composition response following chlorine and chloramine disinfection on nitrogenous disinfection byproduct formation and toxicity risk in drinking water distribution systems.

In practical drinking water treatment, chlorine and chloramine disinfection exhibit different mechanisms that affect biofilm growth. This study focused on the influence of biofilm composition changes, especially extracellular polymeric substance (EPS) fractions, on the potential formation and toxicity of nitrogenous disinfection by-products (N-DBP). Significant differences in microbial diversity and community structure were observed between the chlorine and chloramine treatments. Notably, the biofilms from the chloramine-treated group had higher microbial dominance and greater accumulation of organic precursors, as evidenced by the semi-quantitative confocal laser-scanning microscopy assay of more concentrated microbial aggregates and polysaccharide proteins in the samples. Additionally, the chloramine-treated group compared with chlorine had a higher EPS matrix content, with a 13.5 % increase in protein. Furthermore, the protein distribution within the biofilm differed; in the chlorine group, proteins were concentrated in the central region, whereas in the chloramine group, proteins were primarily located at the water-biofilm interface. Notably, functional prediction analyses of protein fractions in biofilms revealed specific functional regulation patterns and increased metabolism-related abundance of proteins in the chlorine-treated group. This increase was particularly pronounced for proteins such as dehydrogenases, reductases, transcription factors, and acyl-CoA dehydrogenases. By combining the Fukui function and density functional calculations to further analyse the effect of biofilm component changes on N-DBP production under chlorine/chloramine and by assessing the toxicity risk potential of N-DBP, it was determined that chloramine disinfection is detrimental to biofilm control and the accumulation of protein precursors has a higher formation potential of N-DBPs and toxicity risk, increasing the health risk of drinking water.