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Atmospheric volatile organic compounds (VOCs) measurement was carried out using gas chromatography-flame ionization detector (GC-FID) technique (Airmo VOCs online analyzer) in a typical urban area in Beijing from April 2014 to January 2015. Ambient levels, variation characteristics and influential factors contributing to the formation of near-ground-ozone and secondary organic aerosols as well as health risk assessment of VOCs were analyzed. Based on these analyses, the important VOC species that should be given more attention for pollution control were identified and the source apportionment of VOCs was made. Suggestions for VOCs pollution control countermeasures were put forward. The annual average concentration of 84 VOCs was 119 μg·m−3 and the hourly mean concentration was 9.11–567 μg·m−3. Ambient level of VOCs in Beijing has been alleviated in recent years, but is still severe compared to some other cities. VOCs with the largest proportion were alkanes in spring and halogenated hydrocarbons in summer, autumn and winter. The variation of 84 VOCs concentrations was consistent with that of the ambient air quality index, indicating that VOCs had a strong influence on ambient air quality. Influenced by the concentration and activity of VOCs, the largest contribution to ozone formation potential and secondary organic aerosol formation potential came from alkenes and aromatic hydrocarbons, respectively. Five VOCs species such as benzene pose carcinogenic risk to exposed populations. Contrary to some previous studies, benzene was found to have potential cancer risk in some urban areas in China. The main sources of VOCs in the study area were vehicle exhaust, solvent usage, and industrial processes. In order to improve air quality in Beijing and reduce the infection rate of air pollutant related diseases, it is necessary to strengthen the control the emission of VOCs from those three sources.

The BTEX compounds (benzene, toluene, ethylbenzene, and xylenes) and formaldehyde (FA) have harmful impacts on human health and are also important precursors of tropospheric ozone and secondary organic aerosols (SOA). Thus, the objective of this study was to perform a human health risk assessment considering the lifetime carcinogenic (LCR) and non-carcinogenic (as hazard quotient (HQ)) risks for 3 different age groups associated with exposure to BTEX and FA by inhalation using a probabilistic approach with Monte Carlo simulation, as well as to evaluate the contributions of these compounds to ozone formation potential (OFP) and SOA formation potential (SOAFP), at seven sites in the city of Salvador, Bahia, Brazil, during the dry and rainy periods. The HQ values associated with BTEX and FA compounds were below the limit set by the USEPA (HQ = 1) for all groups in both periods. The LCR values for benzene and FA at the 95th percentile considering 3 evaluated groups were 2.49 × 10−6, 3.56 × 10−6, 9.16 × 10−6 and 1.83 × 10−5, 2.53 × 10−5, 6.55 × 10−5 in the dry period and 2.83 × 10−6, 3.94 × 10−6, 1.01 × 10−5 and 7.97 × 10−6, 1.02 × 10−5, 2.40 × 10−5 in the rainy period, respectively, being all values above the acceptable limit by the USEPA (1.0 × 10−6). For all 3 groups of the population, the LCR values for benzene and FA were higher during the rainy period and dry period, respectively, following the same pattern as the concentrations. FA, xylenes, and toluene accounted for up to 97.0% of total OFP, whereas toluene, benzene, and xylenes contributed up to 88.5% of total SOAFP. The results obtained showed the need to adopt measures to reduce BTEX and FA emissions in order to minimize the impacts on health of the exposed population and on air quality.

Ambient Volatile Organic Compounds (VOCs) were investigated to determine their characteristics, Ozone Formation Potentials (OFPs), and health risks in two crude oil production plants (Nusaybin and Egil plants) in southeastern Türkiye. Benzene, toluene, ethylbenzene, m + p xylene, o xylene, and 1,3,5-trimethylbenzene were measured at eight passive sampling points in each plant. Samples were analyzed using gas chromatography coupled with a flame ionization detector and a thermal desorption. The concentration of ∑ 6 VOC ranged from 5.03 to 88.43 μg/m 3 in the Nusaybin Plant and from 7.70 to 154.35 μg/m 3 in the Egil Plant. Toluene and xylenes were predominant in both plants. In the Nusaybin Plant, VOCs were mainly associated with crude oil production, while in the Egil Plant, they were associated with a combination of crude oil production and mobile vehicle activities. The OFP of ∑ 6 VOC was 297.47 μg/m 3 in the Nusaybin Plant, and 249.25 μg/m 3 in the Egil Plant. M + p xylene, toluene, and 1,3,5-trimethylbenzene together contributed 86% and 84% of the total OFP in the Nusaybin and Egil plants, respectively. Benzene exposure posed a possible cancer risk to oil workers in both plants. Non-cancer health risk was at a potential level in the Egil Plant but negligible in the Nusaybin Plant. This study is expected to enhance knowledge regarding the effects of crude oil production plants on air quality and workplace exposure. Graphical Abstract

Surface ozone observations in Doon Valley (Dehradun: 30.3oN, 78.0oE, 700 m), which acts as a bridge between the Himalayas and the Indo-Gangetic Plain, showed daytime higher values, suggesting a typical urban behaviour in proximity of the Himalayas. Ozone exhibited a maximum in spring (49.2 ± 24.8 ppbv in May) with an hourly average of more than 110 ppbv, followed by a secondary maximum in autumn and the lowest level occurring in the summer-monsoon (~ 13 ppbv in July-August). Ozone levels exceeded the 8-hour National Air Quality Standard limit (50 ppbv) throughout the year, except in July-September. The observed spring maximum was found to be triggered by biomass burning, leading to 9–50% enhancement in ozone during the high-fire activity period (April-May). Using a box model, in-situ photochemical ozone production and loss were estimated at ~ 41 ppbv and ~ 8 ppbv, respectively. The model highlighted the dominant role of the HO2 + NO reaction (85.6%) in ozone production and the O3 + HO2 reaction (56.2%) in ozone loss. Exposure metrics analysis (M7 and AOT40) estimated an annual loss of 27–37 kilotons of wheat and 14–32 kilotons of rice production due to elevated ozone levels. Furthermore, hazard ratios for non-methane hydrocarbons and lifetime cancer risk values for benzene and ethylbenzene exceeded the standard limits (USEPA and WHO), indicating significant health risks to the population. Model and satellite-based studies demonstrated the NOx-sensitive behaviour of ozone production in this Himalayan region, where aromatics exhibited the maximum ozone formation potential among different NMHCs.

In this study, the ambient concentrations of volatile organic compounds (VOCs) were intensively measured from January 2012 to December 2016 using an evacuated canister and were analyzed using a gas chromatography/mass spectrophotometer (GC/MS) based on the US EPA TO-15 in the community and industrial areas of the largest petroleum refinery and petrochemical industrial complex in Map Ta Phut Thailand. The ternary diagram was used to identify the source of VOCs. Reactivity of VOCs on their ozone formation potential (OFP) were quantified by the maximum incremental reactivity coefficient method (MIR) and propylene-equivalent concentration methods. Results from the study revealed that aromatic hydrocarbon was the dominant group of VOCs greatly contributing to the total concentration of measured VOCs. Among the measured VOCs species, toluene had the highest concentration and contributed as the major precursor to ozone formation. The ternary analysis of benzene:toluene:ethybenzene ratios indicated that VOCs mainly originated from mobile sources and industrial processes. Within the industrial area, measured VOC concentration was dominated by halogenated hydrocarbons, and alkene was the highest contributor to ozone formation. The propylene-equivalent concentration method was also used to evaluate the reactivity of VOCs and their role in ozone formation, and secondly to support findings from the MIR method.

The Fenwei Plain (FWP), one of China’s most polluted regions, has experienced severe ozone (O3) pollution in recent years. Volatile organic compounds (VOCs), key O3 precursors, undergo significant photochemical degradation, yet their loss and the implications for source apportionment and ozone formation potential (OFP) in this region remain unclear. This study conducted summertime VOC measurements in two industrial cities in the FWP, Hancheng (HC) and Xingping (XP), to quantify photochemical losses of VOCs and assessed their impact on source attribution and OFP with photochemical age-based parameterization methods. Significant VOC photochemical losses were observed, averaging 3.6 ppbv (7.1% of initial concentrations) in HC and 1.9 ppbv (5.6%) in XP, with alkenes experiencing the highest depletion (22–30%). Source apportionment based on both initial (corrected) and observed concentrations revealed that industrial sources (e.g., coking, coal washing, and rubber manufacturing) dominated ambient VOCs. Ignoring photochemical losses underestimated contributions from natural gas combustion and biogenic sources, while it overestimated the secondary source. OFP calculated with lost VOCs (OFPloss) reached 34 ppbv in HC and 15 ppbv in XP, representing 20% and 25% of OFP based on observed concentrations, respectively, with reactive alkenes accounting for over 90% of OFPloss. The results highlight the importance of accounting for VOC photochemical losses for accurate source identification and developing effective O3 control strategies in the FWP.

Alternative-fueled vehicles have been introduced to solve the problem of the energy crisis and address air pollution. However, typical pollutants (e.g., methane and methanol) are emitted through combustion of the alternative fuel. In this study, the concentrations of regulated pollutants (CO, NO) and unregulated pollutants (CH 4 , methanol, formaldehyde, and 8 NMHC species) in the exhaust from methanol, CNG, and gasoline-fueled vehicles (MV, NGV, and GV) were measured systematically on a chassis dynamometer during an in-use vehicle driving cycle. The emission factors of these gaseous pollutants were calculated, and the ozone formation potential (OFP) of each ozone precursor measured in this work was evaluated with the MIR scale. The results showed that NO and NMHC species exhausted from the MV and NGV decreased significantly than that from the GV. However, the unburned pollutants exhausted from MV and NGV warrant attention. For the OFPs, CO was the largest contributor for all tested vehicles. Formaldehyde was ranked the second for the MV and NGV. Among the tested vehicles, the OFPs of NGV were the lowest. The results are helpful in quantitating analysis of the vehicle emissions and evaluating the impacts of alternative-fueled vehicles on atmospheric environment.

Oil depots are continuous sources of volatile organic compounds (VOCs), which contribute to ground-level ozone (O3) and secondary organic aerosol formation, posing threats to air quality and public health. This study investigated typical crude and refined oil depots in the Xigu District of Lanzhou by measuring VOC source profiles and establishing an emission inventory. The maximum incremental reactivity (MIR) method was applied to assess the chemical reactivity of VOCs; both the emission inventory and VOC profiles were incorporated into the WRF-CMAQ model for numerical simulations. Results showed that the average ambient VOC concentrations were 49.8 μg/m3 for the crude oil depot and 66.1 μg/m3 for the refined oil depot. The crude oil depot was dominated by alkanes (37.1%), aromatics (25.1%), and OVOCs (22.5%), while the refined oil depot was dominated by alkanes (57.3%) and OVOCs (16.7%), with isopentane identified as the most abundant species in both depots. The ozone formation potentials (OFPs) of the crude oil and refined oil depots were 153.1 μg/m3 and 178.3 μg/m3, respectively. Aromatics (47.0%) and OVOCs (29.0%) were the primary contributors at the crude oil depot, with isopentane, o-xylene, etc., as the dominant reactive species. In the refined oil depot, the main contributors were alkanes (27.8%), alkenes and alkynes (26.6%), OVOCs (24.5%), and aromatics (20.5%), among which isopentane, trans-2-butene, etc., were most prominent. In 2023, VOC emissions from the crude oil and refined oil depots were estimated at 1605.3 t and 1287.8 t, respectively, mainly from working loss (96.6%) in the crude oil depot and deck fitting loss (60.7%) and working loss (31.3%) in the refined oil depot. Numerical simulations indicated that oil depot emissions could increase regional MDA8 O3 concentrations by up to 40.0 μg/m3. At the nearby Lanlian Hotel site, emissions contributed 15.1% of the MDA8 O3, equivalent to a 6.1 μg/m3 increase, while the citywide average was 1.7 μg/m3. This study enriches the VOC source profile database for oil depots, reveals their significant role in regional O3 formation, and provides a scientific basis for precise O3 control and differentiated emission reduction strategies in Northwest China.

Volatile organic compounds (VOCs) were monitored online at three photochemical assessment monitoring stations (MDS, WQS and HGS) in the Pearl River Delta region during the summer of 2016. Measured levels of VOCs at the MDS, WQS and HGS sites were 34.78, 8.54 and 8.47 ppbv, respectively, with aromatics and alkenes as major ozone precursors and aromatics as major precursors to secondary organic aerosol (SOA). The positive matrix factorization (PMF) model revealed that VOCs at the sites mainly came from vehicle exhaust, petrochemical industry, and solvent use. Vehicle exhaust and industrial processes losses contributed most to ozone formation potentials (OFP) of VOCs, while industrial processes losses contributed most to SOA formation potentials of VOCs. Potential source contribution function (PSCF) analysis revealed a north-south distribution for source regions of aromatics occurring at MDS with emission sources in Guangzhou mainly centered in the Guangzhou central districts, and source regions of aromatics at WQS showed an east-west distribution across Huizhou, Dongguan and east of Guangzhou, while that at HGS showed a south-north distribution across Guangzhou, Foshan, Zhaoqing and Yangjiang. This study demonstrates that multi-point high time resolution data can help resolve emission sources and locate emission areas of important ozone and SOA precursors.

Enhanced ozone (O3) pollution has emerged as a pressing environmental concern in China, particularly for densely populated megacities and major city clusters. However, volatile organic compounds (VOCs), the key precursors to O3 formation, have not been routinely measured. In this study, we characterize the spatial and temporal patterns of VOCs and examine the role of VOCs in O3 production in five cities (Dongying (DY), Rizhao (RZ), Yantai (YT), Weihai (WH), and Jinan (JN)) in the North China Plain (NCP) for two sampling periods (June and December) in 2021 through continuous field observations. Among various VOC categories, alkanes accounted for the largest proportion of VOCs in the cities. For VOCs, chemical reactivities, aromatic hydrocarbons, and alkenes were dominant contributors to O3 formation potential (OFP). Unlike inland regions, the contribution to OFP from OVOCs increased greatly at high O3 concentrations in coastal regions (especially YT). Model simulations during the O3 episode show that the net O3 production rates were 27.87, 10.24, and 10.37 ppbv/h in DY, RZ, and JN. The pathway of HO2 + NO contributed the most to O3 production in JN and RZ, while RO2 + NO was the largest contributor to O3 production in DY. The relative incremental reactivity (RIR) revealed that O3 formation in DY was the transitional regime, while it was markedly the VOC-limited regime in JN and RZ. The O3 production response is influenced by NOx concentration and has a clear daily variation pattern (the sensitivity is greater from 15:00 to 17:00). The most efficiencies in O3 reduction could be achieved by reducing NOx when the NOx concentration is low (less than 20 ppbv in this study). This study reveals the importance of ambient VOCs in O3 production over the NCP and demonstrates that a better grasp of VOC sources and profiles is critical for in-depth O3 regulation in the NCP.