VOC Sources Research Articles

Emission of VOCs from service stations in Beijing: Species characteristics and pollutants co-control based on SOA and O3

Currently, air pollution is primarily characterized by PM2.5 and O3. Therefore, the co-control of PM2.5 and O3 has become an important task of atmosphere pollution prevention and control in China. However, few studies have been conducted on the emissions from vapor recovery and processes, which is an important source of VOCs. This paper analyzed the VOC emissions of three vapor process technologies in service stations and first proposed key pollutants for priority control based on the coordinated reactivity of O3 and SOA. The concentration of VOCs emitted from the vapor processor was 3.14–9.95 g m−3, compared to 631.2–717.8 g m−3 for uncontrolled vapor. Alkanes, alkenes, and halocarbons accounted for a high proportion of the vapor both before and after control. Among the emissions, i-pentane, n-butane, and i-butane were the most abundant species. Then, the species of OFP and SOAP were calculated through the maximum incremental reactivity (MIR) and fractional aerosol coefficient (FAC). The average source reactivity (SR) value of the VOC emissions from three service stations was 1.9 g g−1, while the OFP ranged from 8.2 to 13.9 g m−3 and SOAP ranged from 0.18 to 0.36 g m−3. By considering the coordinated chemical reactivity of O3 and SOA, a comprehensive control index (CCI) was proposed for the control of key pollutant species that have multiplier effects on environment. For adsorption, trans-2-butene and p-xylene were the key co-control pollutants, while toluene and trans-2-butene were the most important for membrane and condensation + membrane control. A 50% emission reduction of the top two key species that emission account for 4.3% averagely will reduce O3 by 18.4% and SOA by 17.9%.

Personal VOCs Exposure with a Sensor Network Based on Low-Cost Gas Sensor, and Machine Learning Enabled Indoor Localization

Indoor locations with limited air exchange can easily be contaminated by harmful volatile compounds. Thus, is of great interest to monitor the distribution of chemicals indoors to reduce associated risks. To this end, we introduce a monitoring system based on a Machine Learning approach that processes the information delivered by a low-cost wearable VOC sensor incorporated in a Wireless Sensor Network (WSN). The WSN includes fixed anchor nodes necessary for the localization of mobile devices. The localization of mobile sensor units is the main challenge for indoor applications. Yes. The localization of mobile devices was performed by analyzing the RSSIs with machine learning algorithms aimed at localizing the emitting source in a predefined map. Tests performed on a 120 m2 meandered indoor location showed a localization accuracy greater than 99%. The WSN, equipped with a commercial metal oxide semiconductor gas sensor, was used to map the distribution of ethanol from a point-like source. The sensor signal correlated with the actual ethanol concentration as measured by a PhotoIonization Detector (PID), demonstrating the simultaneous detection and localization of the VOC source.

Variation Characteristics and Source Apportionment of Atmospheric VOCs at Multi-sites in Zhengzhou

From July 2020 to June 2021, monthly offline sampling of atmospheric VOCs was carried out and analyzed at three urban sites and one suburban site in Zhengzhou. Then, the volume fraction levels, composition characteristics, reactivity, and source apportionment of atmospheric VOCs were discussed. The results showed that the volume fraction of atmospheric VOCs in Zhengzhou was (37.50±14.30)×10-9 during the sampling period, and the proportion of components was represented by alkanes (33%)>OVOCs (24%)>halogenated hydrocarbons (23%)>aromatic hydrocarbons (8%)>alkenes (7%)>alkynes (4%)>sulfides (1%). The seasonal variation characteristics were winter>autumn>summer>spring, and the monthly average value of VOCs had the highest value in January and the lowest value in May; the spatial variation characteristics were Zhengzhou University (ZD)>Jiancezhan (JCZ)>Jingkaiqu (JKQ)>Gangli Reservoir (GLR). The average·OH loss rate (L·OH) was 4.24 s-1, and the average ozone formation potential (OFP) was 172.27 μg·m-3; the top ten species of L·OH and OFP at each site and in each season were dominated by alkenes, OVOCs, and aromatic hydrocarbons. The results of positive matrix factorization (PMF) showed that the main sources of VOCs were vehicle emissions (28%), solvent utilization (24%), industrial emissions (24%), and oil and gas volatilization (19%) and plant emissions (5%).

New insight into formation mechanism, source and control strategy of severe O3 pollution: The case from photochemical simulation in the Wuhan Metropolitan Area, Central China

The Wuhan Metropolitan Area, located in Central China, has experienced severe O3 pollution in recent years; thus urging to diagnose formation regime and propose reasonable control strategies. Multi-source data of air pollutants and meteorological factors in 4 cities during August 2019 when severe regional O3 pollution occurred were obtained; then, in-situ O3 formation mechanism, the O3-precursors sensitivity, the sources and control strategies of O3 were evaluated based on the combination of the 0-D photochemical observation-based model and the positive matrix factorization model through the analysis of local ozone budget, the relative incremental reactivity, an empirical kinetic model approach and source apportionment. The results indicated the P(O3) (net O3 production rate) was 25 ppbv h−1 in Ezhou and 11–13 ppbv h−1 in other 3 cities. The dominated photochemical production of O3 was NO + HO2 reaction (62–71%), whereas the main pathway to destroy O3 during daytime was NO2 + OH (>70%) and nocturnal loss of O3 with alkenes even reached up to 39–46%. Generally, O3 formation was sensitive to AVOC (Anthropogenic Volatile Organic Compounds), in which reactive aromatics, OVOCs (Oxygenated VOCs), and alkenes (xylenes, ethylene, isoprene, methyl vinyl ketone, hexanal, toluene and methacrolein, specifically) as well as abundant i-pentane should be targeted to alleviate O3 pollution. The highly reactive VOCs sources for O3 formation in this region were vehicular exhaust (28–41%), industrial emissions (20–29% except Ezhou), and solvent use (17–29% except Huangshi). Co-reduction of O3 precursors in aforementioned reactive emissions according to optimal ratios of AVOC to NO2, i.e., 5:1 (Wuhan and Huanggang), 4:1 (Ezhou), and 6:1 (Huangshi), could achieve local O3 effective mitigation. Surprisingly, P(O3) could reduce by 38% and 48% under 40% AVOC cut accompanied by NO2 in more contaminated cities (Wuhan and Ezhou). Overall, our study provides new insight to future collaborative O3 alleviation strategies formulation in Central China, which quantified O3 formation at different precursors levels in different cities suffering from regional O3 pollution, concluded best precursors control ratios and confirmed validity of O3 mitigation through precursors-oriented emission reduction in vital sources.

HPB P01 Volatile Organic Compounds for the Detection of Hepatocellular Carcinoma – a Scoping Review

Abstract Background Hepatocellular carcinoma (HCC) is an increasingly common disease and is classified as one of the most common cancers leading to mortality worldwide. Only a small percentage of patients with this disease are eligible to curative treatment. Quite often the main reason is the late diagnosis of the disease. In the last decade, a Nobel prize awarded discovery of the volatile organic compounds in the breath opened the frontiers for new diagnostic tools and methods for several diseases. Cancer is one of the target diseases that appears to have unique biomarkers in the breath of the affected individuals. This have been found true in colorectal, breast, lung cancers. This systematic review aims to answer the question if markers specific to hepatocellular carcinoma exist in exhaled breath and what is the current knowledge regarding its detection. Methods A systematic search was conducted by two reviewers and the Royal College of Surgeons of Edinburgh librarian using the Embase, Medline, PubMed and Web od Science databases. Search strategy included all studied published until the 24th of March 2021 containing combination of keywords (Hepatocellular carcinoma, hepatocellular neoplasm, hepatocellular cancer, hepatocellular tumor, hepatocellular tumour, HCC, liver cancer, liver carcinoma, liver neoplasm, liver tumor, liver tumour AND volatile organic compound, VOC, volatilome, volatilomics, metabolome, metabolomics, breath analysis). Results The search yielded 6 publications using PRISMA pathway. Two of the studies described in vitro experiments and four were conducted on a small number of groups of patients. Overall, in the in vitro studies 42 headspace gases were analysed. Clinical studies included 164 patients with HCC and as control groups - 110 patients with cirrhosis and 130 healthy individuals. Multiple VOCs were found in the studies. Following their identification in PubChem library, a pathway analysis was performed using the Kyoto Encyclopaedia of Genes and Genomes (KEGG). Only three VOCs were annotated in the KEGG maps and out of those, two could be traced back to their biological pathways. These are acetaldehyde and ethanol which participate in glycolysis and gluconeogenesis (Figure 1). Conclusions At present time there are no specific volatile biomarker in exhaled breath characterising hepatocellular carcinoma. Data on extracted studies emphasised lack of unified methodology. This review, however, highlighted metabolic pathway which might be the source of VOCs produced by cancerous hepatocytes. Large population studies are required to verify this finding.

Emission characteristics, risk assessment and scale effective control of VOCs from automobile repair industry in Beijing

Automobile repair is regarded as a typical domestic source of VOCs in China characterized by numerous sites, wide dispersion and intermittent VOCs emissions. It is of great importance to study and control VOCs from such activities. In this research, emission characteristics, risk assessment and scale effective control of VOCs from automobile repair in Beijing were studied. Results showed that coating spraying and baking were the main processes of VOCs and the major species determined were mostly oxygen-containing VOCs and aromatic hydrocarbons in the case of solvent-based coating usage. Meanwhile, alkanes were determined and accounted for 40 % of total VOCs emissions during the water-based coating spraying and baking. Generally, the total determined VOCs during the automobile repair processes were 1.06–1.27 mg/m3 and 2.93–53.46 mg/m3 for the usage of water-based and solvent-based paint, respectively. Health risk assessments indicated that the residents in the region about 30 m high within a radius of 20 m around the automobile repair plants might suffer from both serious non-carcinogenic and carcinogenic risk threats in the case of solvent-based coating usage in that the values of total hazard index (HI) represented by dichloropropane and acrolein were higher than 1 and the value of lifetime cancer risk (LCR) represented by dichloroethane was higher than 10−5. Besides, those in the region about 30 m high and within a wider radius of 340 m might suffer from carcinogenic risk threat with a certain probability (LCR > 10−6) no matter either solvent-based or water-based coatings were used. As for the scale control of VOCs from automobile repair, independent adsorption by activated carbon combined with mobile regeneration by catalytic combustion was also proposed as an efficient way.

Determining an optimal control strategy for anthropogenic VOC emissions in China based on source emissions and reactivity

An evidence-based control strategy for emission reduction of VOC sources can effectively solve the regional PM2.5 and O3 compound pollution in China. We estimated the anthropogenic VOC emission inventory in China in 2018 and established a source profile database containing 129 sources based on localized detection and the latest research results. Then, the distribution of the ozone formation potential (OFP) and secondary organic aerosol formation potential (SOAFP) for emission sources was analyzed. Moreover, priority control routes for VOC emission sources were proposed for different periods. Anthropogenic VOC emissions in China reached 27,211.8 Gg in 2018, and small passenger cars, industrial protective coatings, biomass burning, heavy trucks, printing, asphalt paving, oil storage and transportation, coking, and oil refining were the main contributors. Industrial protective coatings, small passenger cars, and biomass burning all contributed significantly to OFP and SOAFP. Priority in emission reduction control should be given to industrial protective coatings, small passenger cars, heavy trucks, coking, printing, asphalt paving, chemical fibers, and basic organic chemical sources over the medium and long term in China. In addition, the priority control route for VOC emission sources should be adjusted according to the variations in VOC emission characteristics and regional differences, so as to obtain the maximum environmental benefits.

How a winding-down oil refinery park impacts air quality nearby?

It is always difficult to compare, let alone estimate, the difference of air pollutant concentrations before and after closure of a major source because the pollutants cannot be traced or predicted after entering the ambient. Indeed, we are not aware of any studies specifically related to the air pollutants impacted by a winding-down source. In this work, we applied nine years (2010–2018) online measurement of air pollutants (including PM10, PM2.5, NO2, SO2, O3 and VOCs) to investigate (i) the temporal behavior of air pollutants before and after closure of an oil refinery park by using pair-wise statistics and correlations between wind speed and direction, and (ii) the source impacts on O3 concentrations using PMF coupled with multiple linear regression (MLR) analysis (PMF-MLR). Example applications are presented at two monitoring sites (A and B) close to the Kaohsiung Oil Refinery (KOR), located in the southern industrial city of Taiwan. The results show that the KOR shutdown changed air pollutant concentrations to a certain extent in these study areas. We also conclude that, instead of using propylene-equivalent and ozone formation potential (OFP) concentrations, it is better to estimate the formation of O3 based on PMF-MLR analysis as developed in this study. The PMF analysis has identified various VOCs sources at both sites including solvent usage, petrochemical industrial sources, industrial emissions, vehicle-related sources, vegetation emissions and aged air-masses. Also, the MLR model shows that both the background sources and petrochemical industrial sources may significantly change O3 concentrations.

Characteristics and Source Apportionment of Volatile Organic Compounds in August in the Chang-Zhu-Tan Urban Area

Continuous sampling using the tank sampling method were conducted in Changsha, Zhuzhou, and Xiangtan cities from August 18 to 27, 2020, and 106 VOCs species were analyzed using GC-MS analysis. Then, the regional VOCs concentrations, generation potential, and source of VOCs were studied. The results showed that the average φ(VOCs) was (20.5±10.5)×10-9 in the Changsha-Zhuzhou-Xiangtan area, in which OVOCs (33.5%) and alkanes (28.2%) accounted for the highest proportion. The ozone formation potential (OFP) of VOCs was 118.5 μg·m-3, and the contributions of aromatic hydrocarbons, olefin, and OVOCs to OFP were 37.4%, 24.2%, and 23.6%, respectively. The average secondary organic aerosol formation potential (SOAp) of the VOCs was 0.5 μg·m-3, and the contribution of aromatic hydrocarbons to SOAp was 97.0%, among which C8 aromatic hydrocarbons contributed 41.7%. Toluene, m/p-xylene, and o-xylene were the common dominant species that contributed significantly to OFP and SOAp. The characteristic ratio results showed that VOCs in Changsha were relatively influenced by industrial processes and solvent use, whereas Zhuzhou and Xiangtan were more affected by coal and biomass combustion. The PMF results showed that the VOCs mainly came from vehicle exhaust and oil and gas volatilization (27.2%), coal and biomass combustion (23.7%), industrial processes (20.4%), solvent use (17.2%), and natural sources (11.5%) in the Changsha-Zhuzhou-Xiangtan area.

1D model for n-butane adsorption and thermal variation for EVAP canister of gasoline-fueled vehicles: Validation with experimental results and DFSS optimization

Gasoline evaporation from vehicle fuel tanks is a major source of VOCs, that represents a serious threat for both human health and environment. To limit these emissions, the most adopted strategy is to use a carbon canister filter to store fuel vapors and then burn them inside the engine along with the fresh charge. However, the canister saturation level is usually unknown, and it can easily reach the full saturation, especially in particular conditions. As hybrid vehicles are becoming more popular in the market, this issue becomes even more important, since canister purging phase has even less time to be performed. In this activity, a 1D transient, non-isothermal, non-adiabatic model has been developed to specifically simulate the carbon canister filter of a common EVAP system and analyze its behavior during fuel vapor adsorption, with particular attention to the mutual influence of carbons adsorption performance and temperature variation. The model presented is based on an adsorption isotherm derived from the potential theory of adsorption, and it has been developed to be usable with only few canister properties. A system of two coupled PDEs has been coded and solved in MATLAB® environment, and results have been compared to experimental data in terms of mass and internal temperature variation on a common European canister, found in a previous study, with a standard loading flow rate of n-butane mixture and standard environmental temperature. The model has then been analyzed by using the Design For Six Sigma (DFSS) method, which has allowed a good optimization on calibration parameters with a relatively low amount of tests. Results show a significant increment in the predictive capabilities of the optimized model (up to 90% of the experimental value), with respect to the first simulations. This model helps to understand and evaluate the influence of environmental temperature on the canister filter performance, and can be used for both canister design and control of the purging strategies performed by an on-road vehicle.

Speciated Emission Inventory of VOCs from Industrial Sources and Their Ozone Formation Potential in Chongqing

Based on the basic information of the Second National Pollution Source Census and the VOCs source profiles of industrial industries, we established the speciated emission inventory of major industrial sources in Chongqing in 2017, estimated their ozone formation potential (OFP), and identified the key control species of industrial VOCs and their sources. The results showed that the total VOCs emission from industrial sources and their OFPs were 144.12 kt and 477.34 kt, respectively. Automobile manufacturing, equipment manufacturing, plastic manufacturing, and chemical raw materials and chemical products were all industries that contributed significantly to VOCs emissions and OFP, with VOCs emissions of 37.18, 33.09, 19.47, and 18.14 kt and OFP of 191.43, 153.69, 27.21, and 57.51 kt, respectively. Aromatics were the components with the largest contribution to VOCs emissions and OFP, accounting for 62.55% of the total VOCs emissions and 82.15% of the total OFP, mainly from metal surface coating and petrochemical industries. The major reactive species of industrial source VOCs were m/p-xylene, toluene, ethylbenzene, o-xylene, and propylene, with OFP of 130.47, 103.37, 46.37, 42.83, and 28.26 kt, respectively, cumulatively accounting for 71.11% of the total OFP. In terms of spatial distribution, the emission intensity of VOCs and O3 pollution degree in all districts and counties of Chongqing were relatively consistent; the high value points of VOCs emissions and OFP were mainly distributed in the main urban area and the western area, and the sources of VOCs emission in the main urban area and western area were mainly in metal surface coating and the petrochemical industry, respectively.

Using Real Time Measurements to Derive the Indoor and Outdoor Contributions of Submicron Particulate Species and Trace Gases.

The indoor environment is usually more polluted than outdoors due to emissions of gas and particle-phase pollutants from multiple sources, leading to their accumulation on top of the infiltration of outdoor pollution. While it is widely recognized that negative health effects arise from the exposure to outdoor air pollution, exposure to indoor pollutants also needs to be well assessed since we spend most of our time (~90%) breathing indoors. Indoor concentrations of pollutants are driven by physicochemical processes and chemical transformations taking place indoors, acting as sources and/or sinks. While these basic concepts are understood, assessing the contribution of each process is still challenging. In this study, we deployed online instrumentation in an unoccupied room to test a methodology for the apportionment of indoor and outdoor pollutant sources. This method was successfully applied to the apportionment of PM1 and VOCs, however, there are limitations for reactive gases such as O3. The results showed that this unoccupied indoor environment acts as a source of VOCs and contributes 87% on OVOCs and 6% on CxHy, while it acts as a sink for particles, likely due to losses through volatilization up to 60%.

Air Pollutants and CO2 Emissions in Industrial Parks and Evaluation of Their Green Upgrade on Regional Air Quality Improvement: A Case Study of Seven Cities in Henan Province

Although central to the promotion of regional economic development, industrial parks discharge large quantities of air pollutants and CO2, counter to the goals of air quality improvement and CO2 reductions in China. In this study, 13 industrial parks in seven cities in Henan Province were chosen to evaluate their emission of air pollutants and CO2 in 2017, their reduction potential under different green measures, and their air quality improvements under a Green Upgrade scenario. The results show that: (1) The total emissions of SO2, NOx, CO, PM10, PM2.5, VOCs and CO2 in the 13 industrial parks were 43, 39, 351, 19, 7, 18, 2 kt and 36 Mt, and would decrease by 72, 56, 19, 30, 26, 77 and 30%, respectively, under the Green Upgrade scenario. (2) The industrial process was the major source of CO, PM2.5, VOCs and NH3, whereas power plants were the largest source of SO2 and NOx, and they would be reduced by 93, 59, 94, 91, 23 and 28%, respectively, under the Green Upgrade scenario. (3) The terminal energy use sector (including industrial boilers and industrial process sources) was the main source of CO2, accounting for 75% of total CO2 emissions, and would be reduced by 76% under the Green Upgrade scenario. (4) WRF-CMAQ simulation results show that, under the Green Upgrade scenario, the concentration of PM2.5 in a transmission channel city would be improved by 1–36 μg/m3, with an annual average value of 9 μg/m3. Our results demonstrate the significant effect of the synergistic reduction in air pollutants and CO2 emissions using Green Technologies in industrial parks and the subsequent improvement in regional air quality.

Improved Performance of PMF Source Apportionment for Volatile Organic Compounds Based on Classification of VOCs' Aging Degree in Air Mass

VOCs are the key precursors of ozone and secondary organic aerosols. The results of source apportionment for VOCs are very important for the coordinated control of ozone and second organic particulate matter. However, VOCs do not fully meet the assumption of the receptor model because the VOCs released from each source are relatively unstable in the transmission process for their reactivity. As a result, we do not accurately obtain the actual source contribution when the receptor model is used for the source apportionment of VOCs. In order to solve the problem that the relative changes in the components caused by VOCs reactivity are not consistent with the PMF model hypothesis, the aging degree of VOCs was introduced to distinguish the state characteristics after their photochemical reactions in the ambient air. According to the ratio of ethylbenzene to m/p-xylene, VOCs monitored at Wuhai were divided into three aging states:high, medium, and low. The results showed that the model parameters, such as regression equation parameters (slope and intercept), standard error, determination coefficient, and pass rate of residual error, were improved obviously compared to the sample set after classification. Because the degree of aging is closely related to the transport time of air mass and the atmospheric oxidation in the atmosphere, it also reflects the different sources of air mass to some extent. In the high-aging VOCs samples, the coking source occupied a high proportion (up to 47.20%). In the low-aging VOCs samples, the combustion source and coking source accounted for a higher proportion, 28.67% and 24.39%, respectively. After the classification according to the aging degree, the results of VOCs source apportionment by PMF are more consistent with the actual contribution of emission sources.

Volatile organic compounds released in the mainstream smoke of flavor capsule cigarettes

In this study, the composition of mainstream smoke was investigated with an emphasis on a list of volatile organic compounds (VOCs: e.g., isoprene, acrylonitrile, methyl ethyl ketone, benzene, toluene, m-xylene and styrene) using the two types of flavor capsule cigarettes (FCCs, here coded as F1 and F2) in reference to one commercial, non-flavored (NF) and 3R4F cigarette. The concentrations of all the target compounds from FCCs were quantified under two contrasting conditions (i.e., with and without breaking the capsules). The effect of breaking the capsule was apparent in the FCC products with the enhancement of VOC levels, specifically between after and before breaking the capsules (e.g., 1.10–1.58 folds (benzene) and 1.30–1.53 folds (acetonitrile)). Such increases were apparent in both FCC samples if assessed in terms of the total amount of VOCs (TVOC): (1) F1 (from 2159 to 2530 μg cig−1 (p = 9.42 × 10−6)) and (2) F2 (from 1470 to 2014 μg cig−1 (p = 0.05)). In addition, these TVOC levels determined from the FCCs were 1.62- to 1.83- and 1.29- to 1.46-fold higher than those of the NF cigarette and the 3R4F cigarette, respectively. Thus, these FCC products are suspected to play a role as stronger sources of VOCs than the general cigarette products.

Source Identification of VOCs and their Environmental Health Risk in a Petrochemical Industrial Area

Ambient VOCs in the vicinity of a petrochemical industrial area were analyzed for their health impact and potential emission sources. Comprehensive measurements of VOCs were conducted based on U.S. EPA TO-15. Potential carcinogenic and non-carcinogenic inhalation risks were evaluated by comparing the measured concentrations with the inhalation unit risk (IUR) and reference concentration (RfC). The results indicated that a high carcinogenic risk occurred from 1,2 dibromoethane and benzene, while non-carcinogenic risks were attributed to 1,3 butadiene, 1,1,2 trichloroethane, and 3-chloropropene. The Positive Matrix Factorization (PMF) Version 5.0 was further utilized to estimate the contribution of specific sources to the VOC mixing ratio. The results revealed that the average VOC concentration in the community area was dominated by aromatic hydrocarbons, with toluene having the highest concentration. Vehicle exhaust was evaluated as the most contributing emission source of the VOC mixing ratio, followed by industrial processes. Specific VOC ratios were also applied to identify VOC sources. The T/B ratio was within the range 3.54–5.15, confirming that vehicle emissions were the main source of pollutants during the entire investigated period in the community area. As for the industrial area, the average VOC concentration was dominated by alkenes. Industrial processes and the petrochemical industry were the major sources of VOCs. The health risk assessment in the industrial area indicated that acrolein had the highest risk for non-carcinogens. 1,2-dichloroethane and 1,3-butadiene showed high potential as carcinogens.

Identification of Key Anthropogenic Voc Species and Sources Controlling Summer Ozone Formation in China

Identification of Key Anthropogenic Voc Species and Sources Controlling Summer Ozone Formation in China

Identification of decadal trends and associated causes for organic and elemental carbon in PM2.5 at Canadian urban sites.

Chemically resolved data for fine particulate matter (PM2.5) have been collected across Canada since 2003 through the National Air Pollution Surveillance (NAPS) network. Seven urban sites that have 10-17years (2003-2019) of PM2.5 organic carbon (OC) and elemental carbon (EC) data were selected for analysis of decadal trends of OC, EC, and OC/EC ratio using the Ensemble Empirical Mode Decomposition method. Results showed that OC and EC decreased by 0.009-0.072μgm-3 yr-1 and 0.028-0.049μgm-3 yr-1, or 0.77-3.1%yr-1 and 3.2-6.7%yr-1, respectively, depending on the location. The more rapid decrease in EC than OC resulted in an increasing trend in the OC/EC ratio of 0.03-0.19yr-1 across the sites. Macro-tracer approach was used to estimate source attributions of OC and EC from wood burning, fossil fuel combustion, and secondary aerosol formation. Using this approach, it was identified that the significant decrease in EC during the past decade was predominately caused by reduced on-road emissions. The decreased emissions from wood burning and transportation dominated the decline of OC, but such a decline was largely offset by the enhanced secondary organic aerosol (SOA) formation, resulting in much weaker decline of OC than EC. The enhanced SOA formation was due to the increased biogenic emissions fully offsetting the decreased anthropogenic emissions for volatile organic compounds. These findings highlight the need for quantifying biogenic sources of VOCs and other oxidants that are involved in OC formation at the national scale.

Accurate Identification of Key Vocs Sources Contributing to O3 Formation Along the Liaodong Bay Based on Emission Inventories and Ambient Observations

Accurate Identification of Key Vocs Sources Contributing to O3 Formation Along the Liaodong Bay Based on Emission Inventories and Ambient Observations

Source Apportionment of VOCs and O3 Production Sensitivity at Coastal and Inland Sites of Southeast China

Urbanization and industrialization levels have a significant impact on the pollution of O3 and its precursors. However, current studies of VOC sources and O3 formation sensitivity in the regions with different urbanization and industrialization levels remained limited. Therefore, offline and online VOC observations were conducted at coastal sites (CS) and inland sites (IS) of southeast China to analyze spatial-temporal characteristics, source apportionment of VOCs based on the positive matrix factorization (PMF) model, and their effects on O3 formation using the observation-based model (OBM). The results showed that the average concentrations of TVOCs at CS and IS were 49.1 ± 14.4 and 28.4 ± 9.6 ppb, respectively, with higher levels in autumn compared to those in spring and summer. Alkene species contributed the largest to the OH radical loss rate (LOH) and ozone formation potential (OFP). The contributions of vehicle exhaust and combustion sources, industrial sources, solvent usage, biogenic sources, and fuel evaporation at CS and IS were 42.2% and 34.5%, 22.4% and 18.2%, 12.7% and 4.5%, 11.7% and 19.4%, and 11.0% and 23.4%, respectively. Meanwhile, vehicle exhaust and combustion sources (31.8%), fuel evaporation (21.3%) were the major contributors to O3 formation in Ningde. The results of sensitivity analysis indicated that O3 formation at CS was mainly VOC control in spring and autumn, and controlled by both VOCs and NOx in summer, but the VOCs is the key factor for the O3 formation at IS, and the emission control of alkenes and aromatics was conductive to decrease O3 levels. The scenario analysis suggested that the 20% reduction of VOC concentrations and 3% reduction of NOx concentrations could realize the 5% reduction of O3 concentrations. This study might enhance the understanding of O3 and its precursors in southeast China with different urbanization levels, as well as the emission reduction strategies.