Obscured Contribution of Oxygenated Intermediate-Volatility Organic Compounds to Secondary Organic Aerosol Formation from Gasoline Vehicle Emissions.

Secondary organic aerosol (SOA) formation from gasoline vehicles spanning a wide range of emission types was investigated using an oxidation flow reactor (OFR) by conducting chassis dynamometer tests. Aided by advanced mass spectrometric techniques, SOA precursors, including volatile organic compounds (VOCs) and intermediate/semivolatile organic compounds (I/SVOCs), were comprehensively characterized. The reconstructed SOA produced from the speciated VOCs and I/SVOCs can explain 69% of the SOA measured downstream of an OFR upon 0.5-3 days' OH exposure. While VOCs can only explain 10% of total SOA production, the contribution from I/SVOCs is 59%, with oxygenated I/SVOCs (O-I/SVOCs) taking up 20% of that contribution. O-I/SVOCs (e.g., benzylic or aliphatic aldehydes and ketones), as an obscured source, account for 16% of total nonmethane organic gas (NMOG) emission. More importantly, with the improvement in emission standards, the NMOG is effectively mitigated by 35% from China 4 to China 6, which is predominantly attributed to the decrease of VOCs. Real-time measurements of different NMOG components as well as SOA production further reveal that the current emission control measures, such as advances in engine and three-way catalytic converter (TWC) techniques, are effective in reducing the "light" SOA precursors (i.e., single-ring aromatics) but not for the I/SVOC emissions. Our results also highlight greater effects of O-I/SVOCs to SOA formation than previously observed and the urgent need for further investigation into their origins, i.e., incomplete combustion, lubricating oil, etc., which requires improvements in real-time molecular-level characterization of I/SVOC molecules and in turn will benefit the future design of control measures.

Characteristics of typical intermediate and semi volatile organic compounds in Shanghai during China International Import Expo event.

To ensure good air quality during the China International Import Expo (CIIE) event, stringent emission-reduction measures were implemented in Shanghai. To assess the efficacy of these measures, this study measured typical categories of intermediate/semi volatile organic compounds (I/SVOCs), including alkanes (C10-C26 n-alkanes and pristane), EPA-priority polycyclic aromatic hydrocarbons (PAHs), alkylnaphthalenes, benzothiazole (BTH) and chlorobenzenes (CBs), at an urban site of Shanghai before and during two CIIE events (2019 and 2020; non-CIIE versus CIIE). The average concentrations of alkanes and PAHs during both 2019 and 2020 CIIE events decreased by approximately 41% and 17%, respectively, compared to non-CIIE periods. However, the decline in BTH and CBs was only observed during CIIE-2019. Secondary organic aerosol (SOA) formation from alkanes, PAHs and BTH was evaluated under atmospheric conditions, revealing considerable SOA contributions from dimethylnaphthalenes and BTH. Positive matrix factorization (PMF) analysis further revealed that life-related sources, such as cooking and residential emissions, make a noticeable contribution (21.6%) in addition to the commonly concerned gasoline-vehicle sources (31.5%), diesel-related emissions (20.8%), industrial emissions (18.6%) and ship emissions (7.5%). These findings provide valuable insights into the efficacy of the implemented measures in reducing atmospheric I/SVOCs levels. Moreover, our results highlight the significance of exploring additional individual species of I/SVOCs and life-related sources for further research and policy development.

Enigma of Urban Gaseous Oxygenated Organic Molecules: Precursor Type, Role of NOx, and Degree of Oxygenation.

Oxidation of volatile organic compounds (VOCs) forms oxygenated organic molecules (OOMs), which contribute to secondary pollution. Herein, we present measurement results of OOMs using chemical ionization mass spectrometry with nitrate as the reagent ion in Shanghai. Compared to those in forests and laboratory studies, OOMs detected at this urban site were of relatively lower degree of oxygenation. This was attributed to the high NOx concentrations (∼44 ppb), which overall showed a suppression on the propagation reactions. As another result, a large fraction of nitrogenous OOMs (75%) was observed, and this fraction further increased to 84% under a high NO/VOC ratio. By applying a novel framework on OOM categorization and supported by VOC measurements, 50 and 32% OOMs were attributed to aromatic and aliphatic precursors, respectively. Furthermore, aromatic OOMs are more oxygenated (effective oxygen number, nOeff = 4-6) than aliphatic ones (nOeff = 3-4), which can be partly explained by the difference in initiation mechanisms and points to possible discrimination in termination reactions. This study highlights the roles of NOx in OOM formation in urban areas, as well as the formation of nitrogenous products that might show discrimination between aromatic and aliphatic VOCs.

Fate of Oxygenated Volatile Organic Compounds in the Yangtze River Delta Region: Source Contributions and Impacts on the Atmospheric Oxidation Capacity.

The Community Multiscale Air Quality model (CMAQv5.2) was implemented to investigate the sources and sinks of oxygenated volatile organic compounds (OVOCs) during a high O3 and high PM2.5 season in the Yangtze River Delta (YRD) region, based on constraints from observations. The model tends to overpredict non-oxygenated VOCs and underpredict OVOCs, which has been improved with adjusted emissions of all VOCs. The OVOCs in the YRD are dominated by ketones, aldehydes, and alcohols. Ketones and aldehydes mainly originate from direct emissions and secondary formation in the northern YRD, and primarily originate from secondary formation in the southern part influenced by biogenic emissions. The concentration of secondary organic aerosols (SOA) produced by OVOCs is 0.5-1.5 µg/m3, with 40-80% originated from organic nitrates, 20-70% originated from dicarbonyls, and 0-20% originated from isoprene epoxydiols. The influences of OVOCs on the atmospheric oxidation capacity are dominated by the OH• pathway during the day (∼350%) and by the NO3• pathway at night (∼150%). Consequently, O3 is enhanced by 30-70% in the YRD. Aerosols are also enhanced by 50-140%, 20-80%, and ∼20% for SOA, nitrate, and sulfate, respectively.

An online method for monitoring atmospheric intermediate volatile organic compounds with a thermal desorption-gas chromatography/mass spectrometry.

As one of important precursors of secondary organic aerosol (SOA), intermediate volatile organic compounds (IVOCs) have attracted much attention in recent years. Most of the previous studies however largely focused on characteristics of IVOCs from different emission sources, while data from field observations to study their temporal variations was limited for lacking the sufficient time resolution monitoring data. In this study, an online thermal desorption-gas chromatography/mass spectrometry (TD-GC/MS) method was developed to generate monitor data with a three-hour time resolution for gaseous atmospheric IVOCs. The method used two multi-sorbent traps that alternated for conducting sample collection and sample analysis. Compounds of C12C22 n-alkanes and 2-4 ring PAHs were chosen as surrogates to evaluate the performance of this method. Regression coefficients of external calibration curves were greater than 0.93 and 0.96 for all individual n-alkanes and PAHs, respectively. Average relative standard deviation (RSD) values among replicate samples spiked at 3 ng for each individual standard were 9% ± 5%. The detection limits of this method for individual n-alkanes and PAHs were 3.1-16.2 ng/m3 and 1.0-2.7 ng/m3, respectively. Atmospheric IVOCs were continuously monitored from September 28 to 30 and October 22 to November 9 in 2018, in an urban area of Shanghai. Besides targeted n-alkanes and PAHs, unspeciated complex mixtures (UCM) of IVOCs as well as total-IVOCs concentrations in the atmosphere were also determined. Measured concentrations and compositions of gaseous IVOCs in the atmosphere in this study were comparable to other similar studies.

Field Detection of Highly Oxygenated Organic Molecules in Shanghai by Chemical Ionization-Orbitrap.

Secondary organic aerosol, formed through atmospheric oxidation processes, plays an important role in affecting climate and human health. In this study, we conducted a comprehensive campaign in the megacity of Shanghai during the 2019 International Import Expo (EXPO), with the first deployment of a chemical ionization─Orbitrap mass spectrometer for ambient measurements. With the ultrahigh mass resolving power of the Orbitrap mass analyzer (up to 140,000 Th/Th) and capability in dealing with massive spectral data sets by positive matrix factorization, we were able to identify the major gas-phase oxidation processes leading to the formation of oxygenated organic molecules (OOM) in Shanghai. Nine main factors from three independent sub-range analysis were identified. More than 90% of OOM are of anthropogenic origin and >60% are nitrogen-containing molecules, mainly dominated by the RO2 + NO and/or NO3 chemistry. The emission control during the EXPO showed that even though the restriction was effectual in significantly lowering the primary pollutants (20-70% decrease), the secondary oxidation products responded less effectively (14% decrease), or even increased (50 to >200%) due to the enhancement of ozone and the lowered condensation sink, indicating the importance of a stricter multi-pollutant coordinated strategy in primary and secondary pollution mitigation.

Intermediate volatile organic compounds emissions from vehicles under real world conditions.

Real-world vehicle emission factors (EFs) for the total intermediate volatile organic compounds (total-IVOCs) and volatile organic compounds (VOCs) from mixed fleets of vehicles were quantified in the Yangtze tunnel in Shanghai. Relationships of EFs of IVOCs with fleet compositions and vehicle speed as well as secondary organic formation potentials (SOAFPs) from IVOCs and VOCs were studied. Multiple linear regression (MLR) was used to estimate EFs of total-IVOCs for gasoline and diesel vehicles. IVOCs were classified into unresolved complex mixtures (unspeciated cyclic compounds and branched alkanes (b-alkanes)) and speciated targets (11 n-alkanes and ten polycyclic aromatic hydrocarbons (PAHs)). The results showed that the average EF of total-IVOCs was 24.9 ± 7.8 mg/(km·veh), which was comparable to that of VOCs. Unspeciated cyclic compounds and b-alkanes dominated the main composition (~77% and ~19%), followed by n-alkanes (~4%) and PAHs (~1%). EFs of IVOCs showed a significant, positive relationship with diesel vehicle fractions (p < 0.05). EFs of IVOCs dropped notably with the decrease of the diesel vehicle fractions. SOAFP produced by the total organic compounds (IVOCs + VOCs) was 8.9 ± 2.5 mg/(km·veh), in which up to 86% of SOAFP was from IVOCs. Estimated EFs of total-IVOCs for gasoline vehicles and diesel vehicles were 15.3 and 219.8 mg/(km·veh) respectively. Our results demonstrate that IVOCs emitted from diesel vehicles are the main emission sources under real world conditions and significant contributions of IVOCs emissions to SOA formation is evident, which indicates the necessity of making control policies to reduce IVOCs emissions from vehicles.

[Characterization of Volatile Organic Compounds (VOCs) Using Mobile Monitoring Around the Industrial Parks in the Yangzte River Delta Region of China].

Volatile organic compounds (VOCs) play important roles in the formation of ozone and fine particles in the troposphere. Industrial parks emit significant amounts of VOCs in China, while few studies have characterized them. In the present study, a mobile platform was employed to measure the levels and composition VOCs around industrial parks in the Yangzte River Delta region. The average concentration of VOCs ranged from 39 µg·m-3 (5% percentile) to 533 µg·m-3 (95% percentile) with an average of 183 µg·m-3, which was three times that of ambient concentrations. Maximum VOC concentrations ranged from 307 µg·m-3 (5% percentile) to 12006 µg·m-3 (95% percentile) with an average of 2812 µg·m-3. The frequency of abnormal peak values was as high as 64% across all the industrial parks, of which toluene (32%), xylene (18%), benzene (9%), and>C9 aromatics (19%) were the most common species. Differences in VOC characteristics were observed among the different types of industrial parks. Specifically, highest concentrations of VOCs were observed in textile industrial parks followed by chemical, painting, and petrochemical industrial parks, and VOC concentrations in electronics industrial parks were the lowest. Importantly, species measured using the mobile platform only contributed~50% of VOCs present in ambient samples, indicating that the concentrations of VOCs in the industrial parks were underestimated overall. These results can inform measures to control VOC pollution in industrial parks in China.

[Source Apportionment of Ambient Carbonyl Compounds Based on a PMF and Source Tracer Ratio Method: A Case Based on Observations in Nanjing].

Ambient carbonyl compounds play an important role in tropospheric atmospheric chemistry. Primary emissions and photochemical formation are both sources of carbonyls, and therefore it is challenging work to analyze their sources. In this study, carbonyl sources were apportioned using the source tracer ratio method (STR) and positive matrix factorization model (PMF) based on offline carbonyls observations at a site in Nanjing during March 2017. Eleven carbonyl compounds were detected, and their total concentrations were in the range of 2.57×10-9-22.83×10-9. Formaldehyde, acetaldehyde, and acetone were the main components, accounting for 36.8%, 21.6%, and 18.5% of the average concentration of eleven carbonyl compounds, respectively. The influences of tracer selection and background concentrations on the results of source apportionment using the STR method based on comparing the results of acetylene and toluene as tracers and the 5th and 10th percentages as background concentrations are presented. Five sources were resolved by PMF, including traffic emission, the petrochemical & chemical industry, paint & solvent use, secondary formation & background, and the chemical industry. Secondary formation & background sources were the largest contributors of carbonyl compounds, contributing 56.4%, 48.2%, and 58.3% to formaldehyde, acetaldehyde, and acetone, respectively. By comparing the carbonyl source apportionment results by STR and PMF, it was found that the STR depends on the selection of tracers. When the STR is applied in the areas with complex sources, it is difficult to use a tracer to indicate anthropogenic source emissions, and therefore it is not a suitable method for carbonyl source apportionment.

[Characteristics and Reactivity of Ambient VOCs in Urban Hangzhou, China].

The ambient concentration of 122 volatile organic compound (VOC) species were continuously measured in urban Hangzhou, China from May 2018 to April 2019. The average mixing ratio of VOCs was (59.4±23.6)×10-9 and the oxygenated VOCs (OVOC) were the largest component. There was no clear "weekend effect" in urban Hangzhou, while the concentration of VOCs had a sharp decrease during long holidays. The concentration of VOCs had a positive correlation with air quality index (AQI) and reached the highest level when the primary pollutant was PM2.5. The assessment results of atmospheric chemical reactivity with·OH radical loss rate (L·OH) and ozone formation potential (OFP) showed the average value of L·OH was 7.5 s-1 and that of OFP was 152.1×10-9, among which carbonyl compounds, aromatics, and alkenes were the most abundant components. The overall chemical reactivity level of VOCs in Hangzhou was equivalent to 2-methylpentane. The average value of toluene/benzene (T/B) was 1.95, which implied the ambient VOCs in Hangzhou were influenced by vehicle exhaust. Secondary formation (17.6%), combustion (11.8%), industrial processing (12.3%), solvent use (18.1%), biogenic source (4.5%), and vehicle exhaust (35.7%) were identified as six major sources of VOCs in Hangzhou through the positive matrix factorization (PMF) model.

[Characteristics and Reactivity of VOCs in Hangzhou During a Typical Photochemical Pollution Episode].

An intensive observation of ambient volatile organic compounds (VOCs) was carried out in Hangzhou, a key city in the Yangtze River Delta, during a typical photochemical pollution episode from September 14-23, 2018. The analysis results of 80 effective samples showed that the average concentration of 122 compounds of VOCs was (59.5±19.8)×10-9 during the observation period, and oxygenated VOCs (OVOCs) were the most abundant component. The assessment results of atmospheric reaction activity with ozone formation potential (OFP) showed that the average value of OFP was 145×10-9 during the observation period, of which alkenes and carbonyl compounds were the most abundant components. The chemical reactivity of VOCs in Hangzhou was equivalent to acrylonitrile. Based on the positive matrix factorization (PMF) model, five major sources of VOCs in Hangzhou were identified, including secondary formation (25.2%), combustion and industrial processing (27.2%), solvent use (17.3%), biogenic sources (9.2%), and vehicular exhaust (21.2%). The results can provide guidance for further understanding of VOC characteristics and the basis for scientific prevention and control measures in Hangzhou.

Estimating Secondary Organic Aerosol Production from Toluene Photochemistry in a Megacity of China.

The production of secondary organic aerosols (SOA) from toluene photochemistry in Shanghai, a megacity of China, was estimated by two approaches, the parametrization method and the tracer-based method. The temporal profiles of toluene, together with other fifty-six volatile organic compounds (VOCs), were characterized. Combing with the vapor wall loss corrected SOA yields derived from chamber experiments, the estimated toluene SOA by the parametrization method as embodied in the two-product model contributes up to ∼40% of the total SOA budget during summertime. 2,3-Dihydroxy-4-oxopentanoic acid (DHOPA), a unique product from the OH-initiated oxidation of toluene in the presence of elevated NOx, was used as a tracer to back calculate the toluene SOA concentrations. By taking account for the effect of gas-particle partitioning processes on the fraction of DHOPA in the particle phase, the estimated toluene SOA concentrations agree within ∼33% with the estimates by the parametrization method. The agreement between these two independent approaches highlight the need to update current model frameworks with recent laboratory advances for a more accurate representation of SOA formation in regions with substantial anthropogenic emissions.

[Chemical Compositions, Mass Concentrations, and Emission Factors of Particulate Organic Matters Emitted from Catering].

Catering is an important emission source of atmospheric particulate organic matters (POMs). Mass concentrations, chemical compositions, and emission factors of POMs emitted from catering were studied based on simulation experiments. The effects of different cooking methods, various ingredients, oils, and other factors were investigated. The results showed that the species of POMs emitted from catering were largely influenced by cooking methods, ingredients, and oils. Among all the quantified POMs, the average mass fraction was 68.9%, 20.3%, and 4.2% for N-alkanes, sterols, and fatty acids (including saturated fatty acids and unsaturated fatty acids), respectively. The remaining 5.42% was constituted by dicarboxylic acids, polycyclic aromatic hydrocarbons, monosaccharide anhydrides, and hopane compounds. The average ingredient emission factor was 0.0131 g·kg-1, ranging from 0.0014 g·kg-1 to 0.0271 g·kg-1. The ingredient emission factors of the meat cooking process were much larger than those of the vegetable cooking process. The average oil emission factor was 1.8230 g·kg-1, ranging from 0.0019 g·kg-1 to 10.1730 g·kg-1. The oil emission factors of barbecuing were much larger than those of other cooking methods.

[Characterization of Volatile Organic Compounds from Cooking Emissions].

Volatile organic compounds (VOCs) do great harm to human health, and also have some impact on air quality. Cooking is one of the important sources of VOCs, so the study of cooking emissions is of great significance. By simulating the heating of oil and cooking, the characteristics and chemical composition of VOCs emissions for different types of oil fumes were analyzed by gas chromatography-mass spectrometry (GC-MS), using different oils, seasonings, and dishes as variables. The results show that the emission factors of the oils range from 0.81 to 2.53 g·kg-1, and the emissions are dominated by halogenated hydrocarbons and alkanes. The emission factors of the seasonings range from 25.06 to 40.18 g·kg-1, and the seasonings mainly emit alkanes. The quantity of emissions from chili fried meat is much higher than that of tomato scrambled eggs, and the chili fried meat mainly emits halogenated hydrocarbons, while tomato scrambled eggs mainly emit aromatic hydrocarbons and alkanes.

Intermediate Volatility Organic Compound Emissions from a Large Cargo Vessel Operated under Real-World Conditions.

Intermediate volatility organic compound (IVOC) emissions from a large cargo vessel were characterized under real-world operating conditions using an on-board measurement system. Test ship fuel-based emission factors (EFs) of total IVOCs were determined for two fuel types and seven operating conditions. The average total IVOC EF was 1003 ± 581 mg·kg-fuel-1, approximately 0.76 and 0.29 times the EFs of primary organic aerosol (POA) emissions from low-sulfur fuel (LSF, 0.38 wt % S) and high-sulfur fuel (HSF, 1.12 wt % S), respectively. The average total IVOC EF from LSF was 2.4 times that from HSF. The average IVOC EF under low engine load (15%) was 0.5-1.6 times higher than those under 36%-74% loads. An unresolved complex mixture (UCM) contributed 86.1 ± 1.9% of the total IVOC emissions. Ship secondary organic aerosol (SOA) production was estimated to be 546.5 ± 284.1 mg·kg-fuel-1; IVOCs contributed 98.9 ± 0.9% of the produced SOA on average. Fuel type was the dominant determinant of ship IVOC emissions, IVOC volatility distributions, and SOA production. The ship emitted more IVOC mass, produced higher proportions of volatile organic components, and produced more SOA mass when fueled with LSF than when fueled with HSF. When reducing ship POA emissions, more attention should be paid to commensurate control of ship SOA formation potential.

Emission factors of particulate and gaseous compounds from a large cargo vessel operated under real-world conditions.

On-board emissions measurements were performed on a Handysize-class bulk carrier operating under real-world conditions. Emission factors (EFs) were determined for criteria pollutants such as NOx, CO, total hydrocarbons (THC), and PM; PM composition, including organic and elemental carbon (OC and EC), inorganic species, and a variety of organic compounds and VOC species (including alkanes, alkenes, single-ring aromatics, and oxygenated VOCs) were also analyzed. To investigate the impacts of engine type, fuel, and operating conditions on emissions, measurements were conducted on one main and one auxiliary engines using low- and high-sulfur fuels (LSF and HSF) under actual operating conditions, including at-berth, maneuvering, and cruising at different engine loads. OC was the most abundant PM component (contributing 45-65%), followed by sulfate (2-15%) and EC (1-20%). Compounds with 3 or 4 aromatic rings, including phenanthrene, fluoranthene, pyrene, and benzo[b+k]fluoranthene, dominated the particulate polycyclic aromatic hydrocarbons (PAHs) emitted from the ship, accounting for 69-89% of the total PAHs. Single-ring aromatics constituted 50-78% of the emitted VOCs and were dominated by toluene. In this study, switching from HSF (1.12% S) to LSF (0.38% S) reduced emitted PM by 12%, OC by 20%, sulfate by 71%, and particulate PAHs by 94%, but caused an increase in single-ring aromatics. The power-based EFs generally decreased with increasing engine loads. However, decreasing the ship engine load also reduced the vessel speed and, thus, decreased emissions over a given voyage distance. Herein, a Vessel Speed Reduction (VSR) from 11 to 8-9 knots decreased NOx and PM emissions by approximately 33% and 36%, respectively, and OC, EC, sulfate, and particulate PAHs in PM emissions by 34%, 83%, 29%, and 11%. These data can be used to minimize uncertainty in the emission factors used in ship emissions calculations.

[Treatment Status and Emission Characteristics of Volatile Organic Compounds from Typical Industrial Sources].

The status of treatment equipment, the emission characteristics, and the ozone formation potential (OFP) of volatile organic compounds (VOCs) for 11 typical enterprises, which were categorized into the 8 major VOC emission industries identified by the emission inventory of a typical city in the Yangtze River Delta, are discussed in this paper. There was a large difference in the removal efficiency of non-methane hydrocarbon (NMHC) between different treatment techniques, and even an increase in concentration occurred after some of the treatments. The current treatment equipment for VOCs needs further optimization. The emissions of NMHC, benzene, toluene, and xylene in most of the surveyed enterprises exceeded their corresponding standards, with toluene the worst offender. The most abundant compounds in the eight emission industries were aromatic hydrocarbons and oxygenated VOCs, whereas aromatic hydrocarbons contributed the most to ozone formation potential. There were large differences in emission characteristics of VOCs from different industries. Priority should be placed on the industries that have large OFP when control strategies of VOCs are considered.

[Quantification of the Influence of Industrial Emissions on Volatile Organic Compounds (VOCs) Using PMF Model: A Case Study of Jiangbei Industrial Zone in Nanjing].

Volatile organic compounds(VOCs)are important precursors of ozone and secondary organic aerosol. The effect of industrial emissions on ambient VOC concentrations in the Jiangbei Industrial Zone in Nanjing was evaluated using the ambient VOCs measurements taken at Nanjing University of Information Science and Technology (NUIST) during March 2017. The monitoring data showed that the sum of 92 measured VOCs (TVOCs) ranged from 10.3×10-9 to 200.5×10-9. Some VOC species, such as ethylene, propene, benzene, styrene, and dichloromethane had abnormally high values. Positive matrix factorization model (PMF) was used to identify the main sources of VOCs. The results showed that industrial emissions on average accounted for 50.0% of TVOCs, while petrochemical industry, chemical industry, and paints & solvents use accounted for 14.9%, 19.3% and 15.8%, respectively. During a VOC pollution episode, the contribution of industrial emissions reached 74.9%. The direction of industrial sources was determined by combining the wind speed and wind direction data.

[Pollutant Emissions from Diesel Buses Fueled with Waste Cooking Oil Based Biodiesel].

Two diesel buses respectively certified to meet China Ⅲ and China Ⅴ emission standards were used as prototype vehicles, fixed on a heavy-duty chassis dynamometer and driven according to a typical city bus driving cycle to analyze the pollutant emissions and volatile organic compounds (VOCs). The buses were fueled with diesel and waste cooking oil based biodiesel with 10 vol% blend ratio (B10). The emissions of total hydrocarbon(THC), CO, particulate matter (PM), and the number of solid particles with a diameter of 23 nm to 2.5 µm (referred to as "solid particulate number of PM2.5") from the bus certified to meet China Ⅴ (referred to as "China V bus") were 39.3%, 19.9%, 77.4%, and 28.4% lower than those from the other bus certified to meet China Ⅲ (referred to as "China Ⅲ bus"), while NOx emissions were 31.7% higher. Moreover, alkanes, alkenes, aromatic hydrocarbons, and oxygenated compounds in VOCs emitted from the China V bus were lower than those emitted from the China Ⅲ bus, suggesting lower atmospheric reactivity and smaller potential of secondary organic aerosol formation. Compared with the emission results of two diesel-fueled buses, the B10-fueled buses emitted smaller amounts of THC, CO, PM, and solid particulate number of PM2.5, lower oxygenated compounds but higher alkenes; slightly higher NOx emissions than China Ⅲ but slightly lower NOx emissions than China V. Consequently, the atmospheric reactivity of VOCs in exhaust gas from the bus fueled with B10 was higher than that from the diesel-powered bus.

[Estimation of Fine Particle (PM2.5) Emission Inventory from Cooking: Case Study for Shanghai].

Cooking is one of important emission sources of fine particles (PM2.5). This study using the catering enterprises of Shanghai as an example, presents a method to estimate the PM2.5 emission inventory from cooking according to the number of stoves, cooking time, and number of customers. Based on in situ measurements, the concentrations of PM2.5 emissions ranged from 0.1 mg ·m-3 to 1.8 mg ·m-3, which exceeded the limit (1.0 mg ·m-3 for lampblack) in the national standard. Organic carbon dominated the PM2.5 emitted from cooking, accounting for more than 50%. Extremely high ratios of organic carbon to elemental carbon were observed, ranging from 58.8 to 752.3, which could be used as an indicator of cooking emissions. The emission factors of PM2.5 in the catering industry are closely related to the scale of the catering enterprises. The emission factors of large-and medium-sized enterprises are obviously higher than those of small and micro enterprises. The PM2.5 emissions of catering enterprises are mainly attributed to high emission loads of large enterprises and those for a large number of small and medium enterprises. The PM2.5 emission inventory of cooking in Shanghai was calculated according to the three emission factors above, and the results were very close. Therefore, the method for estimating the PM2.5 emission inventory for cooking presented in this study is helpful for other Chinese cities to calculate their PM2.5 emission inventory from cooking.