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A rapid reaction occurs near the exhaust nozzle when vehicle emissions contact the air. Twenty diesel vehicles were studied using a new multipoint sampling system that is suitable for studying the exhaust plume near the exhaust nozzle. The variation characteristics of fine particle matter (PM2.5) and its components in diesel vehicle exhaust plumes were analyzed. The PM2.5 emissions gradually increased with increasing distance from the nozzle in the plume. Elemental carbon emissions remained basically unchanged, organic carbon and total carbon (TC) increased with increasing distance. The concentrations of SO42-, NO3- and NH4+ (SNA) directly emitted by the vehicles were very low but increased rapidly in the exhaust plume. The selective catalytic reduction (SCR) reduced 42.7% TC, 40% NO3- emissions, but increased 104% SO42- and 36% NH4+ emissions, respectively. In summary, the SCR reduced 29% primary PM2.5 emissions for the tested diesel vehicles. The NH4NO3 particle formation maybe more important in the plume, and there maybe other forms of formation of NH4+ (eg. NH4Cl). The generation of secondary organic carbon (SOC) plays a leading role in the generation of secondary PM2.5. The SCR enhanced the formation of SOC and SNA in the plume, but comprehensive analysis shows that the SCR more enhanced the SNA formation in the plume, which is mainly new particles formation process. The inconsistency between secondary organic aerosol (SOA) and primary organic aerosol definitions is one of the important reasons for the difference between SOA simulation and observation.

To investigate the structural evolution of vanadate catalysts in the presence of SO2 and its influence on DeNOx behaviors, three typical vanadate catalysts (unsupported Mn2V2O7, Mn2V2O7/TiO2, and sulphated Mn2V2O7/TiO2) were designed for the selective catalytic reduction of NO with NH3. The XRD, Raman, and S 2p XPS spectra and TG results confirmed the SO2-promoted decomposition of supported Mn2V2O7 to form VOx species and MnSO4 on TiO2. The XPS spectra of V 2p and (HR)TEM images further indicated the fusion of the decomposed VOx with TiO2 with increased dispersity for the active V species. The decomposition and sulfation of supported Mn2V2O7 markedly increased the specific surface area with the exposure of more active Mn/V sites, Oα species and acid sites as demonstrated by the XPS spectra of O 2p and BET, NH3-TPD and H2-TPR results. The catalytic test exhibited that the formation of MnSO4 devitalized the Mn-based low-temperature active sites and worsened the low-temperature DeNOx performance below 250 °C, but the decomposition and sulfation of the supported Mn2V2O7 significantly enhanced the catalytic activity and N2 selectivity above 250 °C owing to the exposure of more active V sites, Oα species and acid sites. These research results imply that the vanadate catalysts may be unstable in the presence of SO2 and more suitable for the purification of sulfur-free or pre-desulfurization flue gases in the high temperature range.

Black carbon (BC) as an important part of atmospheric aerosols imposes adverse effects on atmospheric visibility, health, and climate change. Mass absorption cross-section (MACBC) is an essential parameter in BC quantitative and model research, which is of growing concern in recent decades. In this study, we conducted real-world measurements on BC emissions from two major sources of residential biofuel stoves and diesel trucks. BC emissions and MACBC values are quantified based on the photoacoustic and thermo-optical methods. The impacts of typical factors from biofuel stoves (biofuel and stove types) and diesel trucks (vehicle types, emission standards, and driving conditions) on BC/EC, MACBC values, and the relationships between BC and EC, BC/PM2.5 and MACBC are analyzed comprehensively. We find the BC and EC emissions from these two sources present good correlations, and those emissions are almost equal from diesel trucks, while the EC emissions from biofuel burning are slightly higher than BC. The typical factors for analysis may affect the optical properties of BC, and then will affect the mass ratio of BC/EC, indirectly. We have calculated the equivalent MACBC values and compared those with previous studies. Then, we further divided the equivalent MACBC values under several typical factors, which are 5.84 and 2.71 m2/g for improved and simple biofuel stoves, and 5.91 and 4.64 m2/g for light-duty and heavy-duty diesel trucks, respectively. Furthermore, the MACBC and BC/PM2.5 under the main operational metrics generally present good correlations. Our results will help to enhance the understanding of MACBC and provide effective data support for BC quantification and atmospheric model research.

Humans are more likely to be exposed to ultrafine particles (UFPs) emitted by light-duty gasoline vehicles (LDGVs) in urban road traffic, which can cause serious bodily harm. In this study, we conducted on-road measurement of the Particle Number (PN) emissions from 18 China-3, China-4, and China-5 LDGVs on representative roads in Beijing. To clarify the impact of key parameters (standards, driving conditions, and technology) on the PN emissions, we conducted a comprehensive analysis of the emission results. We found the PN emission factors (EFs) of port fuel injection (PFI) vehicles have declined considerably under stricter standards. Furthermore, we found the average EF of China-5 LDGVs with gasoline direct injection (GDI) was 10 times that of PFI vehicles, and the PN EFs of PFI vehicles increase as the age of the engine increases (R2 = 0.59). In different operating conditions, the PN EFs of all test vehicles under highway driving conditions were lower than those under non-highway driving conditions (6.5%–82.0%). The PN EFs of PFI LDGVs going uphill are 1.4–2.8 times those when going downhill. The PN EFs of LDGVs under start-up were 18–47% higher than under hot-running. PN emissions were high under positive engine power and increased with vehicle specific power. The dilution ratio has a significant impact on the test results, especially in a higher vehicle specific power interval, indicating that a high dilution ratio may lead to deviation of test values. Further research needs to determine the optimal dilution ratio to minimize test deviation. This study provides important data support for PN emission control. The optimal upper limit of the primary dilution ratio should be further studied and specified as a standard.

Modeling studies have highlighted that accurate simulations of radiative effect of black carbon (BC) require knowledge about the particle size and mixing state of freshly emitted BC from combustion sources. However, the information is absent in China due to lack of available measurements. In this study, we present the particle size and mixing state of fresh BC emitted from diesel vehicles (DV), brick kilns (BK), residential crop residue burnings (CR), and residential firewood burnings (FW) in September-October 2014 at North China Plain by field measurement. The mass median diameters of BC cores (whole particles including cores and coatings) above the limit of measurement (i.e.,70 nm) from these sources are ∼155 (∼194), ∼230 (∼306), ∼250 (∼438) and ∼273 (∼426) nm, respectively, and corresponding size ratios (i.e., mixing state) are ∼1.25, ∼1.33, ∼1.75, and ∼1.56, respectively. Compared with the values commonly used in model based on the laboratory experiments and the field measurements in developed countries, larger particle sizes and higher mixing sate of freshly emitted BC in China may enhance their light absorption and cloud condensation nuclei activities during atmospheric transport. The available data could be used to improve future model development on radiative effect of BC in China.

Medium-flow atmospheric samplers were used to collect particulate (PM2.5) and gaseous samples from the indoor kitchen of each of 35 randomly selected rural houses in North China while a meal was being cooked. The concentrations of 16 polycyclic aromatic hydrocarbons (PAHs) and 9 nitro-PAHs (NPAHs) in the samples were quantified by high-performance liquid chromatography (HPLC). This study provided the real PAH and NPAH pollution characteristics and carcinogenic risk produced by cooking in rural indoor kitchens in North China. The mean PAH and NPAH concentrations in air in the indoor kitchens during cooking periods were 4049.1 and 1741.6 ng/m3, respectively. The PAH and NPAH concentrations were lower in the particulate phase than the gaseous phase. The mean PAH and NPAH concentrations were much higher for cooking using coal than for cooking using liquefied petroleum gas (LPG) or electricity. The PAH and NPAH benzo[a]pyrene toxic equivalent (TEQBaP) concentrations for cooking using coal were 1823.3 and 2760.9 ng/m3, respectively. Lower PAH and NPAH concentrations were found in kitchens with than without range hoods. Range hoods decreased the PAH and NPAH TEQBaP concentrations by 68.8% and 61.9%, respectively. Appropriate fuel and ventilation choice will improve air pollution in indoor kitchens during cooking. The results provide important evidence for changing cooking habits and developing policies for cooking in rural China.

The real-world exhaust emissions and fuel consumption of on-road diesel vehicles, fueled by waste cooking oil biodiesel blends, were measured using a portable emission measurement system (PEMS). Two light-duty diesel trucks (LDDTs) and two heavy-duty diesel trucks (HDDTs) filled with four mixed fuels with blend ratios of 0% (neat diesel), 5% (B5), 20% (B20), and 100% (B100) (biodiesel in traditional fossil diesel) were tested. The results show that the total fuel consumption (biodiesel + traditional fossil diesel) did not clearly decrease, but blending biodiesel into traditional fossil diesel could clearly decreased the consumption of traditional fossil diesel, reduce the countries' dependence on oil imports. Converting waste cooking oil into biofuel and blending with diesel is a three-win alternative, dealing simultaneously with greenhouse gas (GHG) emission, food security, and energy security. The CO, HC, NOX and PM2.5 emissions for all of the tested vehicles decreased with increasing biodiesel content in the blend, with the exception of PM2.5 and NOX for D3, the NOX emissions showed a decrease with increasing biodiesel content in the blend for most vehicles in this study. The effect of emission reduction for all biodiesel blending proportions under highway (HW) condition is better than that under Non-highway (NHW) condition. The degree of reduction in CO, HC, NOX, and PM2.5 emission increased with increasing biodiesel content in the blend under HW section. Under the NHW section, the emission factors for lower biodiesel blend proportions (below 12.5%) especially for B5 were higher than those for neat diesel. The biodiesel blend reduced CO, HC, NOX and PM2.5 emissions compared with neat diesel under different driving modes except for individual condition (especially for B5 under acceleration mode). Increasing the biodiesel content of the blend lowered the CO, HC, NOX, and PM2.5 emissions for acceleration and deceleration modes.

Ion exchange membranes (IEMs) are undergoing prosperous development in recent years. More than 30,000 papers which are indexed by Science Citation Index Expanded (SCIE) have been published on IEMs during the past twenty years (2001-2020). Especially, more than 3000 papers are published in the year of 2020, revealing researchers' great interest in this area. This paper firstly reviews the different types (e.g., cation exchange membrane, anion exchange membrane, proton exchange membrane, bipolar membrane) and electrochemical properties (e.g., permselectivity, electrical resistance/ionic conductivity) of IEMs and the corresponding working principles, followed by membrane synthesis methods, including the common solution casting method. Especially, as a promising future direction, green synthesis is critically discussed. IEMs are extensively applied in various applications, which can be generalized into two big categories, where the water-based category mainly includes electrodialysis, diffusion dialysis and membrane capacitive deionization, while the energy-based category mainly includes reverse electrodialysis, fuel cells, redox flow battery and electrolysis for hydrogen production. These applications are comprehensively discussed in this paper. This review may open new possibilities for the future development of IEMs.

Rural vehicles (RVs) could contribute significantly to on-road vehicle emissions, especially PM2.5 and NOx; This study tested 10 three-wheeled (3-W) RVs and 8 four-wheeled (4-W) RVs on real roads in Hebei Province using a portable emissions measurement system to investigate gaseous concentrations (CO, NOx, and HC) and the carbonaceous composition (EC and OC) of the PM2.5 emitted. The results showed that the tightening emission standards resulted in the CO, HC, and PM2.5 emissions for China II RVs decreasing, but may increasing NOx emission for China II 3-W RVs. The emission level of PM2.5 for China II RVs is between Euro II LDDTs and Euro III LDDTs. The emission factors (EFs) of OC and EC for 3-W RVs were 0.035 ± 0.019 and 0.058 ± 0.055 g km-1, respectively, and for 4-W RVs, they were 0.046 ± 0.018 and 0.031 ± 0.024 g km-1, respectively. The carbonaceous component represents the main fraction of PM2.5 emitted from RVs (84.6% and 87.2% for 3-W and 4-W RVs, respectively), similar to other diesel vehicles. The average distance-based EFs of OC increased with increasing vehicle size (3-W RVs < 4-W RVs). The CO2-based EFs of OC and EC decreased with increasing vehicle mass, consistent with the emission laws of light-, medium-, and heavy-duty diesel trucks. Driving cycles that included more cruise mode and less creep mode resulted in a higher average EC/OC ratio (1.57) for 3-W RVs than for 4-W RVs (0.63), and resulted in the average EC/OC ratios for both types of RV were lower than for highway LDDTs.

Biofuel stoves are an important source of black carbon (BC) emissions, which have adverse effects on the environment and human health, especially in rural areas. However, there have been only limited studies of BC emissions from residential biofuel stoves based on real-time measurements. In this study, a photo-acoustic extinctiometer (PAX)-based real-time measurement system was employed to monitor the emission characteristics of corncobs, corn stalks, cotton stalks and poplar branches in simple or improved stoves (with a total of 16 units) in Hebei Province, China. The real-time and phased emissions of BC, fine particulate matter (PM2.5), carbon monoxide (CO) and carbon dioxide (CO2) were assessed, and the effects of stove type and fuel on emissions were analyzed. Under the same conditions, polar branches were associated with the highest BC emission factors (EFs) of up to 2.64 ± 0.42 g kg−1, while the EFs for improved stoves were higher than those for simple stoves. During the ignition phase, BC emissions were found to be low, while the later addition of fuel dramatically increased emissions, followed by a gradual decrease until the next fuel addition. The phased results show that the flaming phase had the highest BC emission rate, the fuel addition phase was associated with the highest BC EF. The BC emission rates and EFs for the ignition, fuel addition, flaming and smoldering phases ranged from 0.0014–0.014, 0.11–6.32, 0.18–2.24 and 0.03–0.32 mg s−1, and from 0.04–0.18, 0.38–9.53, 0.45–3.55 and 0.12–1.01 g kg−1, respectively. This study assessed the BC emissions from residential biofuel stoves using a larger sample size than in prior work. The results increase our understanding of the BC emissions process, which is helpful in terms of improving the accuracy of BC EF estimations. The real-time measurement process described herein is also expected to provide new approaches to minimizing BC emissions.

Microorganisms play important roles in the degradation of volatile organic compounds. Aeromonas salmonicida strain (AEP-3) generated from biomass in the citric acid fermentation industry was screened and subjected to denaturing gradient gel electrophoresis (DGGE) fingerprinting and 16S rDNA gene sequencing. The growth conditions of AEP-3 in Luria-Bertani broth were optimized at 25 °C and approximately pH 7. AEP-3 was used to degrade ethyl formate, propionic aldehyde, or acetone alone and their mixture. The concentrations of ethyl formate, propionic aldehyde, and acetone were below 7500, 600, and 800 mg L-1, respectively, and their maximum degradation efficiencies were 100%, 92.41%, and 34.75%. AEP-3 first degraded acetone and propionic aldehyde in the mixture, followed by ethyl formate. The degradation pathways of these organic compounds in the mixture and their substrate interactions during degradation were explored. Propionic aldehyde was first converted into propionic acid in the metabolic process and was involved in the subsequent carboxylic acid cycle. By contrast, ethyl formate was first hydrolyzed into formic acid and ethanol. Then, formic acid participated in the cyclic metabolism of carboxylic acid, whereas, ethanol was hydrolyzed into acetaldehyde and acetic acid through alcohol and aldehyde dehydrogenase. Additionally, acetone directly interacted with nitrate in the medium under the action of hydrogen ions and produced carbon dioxide, water, and nitrogen. Overall, this study provides a new degrading bacterium biodegradability toward the exhaust gas of citric acid fermentation.

To study the formation process of secondary organic aerosols (SOA) in a vehicle exhaust plume near the exhaust gas discharge outlet, a new multipoint sampling system was established. The system has five sampling heads and includes a particulate matter multi-channel film sampling system, a CO2/CO analyzer system, a volatile organic compound (VOC) sampling system, a particulate matter real-time analyzer system, and sensor interfaces. The vehicle exhaust near the exhaust nozzle can be sampled at multiple locations simultaneously using the new multipoint sampling system. Additionally, the system can be used to measure and analyze variations in the fine particulate matter, including the carbonaceous and ionic components, and organic compounds in the plume near the exhaust nozzle. This paper introduces the construction and application of the multipoint sampling system. The motor vehicle exhaust multipoint sampling system is reliable and can accurately capture the characteristics of the exhaust plume near the discharge outlet area. Changes in the CO2 concentration were used to determine whether exhaust was accurately collected at the sampling points. The relationship between the dilution rate and distance was calculated on the basis of on-road test results using the following equation: DR = 21.4X1.16. This equation can be used for modeling purposes, especially in comparisons of model results and observations and in the evaluation of dispersion models.

Polycyclic aromatic hydrocarbon (PAH) and nitro-polycyclic aromatic hydrocarbon (NPAH) emissions from 18 diesel trucks of different sizes and with different emission standards were tested in Beijing using a portable emission measurement system (PEMS). Both the gaseous- and particulate-phase PAHs and NPAHs were quantified by high-performance liquid chromatography (HPLC) in the laboratory. The emission factors (EFs) of the total PAHs from light-duty diesel trucks (LDDTs), medium-duty diesel trucks (MDDTs) and heavy-duty diesel trucks (HDDTs) were 82229.11 ± 41906.06, 52867.43 ± 18946.47 and 93837.35 ± 32193.14 μg/km, respectively, much higher than the respective values of total NPAHs from their counterpart vehicles. The gaseous phase had an important contribution to the total PAHs and NPAHs, with a share rate of approximately 69% and 97% on average, respectively. The driving cycle had important impacts on the emissions of PAHs and NPAHs, especially for LDDTs and HDDTs. Higher emissions of PAHs and NPAHs were detected on non-highway roads compared to that on highways for these two types of vehicles. Compared to the results of different studies, the difference in the EFs of PAHs and NPAHs can reach several orders of magnitudes, which would introduce errors in the development of an emission inventory of PAHs and NPAHs.

The concentrations and characteristics of 16 polycyclic aromatic hydrocarbons (PAHs) in 48 oil samples randomly collected from 30 catering services that employ six cooking methods were quantified via high-performance liquid chromatography (HPLC). These 16 PAHs were detected in almost all of the samples. The levels of Σ16PAHs, Σ4PAHs, benzo[a]pyrene (BaP), and total BaP equivalents (ΣBaPeq) for the six cooking methods exceeded the legal limit. The concentrations of Σ4PAHs were approximately 9.5 to 16.4 times the legal limit proposed by the European Commission (Off J Eur Union 215:4-8, 2011), and the level of BaP exceeded the national standard in China by 4.7- to 10.6-fold, particularly in oil from fried foods. Low molecular weight PAHs (LMW PAHs) were predominant in fried food oil from different catering services and accounted for 94.8 % of these oils, and the ΣBaPeq of the high molecular weight PAHs (HMW PAHs) was 11.5-fold higher than that of the LMW PAHs. The concentrations of Σ16PAHs (3751.9-7585.8 μg/kg), Σ4PAHs (144.6-195.7 μg/kg), BaP (79.7-135.8 μg/kg), and ΣBaPeq (231.0-265.4 μg/kg) were highest in the samples from fast food restaurants/buffets (FB), followed by those from fried food stalls (FS) and then cooking restaurants/cafeterias (RC). The results of this study suggest that the government should strengthen control and supervision of PAH contamination in food and edible oils.

Changes in the 16 PAHs in rapeseed, soybean, peanut and olive oil during deep-frying were examined to evaluate PAH levels in edible oils and the effects of deep-frying time. Chicken nuggets and potatoes were deep-fried in four types of oil for 15, 30 and 45 min. PAH concentrations were quantified via high-performance liquid chromatography (HPLC). The results show that all four fresh (unused) edible oils contain PAHs (189.9–2754.8 μg/kg) and mainly low-ring (2- to 4-ring) PAHs. PAH concentrations in the edible oils increased with increasing deep-frying time, especially among the high-ring (5-ring and above) PAHs. The mean values of high-ring PAHs (5-ring and above) in the samples deep-fried for 45 min were 1.9-fold higher than the oil samples that were deep-fried for 15 min and 31.5-fold higher than the levels for the fresh oils. The mean concentrations of benzo[a]pyrene in the deep-fried peanut and olive oils were 6.1- and 5.2-fold, respectively, the control value established in China (10 μg/kg). Average levels of ∑4PAH (consisting of benzo[a]anthracene, chrysene, benzo[b]fluoranthene, and benzo[a]pyrene) for the two deep-fried oils also exceeded the maximum permitted limit (10 μg/kg) set by the European Union (9.2- and 6.8-fold higher, respectively). At present, regulations imposed in China limit only concentrations of benzo[a]pyrene. The results of this study show that more standards and regulations on PAHs in edible oils must be established. In addition, the repeated use of edible oils must be avoided.

The development of efficient materials and processes is a long-term goal for the integrated flue gas purification in industry. In this study, a large-size V-based catalytic filter (L3000 mm &times, &Phi, 150 mm) was prepared by loading the catalyst emulsion into a blank filter, which demonstrated excellent performance for simultaneously removing NOx, SOx and dust. The laboratory investigation found that the small catalytic particles, high catalyst loading and low face velocity could improve the DeNOx efficiency, and above 80% NO conversion could be achieved in the temperature range of 250&ndash, 400 &deg, C on the condition of &lt, 300 nm catalytic particle size, &gt, 7.41 wt % catalyst loading and &lt, 1.00 Nm/min face velocity. The negative effect of SO2/H2O was only observed below 300 &deg, C, and the dust had little negative effects on DeNOx efficiency except for the increase of pressure drop. Moreover, a 90-day industrial test of 2380 catalytic filters over 100,000 Nm3/h of flue gas (0.50 Nm/min) from a glass kiln demonstrated that the removal efficiency of both NOx and SOx could be maintained above 95% with great stability at 320&ndash, 350 &deg, C, and 99% dust could be removed with a pressure drop of less than 1.40 KPa. The results reported herein indicate the promising application prospect of large-size V-based catalytic filters for integrated flue gas purification in industry.

This work assessed the effects of biodiesel on carbonyl emissions from diesel trucks. Biodiesel converted from waste cooking oil was employed and mixed with commercial fossil diesel to produce four blends: B0 (pure conventional diesel fuel), B5 (5% v/v biodiesel), B20 (20% v/v biodiesel) and B100 (pure biodiesel). Four diesel trucks were tested under real-world conditions using a portable emissions measurement system, including one China III light-duty diesel truck (LDDT), one China IV LDDT, one China III heavy-duty diesel truck (HDDT) and one China IV HDDT. A driving cycle including highway (HW) and non-highway (NHW) driving conditions was employed and carbonyls were sampled using 2,4-dinitrophenylhydrazine cartridges and analyzed via high performance liquid chromatography. Seven carbonyl compounds were detected, and formaldehyde, acetaldehyde, acetone and butyraldehyde were the primary carbonyls. Total carbonyl emissions from the China III LDDT, China III HDDT and China IV HDDT vehicles with selective catalytic reduction decreased monotonically with increases in the biodiesel proportion, while the China IV LDDT with a particle oxidation catalyst system showed an increasing trend. With increases in the biodiesel proportions, complementary variations were observed in the proportions of formaldehyde and butyraldehyde obtained using the China III LDDT, China IV LDDT and China III HDDT vehicles. However, in the case of the China IV HDDT trials, the formaldehyde and acetaldehyde emissions exhibited complementary variations. Under different driving conditions, the effects of adding biodiesel on carbonyl emission factors were different. In China III LDDT trials, biodiesel reduced carbonyl emissions to a greater extent under HW conditions, but the opposite occurred in China III HDDT tests. Using the China IV LDDT vehicle, the emission factors did not increase as much during HW trials compared with NHW trials when the B5 and B20 fuels were used, but were significantly higher than the NHW values when pure biodiesel was employed. In China III LDDT data, the proportions of formaldehyde, acetaldehyde and butyraldehyde showed opposite variations under the two driving conditions. Using the China IV LDDT vehicle, a significant increase in formaldehyde and decrease in butyraldehyde were found during HW trials, but not NHW trials. Ozone formation potentials were obtained from carbonyls emission factors using the maximum incremental reactivity method and their variations were similar to those of the carbonyl emission factors.

A considerable amount of volatile organic compounds (VOCs) is emitted, and a vast amount of citric acid residue (CAR) waste is simultaneously produced during citric acid production. Thus, a suitable method realizing the clean production of citric acid must be developed. This study investigated the adsorption of the multicomponent VOCs in a homemade CAR waste-based activated carbon (CAR-AC). A fixed-bed experimental setup was used to explore the adsorption and desorption of single- and multi-component VOCs. Surface adsorption and diffusion molecular models with different defects were built to study the underlying adsorption and diffusion mechanisms of multicomponent VOCs on CAR-AC. The adsorption amount of ethyl acetate in CAR-AC from multicomponent VOCs was 3.04 and 5.91 times higher than those of acetone and acetaldehyde, respectively, and the interaction energy between ethyl acetate and C surfaces was low at −13.41 kcal/mol. During desorption, the most weakly adsorbed acetaldehyde desorbed from the surface of CAR-AC first, followed by acetone and ethyl acetate. The regeneration efficiencies of acetaldehyde, acetone, and ethyl acetate reached 88.77, 85.55, and 91.46 %, respectively, after four adsorption/desorption cycles. We aimed to provide a new strategy to realize the recycle use of CAR and the clean production of citric acid.

The polycyclic aromatic hydrocarbon (PAH) and nitro-polycyclic aromatic hydrocarbon (NPAH) emissions from 16 gasoline passenger cars, encompassing five emission standards and two driving conditions, were tested using a portable emission measurement system (PEMS) in Beijing under on-road conditions. In total, 16 PAHs and 9 NPAHs were quantified in both the gaseous and particulate phases by high-performance liquid chromatography (HPLC). The results indicated that lower PAH and NPAH emissions were observed with improved emission standards, especially for China 3 to China 5 vehicles (P 0.05). Higher emission factors (EFs) were detected on nonhighway roads than on highway roads due to incomplete combustion. Although most PAHs and NPAHs were in the gas-phase, the TEQ

This study is the third in a series of three papers aimed at characterizing the VOC emissions of vehicles in Beijing. In this study, 30 light-duty vehicles fueled with gasoline were evaluated using a portable emission measurement system (PEMS) as they were driven on a predesigned, fixed test route. All of the tested vehicles were rented from private vehicle owners and spanned regulatory compliance guidelines ranging from Pre-China I to China IV. Alkanes, alkenes, aromatics and some additional species in the exhaust were collected in Tedlar bags and analyzed using gas chromatography/mass spectrometry (GC–MS). Carbonyls were collected on 2,4-dinitrophenyhydrazine (DNPH) cartridges and analyzed using high-performance liquid chromatography (HPLC). Overall, 74 VOC species were detected from the tested vehicles, including 22 alkanes, 6 alkenes, 1 alkyne, 16 aromatics, 3 cyclanes, 10 halohydrocarbons, 12 carbonyls and 4 other compounds. Alkanes, aromatics and carbonyls were the dominant VOCs with weight percentages of approximately 36.4%, 33.1% and 17.4%, respectively. The average VOC emission factors and standard deviations of the Pre-China I, China I, China II, China III and China IV vehicles were 469.3 ± 200.1, 80.7 ± 46.1, 56.8 ± 37.4, 25.6 ± 11.7 and 14.9 ± 8.2 mg/km, respectively, which indicated that the VOC emissions significantly decreased under stricter vehicular emission standards. Driving cycles also influenced the VOC emissions from the tested vehicles. The average VOC emission factors based on the travel distances of the tested vehicles under urban driving cycles were greater than those under highway driving cycles. In addition, we calculated the ozone formation potential (OFP) using the maximum incremental reactivity (MIR) method. The results of this study will be helpful for understanding the true emission levels of light-duty gasoline vehicles and will provide information for controlling VOC emissions from vehicles in Beijing, China.