Emissions Of Alkenes Research Articles

Atmospheric Oxidation Capacity Elevated during 2020 Spring Lockdown in Chengdu, China: Lessons for Future Secondary Pollution Control.

This study presents the measurement of photochemical precursors during the lockdown period from January 23, 2020, to March 14, 2020, in Chengdu in response to the coronavirus (COVID-19) pandemic. To derive the lockdown impact on air quality, the observations are compared to the equivalent periods in the last 2 years. An observation-based model is used to investigate the atmospheric oxidation capacity change during lockdown. OH, HO2, and RO2 concentrations are simulated, which are elevated by 42, 220, and 277%, respectively, during the lockdown period, mainly due to the reduction in nitrogen oxides (NOx). However, the radical turnover rates, i.e., OH oxidation rate L(OH) and local ozone production rate P(O3), which determine the secondary intermediates formation and O3 formation, only increase by 24 and 48%, respectively. Therefore, the oxidation capacity increases slightly during lockdown, which is partly attributed to unchanged alkene concentrations. During the lockdown, alkene ozonolysis seems to be a significant radical primary source due to the elevated O3 concentrations. This unique data set during the lockdown period highlights the importance of controlling alkene emission to mitigate secondary pollution formation in Chengdu and may also be applicable in other regions of China given an expected NOx reduction due to the rapid transformation to electrified fleets in the future.

Characterizing BVOC emissions of common plant species in northern China using real world measurements: Towards strategic species selection to minimize ozone forming potential of urban greening

Biogenic volatile organic compounds (BVOCs) emitted by plants play a crucial role in ozone (O3) formation. Avoiding urban air quality trade-offs of urban greening involves selecting low-emission and O3 forming potential (OFP) plants. Using a dynamic enclosure system and the TD-GC-MS technique, we measured BVOC emissions from 47 common urban greening plant species in northern China. The potential to form O3 was estimated based on the emission quantification of 63 compounds and their maximum incremental reactivity (MIR) values. The results indicated that isoprene and most of monoterpene dominated BVOC emissions. Most of the broad-leaved trees were isoprene emitter, whereas needle-leaved and some broad-leaved trees emitted monoterpene and sesquiterpene. Alkene emissions, such as 1-hexene, were relatively low, while Phoebe zhennan exhibited higher aromatics such as m-ethyltoluene. Broad-leaved trees had a higher potential for O3 generation compared to needle-leaved trees. BVOC emission rates and OFP varied significantly among plant species, ranging from 0.08 to 112.23 μg/(g h) and 0.33–1130.75 μg/(g h), respectively. To minimize BVOC emissions and O3 pollution, we determined a list of preferred urban greening plants using hierarchical cluster analysis combined BVOC emission rates and OFPs. Based on our findings, we recommend incorporating plants with low BVOC emissions and OFPs, such as Eucommia ulmoides, Firmiana platanifolia, and Cercis chinensis, in future urban greening plans to prevent strengthening O3 pollution in northern China.

Speciated VOCs emissions and ozone formation potential from on-road vehicles in North China Plain based on detailed and localized source profiles

One of China's most heavily ozone (O3) contaminated regions is the North China Plain (NCP). On-road vehicles are major contributors to volatile organic compound (VOC) emissions. We established localized speciated VOC emission inventories for 153 sub-sources using detailed and comprehensive source profiles based on local measurements. The survival ratio of the cars was used to perform a more accurate investigation of vehicle populations. The O3 formation potential (OFP) was calculated based on the speciated VOCs emissions, and key reactive species and sources were identified. Total VOC emissions and OFPs from the on-road vehicles in the NCP were 319.49 kt and 1480 kt, respectively. The emissions of alkanes, alkenes, alkynes, aromatics, halohydrocarbons, and oxygenated VOCs (OVOCs) were 130.53, 50.60, 14.21, 63.07, 3.42, and 57.67 kt, respectively. Formaldehyde, isopentane, and acetylene dominated emissions. Alkenes contributed the most to the OFPs, accounting for 34.47%, followed by aromatics and OVOCs. Formaldehyde, ethylene, and propene were the most common contributors to the OFPs. The emissions and OFPs varied by city, vehicle type, fuel type, and emission standards. Beijing and Xuzhou had the highest emissions, primarily because of their high vehicle populations, while Beijing and Tianjin had the highest OFPs. In addition, high emissions and OFP were detected in Jiangsu, Anhui, Shandong, and Henan (JASH) border areas, as well as in cities with developed industries such as Zhengzhou, Baoding, and Shijiazhuang. For both VOCs emissions and OFP, passenger car was the dominant source among the different vehicle types; petrol vehicle was the dominant source among various fuel types; vehicle under China 3 standard was the dominant source among different standards. The primary contributors to VOC emissions were 4-stroke petrol motorcycle (4-stroke < 250 cm3) under China 0 while the major sources to O3 pollution were heavy-duty diesel trucks with rigidities of 40–50 t under China 3 standard.

Influence of combined hydric and thermal stresses on Rosmarinus officinalis and Cistus albidus

Background Wildfires are a growing threat, especially in Mediterranean climate areas during periods of drought. The wildfire research community continues to investigate propagation mechanisms considering thermal transfer and fluid mechanics and sometimes a simplified chemistry taking into account the main combustion products such as CO, CO2, H2O, H2 and CH4. However, volatile organic compounds (VOCs) cannot be neglected and have a major role in vegetation ignition. Despite this, knowledge on the influence of wildfire on plant emissions remains lacking.Aims This work addresses the effect of combined hydric and thermal stresses on the physiology and emissions of Rosmarinus officinalis and Cistus albidus, which are widely consumed in Mediterranean wildfires.Methods Plants were submitted to hydric stress inside a greenhouse, then to thermal stress inside a heated hermetic enclosure while collecting emissions with adsorbent elements for analysis. Simultaneously, heating experiments were carried out with leaves sampled to analyse their emissions.Key results The heating tests showed significant variations in monoterpene, fatty acid and alkane emissions between stressed and unstressed plants with different results between Rosmarinus officinalis and Cistus albidus.Conclusion/implication Further experiments with other plant species and quantification of emissions may help to better know why Mediterranean wildfires are a particular threat and how to improve firefighting methods.

Emissions of biogenic volatile organic compounds from adjacent boreal fen and bog as impacted by vegetation composition

Peatland ecosystems emit biogenic volatile organic compounds (BVOC), which have a net cooling impact on the climate. However, the quality and quantity of BVOC emissions, and how they are regulated by vegetation and peatland type remain poorly understood. Here we measured BVOC emissions with dynamic enclosures from two major boreal peatland types, a minerotrophic fen and an ombrotrophic bog situated in Siikaneva, southern Finland and experimentally assessed the role of vegetation by removing vascular vegetation with or without the moss layer. Our measurements from four campaigns during growing seasons in 2017 and 2018 identified emissions of 59 compounds from nine different chemical groups. Isoprene accounted for 81 % of BVOC emissions. Measurements also revealed uptake of dichloromethane. Total BVOC emissions and the emissions of isoprene, monoterpenoids, sesquiterpenes, homoterpenes, and green leaf volatiles were tightly connected to vascular plants. Isoprene and sesquiterpene emissions were associated with sedges, whereas monoterpenoids and homoterpenes were associated with shrubs. Additionally, isoprene and alkane emissions were higher in the fen than in the bog and they significantly contributed to the higher BVOC emissions from intact vegetation in the fen. During an extreme drought event in 2018, emissions of organic halides were absent. Our results indicate that climate change with an increase in shrub cover and increased frequency of extreme weather events may have a negative impact on total BVOC emissions that otherwise are predicted to increase in warmer temperatures. However, these changes also accompanied a change in BVOC emission quality. As different compounds differ in their capacity to form secondary organic aerosols, the ultimate climate impact of peatland BVOC emissions may be altered.

Hydrocarbon Tracers Suggest Methane Emissions from Fossil Sources Occur Predominately Before Gas Processing and That Petroleum Plays Are a Significant Source.

We use global airborne observations of propane (C3H8) and ethane (C2H6) from the Atmospheric Tomography (ATom) and HIAPER Pole-to-Pole Observations (HIPPO), as well as U.S.-based aircraft and tower observations by NOAA and from the NCAR FRAPPE campaign as tracers for emissions from oil and gas operations. To simulate global mole fraction fields for these gases, we update the default emissions’ configuration of C3H8 used by the global chemical transport model, GEOS-Chem v13.0.0, using a scaled C2H6 spatial proxy. With the updated emissions, simulations of both C3H8 and C2H6 using GEOS-Chem are in reasonable agreement with ATom and HIPPO observations, though the updated emission fields underestimate C3H8 accumulation in the arctic wintertime, pointing to additional sources of this gas in the high latitudes (e.g., Europe). Using a Bayesian hierarchical model, we estimate global emissions of C2H6 and C3H8 from fossil fuel production in 2016–2018 to be 13.3 ± 0.7 (95% CI) and 14.7 ± 0.8 (95% CI) Tg/year, respectively. We calculate bottom-up hydrocarbon emission ratios using basin composition measurements weighted by gas production and find their magnitude is higher than expected and is similar to ratios informed by our revised alkane emissions. This suggests that emissions are dominated by pre-processing activities in oil-producing basins.

Emissions of gaseous pollutants released by forest fire in relation to litter fuel moisture content

The moisture content of forest floor fuel influences fire initiation and spread, but little is known about its impact on the emissions of pollutants. This study aimed to estimate quantitatively the characteristic change of pollutants emitted by forest fires at various fuel moisture content. Thus, litter fuel (both branches and leaves) of two dominant coniferous species (Cunninghamia lanceolata and Pinus massoniana) and two dominant broad-leaved species (Eucalyptus robusta and Cinnamomum camphora) in Southeast China were experimentally burned in an indoor biomass combustion facility, and smoke and non-methane hydrocarbons (NMHCs) were analyzed by gas chromatography-mass spectrometry. The results showed that CO, CO2, NOx, and SO2 reached peak concentrations faster at low moisture content. However, emission factors of CO increased, whereas emission factors of CO2, NOx, and SO2 decreased as the moisture content of fuels increased. Emission factors of CO, CO2, NOx and SO2 released from combustion of conifer fuels significantly increased with fuel moisture content compared to broad-leaved fuels. Total NMHCs emission was positively affected by the fuel moisture content. As the moisture content of the fuels increased, multi-branched and long-chain alkane emissions increased, whereas olefin and aromatic hydrocarbon emissions decreased but emissions of olefins and aromatic hydrocarbons with more branched chains increased. The findings provide valuable insight about the impact of forest fire on atmospheric environment and fire prevention measures.

Investigating the mechanism of morning ozone concentration peaks in a petrochemical industrial city

The temporal variation in ground-level ozone (O3) is influenced by photochemical reactions associated with solar radiation and usually culminates in the afternoon. However, Lanzhou, a petrochemical industrial city located in a river valley in northwestern China, often experiences morning O3 concentration peaks, which has not been reported in previous studies. We defined the morning ozone peak (MOP) phenomenon as a daily maximum hourly O3 concentration that occurs in the morning (9:00–12:00, local time). Observations from May to August 2015–2018 showed that the proportion of MOP days to the total number of days was 32.5% at the LH station in Lanzhou. The Weather Research and Forecasting model coupled with chemistry (WRF-Chem) was employed to clarify the physical and chemical causes of the MOP phenomenon in the summer of 2016. Compared to the observations, the WRF-Chem model reproduced local meteorological circulation conditions and performed well in MOP simulations. The results indicated that the mountain topography and urban underlying surface did not alter the morning peak of O3. On MOP days, the contributions of photochemical reactions and the vertical downward transport of O3 to MOP formation were 60.2% and 39.8% at the LH station, respectively. Alkenes accounted for more than 65% of the initial VOC reactivity. The MOP phenomenon disappeared after alkenes emitted from the petrochemical industry were deactivated. Therefore, to control MOP events in Lanzhou, we should focus on alkene emissions reduction. This study is highly important to better understand the mechanism of O3 formation and provides basic information for developing scientific O3 pollution control strategies and improving the air quality in industrial cities.

Long-term atmospheric emissions for the Coal Oil Point natural marine hydrocarbon seep field, offshore California

Abstract. In this study, we present a novel approach for assessing nearshore seepage atmospheric emissions through modeling of air quality station data, specifically a Gaussian plume inversion model. A total of 3 decades of air quality station meteorology and total hydrocarbon concentration, THC, data were analyzed to study emissions from the Coal Oil Point marine seep field offshore California. THC in the seep field directions was significantly elevated and Gaussian with respect to wind direction, θ. An inversion model of the seep field, θ-resolved anomaly, THC′(θ)-derived atmospheric emissions is given. The model inversion is for the far field, which was satisfied by gridding the sonar seepage and treating each grid cell as a separate Gaussian plume. This assumption was validated by offshore in situ data that showed major seep area plumes were Gaussian. Plume total carbon, TC (TC = THC + carbon dioxide, CO2, + carbon monoxide), 18 % was CO2 and 82 % was THC; 85 % of THC was CH4. These compositions were similar to the seabed composition, demonstrating efficient vertical plume transport of dissolved seep gases. Air samples also measured atmospheric alkane plume composition. The inversion model used observed winds and derived the 3-decade-average (1990–2021) field-wide atmospheric emissions of 83 400 ± 12 000 m3 THC d−1 (27 Gg THC yr−1 based on 19.6 g mol−1 for THC). Based on a 50 : 50 air-to-seawater partitioning, this implies seabed emissions of 167 000 m3 THC d−1. Based on atmospheric plume composition, C1–C6 alkane emissions were 19, 1.3, 2.5, 2.2, 1.1, and 0.15 Gg yr−1, respectively. The spatially averaged CH4 emissions over the ∼ 6.3 km2 of 25 × 25 m2 bins with sonar values above noise were 5.7 µM m−2 s−1. The approach can be extended to derive emissions from other dispersed sources such as landfills, industrial sites, or terrestrial seepage if source locations are constrained spatially.

Simulation of ozonolysis of volatile organic compounds: Effect on flue gas composition

This study shows that the reaction of ozone with various volatile organic compounds (VOC) yields different flue gas composition in terms of the carbon dioxide, oxygen and moisture contents. Steam production and thermal output requirements from a combustion system (i.e., a boiler) may dictate the range of operating conditions, such as the air to fuel mass flow rates. To improve the combustion efficiency in these operating conditions, low temperature plasmas have been used to ionize air and generate ozone as an oxidant for ozonolysis with the VOC. Therefore, this study simulates the reaction mechanism of the ozonolysis of VOC and the effect on the flue gas composition, which affects the combustion efficiency. Simulation results show that residual oxygen in the flue gas reduces, reducing the excess air. Thus, the corresponding efficiency loss through dry flue gas would be reduced. Literature data shows that emissions of alkanes, alkynes and alkenes per unit mass of solid fuel is evident for both coal and biomass, and thus ozonolysis of these VOC would reduce the excess air, improving the combustion efficiency.

Sensitivities of Ozone Air Pollution in the Beijing-Tianjin-Hebei Area to Local and Upwind Precursor Emissions Using Adjoint Modeling.

Effective mitigation of surface ozone pollution entails detailed knowledge of the contributing precursors' sources. We use the GEOS-Chem adjoint model to analyze the precursors contributing to surface ozone in the Beijing-Tianjin-Hebei area (BTH) of China on days of different ozone pollution severities in June 2019. We find that BTH ozone on heavily polluted days is sensitive to local emissions, as well as to precursors emitted from the provinces south of BTH (Shandong, Henan, and Jiangsu, collectively the SHJ area). Heavy ozone pollution in BTH can be mitigated effectively by reducing NOx (from industrial processes and transportation), ≥C3 alkenes (from on-road gasoline vehicles and industrial processes), and xylenes (from paint use) emitted from both BTH and SHJ, as well as by reducing CO (from industrial processes, transportation, and power generation) and ≥C4 alkanes (from industrial processes, paint and solvent use, and on-road gasoline vehicles) emissions from SHJ. In addition, reduction of NOx, xylene, and ≥C3 alkene emissions within BTH would effectively decrease the number of BTH ozone-exceedance days. Our analysis pinpoint the key areas and activities for locally and regionally coordinated emission control efforts to improve surface ozone air quality in BTH.

Impacts of Emissions of C2‐C5 Alkanes From the U.S. Oil and Gas Sector on Ozone and Other Secondary Species

AbstractInside many U.S. oil and gas‐producing regions, the oil and gas sector dominates local anthropogenic emission fluxes of C2‐C5 alkanes. Here, we present a detailed analysis of the impact of these emissions on secondary species production over the continental United States using the GEOS‐Chem model. Oil‐ and gas‐producing areas in the central United States show the highest summertime surface ozone (O3) enhancements due to oil and gas C2‐C5 alkane emissions. The Colorado Front Range is the most impacted 8‐hr O3 non‐attainment area in the United States with 3‐hr daytime instantaneous O3 enhancements &gt;4 ppb. From three selected non‐attainment areas, the Colorado Front Range has (1) the lowest monthly mean VOC reactivity (1.5 s−1); (2) the highest percent contribution of oil and gas sources (52%) to calculated VOC reactivity; and (3) the largest relative increases in PAN (peroxyacetyl nitrate), PPN (peroxypropionyl nitrate), and &gt;C4 alkyl nitrates. Enhanced abundances of PAN, PPN, and &gt;C4 alkyl nitrates have the potential to perturb remote O3 production through increased NOx export to remote regions via PAN chemistry. Globally, simulated C2‐C5 alkane emissions from the U.S. oil and gas sector contribute 0.5 Tg (~0.17%) to the tropospheric O3 burden with a ~0.27% contribution in the Northern Hemisphere.

Emissions and potential controls of light alkenes from the marginal seas of China

Marine-derived reactive gases constitute a substantial fraction of volatile organic compounds and directly impact atmospheric chemistry and the global climate. Light alkene emissions from marginal seas are limited, and their contribution to atmospheric concentrations is likely underestimated. We surveyed oceanic emissions of ethylene, propylene, and isoprene, as well as their potential controlling factors in the marginal seas of China during the cruises in 2014–2015. Significant temporal-spatial variations in ethylene, propylene, and isoprene concentrations were observed, with the highest occurring in summer near the coastal regions. Isoprene concentrations were primarily controlled by phytoplankton biomass (i.e., Chl-a) in coastal regions, while the elevated concentrations of ethylene and propylene were attributed to photochemical reactions with the high levels of dissolved organic matter (DOM). Additionally, the vertical distributions of ethylene and propylene mirrored light penetration, with exponential decrease in concentrations with depth. However, there were high values of ethylene and propylene observed at deep chlorophyll maximum, suggesting the existence of non-photochemical production pathways, most likely biological origin. Emissions of ethylene, propylene, and isoprene from the marginal seas of China were estimated to be 0.022, 0.024, and 0.011 Tg C yr−1, respectively, indicating they are important contributors to global non-methane hydrocarbons. Due to the scarcity of alkene emission data for marginal seas, current global emissions have been underestimated to some extent. It is essential to incorporate the contributions from marginal seas to accurately estimate alkene budgets on global scales.

Research on emissions controlling of coal-made Fischer–Tropsch process diesel/methanol unconventional pollutants

ABSTRACT Thirty unconventional gaseous substances in Fischer–Tropsch process diesel/methanol-mixed fuel with different methanol blending ratios were measured and classified for diesel engine pollutant discharge. The measurement results showed high concentrations of several unconventional pollutants, including propylene, 1,3 butadiene, acrolein, benzene, toluene, ethylbenzene, and xylene, accounting for approximately 83% of the total concentration. The methanol blending ratio was increased from 0 to 15%, the amounts of unconventional pollutants such as olefins, alkanes, and aromatic hydrocarbons were decreased by 38.4%, 27.7%, and 23.7%, respectively, and the amounts of aldehydes and ketones were increased by 31.2%. The amounts of unconventional pollutants such as 1,3 butadiene, n-hexane, and benzene were decreased by 36.6%, 28.8%, and 29.2%, and the amount of acrolein was increased by 28.7%. At maximum torque, aromatic hydrocarbon emissions were reduced by 23.8%, aldehyde and ketone emissions were reduced by 44.8%, olefin emissions were increased by 142.8%, and alkane emissions were reduced by 14.5%; compared to maximum torque conditions, olefins under calibration category emissions were increased by 41.2%, alkane emissions were increased by 8.8%, aromatic hydrocarbon emissions were increased by 9.5%, and aldehyde and ketone emissions were increased by 25%.

Experimental study of regulated and unregulated emissions from a diesel engine using coal-based fuels

Both methanol and F-T diesel can be made from coal. The use of coal-based fuels can increase coal utilization and promote the diversified development of diesel fuel. Based on F-T diesel, this study prepared coal-based fuels with methanol volume fractions of 0%, 5%, 10%, and 15%, respectively, which are represented by FM0, FM5, FM10, and FM15. The emissions of regulated and unregulated pollutants were measured on a non-road high-pressure common-rail four-cylinder turbocharged inter-cooled diesel engine. The results showed that at the rated speed (2100r/min), blending methanol with F-T diesel reduced NOX emissions and smoke emissions, but increased CO and HC emissions. Under maximum torque condition (1500r/min, 100%), the total emissions of alkanes, alkenes, aromatic hydrocarbons (AHs) and carbonyl compounds (CBCs) using FM10 are the lowest. Under nominal operating condition (2100r/min, 100%), compared with FM0, the emissions of alkanes, olefins and AHs generated by FM15 were reduced by 28.0%, 38.3% and 23.7%, respectively, and the emissions of CBCs were increased by 31.3%. Compared with other test fuels, the use of FM15 has the smallest O3 generation potential. When using FM10 fuel, the emissions of alkanes, AHs and CBCs were the highest under idle condition, and the emissions of olefins are highest during the nominal operating condition.

Exploring the inconsistent variations in atmospheric primary and secondary pollutants during the 2016 G20 summit in Hangzhou, China: implications from observations and models

Abstract. Complex aerosol and photochemical pollution (ozone and peroxyacetyl nitrate, PAN) frequently occur in eastern China, and mitigation strategies to effectively alleviate both kinds of pollution are urgently needed. Although the effectiveness of powerful control measures implemented by the Chinese State Council has been comprehensively evaluated in terms of reducing atmospheric primary pollutants, the effectiveness in mitigating photochemical pollution is less assessed and therefore the underlying mechanisms are still poorly understood. The stringent emission controls implemented from 24 August to 6 September 2016 during the summit for the Group of Twenty (G20) provide us a unique opportunity to address this issue. Surface concentrations of atmospheric O3, PAN, and their precursors including volatile organic compounds (VOCs) and nitrogen dioxides (NOx), in addition to the other trace gases and particulate matter, were measured at the National Reference Climatological Station (NRCS) (30.22∘ N, 120.17∘ E, 41.7 m a.s.l) in urban Hangzhou. We found significant decreases in atmospheric PAN, NOx, total VOCs, PM2.5, and sulfur dioxide (SO2) under the unfavorable meteorological conditions during G20 (DG20) relative to the adjacent period before and after G20 (BG20 and AG20), indicating that the powerful control measures were effective in reducing the pollutant emissions in Hangzhou. Unlike with the other pollutants, daily maximum 8 h average (DMA8) O3 exhibited a slight increase and then decrease from BG20 to AG20, which was mainly attributed to the variation in the solar irradiation intensity and regional transport in addition to the contribution from the implementation of stringent control measures. Results from an observation-based chemical model (OBM) indicated that acetaldehyde and methylglyoxal (MGLY) were the most important second-generation precursors of PAN, accounting for 37.3 %–51.6 % and 22.8 %–29.5 % of the total production rates including the reactions of OVOCs, propagation of other radicals, and other minor sources. Moreover, we confirmed the production of PAN and O3 was sensitive to VOCs throughout the whole period, specifically dominated by aromatics in BG20 and DG20 but by alkenes in AG20. These findings suggested that reducing emissions of aromatics, alkenes, and alkanes would mitigate photochemical pollution including PAN and O3. Source appointment results attributed the reductions of VOC source and ozone formation potentials (OFPs) during G20 to the effective emission controls on traffic (vehicle exhaust) and industrial processes (solvent utilization and industrial manufacturing). However, fuel combustion and biogenic emissions both weakened such an effect with a sizable contribution to the VOC mixing ratios (18.8 % and 20.9 %) and OFPs (25.6 % and 17.8 %), especially during the latter part of G20 (G20 II) when anthropogenic VOCs were substantially reduced. This study highlights the effectiveness of stringent emission controls in relation to traffic and industrial sources, but a coordinated program related to controlling fuel combustion and biogenic emissions is also required to address secondary pollution.

Characterization of VOC emissions from construction machinery and river ships in the Pearl River Delta of China

Speciated characterization of Volatile Organic Compounds (VOCs), including oxygenated VOCs (OVOCs), from construction machinery and river ships in China is currently lacking. In this regard, we conducted field measurement on speciated VOC (including OVOC) emissions from six construction machinery and five river ships in the Pearl River Delta (PRD) region to identify VOC emission characteristics. We noticed that OVOC emissions from construction machinery and ships accounted for more than 50% of the total VOC emissions, followed by alkenes, aromatics and alkanes. Formaldehyde and acetaldehyde were the most emission species, accounting for 61.8%-83.2% of OVOCs. For construction machinery, the fuel-based emission factors of roller, grader and pile driver were 3.12, 3.12 and 7.36 g/kg, respectively. With the rigorous restraint by the national emission standards, VOC emissions of construction machinery had decreased considerably, especially during stage Ⅲ. Ozone formation potential was also significantly reduced due to the significant decrease in emissions of OVOCs and alkenes with higher reactivity. For river ships, the fuel-based emission factors of cargo ships and speedboat were 1.46 and 0.44 g/kg, respectively. VOC emissions from construction machinery and river ships in Guangdong Province in 2017 were 8851.0 and 4361.0 ton, respectively. This study filled the knowledge gaps of reactive gas emissions from different kinds of non-road mobile sources over the PRD, and more importantly, highlighted the necessity in adding OVOC measurement to give a complete and accurate depiction of reactive gas emissions from non-road mobile sources.

Explicit modeling of background HCHO formation in southern China

Abstract Formaldehyde (HCHO) is an abundant carbonyls and plays important roles in ozone formation and atmospheric oxidizing capacity. To better understand the formation mechanisms of HCHO and its effects on ozone formation, carbonyl compounds were measured at a regional background site of Hong Kong from 20 August to 22 December 2012. Among the total observed carbonyls, Formaldehyde (HCHO, 2.00 ± 1.04 ppbv) presents the most abundant concentration and plays the most important role in OH removal with LOH value of 0.47 s−1. To further dissect the secondary formation mechanism of HCHO at Hok Tsui, detailed modeling analyses were conducted by the OBM-AOCP model for two cases with different meteorological conditions. The result shows that HCHO production was dominated by the reactions of CH3O + O2, and RO + O2 (first-generation precursor of RO was Alkenes). The HCHO destruction pathways during two cases were governed by the reactions with OH and photolysis. The net generation rate of HCHO was controlled by meteorological conditions with alkenes (mainly ethylene (C2H4) and propylene (C3H6)) being the dominant parent hydrocarbons of HCHO. Overall, this study provides some new insights into the formation mechanisms of HCHO, especially their parent hydrocarbon species, underlines the important role of carbonyls in ozone pollution in Hok Tsui. Reducing the emissions of alkenes would be an effective way to mitigate photochemical pollution in the background atmosphere of China.

Compilation of emission inventory and source profile database for volatile organic compounds: A case study for Sichuan, China

The purpose of this paper is to develop an emission inventory and source profile database for volatile organic compounds (VOCs) in Sichuan Province. Based on the test data of the research literatures, the source profiles of species containing no oxygenated volatile organic compounds (OVOCs) were revised and reconstructed to obtain the normalized VOCs source profile. In addition, the source profile-based 1 km × 1 km speciated VOCs emission inventory was established in accordance with the 2015 Air Pollution Source Emission Inventory in Sichuan Province with the ozone formation potential (OFP) estimated to assess the impact on ozone formation. There were 45 profiles and 519 species included in the established VOCs source profile database. Since the profiles were established mainly based on domestic test data, foreign research results were employed to supplement the profiles of some sources that had not been actually tested or had been researched less in China. In addition, the profiles of some sources such as biomass burning and transportation with emissions containing rich OVOCS have been revised and reconstructed, and the profiles including redundant data of many tested sources were simplified accordingly as well. Therefore, the established source profile database is well applicable to the establishment of the speciated VOCs emission inventory and the source apportionment. The VOCs emission inventory showed that the anthropogenic emissions of alkanes, alkenes, alkynes, aromatics, OVOCs, halohydrocarbons and other VOCs in Sichuan Province were 167.1 kt, 77.4 kt, 13.2 kt, 216.7 kt, 202.7 kt, 32.5 kt and 64.2 kt respectively; the total OFP in Sichuan was 2584.9 kt, and the above-mentioned VOCs contributed 6.9%, 26.1%, 0.5%, 42.3%, 23.2%, 0.4% and 0.5% to the total OFP, respectively. Therefore, alkenes, aromatics and OVOCs were the major species for ozone formation among the VOCs emitted in Sichuan Province, and controlling the emissions of such species plays a key role in reducing ozone formation. The major VOCs species emitted in various cities of Sichuan Province were aromatics, OVOCs and alkanes; however, different cities have their own remarkable characteristics. VOCs emissions and major OFP contributing species in Sichuan Province were mainly distributed in the Sichuan Basin as well as some areas in Liangshan and Panzhihua, where the population was relatively dense and the industry was relatively developed. The main source of m-Xylene and toluene was solvent use; therefore, m-Xylene and toluene were more intensively distributed in urban built-up areas. Furthermore, since biomass burning contributed a lot to ethene and formaldehyde emissions, ethene and formaldehyde were substantially distributed in cultivated areas in eastern Sichuan and southern Sichuan.

Speciated VOCs Emission Inventory and Ozone Formation Potential in Sichuan Province

Based on the measured data in the literature, VOCs (volatile organic compounds) source profiles were revised and reconstructed without OVOCs (oxygenated volatile organic compounds) species to obtain the normalized VOCs source profiles. Using the 2015 Sichuan emission inventory, source profiles based on the 1 km×1 km gridded speciated VOCs emission inventory were developed, and the ozone formation potentials of the species were estimated to assess the environmental impact on ozone formation. The established VOCs source profile database consists of 45 source profiles and 519 species. Since the source profiles were established based on the revision and reconstruction of pollution sources, such as biomass burning and transportation, that are rich in OVOCs, the source profile database is better applicable to establishing the speciated VOCs emission inventory and source apportionment. The speciated VOCs emission inventory showed that the total anthropogenic emission of VOCs in Sichuan Province was 773.8 kt, of which the emissions of alkanes, olefins, alkynes, aromatics, OVOCs, halohydrocarbons, and other VOCs accounted for 21.6%, 10.0%, 1.7%, 28.0%, 26.2%, 4.2%, and 8.3% of the total respectively. The total OFP (Ozone formation potential) was 2584.9 kt, of which the OFPs of the VOCs groups mentioned above accounted for 6.9%, 26.1%, 0.5%, 42.3%, 23.2%, 0.4%, and 0.5% respectively. The main VOCs species emitted in all cities of Sichuan Province were aromatics, OVOCs, and alkanes; however, there were some significant regional differences:transportation in Chengdu, Ya'an, Aba, Ganzi, and Liangshan made a greater contribution to VOCs emissions, with alkane emissions accounting for a higher proportion in the total VOCs emission. As a heavy industrial city, Panzhihua suffered most from emissions from industrial processes, which contain a relatively high proportion of alkanes. Solvent use in Deyang, Meishan, Suining, and Ziyang made a great contribution to the VOCs emissions, and the OVOCs emission was relatively high. Emissions of VOCs and species with relatively high OFPs in Sichuan Province were mainly distributed in the Sichuan Basin, which has a dense population and highly developed industry, as well as some areas in Liangshan and Panzhihua. The main source of m-xylene and toluene was solvent use; therefore, m-xylene and toluene were relatively concentrated in developed urban areas. In addition, biomass burning contributed greatly to the emissions of ethene and formaldehyde; therefore, ethene and formaldehyde were mainly distributed in the cultivated areas of agriculturally advanced Eastern Sichuan and Southern Sichuan.