Total Non-methane Volatile Organic Compounds Research Articles

Wintertime ozone surges: The critical role of alkene ozonolysis

Ozone (O3) pollution is usually linked to warm weather and strong solar radiation, making it uncommon in cold winters. However, an unusual occurrence of four high O3 episode days (with maximum hourly concentrations exceeding 100 ppbv and peaking at 121 ppbv) was recorded in January 2018 in Lanzhou city, China. During these episodes, the average daytime concentration of total non-methane volatile organic compounds (TVOCs) reached 153.4 ± 19.0 ppbv, with alkenes—largely emitted from the local petrochemical industry—comprising 82.3 ± 13.1 ppbv. Here we show a photochemical box model coupled with a Master Chemical Mechanism to elucidate the mechanisms behind this unusual wintertime O3 pollution. We find that the typically low temperatures (−1.7 ± 1.3 °C) and weak solar radiation (263.6 ± 60.7 W m-2) of those winter episode days had a minimal effect on the reactivity of VOCs with OH radicals. Instead, the ozonolysis of alkenes generated Criegee intermediates, which rapidly decomposed into substantial ROx radicals (OH, HO2, and RO2) without sunlight. This radical production led to the oxidation of VOCs, with alkene ozonolysis ultimately contributing to 89.6 ± 8.7% of the O3 formation during these episodes. This mechanism did not activate at night due to the depletion of O3 by the NO titration effect. Furthermore, the findings indicate that a reduction of alkenes by 28.6% or NOx by 27.7% in the early afternoon could significantly mitigate wintertime O3 pollution. Overall, this study unravels the unique mechanism of alkene-induced winter O3 pollution and offers a reference for winter O3 reduction strategies in the petrochemical industrial regions.

VOC emissions from Euro 6 vehicles

BackgroundAir pollution is a major health concern in worldwide. Non-methane volatile organic compounds (NMVOCs) are precursors of secondary air pollutants, with road transport being responsible of ~ 90% for the EU-27’s NMVOCs transport emissions in 2021. A series of VOC emissions from 17 modern gasoline, Diesel and Plug-in hybrid (PHEV) vehicles were investigated under various driving conditions and temperatures. All tested vehicles meet the latest European emission standard (Euro 6d and Euro 6d-TEMP). The different VOC species were measured with a Fourier-Transform Infrared Analyzer (FTIR).ResultsDiesel vehicles presented the lowest VOC emissions, while PHEVs operating in charge sustaining mode, with a depleted battery, exhibited very similar behavior to conventional gasoline. Among the VOCs, C5 compounds were the primary contributors to total NMVOCs over WLTC at 23 °C for gasoline and PHEV vehicles. A proportional increase in VOC emissions at colder temperatures, affecting all the studied species, was observed. Significant increases were observed for Aromatics, with an important contribution of < C5 as well. On the other hand, VOC emissions from Diesel vehicles were consistently low and little affected by temperature, except for Aldehydes in tests at − 7 °C. VOC emissions primarily occurred during cold starts, with urban cycle showing higher emission factors due to its shorter distance. VOC emissions remained consistently low during the highway cycle, highlighting a significant reduction in VOC emissions once the after-treatment system (ATS) was warmed up, even under demanding conditions. In Diesel vehicles, total VOCs measured with the FTIR exhibited a slight tendency to exceed Total Hydrocarbons (THC) measured with a Flame Ionization Detector (FID), while for gasoline vehicles and PHEVs, the trend was temperature-dependent.ConclusionsIn summary, the study shows that VOC emissions from Diesel vehicles are significantly lower compared to modern gasoline and PHEV vehicles. Moreover, gasoline and PHEV vehicles exhibit similar levels and emission profiles of VOC emissions. Additionally, ambient temperatures and driving conditions have a significant impact on VOC emissions for all the powertrain technologies investigated.

Observing Downwind Structures of Urban HCHO Plumes From Space: Implications to Non‐Methane Volatile Organic Compound Emissions

AbstractNon‐methane volatile organic compounds (NMVOCs) have a significant impact on air quality in urban areas. Detecting NMVOCs emission with its proxy HCHO on urban scales from space, however, has been limited by the lack of discernible enhancement. Here we show clear urban HCHO plumes from 16 cities over the globe by rotating TROPOspheric Monitoring Instrument HCHO pixels according to wind directions. We fit the downwind structure of the plumes with the exponentially modified Gaussian approach to quantify urban HCHO effective production rates between 7.0 and 88.5 mol s−1. Our results are in line with total NMVOC emissions from the EDGAR inventory (r = 0.76). Our work offers a new measure of total NMVOC emissions from urban areas and highlights the potential of satellite HCHO data to provide new information for monitoring urban air quality.

Real-time measurements of non-methane volatile organic compounds in the central Indo-Gangetic basin, Lucknow, India: source characterisation and their role in O3 and secondary organic aerosol formation

Abstract. Lucknow is the capital of India's largest state, Uttar Pradesh, one of South Asia's most polluted urban cities. Tropospheric photochemistry relies on non-methane volatile organic compounds (NMVOCs), which are ozone and secondary organic aerosol precursors. Using the proton-transfer reaction time-of-flight mass spectrometer (PTR-ToF-MS) at an urban background site in Lucknow, the chemical characterisation of NMVOCs was performed in real time from December 2020 to May 2021. About ∼ 173 NMVOCs from m/z 31.018 to 197.216 were measured during the study period, including aromatics, non-aromatics, oxygenates, and nitrogen-containing compounds. The campaign daily mean concentrations of the NMVOCs were 125.5 ± 37.5 ppbv. The NMVOC daily average concentrations were about ∼ 30 % higher during the winter months (December–February) than in summer (March–May). The oxygenated volatile organic compounds and aromatics were the dominant VOC families, accounting for ∼ 57 %–80 % of the total NMVOC concentrations. Acetaldehyde, acetone, and acetic acid were the major NMVOC species, 5–15 times higher than the other species. An advanced multi-linear engine (ME-2) model was used to perform the NMVOC source apportionment using positive matrix factorisation (PMF). It resolves the five main sources contributing to these organic compounds in the atmosphere. They include traffic (23.5 %), two solid fuel combustion factors, SFC 1 (28.1 %) and SFC 2 (13.2 %), secondary volatile organic compounds (SVOCs) (18.6 %), and volatile chemical products (VCPs) (16.6 %). Aged and fresh emissions from solid fuel combustion (SFCs 1 and 2) were the dominant contributors to the total NMVOCs, and compounds related to these factors had a high secondary organic aerosol (SOA) formation potential. Interestingly, the traffic factor was the second-highest contributor to the total NMVOCs, and compounds related to this factor had a high ozone formation potential. Significant differences in the composition of the two solid fuel combustions indicate the influence of local emissions and transport of regional pollution to the city. The high temperature during summer leads to more volatilisation of oxygenated VOCs, related to the VCP factor. The study is the first attempt to highlight the sources of NMVOCs and their contribution to secondary pollutant (SOA and O3) formation in the city of Lucknow during winter and summer. The insights from the study would help various stakeholders to manage primary and secondary pollutants within the city.

Reconciling the bottom-up methodology and ground measurement constraints to improve the city-scale NMVOCs emission inventory: A case study of Nanjing, China

Reliable emission estimate of non-methane volatile organic compounds (NMVOCs) is important for understanding the atmospheric chemistry and formulating control policy of ozone (O3). In this study, a speciated emission inventory of anthropogenic NMVOCs was developed with the refined “bottom-up” methodology and best available information of individual sources for Nanjing in 2017. The total NMVOCs emissions were calculated at 163.2 Gg. It was broken down into the emissions of over 500 individual species and aromatics took the largest fraction (33.3% of the total emissions). Meanwhile, 105 compounds were measured at 5 sites representing different functional zones of Nanjing for one year. The annual mean concentration of totally 105 species varied from 48.5 ppbv to 63.7 ppbv, and alkanes was the most abundant group with its mass fractions ranging 37.2–40.1% at different sites. Constrained by the emission ratios of individual species versus carbon monoxide (CO) based on ground measurement, the total emissions of 105 species (NMVOCs-105) was estimated at 195.6 Gg, 81.1% larger than the bottom-up estimate of NMVOCs-105 (108.0 Gg). The constrained emissions indicated an overestimation of aromatics and underestimation of OVOCs and halocarbons in the bottom-up emission inventory because of the uncertainties in source profiles. O3 simulation with Community Multi-scale Air Quality (CMAQ) model was conducted for January, April, July and October in 2017 to evaluate the bottom-up and constrained emission estimates. The mean normal bias (MNB) and mean normal error (MNE) values were generally within the criteria (MNB ≤ ±15% and MNE ≤ 30%) for both inventories. The model performance was improved when the constrained estimates were applied, indicating the benefit of ground observation constraints on NMVOCs emission estimation and O3 simulation. Based on the O3 formation potential (OFP), 12 key NMVOCs species mainly from surface coating, on-road vehicles and oil exploitation and refinery were identified as the priority compounds for O3 reduction.

A mass-balance-based emission inventory of non-methane volatile organic compounds (NMVOCs) for solvent use in China

Abstract. Non-methane volatile organic compounds (NMVOCs) are important precursors of ozone (O3) and secondary organic aerosol (SOA), which play key roles in tropospheric chemistry. A huge amount of NMVOC emissions from solvent use are complicated by a wide spectrum of sources and species. This work presents a long-term NMVOC emission inventory of solvent use during 2000–2017 in China. Based on a mass (material) balance method, NMVOC emissions were estimated for six categories, including coatings, adhesives, inks, pesticides, cleaners, and personal care products. The results show that NMVOC emissions from solvent use in China increased rapidly from 2000 to 2014 then kept stable after 2014. The total emission increased from 1.6 Tg (1.2–2.2 Tg at 95 % confidence interval) in 2000 to 10.6 Tg (7.7–14.9 Tg) in 2017. The substantial growth is driven by the large demand for solvent products in both industrial and residential activities. However, increasing treatment facilities in the solvent-related factories in China restrained the continued growth of solvent NMVOC emissions in recent years. Rapidly developing and heavily industrialized provinces such as Jiangsu, Shandong, and Guangdong contributed significantly to the solvent use emissions. Oxygenated VOCs, alkanes, and aromatics were the main components, accounting for 42 %, 28 %, and 21 % of total NMVOC emissions in 2017, respectively. Our results and previous inventories are generally comparable within the estimation uncertainties (−27 %–52 %). However, there exist significant differences in the estimates of sub-categories. Personal care products were a significant and quickly rising source of NMVOCs, which were probably underestimated in previous inventories. Emissions from solvent use were growing faster compared with transportation and combustion emissions, which were relatively better controlled in China. Environmentally friendly products can reduce the NMVOC emissions from solvent use. Supposing all solvent-based products were substituted with water-based products, it would result in 37 %, 41 %, and 38 % reduction of emissions, ozone formation potential (OFP), and secondary organic aerosol formation potential (SOAP), respectively. These results indicate there is still large potential for NMVOC reduction by reducing the utilization of solvent-based products and implementation of end-of-pipe controls across industrial sectors.

Site-specific determination of methane generation potential and estimation of landfill gas emissions from municipal solid waste landfill: a case study in Nam Binh Duong, Vietnam

Landfills are substantial anthropogenic sources of greenhouse gases such as methane (CH4), carbon dioxide (CO2), and non-methane volatile organic compounds (NMVOCs). This study reports a simple and efficient method for determining the environmental loads of landfill gases (LFG) emitted from the Nam Binh Duong landfill, Vietnam, by applying the LandGEM and the IPCC first-order decay models (FOD model). The environmental LFGs loads were quantified based on both the relevant parameters of the generation potential (L0) of 81 m3/Mg and the generation rate (k) of 0.355 year−1 of methane (CH4) as well as the average measurement value of CH4 (57% by volume of the LFGs) obtained throughout the on-site measurements of the investigated landfill (Scenario 1). Then, the quantified emission results of the LFGs were compared to those of the Clean Air Act (CAA) default mode of the model (Scenario 2). During the period from 2004 to 2144, the projected landfill methane emissions add up to 116,377 t of CH4 with an average of 825 t of CH4/year. The paired t test conducted to compare the gas emissions obtained from both scenarios demonstrated that the on-site parameters significantly affect the yield of the LFGs. The estimated total LFG, methane, CO2, and NMVOCs recovery potential can serve as supporting data for policy making on obtaining renewable energy from landfills and minimizing the environmental issues caused by LFGs emissions.

Evaluation of health risks associated with exposure to volatile organic compounds from household fuel combustion in southern India

Volatile organic compounds (VOCs) from household cook-fuel use are a major public health concern in low and middle income countries (LMICs), but health risk assessments have largely been based on measurements of fine particulate matter. We report results from cooking period measurements of 21 non-methane VOCs (NMVOCs) and estimated lifetime cancer risk for women cooks in the Tamil Nadu Air Pollution and Health Effects (TAPHE) cohort in Southern India. We enrolled 112 (56 biomass, 23 kerosene and 33 liquefied petroleum gas (LPG) using) TAPHE households to perform kitchen area measurements during the cooking period. VOC samples were collected on mixed-bed sorbent thermal desorption tubes using low-volume air samplers and analyzed using automated thermal desorption on a GC-MS system. Pentafluorobenzene, 1,4-difluorobenzene and chlorobenzene-d5 were used as internal standards that provided recoveries ranging from 81.7% to 119.9%. Total VOC concentrations were 4617 µg/m3, 2839 µg/m3 and 1639 µg/m3 while total BTEXS (i.e. benzene, toluene, ethylbenzene, m,p-xylene, o-xylene and styrene) concentrations were 139 µg/m3,121 µg/m3 and 245 µg/m3 among biomass, LPG and kerosene using households, respectively. Sampling season, type of food cooked and kitchen ventilation were significantly associated with measured total NMVOC concentrations. Lifetime cancer risks were estimated to be 2.93 × 10−3, 1.55 × 10−4 and 8.18 × 10−5, for biomass, kerosene and LPG fuel users, respectively with 1,2,3-trichloropropane, benzene, 1,4-dichlorobenze, 1,2-dibromoethane and chloroform contributing maximally to excess cancer risks. Health risk assessments for women cooks in LMICs should be expanded to include NMVOCs as these risks may not be adequately addressed through measurements of fine particulate matter (PM2.5) pollution alone.

Emissions of non-methane volatile organic compounds from combustion of domestic fuels in Delhi, India

Abstract. Twenty-nine different fuel types used in residential dwellings in northern India were collected from across Delhi (76 samples in total). Emission factors of a wide range of non-methane volatile organic compounds (NMVOCs) (192 compounds in total) were measured during controlled burning experiments using dual-channel gas chromatography with flame ionisation detection (DC-GC-FID), two-dimensional gas chromatography (GC × GC-FID), proton-transfer-reaction time-of-flight mass spectrometry (PTR-ToF-MS) and solid-phase extraction two-dimensional gas chromatography with time-of-flight mass spectrometry (SPE-GC × GC–ToF-MS). On average, 94 % speciation of total measured NMVOC emissions was achieved across all fuel types. The largest contributors to emissions from most fuel types were small non-aromatic oxygenated species, phenolics and furanics. The emission factors (in g kg−1) for total gas-phase NMVOCs were fuelwood (18.7, 4.3–96.7), cow dung cake (62.0, 35.3–83.0), crop residue (37.9, 8.9–73.8), charcoal (5.4, 2.4–7.9), sawdust (72.4, 28.6–115.5), municipal solid waste (87.3, 56.6–119.1) and liquefied petroleum gas (5.7, 1.9–9.8). The emission factors measured in this study allow for better characterisation, evaluation and understanding of the air quality impacts of residential solid-fuel combustion in India.

Emission inventory of air pollutants and chemical speciation for specific anthropogenic sources based on local measurements in the Yangtze River Delta region, China

Abstract. A high-resolution air pollutant emission inventory for the Yangtze River Delta (YRD) region was updated for 2017 using emission factors and chemical speciation based mainly on local measurements in this study. The inventory included 424 non-methane volatile organic compounds (NMVOCs) and 43 fine particulate matter (PM2.5) species from 259 specific sources. The total emissions of SO2, NOx, CO, NMVOCs, PM10, PM2.5, and NH3 in the YRD region in 2017 were 1552, 3235, 38 507, 4875, 3770, 1597, and 2467 Gg, respectively. SO2 and CO emissions were mainly from boilers, accounting for 49 % and 73 % of the total. Mobile sources dominated NOx emissions, contributing 57 % of the total. NMVOC emissions, mainly from industrial sources, made up 61 % of the total. Dust sources accounted for 55 % and 28 % of PM10 and PM2.5 emissions, respectively. Agricultural sources accounted for 91 % of NH3 emissions. Major PM2.5 species were OC, Ca, Si, PSO4, and EC, accounting for 9.0 %, 7.0 %, 6.4 %, 4.6 %, and 4.3 % of total PM2.5 emissions, respectively. The main species of NMVOCs were aromatic hydrocarbons, making up 25.3 % of the total. Oxygenated volatile organic compounds (OVOCs) contributed 21.9 % of the total NMVOC emissions. Toluene had the highest comprehensive contribution to ozone (O3) and secondary organic aerosol (SOA) formation potentials, while other NMVOCs included 1,2,4-trimethylbenzene, m,p-xylene, propylene, ethene, o-xylene, and ethylbenzene. Industrial process and solvent-use sources were the main sources of O3 and SOA formation potential, followed by motor vehicles. Among industrial sources, chemical manufacturing, rubber and plastic manufacturing, appliance manufacturing, and textiles made significant contributions. This emission inventory should provide scientific guidance for future control of air pollutants in the YRD region of China.

Develop a clean air action plan based on scientific data: a case of Ho Chi Minh city

Ho Chi Minh City (HCMC) has quickly become a modernized and industrialized city undergoing a rapid population growth affecting on the local environment, especially the air quality and human health. It's urgent need to have a Clean Air Action Plan (CAP) for HCMC. The aim of this research is to develop a clean air plan for HCMC based on scientific basis by integrating results of emissions inventory, air emssion loading capacties and results of the impact of air pollution on people's health. This research applied the Clean Air For Smaller City in ASEAN Region project (CASC) method of Germany to develop the CAP. Emission inventory resulted from the integration of two approaches of bottom-up and top-down. The results of simulation of air pollution dispersion and air emission loading capacities were from the TAPM-CTM model system. Method of calculating the impact of air pollution on the health of people in Ho Chi Minh City was based on BENMAP model theory. The results showed that the source of traffic accounts for the largest emissions of all pollutants, contributed respectively, 99%, 97%, 93%, 78%, 23%, 64% and 45% of total CO, NMVOC emissions, NOx, SO2, TSP, CH4, and PM2:5 of the whole HCMC. For some central areas, the city was no longer able to receive more emissions of CO and NOx. Assessing the impact of air pollution on health showed that the great impact of PM2:5 on public health accounted for 81.45% of the total deaths caused by all three pollutants ( PM2:5, SO2, NO2). Finally, a CAP was suggested with 13 proposals and 1 recommendation for reducing air pollution in HCMC for the period of 2020–2025. This is the first comprehensive study on CAP in Vietnam. This result supports government authorities to promulgate plans and actions to reduce emissions protecting human health and the environment for a sustainable development.

Atmospheric reactivity and oxidation capacity during summer at a suburban site between Beijing and Tianjin

Abstract. Hydroxyl (OH) radicals, nitrate (NO3) radicals and ozone (O3) play central roles in the troposphere because they control the lifetimes of many trace gases that result from anthropogenic and biogenic origins. To estimate the air chemistry, the atmospheric reactivity and oxidation capacity were comprehensively analyzed based on a parameterization method at a suburban site in Xianghe in the North China Plain from 6 July 2018 to 6 August 2018. The total OH, NO3 and O3 reactivities at the site varied from 9.2 to 69.6, 0.7 to 27.5 and 3.3×10-4 to 1.8×10-2 s−1 with campaign-averaged values of 27.5±9.7, 2.2±2.6 and 1.2±1.7×10-3 s−1 (± standard deviation), respectively. NOx (NO+NO2) was by far the main contributor to the reactivities of the three oxidants, with average values of 43 %–99 %. Alkenes dominated the OH, NO3 and O3 reactivities towards total nonmethane volatile organic compounds (NMVOCs), accounting for 42.9 %, 77.8 % and 94.0 %, respectively. The total OH, NO3 and O3 reactivities displayed similar diurnal variations with the lowest values during the afternoon but the highest values during rush hours, and the diurnal profile of NOx appears to be the major driver for the diurnal profiles of the reactivities of the three oxidants. A box model (a model to Simulate the concentrations of Organic vapors, Sulfuric Acid and Aerosols; SOSAA) derived from a column chemical transport model was used to simulate OH and NO3 concentrations during the observation period. The calculated atmospheric oxidation capacity (AOC) reached 4.5×108 moleculescm-3s-1, with a campaign-averaged value of 7.8×107 moleculescm-3s-1 dominated by OH (7.7×107 moleculescm-3s-1, 98.2 %), O3 (1.2×106 moleculescm-3s-1, 1.5 %) and NO3 (1.8×105 moleculescm-3s-1, 0.3 %). Overall, the integration of OH, NO3 and O3 reactivities analysis could provide useful insights for NMVOC pollution control in the North China Plain. We suggest that further studies, especially direct observations of OH and NO3 radical concentrations and their reactivities, are required to better understand trace gas reactivity and AOC.

Urban VOC profiles, possible sources, and its role in ozone formation for a summer campaign over Xi’an, China

To insight the urban volatile organic compound (VOC) profiles and its contribution to ozone, four-time per day (8:00-9:00, 15:00-16:00, 19:00-20:00, and 23:00-24:00) off-line VOC samples were collected from 16th July to 28th July 2018 for a summer investigation campaign over Xi'an, China. The diurnal variation was significant that the lowest TVOC concentrations were observed in the midnight period (28.4 ± 25.6ppbv) while the highest was shown in the morning (49.6 ± 40.1ppbv). The differences of total non-methane VOCs (TVOCs) between weekdays and weekend were also significant that the weekend showed significantly high VOC levels than weekdays (p< 0.05) but did not lead to significant ambient O3 increase (p> 0.05). Isopentane, a general marker for vehicle exhaust, showed descending concentrations from morning to midnight and good correlation with vehicle numbers on road, indicating a potential source to the VOCs at this site. The results from PMF proved that vehicular exhaust was the largest source to the VOCs in this study (64.4%). VOC categories showed a reverse sequence in abundance of concentrations and OFP contributions that alkenes showed the highest OFPs although with the lowest abundance in TOVCs due to their high reactivity in photochemical reactions. High OFPs from ethylene and isopentane indicated that vehicular emissions could be the largest potential OFP source in this site. OFPs from isoprene (from 1.85 to 13.4ppbv) indicated that biogenic VOCs should not be negligible in urban Xi'an city when controlling O3 pollutants. Comparison of two OFP methods was conducted and MIR method was proved to be more reasonable and scientific in summer Xi'an. Therefore, vehicular emission, the largest contributor to ambient VOCs and also OFPs, as well as biological source should be priority controlled in guiding VOC emissions and reducing O3 control policies.

Persistent growth of anthropogenic non-methane volatile organic compound (NMVOC) emissions in China during 1990–2017: drivers, speciation and ozone formation potential

Abstract. Non-methane volatile organic compounds (NMVOCs) are important ozone and secondary organic aerosol precursors and play important roles in tropospheric chemistry. In this work, we estimated the total and speciated NMVOC emissions from China's anthropogenic sources during 1990–2017 by using a bottom-up emission inventory framework and investigated the main drivers behind the trends. We found that anthropogenic NMVOC emissions in China have been increasing continuously since 1990 due to the dramatic growth in activity rates and absence of effective control measures. We estimated that anthropogenic NMVOC emissions in China increased from 9.76 Tg in 1990 to 28.5 Tg in 2017, mainly driven by the persistent growth from the industry sector and solvent use. Meanwhile, emissions from the residential and transportation sectors declined after 2005, partly offsetting the total emission increase. During 1990–2017, mass-based emissions of alkanes, alkenes, alkynes, aromatics, oxygenated volatile organic compounds (OVOCs) and other species increased by 274 %, 88 %, 4 %, 387 %, 91 % and 231 %, respectively. Following the growth in total NMVOC emissions, the corresponding ozone formation potential (OFP) increased from 38.2 Tg of O3 in 1990 to 99.7 Tg of O3 in 2017. We estimated that aromatics accounted for the largest share (43 %) of the total OFP, followed by alkenes (37 %) and OVOCs (10 %). Growth in China's NMVOC emissions was mainly driven by the transportation sector before 2000, while industry and solvent use dominated the emission growth during 2000–2010. Since 2010, although emissions from the industry sector and solvent use kept growing, strict control measures on transportation and fuel transition in residential stoves have successfully slowed down the increasing trend, especially after the implementation of China's clean air action since 2013. However, compared to large emission decreases in other major air pollutants in China (e.g., SO2, NOx and primary PM) during 2013–2017, the relatively flat trend in NMVOC emissions and OFP revealed the absence of effective control measures, which might have contributed to the increase in ozone during the same period. Given their high contributions to emissions and OFP, tailored control measures for solvent use and industrial sources should be developed, and multi-pollutant control strategies should be designed to mitigate both PM2.5 and ozone pollution simultaneously.

Establishment of county-level emission inventory for industrial NMVOCs in China and spatial-temporal characteristics for 2010–2016

Volatile organic compounds (VOCs) pollution, which is closely linked to photochemical smog and secondary organic aerosols, has become a severe concern in China. Therefore, we compiled a new high-resolution emission inventory for the industrial non-methane Volatile organic compounds (NMVOCs) using “bottom-up” approaches throughout 2010 and 2016. In this work, the industrial sources were divided into five major categories, and 108 specific sources, as well as an emission factor database, was developed for industrial NMVOCs. Results indicated that the total NMVOCs emissions from industrial sources increased from 16.88 Tg in 2010 to 21.04 Tg in 2016 at an annual average rate of 3.7%. The five major source categories including “production of VOCs”, “storage and transportation”, “industrial processes using VOCs as raw material”, “processes using VOCs-containing products”, and “fossil fuel combustion” generated 1.92 Tg, 0.94 Tg, 6.54 Tg, 10.04 Tg, and 1.60 Tg NMVOCs, respectively, in 2016. Coke production, plastic manufacturing, raw medicine industry, and architectural decoration were the primary sources of industrial NMVOCs and emissions of these sources increased by 140 Gg, 190 Gg, 640 Gg, and 700 Gg between 2010 and 2016. The emissions displayed distinct spatial characteristics, with significantly higher emissions in the Beijing-Tianjin-Hebei region, the Pearl River Delta, the Yangtze River Delta, and the Cheng-Yu region than in other areas. Shandong, Guangdong, Jiangsu, Zhejiang, and Henan were the top five provinces with the highest NMVOCs emissions, while the emission hotspots in the county-level were mainly distributed in Guangzhou urban area, Shanghai Pudong New Area, Hangzhou urban area, and Shenzhen urban area. The emissions in Henan province, Hubei province, and Cheng-Yu region increased significantly during the study period. Instead, emissions in some counties of Zhejiang province and Hebei province decreased than in 2010.

Estimates of reactive trace gases (NMVOCs, CO and NOx) and their ozone forming potentials during forest fire over Southern Himalayan region

In the present study, emission of trace gases [non-methane volatile organic compounds (NMVOCs), carbon monoxide (CO) and oxides of nitrogen (NOx)], their ozone forming potentials and ozone sensitivities have been investigated during the forest fire period (2003–2016) over the Southern Himalayan region. Reanalysis data of Global Fire Assimilation System model is used to retrieve the various parameters such as fire radiative power and emission rates of various trace gases. April 2016 is noticed to be anomalous in terms of fire events in the last fourteen years (2003–2016) over the lower Southern Himalayan region. Our estimation shows major contribution of oxygenated compounds (55.2%) amidst all NMVOCs. Mean CO and NOx emission rates are 533.81 and 13.66 mg/m2/day, respectively during the forest fire of April months for fourteen years. The emissions of NMVOCs, CO and NOx increased by 90.4, 110.6 and 132.5% and reaches up to 121.1, 958.3 and 25.3 mg/m2/day in April 2016 with respect to non-burning period (April 2015). Ozone forming potentials (OFP) of NMVOCs are also examined using the maximum incremental reactivity (MIR) method, which shows ~2 times higher OFP for total NMVOCs during 2016 as compared to 2015. Based on the MIR scale, the contribution of top 10 species to OFP are in the decreasing order of formaldehyde, acetaldehyde, ethane, propene, toluene, butane, isoprene, methanol, pentene and hexane. The ratio of NMVOCs/NOx is <8, which indicates that the photochemical production of O3 is mainly controlled by the levels of NMVOCs. The surface observations of ozone and CO from a Himalayan station Nainital also showed substantial increase in concentration during the forest fire of April 2016. Our results are valuable for the better understanding of chemical composition of trace gases, their role in O3 formation and effective control strategies of O3 pollution during the forest fire events over the lower Himalayan region.

Gridded Emissions of CO, NO x, SO2, CO2, NH3, HCl, CH4, PM2.5, PM10, BC, and NMVOC from Open Municipal Waste Burning in India.

Accurate emission inventories serve as critical inputs for air quality and climate models but are poorly constrained over India. We present a new municipal open waste burning emission inventory from India (OWBEII), at a resolution of 0.1° × 0.1°. Out of the 216 (201-232) Tg y-1 of waste produced in the year 2015, 68 (45-105) Tg y-1 was burned in the open. To determine emissions from waste burning, emission factors of 59 non-methane volatile organic compounds (NMVOCs), CH4, CO2, CO, and NO x were measured from garbage fires in rural and urban sites in India. The NMVOC emissions from open waste burning of 1.4-2 Tg y-1 increase India's total anthropogenic NMVOC budget by 8-12%, while BC emissions (40-110 Ggy-1) increase the total anthropogenic BC emissions by 8-12%. Open waste burning in India emits 3-7 Tg y-1 of CO and 58-130 Tg y-1 of CO2. Emissions increase the total anthropogenic CO and CO2 in the MIX-Asia inventory by 4-11% and 2-6%, respectively. Open waste burning may affect atmospheric OH reactivity and ozone formation rates downwind of urban centers through the emission of other highly reactive compounds such as acetaldehyde (20-320 Gg y-1), propene (50-170 Gg y-1), and ethene (50-190 Gg y-1) and is s source of carcinogenic benzene (30-280 Gg y-1).

Effect of Stove Technology and Combustion Conditions on Gas and Particulate Emissions from Residential Biomass Combustion.

We have systematically examined the gas and particle phase emissions from seven wood combustion devices. Among total carbon mass emitted (excluding CO2), CO emissions were dominant, together with nonmethane volatile organic compounds (NMVOCs) (10-40%). Automated devices emitted 1-3 orders of magnitude lower CH4 (0.002-0.60 g kg-1 of wood) and NMVOCs (0.01-1 g kg-1 of wood) compared to batch-operated devices (CH4: 0.25-2.80 g kg-1 of wood; NMVOCs: 2.5-19 g kg-1 of wood). 60-90% of the total NMVOCs were emitted in the starting phase of batch-operated devices, except for the first load cycles. Partial-load conditions or deviations from the normal recommended operating conditions, such as use of wet wood/wheat pellets, oxygen rich or deficit conditions, significantly enhanced the emissions. NMVOCs were largely dominated by small carboxylic acids and alcohols, and furans. Despite the large variability in NMVOCs emission strengths, the relative contribution of different classes showed large similarities among different devices and combustion phases. We show that specific improper operating conditions may even for advanced technology not result in the emission reduction of secondary organic aerosol (SOA) forming compounds and thus not reduce the impact of wood combustion on climate and health.

Persistent growth of anthropogenic NMVOC emissions in China during 1990-2017: drivers, speciation, and ozone formation potential

Abstract. Non-methane volatile organic compounds (NMVOC) are important ozone and secondary organic aerosol precursors and play important roles in tropospheric chemistry. In this work, we estimated the total and speciated NMVOC emissions from China’s anthropogenic sources during 1990–2017 by using a bottom-up emission inventory framework, and investigated the main drivers behind the trends. We found that, anthropogenic NMVOC emissions in China have been increased continuously since 1990 due to the dramatic growth in activity rates and absence of effective control measures. We estimated that, anthropogenic NMVOC emissions in China increased from 9.76 Tg in 1990 to 28.5 Tg in 2017, mainly driven by persistent growth from the industry sector and solvent use. In the meanwhile, emissions from the residential and transportation sectors declined after 2005, partly offset the total emission increase. During 1990–2017, mass-based emissions of alkanes, alkenes, alkynes, aromatics, oxygenated VOCs (OVOC) and other species increased by 274 %, 88 %, 4 %, 387 %, 91 %, and 231 % respectively. Following the growth in total NMVOC emissions, the corresponding ozone formation potential (OFP) increased form 38.2 Tg-O 3 in 1990 to 99.7 Tg-O 3 in 2017. We estimated that aromatics accounted for the largest share (43 %) of total OFP, followed by alkenes (37 %) and OVOC (10 %). Growth in China's NMVOC emissions were mainly driven by the transportation sector before 2000, while industrial sector and solvent use dominated the emission growth during 2000–2010. After 2010, although emissions from the industry sector and solvent use kept growing, strict control measures on transportation and fuel transition in residential stoves have successfully slowed down the increase trend, especially after the implementation of China's clean air action since 2013. However, compared to large emission decreases of other criteria air pollutants in China (e.g., SO 2 , NO x , and primary PM) during 2013–2017, the relatively flat trend in NMVOC emissions and OFP revealed the absence of effective control measures, which might have contributed to the increase of ozone during the same period. Given their high contributions to emissions and OFP, tailored control measures for solvent use and industrial sources should be developed, and collaborative control strategies should be designed to mitigate both PM 2.5 and ozone pollution simultaneously.

Emission characteristics of 99 NMVOCs in different seasonal days and the relationship with air quality parameters in Beijing, China

In recent years, the haze incidents have occurred frequently in China. Therefore, more attention should be taken in comprehensively determination and analysis of the extended-ranges of volatile organic compounds (VOCs). Here, up to 99 non-methane VOCs (NMVOCs), including not frequently reported partial halocarbons and oxygenated VOC (OVOC) species, were monitored in atmosphere of Beijing. The mean concentration of total NMVOC (TNMVOC) decreased in the order of winter polluted days (216.05 μg m−3) > summer polluted days (127.01 μg m−3) > summer normal days (95.63 μg m−3) > winter normal days (50.25 μg m−3). The ethane to n-butane, ethylene to 1-butene, BTEX, acetaldehyde, acetone, n-hexanal, dichloromethane, chloroform and 1,2-dichloroethane, were determined to be the main composition in their respective alkane, alkene, aromatic, OVOC and halocarbon classes. The minor propylbenzene, diethylbenzene, ethyltoluene, and trimethylbenzene isomer ratios were within the narrow range of 1.3–3.21. Generally, the most abundant NMVOCs were alkanes in winter but OVOCs in summer. TNMVOC significantly positively correlated with PM10, PM2.5, CO, RH, SO2 (winter), NO2 (winter), but negatively with windspeed, SSD and PRS (winter). The opposite correlation was observed between TNMVOC and O3 in winter and summer. There was no meaningful correlation between TNMVOC and T, PRS (summer), SO2 (summer) and NO2 (summer). 3D surface graphs, built by MATLAB, were drawn to investigate the relationship between PM2.5 and NMVOC taking air quality parameters into account. The PM2.5 concentration increased non-linearly as TNMVOC concentration increased, with various surface graphs. Unlike other air quality parameters, O3 affected the relationship differently between winter and summer. The findings presented herein may provide a new train of thought for occurrence of haze.