Non-methane Volatile Organic Compounds Emissions Research Articles

Displacement Factors for Aerosol Emissions From Alternative Forest Biomass Use

ABSTRACTSubstituting alternative materials and energy sources with forest biomass can cause significant environmental consequences, such as alteration in the released emissions which can be described by displacement factors (DFs). Until now, DFs of wood‐based materials have included greenhouse gas (GHG) emissions and have been associated with lower fossil and process‐based emissions than non‐wood counterparts. In addition to GHGs, aerosols released in combustion processes, for example, alter radiative forcing in the atmosphere and consequently have an influence on climate. In this study, the objective was to quantify the changes in the most important aerosol emission components for cases when wood‐based materials and energy were used to replace the production of high‐density polyethylene (HDPE) plastic, common fossil‐based construction materials (concrete, steel and brick), non‐wood textile materials and energy produced by fossil fuels and peat. For this reason, we expanded the DF calculations to include aerosol emissions of total suspended particles (TSP), respirable particulate matter (PM10), fine particles (PM2.5), black carbon (BC), nitrogen oxides (NOx), sulphur dioxide (SO2) and non‐methane volatile organic compounds (NMVOCs) based on the embodied energies of materials and energy sources. The DFs for cardboard implied a decrease in BC, SO2 and NMVOC emissions but an increase in the other emission components. DFs for sawn wood mainly indicated higher emissions of both particles and gaseous emissions compared to non‐wood counterparts. DFs for wood‐based textiles demonstrated increased particle emissions and reduced gaseous emissions. DFs for energy biomass mainly implied an increase in emissions, especially if biomass was combusted in small‐scale appliances. Our main conclusion highlights the critical need to thoroughly assess how using forest biomass affects aerosol emissions. This improved understanding of the aerosol emissions of the forestry sector is crucial for a comprehensive evaluation of the climate and health implications associated with forest biomass use.

Revising VOC emissions speciation improves the simulation of global background ethane and propane.

Non-Methane Volatile Organic Compounds (NMVOCs) generate ozone (O3) when they are oxidized in the presence of oxides of nitrogen, modulate the oxidative capacity of the atmosphere and can lead to the formation of aerosol. Here, we assess the capability of a chemical transport model (GEOS-Chem) to simulate NMVOC concentrations by comparing ethane, propane and higher alkane observations in remote regions from the NOAA Flask Network and the World Meteorological Organization's Global Atmosphere Watch (GAW) network. Using the Community Emissions Data System (CEDS) inventory we find a significant underestimate in the simulated concentration of both ethane (35%) and propane (64%), consistent with previous studies. We run a new simulation where the total mass of anthropogenic NMVOC emitted in a grid box is the same as that used in CEDS, but with the NMVOC speciation derived from regional inventories. For US emissions we use the National Emissions Inventory (NEI), for Europe we use the UK National Atmospheric Emissions Inventory (NAEI), and for China, the Multi-resolution Emission Inventory for China (MEIC). These changes lead to a large increase in the modelled concentrations of ethane, improving the mean model bias from -35% to -4%. Simulated propane also improves (from -64% to -48% mean model bias), but there remains a substantial model underestimate. There were relatively minor changes to other NMVOCs. The low bias in simulated global ethane concentration is essentially removed, resolving one long-term issue in global simulations. Propane concentrations are improved but remain significantly underestimated, suggesting the potential for a missing global propane source. The change in the NMVOC emission speciation results in only minor changes in tropospheric O3 and OH concentrations.

Constraining non-methane VOC emissions with TROPOMI HCHO observations: impact on summertime ozone simulation in August 2022 in China

Abstract. Non-methane volatile organic compounds (NMVOC), serving as crucial precursors of O3, have a significant impact on atmospheric oxidative capacity and O3 formation. However, both anthropogenic and biogenic NMVOC emissions remain subject to considerable uncertainty. Here, we extended the Regional multi-Air Pollutant Assimilation System (RAPAS) using the ensemble Kalman filter (EnKF) algorithm to optimize NMVOC emissions in China in August 2022 by assimilating TROPOspheric Monitoring Instrument (TROPOMI) HCHO retrievals. We also simultaneously optimize NOx emissions by assimilating in situ NO2 observations to address the chemical feedback among VOCs–NOx–O3. Furthermore, a process-based analysis was employed to quantify the impact of NMVOC emission changes on various chemical reactions related to O3 formation and depletion. NMVOC emissions exhibited a substantial reduction of 50.2 %, especially in the middle and lower reaches of the Yangtze River, revealing a prior overestimation of biogenic NMVOC emissions due to an extreme heat wave. Compared to the forecast with prior NMVOC emissions, the forecast with posterior emissions significantly improved HCHO simulations, reducing biases by 75.7 %, indicating a notable decrease in posterior emission uncertainties. The forecast with posterior emissions also effectively corrected the overestimation of O3 in forecasts with prior emissions, reducing biases by 49.3 %. This can be primarily attributed to a significant decrease in the RO2+NO reaction rate and an increase in the NO2+OH reaction rate in the afternoon, thus limiting O3 generation. Sensitivity analyses emphasized the necessity of considering both NMVOC and NOx emissions for a comprehensive assessment of O3 chemistry. This study enhances our understanding of the effects of NMVOC emissions on O3 production and can contribute to the development of effective emission reduction policies.

Integrated satellite observations unravel the relationship between urbanization and anthropogenic non-methane volatile organic compound emissions globally

As urban areas expand globally, human activities are leading to a sustained increase in non-methane volatile organic compound (NMVOC) emissions, escalating both environmental and health-related concerns. Given their diverse origins, estimating anthropogenic NMVOC emissions levels from global urban areas remains challenging. Here, we integrate TROPOspheric Monitoring Instrument (TROPOMI) formaldehyde (HCHO) column data, Visible Infrared Imaging Radiometer Suite (VIIRS) nighttime light (NTL) radiance data, and the Emission Database for Global Atmospheric Research (EDGAR) to develop a method for estimating global anthropogenic NMVOC emissions. Furthermore, we construct a linear model to analyze the relationship between urbanization and anthropogenic NMVOC emissions. Our research reveals that meticulously filtered TROPOMI HCHO columns have a high Pearson correlation coefficient (r = 0.91) with anthropogenic NMVOC emissions, indicating its reliability as an indicator reflecting the levels of anthropogenic NMVOC emissions. We establish linear models at various scales, including global, continental, and national, linking HCHO columns (as indicators of anthropogenic NMVOC emissions) and NTL radiance (as an indicator of urbanization). The global-scale linear model exhibits an r of 0.81, with a slope of 0.42 × 1015 molec. cm−2 nanoWatts−1 cm2 sr and an intercept of 9.26 × 1015 molec. cm−2. This linear model reflects a positive correlation between urbanization and anthropogenic NMVOC emissions, also serving as a tool for estimating the levels of anthropogenic NMVOC emissions in urban areas. This study offers valuable insights for real-time monitoring of extensive anthropogenic NMVOC emissions.

Spatial Mapping of On-road Traffic Emission for Air Quality Management: A Case of Vinh Phuc Province

Vinh Phuc province is in the northern key economic region of Vietnam. The province has been facing challenges in air quality management as the number of vehicles has rapidly increased to meet the rising demand for transportation resources. This research was aimed to conduct an emission inventory and to build a spatial emission map for traffic activities in an attempt to improve air quality management in Vinh Phuc province. The vehicles were categorized into 5 groups: motorcycles, cars, light-duty vehicles (LDVs), heavy-duty vehicles (HDVs) and buses. Meanwhile, the streets were also categorized into 5 groups: highways, rural roads, urban streets, suburban streets and industrial streets. The results showed that motorcycles were the main means of transportation (93% of total vehicles) and they were also the major contributors to total emissions of NOx, CO, VOCs (volatile organic compounds), CH4, NMVOCs (non-methane volatile organic compounds) and especially in the cases of CO, CH4, VOC and NMVOC emissions which contributed more than 90% of emissions. Cars were the main source of SO2 emissions, contributing 51% of total SO2 road traffic emissions. The emissions of TSP (total suspended particulate), PM10 and PM2.5 were mostly generated from buses (about 32%), followed by motorcycles (about 18%). LDVs and HDVs contributed 18% and 15% to total particulate matter emissions, respectively. Spatial distribution analysis of CO, NOx, SO2, TSP, NMVOC and PM2.5 which involved visual identification in polluted areas, showing that high emissions were in the southeast part of the province and the most polluted areas were Vinh Yen city, followed by Binh Xuyen district and Phuc Yen city. These results provide suggestions for local governments on how to design effective air quality control strategies.

Considering Grouped or Individual Non-Methane Volatile Organic Compound Emissions in Life Cycle Assessment of Composting Using Three Life Cycle Impact Assessment Methods

Composting is a waste management practice that converts organic waste into a product that can be used safely and beneficially as a bio-fertiliser and soil amendment. Non-methane volatile organic compounds (NMVOCs) from composting are known to cause damage to human health and the environment. The impact of waste management on the environment and workers is recognised as a growing environmental and public health concern. Measurements of NMVOCs emitted during composting have been carried out only in a few studies. NMVOC emissions are typically reported as a group rather than as species or speciation profiles. Recognising the need to investigate the issues associated with NMVOCs, the objective of this study is to estimate variation in life cycle assessment (LCA) results when NMVOCs are considered individual emissions compared to grouped emissions and to compare midpoint and endpoint life cycle impact assessment (LCIA) methods. In general, the ReCiPe 2016 LCIA method estimated the highest impact from the composting process in comparison to IMPACT World+ and EF 3.0 for the impact categories of ozone formation, stratospheric ozone depletion, and particulate matter formation. For ReCiPe 2016 and IMPACT World+, the NMVOC emissions were not linked to human toxicity characterisation factors, meaning that the contribution from NMVOC towards human health risks in and around composting facilities could be underestimated. Using individual NMVOCs helps to additionally estimate the impacts of composting on freshwater ecotoxicity and human carcinogenic and non-carcinogenic toxicity potential. If ecotoxicity or toxicity issues are indicated, then LCA should be accompanied by suitable risk assessment measures for the respective life cycle stage.

Bias correction of OMI HCHO columns based on FTIR and aircraft measurements and impact on top-down emission estimates

Abstract. Spaceborne formaldehyde (HCHO) measurements constitute an excellent proxy for the sources of non-methane volatile organic compounds (NMVOCs). Past studies suggested substantial overestimations of NMVOC emissions in state-of-the-art inventories over major source regions. Here, the QA4ECV (Quality Assurance for Essential Climate Variables) retrieval of HCHO columns from OMI (Ozone Monitoring Instrument) is evaluated against (1) FTIR (Fourier-transform infrared) column observations at 26 stations worldwide and (2) aircraft in situ HCHO concentration measurements from campaigns conducted over the USA during 2012–2013. Both validation exercises show that OMI underestimates high columns and overestimates low columns. The linear regression of OMI and aircraft-based columns gives ΩOMI=0.651Ωairc+2.95×1015 molec.cm-2, with ΩOMI and Ωairc the OMI and aircraft-derived vertical columns, whereas the regression of OMI and FTIR data gives ΩOMI=0.659ΩFTIR+2.02×1015 molec.cm-2. Inverse modelling of NMVOC emissions with a global model based on OMI columns corrected for biases based on those relationships leads to much-improved agreement against FTIR data and HCHO concentrations from 11 aircraft campaigns. The optimized global isoprene emissions (∼445Tgyr-1) are 25 % higher than those obtained without bias correction. The optimized isoprene emissions bear both striking similarities and differences with recently published emissions based on spaceborne isoprene columns from the CrIS (Cross-track Infrared Sounder) sensor. Although the interannual variability of OMI HCHO columns is well understood over regions where biogenic emissions are dominant, and the HCHO trends over China and India clearly reflect anthropogenic emission changes, the observed HCHO decline over the southeastern USA remains imperfectly elucidated.

Ozone-assisted degradation of 2-methoxyethanol in a prototype plug flow photocatalytic reactor

Airborne volatile organic compounds (VOCs) present an increasingly relevant health hazard addressed by the EU directive 2016/2284 requiring 40-% reduction in emissions of non-methane VOCs by 2030 in comparison to 2005. Advanced oxidation processes (AOPs) provide a solution for the VOC problem in industry. Among AOPs, pulsed corona discharge (PCD) and photocatalytic oxidation (PCO) are of particular interest in their synergy complementing each other’s strengths in energy-efficient manner. In the present study, air polluted with 2-methoxyethanol (2ME) was treated by using a prototype 21.3 L photocatalytic reactor for the pollutant degradation at its variable concentrations (6–50 ppm), irradiances (65–119 W m−2) and residence times (12–77 sec). Further combination of PCO reactor with forthcoming PCD requires studies in ozone photocatalytic degradation as a standalone byproduct and in combination with 2ME. The analysis of variable conditions resulted in singling out the PCO major restrictive parameters, also demonstrating the degradation enhancement, when both 2ME and ozone were present in air. The PCO treatment combined with ozone resulted in degradation of 2ME and ozone for 40 % and 95 %, respectively.

Investigation of Plant-Level Volatile Organic Compound Emissions from Chemical Industry Highlights the Importance of Differentiated Control in China.

The chemical industry is a significant source of nonmethane volatile organic compounds (NMVOCs), pivotal precursors to ambient ozone (O3), and secondary organic aerosol (SOA). Despite their importance, precise estimation of these emissions remains challenging, impeding the implementation of NMVOC controls. Here, we present the first comprehensive plant-level assessment of NMVOC emissions from the chemical industry in China, encompassing 3461 plants, 127 products, and 50 NMVOC compounds from 2010 to 2019. Our findings revealed that the chemical industry in China emitted a total of 3105 (interquartile range: 1179-8113) Gg of NMVOCs in 2019, with a few specific products accounting for the majority of the emissions. Generally, plants engaged in chemical fibers production or situated in eastern China pose a greater risk to public health due to their higher formation potentials of O3 and SOA or their proximity to residential areas or both. We demonstrated that targeting these high-risk plants for emission reduction could enhance health benefits by 7-37% per unit of emission reduction on average compared to the current situation. Consequently, this study provides essential insights for developing effective plant-specific NMVOC control strategies within China's chemical industry.

High-resolution regional emission inventory contributes to the evaluation of policy effectiveness: a case study in Jiangsu Province, China

Abstract. China has been conducting a series of actions on air quality improvement for the past decades, and air pollutant emissions have been changing swiftly across the country. Provinces are an important administrative unit for air quality management in China; thus a reliable provincial-level emission inventory for multiple years is essential for detecting the varying sources of pollution and evaluating the effectiveness of emission controls. In this study, we selected Jiangsu, one of the most developed provinces in China, and developed a high-resolution emission inventory of nine species for 2015–2019, with improved methodologies for different emission sectors, best available facility-level information on individual sources, and real-world emission measurements. Resulting from implementation of strict emission control measures, the anthropogenic emissions were estimated to have declined 53 %, 20 %, 7 %, 2 %, 10 %, 21 %, 16 %, 6 %, and 18 % for sulfur dioxide (SO2), nitrogen oxides (NOx), carbon monoxide (CO), non-methane volatile organic compounds (NMVOCs), ammonia (NH3), inhalable particulate matter (PM10), fine particulate matter (PM2.5), black carbon (BC), and organic carbon (OC) from 2015 to 2019, respectively. Larger abatement of SO2, NOx, and PM2.5 emissions was detected for the more developed region of southern Jiangsu. During the period from 2016 to 2019, the ratio of biogenic volatile organic compounds (BVOCs) to anthropogenic volatile organic compounds (AVOCs) exceeded 50 % in the month of July, indicating the importance of biogenic sources for summer O3 formation. Our estimates in annual emissions of NOx, NMVOCs, and NH3 were generally smaller than the national emission inventory, MEIC (the Multi-resolution Emission Inventory for China), but larger for primary particles. The discrepancies between studies resulted mainly from different methods of emission estimation (e.g., the procedure-based approach for AVOC emissions from key industries used in this work) and inconsistent information of emission source operation (e.g., the penetration and removal efficiencies of air pollution control devices). Regarding the different periods, more reduction of SO2 emissions was found between 2015 and 2017 and of NOx, AVOCs, and PM2.5 between 2017 and 2019. Among the selected 13 major measures, the ultra-low-emission retrofit in the power sector was the most important contributor to the reduced SO2 and NOx emissions (accounting for 38 % and 43 % of the emission abatement, respectively) for 2015–2017, but its effect became very limited afterwards as the retrofit had been commonly completed by 2017. Instead, extensive management of coal-fired boilers and the upgrade and renovation of non-electrical industry were the most important measures for 2017–2019, accounting collectively for 61 %, 49 %, and 57 % reduction of SO2, NOx, and PM2.5, respectively. Controls on key industrial sectors were the most effective for AVOC reduction in the two periods, while measures relating to other sources (transportation and solvent replacement) have become more important in recent years. Our provincial emission inventory was demonstrated to support high-resolution air quality modeling for multiple years. Through scenario setting and modeling, worsened meteorological conditions were found from 2015 to 2019 for PM2.5 and O3 pollution alleviation. However, the efforts on emission controls were identified to largely overcome the negative influence of meteorological variation. The changed anthropogenic emissions were estimated to contribute 4.3 and 5.5 µg m−3 of PM2.5 concentration reduction for 2015–2017 and 2017–2019, respectively. While O3 was elevated by 4.9 µg m−3 for 2015–2017, the changing emissions led to 3.1 µg m−3 of reduction for 2017–2019, partly (not fully though) offsetting the meteorology-driven growth. The analysis justified the validity of local emission control efforts on air quality improvement and provided a scientific basis to formulate air pollution prevention and control policies for other developed regions in China and worldwide.

Towards sustainable development: Drivers of aggregate and sectoral convergence in per capita non-methane volatile organic compound emissions of OECD countries in two centuries

The purpose of this study is to extend the current literature on convergence of pollutants in five different ways including the examination of the convergence of per capita non-methane volatile organic compound emissions in 20 OECD countries for the period, 1820–2019. According to our knowledge, this is the one of the first attempts to investigate the convergence of per capita non-methane volatile organic compound emissions. The convergence of per capita non-methane volatile organic compound emissions across four sectors (agriculture, industry, residential commercial and others; and waste) in these countries has also been investigated. A residual augmented least squares regression method has been used to investigate the stochastic convergence of the series. Furthermore, conditional convergence and sigma convergence of per capita non-methane volatile organic compound emissions have also been examined. The results provide support for stochastic convergence of the pollutants both at aggregate and sectoral levels. The conditional convergence analysis supports the existence of convergence and shows that population growth rate and real gross domestic product per capita are structural factors that facilitate the existence of convergence in most of the sectors. A policy implication from the results is that a combination of international coordination efforts and country-specific factors including the real gross domestic product per capita and population growth rate must considered, when initiating policies aimed at further reducing emissions in these countries.

A new NMVOC speciated inventory for a reactivity-based approach to support ozone control strategies in Spain

Ozone (O3) pollution is a persistent problem in many regions of Spain, so understanding O3 precursor emissions and trends is essential to design effective control strategies. We estimated the impact of Non-Methane Volatile Organic Compounds (NMVOC) species upon O3 formation potential (OFP) using the maximum incremental reactivity approach. For this, we developed a speciated NMVOC emission inventory for Spain from 2010 to 2019 combining national reported emissions with state-of-the-art speciation profiles, which resulted in a database of emissions for over 900 individual NMVOC species and 153 individual sectors. Additionally, we analysed 2030 emission projections to quantify the expected impact of planned measures on future OFP levels. Overall, the main activities contributing to OFP in Spain are paint manufacturing and applications (20 %), manure management (16 %), and domestic solvent use (6 %). These activities contribute unevenly across regions. The more urbanised areas report a larger contribution from the solvent sector (64 % in Madrid), while in rural areas, manure management and agricultural waste burning gain importance (24 % in Extremadura), indicating that local control measures should be implemented. The top 10 NMVOC species contributing to OFP are ethanol, ethene, xylenes, propene, toluene, formaldehyde, 1,3-butadiene, styrene, n-butane, and cyclopentane, which together are responsible for 54 % of the total OFP. Our trend analysis indicates a reduction of NMVOC emissions and OFP of −5 % and −10 % between 2010 and 2019, respectively. The larger decrease in OFP is driven by a bigger reduction in xylenes (−29 %) and toluene (−28 %) from paint application industries and the road transport sector. By 2030 a significant increase (+37 %) in the OFP from the public electricity sector is expected due to the planned increase in biomass use for power generation. Our results indicate that policies should focus on paint reformulation, limiting aerosol products, and implementing NMVOC control devices in future biomass power plants.

NMVOC Emissions from Solvents Use in Greece: Monitoring and Assessment

The use of solvents and other volatile organic chemicals is a significant source of Non-Methane Volatile Organic Compounds (NMVOCs) emissions. Due to the wide spectrum of applications of solvents and numerous locations where these occur, the estimation of NMVOCs emissions can be challenging. The aim of this paper is to present the methodological framework used in Greece for the estimation of NMVOCs emissions. It covers processes and products that use solvents and other volatile organic chemicals in several industries, as well as in households. The framework is based both on existing methods found in the literature and on new emission factors developed in order to reflect the mitigation potential of EU Directives and national legislation aiming at the reduction of NMVOCs emissions. The developed framework was used to forecast future NMVOCs emissions and assess the implemented mitigation actions. Results were verified by comparison with solvent emission estimates from the European Solvent Industry Group.

Modelling of NMVOC emissions from solvents use in Greece

The use of solvents and other volatile organic chemicals is a significant source of Non-Methane Volatile Organic Compounds (NMVOCs) emissions. Due to the wide spectrum of applications of solvents and numerous locations where these occur, the estimation of NMVOCs emissions can be challenging. The aim of this paper is to present the methodological framework used in Greece for the estimation of NMVOCs emissions. It covers processes and products that use solvents and other volatile organic chemicals in several industries, as well as in households. The framework is based both on existing methods found in the literature and on new emission factors developed in order to reflect the mitigation potential of EU Directives and national legislation aiming at the reduction of NMVOCs emissions. The developed framework was verified by comparing it with solvent emission estimates from the European Solvent Industry Group.

COVID-19 lockdown emission reductions have the potential to explain over half of the coincident increase in global atmospheric methane

Abstract. Compared with 2019, measurements of the global growth rate of background (marine air) atmospheric methane rose by 5.3 ppb yr−1 in 2020, reaching 15.0 ppb yr−1. Global atmospheric chemistry models have previously shown that reductions in nitrogen oxide (NOx) emissions reduce levels of the hydroxyl radical (OH) and lengthen the methane lifetime. Acting in the opposite sense, reductions in carbon monoxide (CO) and non-methane volatile organic compound (NMVOC) emissions increase OH and shorten methane's lifetime. Using estimates of NOx, CO, and NMVOC emission reductions associated with COVID-19 lockdowns around the world in 2020 as well as model-derived regional and aviation sensitivities of methane to these emissions, we find that NOx emission reductions led to a 4.8 (3.8 to 5.8) ppb yr−1 increase in the global methane growth rate. Reductions in CO and NMVOC emissions partly counteracted this, changing (reducing) the methane growth rate by −1.4 (−1.1 to −1.7) ppb yr−1 (CO) and −0.5 (−0.1 to −0.9) ppb yr−1 (NMVOC), yielding a net increase of 2.9 (1.7 to 4.0) ppb yr−1. Uncertainties refer to ±1 standard deviation model ranges in sensitivities. Whilst changes in anthropogenic emissions related to COVID-19 lockdowns are probably not the only important factor that influenced methane during 2020, these results indicate that they have had a large impact and that the net effect of NOx, CO, and NMVOC emission changes can explain over half of the observed 2020 methane changes. Large uncertainties remain in both emission changes during the lockdowns and methane's response to them; nevertheless, this analysis suggests that further research into how the atmospheric composition changed over the lockdown periods will help us to interpret past methane changes and to constrain future methane projections.

Response of Anthropogenic Volatile Organic Compound Emissions to Urbanization in Asia Probed With TROPOMI and VIIRS Satellite Observations

AbstractEmissions of air pollutants and their precursors in urban air closely relate to urbanization involving economic development, population growth, and industrialization. Here we use formaldehyde (HCHO) columns from the TROPOspheric Monitoring Instrument (TROPOMI), night‐time light (NTL) radiance from the Visible Infrared Imaging Radiometer Suite, and population density data as respective proxies to explore how anthropogenic non‐methane volatile organic compound (NMVOC) emissions evolve with urbanization in Asia. HCHO columns correlate moderately to highly (0.64 ≤ r ≤ 0.99) with the NTL radiance within most major Asian countries. On both national (across Asia) and provincial scales (within China), HCHO columns increase monotonically with NTL radiance or population density with a log‐linear pattern, implying anthropogenic NMVOC emissions in Asia may similarly respond to urbanization with no apparent turnover yet. Our study confirms TROPOMI HCHO columns as a proxy of anthropogenic NMVOC emissions.

Effectiveness of emissions standards on automotive evaporative emissions in Europe under normal and extreme temperature conditions

Non-methane volatile organic compounds (NMVOCs) are primary precursors for the formation of ozone and secondary organic aerosol which contribute to increased public health risks. Throughout Europe, passenger vehicles contribute significantly to NMVOC emissions due to automotive evaporative emissions controls that are less stringent than those in the United States, Canada, China, and Brazil. Evaporative NMVOC emissions increase significantly, and associated air quality impacts are exacerbated, during periods of high temperature such as heatwaves, which continue to increase in frequency, duration, and intensity. Adoption of strict evaporative emission standards and controls such as onboard refueling vapor recovery systems (ORVR) can significantly reduce evaporative emissions during such events; however, emissions inventories used to inform policy decisions are developed using average temperature profiles which fail to capture the impact of heatwave events on evaporative emissions. This study evaluates the effectiveness of the previous generation (Euro5), current (Euro6d), and proposed (Euro7) emission control standards on evaporative emissions at high temporal and spatial resolution in western and central Europe during July 2019, a month in which a significant heatwave swept through the region. Using temperatures obtained from the Weather Research and Forecasting (WRF) model with observation data and an improved method for estimating evaporative emissions, it is estimated that per-vehicle evaporative NMVOC emissions within the study domain and period are reduced by 25.0% under current Euro6d standards and controls relative to Euro5 standards, and that proposed Euro7 controls, including ORVR, would provide an additional 35.3% emissions reduction relative to Euro6d. During heatwave periods, Euro7 controls demonstrate improved attenuation of temperature-driven emissions increases relative to Euro6d controls, with associated emissions within the study period and domain increasing by 23.4% on average under Euro7 controls versus 29.4% under Euro6d controls. While this study does not quantify the effect of heatwaves and emissions controls on total annual emissions, the results for the study period of July 2019, combined with the low implementation cost of proposed Euro7 evaporative controls and projected continued dominance of petrol vehicles in the European fleet through the middle of this century, suggest that significant NMVOC emissions reductions and associated air quality and health impacts are achievable through the adoption of these more stringent standards and control systems.

NMVOC emissions and their formation into secondary organic aerosols over India using WRF-Chem model

Non-methane volatile organic compounds (NMVOC) emissions from anthropogenic, open burning, and biogenic sources, and their formation into secondary organic aerosols (SOA) over India have been examined. The emissions databases EDGAR-HTAP (v2.2), Fire Inventory from NCAR (FINN), and the Model of Emission of Gases and Aerosol (MEGAN) were used. India emits 3% of annual global NMVOC at 30.45 Tg (anthropogenic:8.97; open burning: 2.01; biogenic: 19.47 Tg/year). Spatial and temporal variations for SOA were simulated using the WRF-Chem model combined with a secondary organic aerosol model for the year 2018. WRF-Chem model was expanded to include a scheme of parameterization for estimating isoprene-derived SOA. Annual estimated SOA production was 2.93 Tg/year, 4% of the global SOA.The annual SOA concentration over India was 3.19 ± 2.18 μg/m3 (post-monsoon: 5.16 ± 3.29, winter: 3.74 ± 2.55, summer: 2.62 ± 1.78, and monsoon: 1.24 ± 0.84 μg/m3). WRF-Chem model underestimated the SOA levels, possibly due to incomplete emission inventories and missing NMVOC precursors, including biogenic and primary organic carbon emissions that add to SOA formation. The annual anthropogenic and biogenic SOA had a near equal contribution of 50% mostly from populated regions and evergreen forests.

Detailed Speciation of Non-Methane Volatile Organic Compounds in Exhaust Emissions from Diesel and Gasoline Euro 5 Vehicles Using Online and Offline Measurements.

The characterization of vehicle exhaust emissions of volatile organic compounds (VOCs) is essential to estimate their impact on the formation of secondary organic aerosol (SOA) and, more generally, air quality. This paper revises and updates non-methane volatile organic compounds (NMVOCs) tailpipe emissions of three Euro 5 vehicles during Artemis cold urban (CU) and motorway (MW) cycles. Positive matrix factorization (PMF) analysis is carried out for the first time on proton transfer reaction time-of-flight mass spectrometer (PTR-ToF-MS) datasets of vehicular emission. Statistical analysis helped to associate the emitted VOCs to specific driving conditions, such as the start of the vehicles, the activation of the catalysts, or to specific engine combustion regimes. Merged PTR-ToF-MS and automated thermal desorption gas chromatography mass spectrometer (ATD-GC-MS) datasets provided an exhaustive description of the NMVOC emission factors (EFs) of the vehicles, thus helping to identify and quantify up to 147 individual compounds. In general, emissions during the CU cycle exceed those during the MW cycle. The gasoline direct injection (GDI) vehicle exhibits the highest EF during both CU and MW cycles (252 and 15 mg/km), followed by the port-fuel injection (PFI) vehicle (24 and 0.4 mg/km), and finally the diesel vehicle (15 and 3 mg/km). For all vehicles, emissions are dominated by unburnt fuel and incomplete combustion products. Diesel emissions are mostly represented by oxygenated compounds (65%) and aliphatic hydrocarbons (23%) up to C22, while GDI and PFI exhaust emissions are composed of monoaromatics (68%) and alkanes (15%). Intermediate volatility organic compounds (IVOCs) range from 2.7 to 13% of the emissions, comprising essentially linear alkanes for the diesel vehicle, while naphthalene accounts up to 42% of the IVOC fraction for the gasoline vehicles. This work demonstrates that PMF analysis of PTR-ToF-MS datasets and GC-MS analysis of vehicular emissions provide a revised and deep characterization of vehicular emissions to enrich current emission inventories.

OMI formaldehyde column constrained emissions of reactive volatile organic compounds over the Pearl River Delta region of China

In recent years, surface ozone (O3) concentration was high and became the primary air pollutant in the Pearl River Delta (PRD) region. However, as precursors of tropospheric O3, the emissions of reactive nonmethane volatile organic compounds (NMVOCs) were reported to have large uncertainties. Here, combined with the simulated formaldehyde (HCHO) columns from the RAMS-CMAQ modeling system, formaldehyde (HCHO) columns derived from the Ozone Monitoring Instrument (OMI) were used as the constraints to improve the emission estimates of the reactive NMVOCs through the linear regression method over the PRD region in March of 2017. The observed highest HCHO concentration was 2–4 times as high as the original simulated results over the PRD region mostly due to the underestimation in the reactive NMVOC emissions, especially the anthropogenic sources. With the regression coefficients calculated through five sensitivity simulation cases as well as the observed HCHO column, the better quantified emissions of reactive NMVOCs were obtained over the PRD region. It showed that the total emissions of reactive NMVOCs were improved by a factor of 2.1. The emissions derived from anthropogenic, biomass burning and biogenic sources increased from 0.0329, 4.69 × 10−4 and 0.0524 Tg/month to 0.0959, 0.0215 and 0.0620 Tg/month, respectively. As a result, the difference between the observed and modeled high HCHO column decreased to 1–2.5 times, which may be dominated by the enhanced reactive NMVOC emissions derived from anthropogenic sources. Besides, the great improvement in the emissions of reactive NMVOCs contributed to an increase of 20–40 μg/m3 in the maximum daily 8-h average (MDA8) O3 concentration over the PRD region.