Emissions of organic carbon and methane from petroleum and dairy operations in California's San Joaquin Valley

Abstract. Petroleum and dairy operations are prominent sources of gas-phase organic compounds in California's San Joaquin Valley. Ground site measurements in Bakersfield and aircraft measurements of reactive gas-phase organic compounds were made in this region as part of the CalNex (California Research at the Nexus of Air Quality and Climate Change) project to determine the sources contributing to regional gas-phase organic carbon emissions. Using a combination of near-source and downwind data, we assess the composition and magnitude of emissions from these prominent sources that are relatively understudied compared to motor vehicles We also developed a statistical modeling method with the FLEXPART-WRF transport and meteorological model using ground-based data to assess the spatial distribution of emissions in the San Joaquin Valley. We present evidence for large sources of paraffinic hydrocarbons from petroleum extraction/processing operations and oxygenated compounds from dairy (and other cattle) operations. In addition to the small straight-chain alkanes typically associated with petroleum operations, we observed a wide range of branched and cyclic alkanes that have limited previous in situ measurements or characterization in emissions from petroleum operations. Observed dairy emissions were dominated by ethanol, methanol, and acetic acid, and methane. Dairy operations were responsible for the vast majority of methane emissions in the San Joaquin Valley; observations of methane were well-correlated with non-vehicular ethanol, and multiple assessments of the spatial distribution of emissions in the San Joaquin Valley highlight the dominance of dairy operations for methane emissions. The good agreement of the observed petroleum operations source profile with the measured composition of non-methane hydrocarbons in unrefined natural gas associated with crude oil suggests a fugitive emissions pathway during petroleum extraction, storage, or processing with negligible coincident methane emissions Aircraft observations of emission hotspots from operations at oil wells and dairies are consistent with the statistical source footprint determined via transport modeling and ground-based data. At Bakersfield, petroleum and dairy operations each comprised 22–23% of anthropogenic non-methane organic carbon and were each responsible for ~12% of potential precursors to ozone, but their direct impacts as potential SOA precursors were estimated to be minor. A comparison with the California Air Resources Board emission inventory supports the current relative emission rates of reactive organic gases from these sources in the region.

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Emissions of organic carbon and methane from petroleum and dairy operations in California's San Joaquin Valley

Atmospheric Chemistry and Physics ◽

10.5194/acp-14-4955-2014 ◽

2014 ◽

Vol 14 (10) ◽

pp. 4955-4978 ◽

Cited By ~ 41

Author(s):

D. R. Gentner ◽

T. B. Ford ◽

A. Guha ◽

K. Boulanger ◽

J. Brioude ◽

...

Keyword(s):

Spatial Distribution ◽

Air Quality ◽

Organic Carbon ◽

Gas Phase ◽

Organic Compounds ◽

Methane Emissions ◽

Modeling Method ◽

San Joaquin Valley ◽

Source Profiles ◽

Source Profile

Abstract. Petroleum and dairy operations are prominent sources of gas-phase organic compounds in California's San Joaquin Valley. It is essential to understand the emissions and air quality impacts of these relatively understudied sources, especially for oil/gas operations in light of increasing US production. Ground site measurements in Bakersfield and regional aircraft measurements of reactive gas-phase organic compounds and methane were part of the CalNex (California Research at the Nexus of Air Quality and Climate Change) project to determine the sources contributing to regional gas-phase organic carbon emissions. Using a combination of near-source and downwind data, we assess the composition and magnitude of emissions, and provide average source profiles. To examine the spatial distribution of emissions in the San Joaquin Valley, we developed a statistical modeling method using ground-based data and the FLEXPART-WRF transport and meteorological model. We present evidence for large sources of paraffinic hydrocarbons from petroleum operations and oxygenated compounds from dairy (and other cattle) operations. In addition to the small straight-chain alkanes typically associated with petroleum operations, we observed a wide range of branched and cyclic alkanes, most of which have limited previous in situ measurements or characterization in petroleum operation emissions. Observed dairy emissions were dominated by ethanol, methanol, acetic acid, and methane. Dairy operations were responsible for the vast majority of methane emissions in the San Joaquin Valley; observations of methane were well correlated with non-vehicular ethanol, and multiple assessments of the spatial distribution of emissions in the San Joaquin Valley highlight the dominance of dairy operations for methane emissions. The petroleum operations source profile was developed using the composition of non-methane hydrocarbons in unrefined natural gas associated with crude oil. The observed source profile is consistent with fugitive emissions of condensate during storage or processing of associated gas following extraction and methane separation. Aircraft observations of concentration hotspots near oil wells and dairies are consistent with the statistical source footprint determined via our FLEXPART-WRF-based modeling method and ground-based data. We quantitatively compared our observations at Bakersfield to the California Air Resources Board emission inventory and find consistency for relative emission rates of reactive organic gases between the aforementioned sources and motor vehicles in the region. We estimate that petroleum and dairy operations each comprised 22% of anthropogenic non-methane organic carbon at Bakersfield and were each responsible for 8–13% of potential precursors to ozone. Yet, their direct impacts as potential secondary organic aerosol (SOA) precursors were estimated to be minor for the source profiles observed in the San Joaquin Valley.

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Considering the future of anthropogenic gas-phase organic compound emissions and the increasing influence of non-combustion sources on urban air quality

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acp-2017-761 ◽

2017 ◽

pp. 1-69

Author(s):

Peeyush Khare ◽

Drew R. Gentner

Keyword(s):

Air Quality ◽

Chemical Composition ◽

Los Angeles ◽

Gas Phase ◽

Organic Compounds ◽

Consumer Products ◽

Motor Vehicles ◽

Ozone Formation ◽

Wide Range ◽

Emissions Inventories

Decades of policy in developed regions has successfully reduced total anthropogenic emissions of gas-phase organic compounds, especially volatile organic compounds (VOCs), with an intentional, sustained focus on motor vehicles and other combustion-related sources. We examine potential secondary organic aerosol (SOA) and ozone formation in our case study megacity (Los Angeles), and demonstrate that non-combustion-related sources now contribute a major fraction of SOA and ozone precursors. Thus, they warrant greater attention beyond indoor environments to resolve large uncertainties in their emissions, oxidation chemistry, and outdoor air quality impacts in cities worldwide. We constrain the magnitude and chemical composition of emissions via several bottom-up approaches using: chemical analyses of products, emissions inventory assessments, theoretical calculations of emission timescales, and a survey of consumer product material safety datasheets. We demonstrate that the chemical composition of emissions from consumer products, and commercial/industrial products, processes, and materials is diverse across and within product/material-types with a wide range of SOA and ozone formation potentials that rivals other prominent sources, such as motor vehicles. With emission timescales from minutes to years, emission rates and source profiles need to be included, updated, and/or validated in emissions inventories, with expected regional/national variability. In particular, intermediate-volatility and semivolatile organic compounds (IVOCs and SVOCs) are key precursors to SOA but are excluded or poorly represented in emissions inventories, and exempt from emissions targets. We present an expanded framework for classifying VOC, IVOC, and SVOC emissions from this diverse array of sources that emphasizes a lifecycle approach over longer timescales and three emission pathways that extend beyond the short-term evaporation of VOCs: (1) solvent evaporation, (2) solute off-gassing, and (3) volatilization of degradation by-products. Furthermore, we find that ambient SOA formed from these non-combustion-related emissions could be misattributed to fossil fuel combustion due to the isotopic signature of their petroleum-based feedstocks.

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Modelling the evolution of organic carbon during its gas-phase tropospheric oxidation: development of an explicit model based on a self generating approach

Atmospheric Chemistry and Physics ◽

10.5194/acp-5-2497-2005 ◽

2005 ◽

Vol 5 (9) ◽

pp. 2497-2517 ◽

Cited By ~ 191

Author(s):

B. Aumont ◽

S. Szopa ◽

S. Madronich

Keyword(s):

Organic Carbon ◽

Gas Phase ◽

Organic Compounds ◽

Parent Compound ◽

Oxidation Products ◽

Gradual Change ◽

Reaction Products ◽

Test Species ◽

Lack Of Information ◽

Data Processing Tool

Abstract. Organic compounds emitted in the atmosphere are oxidized in complex reaction sequences that produce a myriad of intermediates. Although the cumulative importance of these organic intermediates is widely acknowledged, there is still a critical lack of information concerning the detailed composition of the highly functionalized secondary organics in the gas and condensed phases. The evaluation of their impacts on pollution episodes, climate, and the tropospheric oxidizing capacity requires modelling tools that track the identity and reactivity of organic carbon in the various phases down to the ultimate oxidation products, CO and CO2. However, a fully detailed representation of the atmospheric transformations of organic compounds involves a very large number of intermediate species, far in excess of the number that can be reasonably written manually. This paper describes (1) the development of a data processing tool to generate the explicit gas-phase oxidation schemes of acyclic hydrocarbons and their oxidation products under tropospheric conditions and (2) the protocol used to select the reaction products and the rate constants. Results are presented using the fully explicit oxidation schemes generated for two test species: n-heptane and isoprene. Comparisons with well-established mechanisms were performed to evaluate these generated schemes. Some preliminary results describing the gradual change of organic carbon during the oxidation of a given parent compound are presented.

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Considering the future of anthropogenic gas-phase organic compound emissions and the increasing influence of non-combustion sources on urban air quality

Atmospheric Chemistry and Physics ◽

10.5194/acp-18-5391-2018 ◽

2018 ◽

Vol 18 (8) ◽

pp. 5391-5413 ◽

Cited By ~ 16

Author(s):

Peeyush Khare ◽

Drew R. Gentner

Keyword(s):

Air Quality ◽

Chemical Composition ◽

Volatile Organic Compounds ◽

Gas Phase ◽

Organic Compounds ◽

Motor Vehicles ◽

Ozone Formation ◽

Life Cycle Approach ◽

Volatile Organic ◽

Emissions Inventories

Abstract. Decades of policy in developed regions has successfully reduced total anthropogenic emissions of gas-phase organic compounds, especially volatile organic compounds (VOCs), with an intentional, sustained focus on motor vehicles and other combustion-related sources. We examine potential secondary organic aerosol (SOA) and ozone formation in our case study megacity (Los Angeles) and demonstrate that non-combustion-related sources now contribute a major fraction of SOA and ozone precursors. Thus, they warrant greater attention beyond indoor environments to resolve large uncertainties in their emissions, oxidation chemistry, and outdoor air quality impacts in cities worldwide. We constrain the magnitude and chemical composition of emissions via several bottom-up approaches using chemical analyses of products, emissions inventory assessments, theoretical calculations of emission timescales, and a survey of consumer product material safety datasheets. We demonstrate that the chemical composition of emissions from consumer products as well as commercial and industrial products, processes, and materials is diverse across and within source subcategories. This leads to wide ranges of SOA and ozone formation potentials that rival other prominent sources, such as motor vehicles. With emission timescales from minutes to years, emission rates and source profiles need to be included, updated, and/or validated in emissions inventories with expected regional and national variability. In particular, intermediate-volatility and semi-volatile organic compounds (IVOCs and SVOCs) are key precursors to SOA, but are excluded or poorly represented in emissions inventories and exempt from emissions targets. We present an expanded framework for classifying VOC, IVOC, and SVOC emissions from this diverse array of sources that emphasizes a life cycle approach over longer timescales and three emission pathways that extend beyond the short-term evaporation of VOCs: (1) solvent evaporation, (2) solute off-gassing, and (3) volatilization of degradation by-products. Furthermore, we find that ambient SOA formed from these non-combustion-related emissions could be misattributed to fossil fuel combustion due to the isotopic signature of their petroleum-based feedstocks.

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Modelling the evolution of organic carbon during its gas-phase tropospheric oxidation: development of an explicit model based on a self generating approach

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-5-703-2005 ◽

2005 ◽

Vol 5 (1) ◽

pp. 703-754 ◽

Cited By ~ 2

Author(s):

B. Aumont ◽

S. Szopa ◽

S. Madronich

Keyword(s):

Organic Carbon ◽

Gas Phase ◽

Organic Compounds ◽

Parent Compound ◽

Oxidation Products ◽

Gradual Change ◽

Reaction Products ◽

Test Species ◽

Lack Of Information ◽

Data Processing Tool

Abstract. Organic compounds emitted in the atmosphere are oxidized in complex reaction sequences that produce a myriad of intermediates. Although the cumulative importance of these organic intermediates is widely acknowledged, there is still a critical lack of information concerning the detailed composition of the highly functionalized secondary organics in the gas and condensed phases. The evaluation of their impacts on pollution episodes, climate, and the tropospheric oxidizing capacity requires modelling tools that track the identity and reactivity of organic carbon in the various phases down to the ultimate oxidation products, CO and CO2. However, a fully detailed representation of the atmospheric transformations of organic compounds involves a very large number of intermediate species, far in excess of the number that can be reasonably written manually. This paper describes (1) the development of a data processing tool to generate the explicit gas-phase oxidation schemes of organic compounds under tropospheric conditions and (2) the protocol used to select the reaction products and the rate constants. Results are presented using the fully explicit oxidation schemes generated for two test species: n-heptane and isoprene. Comparisons with well-established mechanisms were performed to evaluate these generated schemes. Some preliminary results describing the gradual change of organic carbon during the oxidation of a given parent compound are presented.

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Emissions of terpenoids, benzenoids, and other biogenic gas-phase organic compounds from agricultural crops and their potential implications for air quality

Atmospheric Chemistry and Physics ◽

10.5194/acp-14-5393-2014 ◽

2014 ◽

Vol 14 (11) ◽

pp. 5393-5413 ◽

Cited By ~ 20

Author(s):

D. R. Gentner ◽

E. Ormeño ◽

S. Fares ◽

T. B. Ford ◽

R. Weber ◽

...

Keyword(s):

Air Quality ◽

Gas Phase ◽

Secondary Organic Aerosol ◽

Organic Aerosol ◽

San Joaquin Valley ◽

Motor Vehicles ◽

Anthropogenic Emissions ◽

Agricultural Crops ◽

Regional Air Quality ◽

Orange Trees

Abstract. Agriculture comprises a substantial, and increasing, fraction of land use in many regions of the world. Emissions from agricultural vegetation and other biogenic and anthropogenic sources react in the atmosphere to produce ozone and secondary organic aerosol, which comprises a substantial fraction of particulate matter (PM2.5). Using data from three measurement campaigns, we examine the magnitude and composition of reactive gas-phase organic carbon emissions from agricultural crops and their potential to impact regional air quality relative to anthropogenic emissions from motor vehicles in California's San Joaquin Valley, which is out of compliance with state and federal standards for tropospheric ozone PM2.5. Emission rates for a suite of terpenoid compounds were measured in a greenhouse for 25 representative crops from California in 2008. Ambient measurements of terpenoids and other biogenic compounds in the volatile and intermediate-volatility organic compound ranges were made in the urban area of Bakersfield and over an orange orchard in a rural area of the San Joaquin Valley during two 2010 seasons: summer and spring flowering. We combined measurements from the orchard site with ozone modeling methods to assess the net effect of the orange trees on regional ozone. When accounting for both emissions of reactive precursors and the deposition of ozone to the orchard, the orange trees are a net source of ozone in the springtime during flowering, and relatively neutral for most of the summer until the fall, when it becomes a sink. Flowering was a major emission event and caused a large increase in emissions including a suite of compounds that had not been measured in the atmosphere before. Such biogenic emission events need to be better parameterized in models as they have significant potential to impact regional air quality since emissions increase by several factors to over an order of magnitude. In regions like the San Joaquin Valley, the mass of biogenic emissions from agricultural crops during the summer (without flowering) and the potential ozone and secondary organic aerosol formation from these emissions are on the same order as anthropogenic emissions from motor vehicles and must be considered in air quality models and secondary pollution control strategies.

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Compilation and evaluation of gas-phase diffusion coefficients of reactive trace gases in the atmosphere: volume 2. Organic compounds and Knudsen numbers for gas uptake calculations

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-15-5461-2015 ◽

2015 ◽

Vol 15 (4) ◽

pp. 5461-5492 ◽

Cited By ~ 1

Author(s):

M. J. Tang ◽

M. Shiraiwa ◽

U. Pöschl ◽

R. A. Cox ◽

M. Kalberer

Keyword(s):

Gas Phase ◽

Organic Compounds ◽

Diffusion Coefficients ◽

Inorganic Compounds ◽

Measurement Data ◽

Gas Uptake ◽

Phase Diffusion ◽

Knudsen Numbers ◽

Wide Range ◽

Cloud Particles

Abstract. Diffusion of organic vapours to the surface of aerosol or cloud particles is an important step for the formation and transformation of atmospheric particles. So far, however, a database of gas phase diffusion coefficients for organic compounds of atmospheric interest has not been available. In this work we have compiled and evaluated gas phase diffusivities (pressure-independent diffusion coefficients) of organic compounds reported by previous experimental studies, and we compare the measurement data to estimates obtained with Fuller's semi-empirical method. The difference between measured and estimated diffusivities are mostly < 10%. With regard to gas-particle interactions, different gas molecules, including both organic and inorganic compounds, exhibit similar Knudsen numbers (Kn) although their gas phase diffusivities may vary over a wide range. Knudsen numbers of gases with unknown diffusivity can be approximated by a simple function of particle diameter and pressure and can be used to characterize the influence of diffusion on gas uptake by aerosol or cloud particles. We use a kinetic multi-layer model of gas-particle interaction to illustrate the effects of gas phase diffusion on the condensation of organic compounds with different volatilities. The results show that gas-phase diffusion can play a major role in determining the growth of secondary organic aerosol particles by condensation of low-volatility organic vapours.

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Development and validation of a portable gas phase standard generation and calibration system for volatile organic compounds

Atmospheric Measurement Techniques ◽

10.5194/amt-3-683-2010 ◽

2010 ◽

Vol 3 (3) ◽

pp. 683-691 ◽

Cited By ~ 45

Author(s):

P. Veres ◽

J. B. Gilman ◽

J. M. Roberts ◽

W. C. Kuster ◽

C. Warneke ◽

...

Keyword(s):

Mass Spectrometry ◽

Volatile Organic Compounds ◽

Organic Carbon ◽

Proton Transfer ◽

Gas Phase ◽

Organic Compounds ◽

Total Carbon ◽

Ionization Mass ◽

Calibration System ◽

Volatile Organic

Abstract. We report on the development of an accurate, portable, dynamic calibration system for volatile organic compounds (VOCs). The Mobile Organic Carbon Calibration System (MOCCS) combines the production of gas-phase VOC standards using permeation or diffusion sources with quantitative total organic carbon (TOC) conversion on a palladium surface to CO2 in the presence of oxygen, and the subsequent CO2 measurement. MOCCS was validated using three different comparisons: (1) TOC of high accuracy methane standards compared well to expected concentrations (3% relative error), (2) a gas-phase benzene standard was generated using a permeation source and measured by TOC and gas chromatography mass spectrometry (GC-MS) with excellent agreement (<4% relative difference), and (3) total carbon measurement of 4 known gas phase mixtures were performed and compared to a calculated carbon content to agreement within the stated uncertainties of the standards. Measurements from laboratory biomass burning experiments of formic acid by negative-ion proton-transfer chemical-ionization mass spectrometry (NI-PT-CIMS) and formaldehyde by proton transfer reaction-mass spectrometry (PTR-MS), both calibrated using MOCCS, were compared to open path Fourier transform infrared spectroscopy (OP-FTIR) to validate the MOCCS calibration and were found to compare well (R2 of 0.91 and 0.99, respectively).

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Compilation and evaluation of gas phase diffusion coefficients of reactive trace gases in the atmosphere: Volume 2. Diffusivities of organic compounds, pressure-normalised mean free paths, and average Knudsen numbers for gas uptake calculations

Atmospheric Chemistry and Physics ◽

10.5194/acp-15-5585-2015 ◽

2015 ◽

Vol 15 (10) ◽

pp. 5585-5598 ◽

Cited By ~ 35

Author(s):

M. J. Tang ◽

M. Shiraiwa ◽

U. Pöschl ◽

R. A. Cox ◽

M. Kalberer

Keyword(s):

Gas Phase ◽

Organic Compounds ◽

Diffusion Coefficients ◽

Inorganic Compounds ◽

Measurement Data ◽

Phase Diffusion ◽

Knudsen Numbers ◽

Wide Range ◽

Gas Molecules ◽

Cloud Particles

Abstract. Diffusion of organic vapours to the surface of aerosol or cloud particles is an important step for the formation and transformation of atmospheric particles. So far, however, a database of gas phase diffusion coefficients for organic compounds of atmospheric interest has not been available. In this work we have compiled and evaluated gas phase diffusivities (pressure-independent diffusion coefficients) of organic compounds reported by previous experimental studies, and we compare the measurement data to estimates obtained with Fuller's semi-empirical method. The difference between measured and estimated diffusivities are mostly < 10%. With regard to gas-particle interactions, different gas molecules, including both organic and inorganic compounds, exhibit similar Knudsen numbers (Kn) although their gas phase diffusivities may vary over a wide range. This is because different trace gas molecules have similar mean free paths in air at a given pressure. Thus, we introduce the pressure-normalised mean free path, λP ≈ 100 nm atm, as a near-constant generic parameter that can be used for approximate calculation of Knudsen numbers as a simple function of gas pressure and particle diameter to characterise the influence of gas phase diffusion on the uptake of gases by aerosol or cloud particles. We use a kinetic multilayer model of gas-particle interaction to illustrate the effects of gas phase diffusion on the condensation of organic compounds with different volatilities. The results show that gas phase diffusion can play a major role in determining the growth of secondary organic aerosol particles by condensation of low-volatility organic vapours.

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