Sources of Formaldehyde in U.S. Oil and Gas Production Regions

Abstract

We analyzed observational and model data to study the sources of formaldehyde over oil and gas production regions and to investigate how these observations may be used to constrain oil and gas volatile organic compound (VOC) emissions. The analysis of aircraft and satellite data consistently found that formaldehyde over oil and gas production regions during spring and summer is mostly formed by the photooxidation of precursor VOCs. Formaldehyde columns over the Permian Basin, one of the largest oil-and gasproducing regions in the United States, are correlated with the production locations. Formaldehyde simulations by the atmospheric chemistry and transport model WRF-Chem, which included oil and gas NO x and VOC emissions from the fuel-based oil and gas inventory, were in very good agreement with TROPOMI satellite measurements. Sensitivity studies illustrated that VOCs released from oil and gas activities are important precursors to formaldehyde, but other sources of VOCs contribute as well and that the formation of secondary formaldehyde is highly sensitive to NO x . We also investigated the ability of the chemical mechanism used in WRF-Chem to represent formaldehyde formation from oil and gas hydrocarbons by comparing against the Master Chemical Mechanism. Further, our work provides estimates of primary formaldehyde emissions from oil and gas production activities, with per basin averages ranging from 0.07 to 2.2 kg h −1 in 2018. A separate estimate for natural gas flaring found that flaring emissions could contribute 5 to 12% to the total primary formaldehyde emissions for the Permian Basin in 2018.

Role of chemical production and depositional losses on formaldehyde in the Community Regional Atmospheric Chemistry Multiphase Mechanism (CRACMM)

“…HCHO is also underestimated over other oil producing areas in Texas and Oklahoma, specifically over the Ft. Worth and Anadarko Basins which could be due to underestimates in primary HCHO, other ROC precursor emissions, and/or secondary production. CTM simulations with WRF-Chem using the fuel-based inventory of oil and gas (FOG) (Gorchov Negron et al, 2018;Francoeur et al, 2021) showed higher HCHO VCDs over the Permian Basin than our simulations here (Dix et al, 2023). Comparisons of FOG to the 2014 NEI have shown that FOG had lower NOX emissions and higher non-methane VOC emissions (Francoeur et al, 2021).…”

“…The emissions inventory used in our simulations is based on the 2017 NEI with some updates (see EQUATES, Foley et al (2023)), and more recent versions of the NEI may show different results. Emissions of both NOX and ROC precursors will both affect HCHO production in this area (Dix et al, 2023). A sensitivity simulation in which NOX and ROC emissions from oil and gas sources were doubled resulted in increases in summer average HCHO VCD at the TROPOMI overpass time of up to 1.4×10 15 molecules cm -2 and increases of surface level 11am-3pm summer average HCHO of up to 0.5 ppb (Fig.…”

“…As part of the FIREX-AQ experiment, in-situ measurements of HCHO (among many other trace gas and aerosol measurements) were taken to assess the chemical evolution of fire plumes by sampling from the NASA DC-8 aircraft during the summer of 2019 (Liao et al, 2021;Warneke et al, 2023). While FIREX-AQ was targeted towards fires, measurements also include conditions outside of wildfire plumes.…”

“…HCHO's short lifetime of only a few hours against photolysis and reaction with the OH radical means impacts of primary HCHO are typically localized near source (characteristic transport of ~30 km for 3 h lifetime with 3 m s -1 wind speed). Secondary production tends to dominate over primary sources in driving total abundance, particularly in warmer months when HCHO levels are the highest (Dix et al, 2023). HCHO is produced from oxidation of nearly every gas-phase reactive organic carbon (ROC) species with isoprene being the biggest source of secondary HCHO.…”

Summertime Ozone Production at Carlsbad Caverns National Park, New Mexico: Influence of Oil and Natural Gas Development

“…Concurrent reduction of both NO x and VOC emissions would also lead to reduced HCHO production, which is important to consider in the context of O 3 given HCHO's key role as a primary radical source. A recent study concluded that over 90% of HCHO over the Permian basin results from secondary formation, and the yield of HCHO is as sensitive to NO x emissions as it is to VOC emissions (Dix et al., 2023).…”