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The United States is now experiencing the most rapid expansion in oil and gas production in four decades, owing in large part to implementation of new extraction technologies such as horizontal drilling combined with hydraulic fracturing. The environmental impacts of this development, from its effect on water quality1 to the influence of increased methane leakage on climate2, have been a matter of intense debate. Air quality impacts are associated with emissions of nitrogen oxides3,4 (NOx = NO + NO2) and volatile organic compounds5,6,7 (VOCs), whose photochemistry leads to production of ozone, a secondary pollutant with negative health effects8. Recent observations in oil- and gas-producing basins in the western United States have identified ozone mixing ratios well in excess of present air quality standards, but only during winter9,10,11,12,13. Understanding winter ozone production in these regions is scientifically challenging. It occurs during cold periods of snow cover when meteorological inversions concentrate air pollutants from oil and gas activities, but when solar irradiance and absolute humidity, which are both required to initiate conventional photochemistry essential for ozone production, are at a minimum. Here, using data from a remote location in the oil and gas basin of northeastern Utah and a box model, we provide a quantitative assessment of the photochemistry that leads to these extreme winter ozone pollution events, and identify key factors that control ozone production in this unique environment. We find that ozone production occurs at lower NOx and much larger VOC concentrations than does its summertime urban counterpart, leading to carbonyl (oxygenated VOCs with a C = O moiety) photolysis as a dominant oxidant source. Extreme VOC concentrations optimize the ozone production efficiency of NOx. There is considerable potential for global growth in oil and gas extraction from shale. This analysis could help inform strategies to monitor and mitigate air quality impacts and provide broader insight into the response of winter ozone to primary pollutants.

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  • 15 October 2014

    Minor changes were made to the Acknowledgements.


  1. 1.

    & Distribution and origin of groundwater methane in the Wattenberg oil and gas field of northern Colorado. Environ. Sci. Technol. 48, 1484–1491 (2014)

  2. 2.

    et al. Methane leaks from North American natural gas systems. Science 343, 733–735 (2014)

  3. 3.

    et al. Air quality over the Canadian oil sands: a first assessment using satellite observations. Geophys. Res. Lett. 39, L04804 (2012)

  4. 4.

    , , , & The data gap: can a lack of monitors obscure loss of clean air act benefits in fracking areas? Environ. Sci. Technol. 48, 893–894 (2014)

  5. 5.

    , , & Source signature of volatile organic compounds from oil and natural gas operations in northeastern Colorado. Environ. Sci. Technol. 47, 1297–1305 (2013)

  6. 6.

    , , , & Extensive regional atmospheric hydrocarbon pollution in the southwestern United States. Proc. Natl Acad. Sci. USA 100, 11975–11979 (2003)

  7. 7.

    et al. Hydrocarbon emissions characterization in the Colorado Front Range: a pilot study. J. Geophys. Res. 117, D04304 (2012)

  8. 8.

    et al. Long-term ozone exposure and mortality. N. Engl. J. Med. 360, 1085–1095 (2009)

  9. 9.

    & Winter ozone formation and VOC incremental reactivities in the Upper Green River Basin of Wyoming. Atmos. Environ. 50, 255–266 (2012)

  10. 10.

    , , & Highly elevated atmospheric levels of volatile organic compounds in the Uintah Basin, Utah. Environ. Sci. Technol. 48, 4707–4715 (2014)

  11. 11.

    et al. Anatomy of wintertime ozone associated with oil and natural gas extraction activity in Wyoming and Utah. Elem. Sci. Anth. 2, 000024 (2014)

  12. 12.

    et al. Strong wintertime ozone events in the Upper Green River Basin, Wyoming. Atmos. Chem. Phys. 14, 4909–4934 (2014)

  13. 13.

    et al. Rapid photochemical production of ozone at high concentrations in a rural site during winter. Nature Geosci. 2, 120–122 (2009)

  14. 14.

    Urban air pollution: state of the science. Science 243, 745–752 (1989)

  15. 15.

    Normal atmosphere: large radical and formaldehyde concentrations predicted. Science 173, 141–143 (1971)

  16. 16.

    et al. Ozone photochemistry in an oil and natural gas extraction region during winter: simulations of a snow-free season in the Uintah Basin, Utah. Atmos. Chem. Phys. 13, 8955–8971 (2013)

  17. 17.

    et al. High levels of the hydroxyl radical in the winter urban troposphere. Geophys. Res. Lett. 31, L18112 (2004)

  18. 18.

    , & The tropospheric degradation of volatile organic compounds: a protocol for mechanism development. Atmos. Environ. 31, 81–104 (1997)

  19. 19.

    et al. Vertically resolved measurements of nighttime radical reservoirs in Los Angeles and their contribution to the urban radical budget. Environ. Sci. Technol. 46, 10965–10973 (2012)

  20. 20.

    & The reactions of ozone with alkenes: an important source of HOx in the boundary layer. Geophys. Res. Lett. 23, 3727–3730 (1996)

  21. 21.

    et al. A large atomic chlorine source inferred from mid-continental reactive nitrogen chemistry. Nature 464, 271–274 (2010)

  22. 22.

    et al. Missing gas-phase source of HONO inferred from zeppelin measurements in the troposphere. Science 344, 292–296 (2014)

  23. 23.

    The dependence of tropospheric ozone production rate on ozone precursors. Atmos. Environ. 39, 575–586 (2005)

  24. 24.

    et al. Urban ozone control and atmospheric reactivity of organic gases. Science 269, 491–495 (1995)

  25. 25.

    et al. Methane emissions estimate from airborne measurements over a western United States natural gas field. Geophys. Res. Lett. 40, 4393–4397 (2013)

  26. 26.

    , , & Reduced emissions of CO2, NOx, and SO2 from U.S. power plants owing to switch from coal to natural gas with combined cycle technology. Earth’s Future 2, 75–82 (2014)

  27. 27.

    , & Trends in OMI NO2 observations over the United States: effects of emission control technology and the economic recession. Atmos. Chem. Phys. 12, 12197–12209 (2012)

  28. 28.

    Economic appraisal of shale gas plays in Continental Europe. Appl. Energy 106, 100–115 (2013)

  29. 29.

    UK shale gas: the story so far. Mar. Pet. Geol. 31, 100–109 (2012)

  30. 30.

    , & Emerging shale gas revolution in China. Environ. Sci. Technol. 46, 12281–12282 (2012)

  31. 31.

    US Energy Information Administration. Technically Recoverable Shale Oil and Shale Gas Resources: An Assessment of 137 Shale Formations in 41 Countries Outside the United States. Analysis and Projections (2013)

  32. 32.

    et al. Hydrogen oxide photochemistry in the northern Canadian spring time boundary layer. J. Geophys. Res. D 116, D22306 (2011)

  33. 33.

    & Comparison of tropospheric gas-phase chemistry schemes for use within global models. Atmos. Chem. Phys. 9, 1831–1845 (2009)

  34. 34.

    et al. HOx observations over West Africa during AMMA: impact of isoprene and NOx. Atmos. Chem. Phys. 10, 9415–9429 (2010)

  35. 35.

    , , & Protocol for the development of the Master Chemical Mechanism, MCM v3 (part A): tropospheric degradation of non-aromatic volatile organic compounds. Atmos. Chem. Phys. 3, 161–180 (2003)

  36. 36.

    & Alkyl nitrate formation from the atmospheric photooxidation of alkanes; a revised estimation method. J. Atmos. Chem. 8, 165–173 (1989)

  37. 37.

    , , & Changes in biologically active ultraviolet radiation reaching the Earth’s surface. J. Photochem. Photobiol. B 46, 5–19 (1998)

  38. 38.

    , , & The role of ozone atmosphere-snow gas exchange on polar, boundary-layer tropospheric ozone - a review and sensitivity analysis. Atmos. Chem. Phys. 7, 15–30 (2007)

  39. 39.

    et al. A sensitive and versatile detector for atmospheric NO2 and NOx basd on blue diode laser cavity ring-down spectroscopy. Environ. Sci. Technol. 43, 7831–7836 (2009)

  40. 40.

    , , & Measurement of atmospheric ozone by cavity ring-down spectroscopy. Environ. Sci. Technol. 45, 2938–2944 (2011)

  41. 41.

    et al. Aircraft instrument for simultaneous, in-situ measurements of NO3 and N2O5 via cavity ring-down spectroscopy. Rev. Sci. Instrum. 77, 034101 (2006)

  42. 42.

    , , , & A thermal dissociation - chemical ionization mass sepctrometry (TD-CIMS) technique for the simultaneous measurement of peroxyacetyl radicals and dinitrogen pentoxide. J. Geophys. Res. 109, D19315 (2004)

  43. 43.

    et al. Peroxyacetyl nitrate (PAN) and peroxyacetic acid (PAA) measurements by iodide chemical ionisation mass spectrometry: first analysis of results in the boreal forest and implications for the measurement of PAN fluxes. Atmos. Chem. Phys. 13, 1129–1139 (2013)

  44. 44.

    et al. Measurement of HONO, HNCO, and other inorganic acids by negative-ion proton-transfer chemical-ionization mass spectrometry (NI-PT-CIMS): application to biomass burning emissions. Atmos. Meas. Tech. 3, 981–990 (2010)

  45. 45.

    et al. Validation of proton transfer reaction-mass spectrometry (PTR-MS) measurements of gas-phase organic compounds in the atmosphere during the New England Air Quality Study (NEAQS) in 2002. J. Geophys. Res. 108, D214682 (2003)

  46. 46.

    et al. A high resolution and high sensitivity proton-transfer-reaction time-of-flight mass spectrometer (PTR-TOF-MS). Int. J. Mass Spectrom. 286, 122–128 (2009)

  47. 47.

    et al. Intercomparison of volatile organic carbon measurement techniques and data at La Porte during the TexAQS 2000 air quality study. Environ. Sci. Technol. 38, 221–228 (2004)

  48. 48.

    et al. Daytime HONO vertical gradients during SHARP 2009 in Houston, TX. Atmos. Chem. Phys. 12, 635–652 (2012)

  49. 49.

    et al. Airborne formaldehyde measurements using PTR-MS: calibration, humidity dependence, inter-comparison and initial results. Atmos. Meas. Tech. 4, 2345–2358 (2011)

  50. 50.

    et al. Baseline Surface Radiation Network (BSRN/WCRP): new precision radiometry for climate research. Bull. Am. Meteorol. Soc. 79, 2115–2136 (1998)

  51. 51.

    et al. Final Report: Uintah Basin Winter Ozone and Air Quality Study 19–24. Report No. EDL/11-039 (Utah State University, 2011)

  52. 52.

    , , & Oxidative capacity of the Mexico City atmosphere - Part 1: A radical source perspective. Atmos. Chem. Phys. 10, 6969–6991 (2010)

  53. 53.

    et al. Ultraviolet photolysis of HCHO: absolute HCO quantum yields by direct detection of the HCO radical photoproduct. J. Phys. Chem. A 112, 12437–12448 (2008)

  54. 54.

    et al. Exploring the atmospheric chemistry of nitrous acid (HONO) at a rural site in Southern China. Atmos. Chem. Phys. 12, 1497–1513 (2012)

  55. 55.

    et al. Study of the unknown HONO daytime source at a European suburban site during the MEGAPOLI summer and winter field campaigns. Atmos. Chem. Phys. 14, 2805–2822 (2014)

  56. 56.

    et al. HONO Emissions from soil bacteria as a major source of atmospheric reactive nitrogen. Science 341, 1233–1235 (2013)

  57. 57.

    et al. Understanding the role of the ground surface in HONO vertical structure: high resolution vertical profiles during NACHTT-11. J. Geophys. Res. 118, 10155–10171 (2013)

  58. 58.

    et al. Long-term observation of atmospheric nitrous acid (HONO) and its implication to local NO2 levels in Shanghai, China. Atmos. Environ. 77, 718–724 (2013)

  59. 59.

    , , , & Vertical profiles of nitrous acid in the nocturnal urban atmosphere of Houston, TX. Atmos. Chem. Phys. 11, 3595–3609 (2011)

  60. 60.

    et al. Nitric acid photolysis on forest canopy surface as a source for tropospheric nitrous acid. Nature Geosci. 4, 440–443 (2011)

  61. 61.

    et al. HONO emissions from snow surfaces. Environ. Res. Lett. 3, 045005 (2008)

  62. 62.

    et al. Vertical fluxes of NOx, HONO, and HNO3 above the snowpack at Summit, Greenland. Atmos. Environ. 36, 2629–2640 (2002)

  63. 63.

    et al. Snowpack photochemical production of HONO: A major source of OH in the Arctic boundary layer in springtime. Geophys. Res. Lett. 28, 4087–4090 (2001)

  64. 64.

    & Boundary layer physics over snow and ice. Atmos. Chem. Phys. 8, 3563–3582 (2008)

  65. 65.

    et al. Measurements of hydrogen peroxide and formaldehyde exchange between the atmosphere and surface snow at Summit, Greenland. Atmos. Environ. 36, 2619–2628 (2002)

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The Uintah Basin Winter Ozone Studies were a joint project led and coordinated by the Utah Department of Environmental Quality (UDEQ) and supported by the Uintah Impact Mitigation Special Service District (UIMSSD), the Bureau of Land Management (BLM), the Environmental Protection Agency (EPA) and Utah State University. This work was funded in part by the Western Energy Alliance, and NOAA’s Atmospheric Chemistry, Climate and Carbon Cycle programme. We thank Questar Energy Products for site preparation and support. Funding for the 2012 LP-DOAS HNO2 measurements was provided by the National Science Foundation (award no. 1212666). S.M.M. acknowledges the National Science Foundation for award no. 1215926. We would like to thank L. Lee and R. Cohen of UC Berkley for their contributions and discussions relating to the representation of alkyl nitrate chemistry in this study.

Author information

Author notes

    • Peter M. Edwards
    • , Martin Graus
    •  & Cora J. Young

    Present addresses: Department of Chemistry, University of York, York YO10 5DD, UK (P.M.E.); Institute of Meteorology and Geophysics, University of Innsbruck, Innsbruck, 6020 Austria (M.G.); Department of Chemistry, Memorial University of Newfoundland, St John’s, Newfoundland A1B 3X7, Canada (C.J.Y.).


  1. NOAA Earth System Research Laboratory, Boulder, Colorado 80305, USA

    • Peter M. Edwards
    • , Steven S. Brown
    • , James M. Roberts
    • , Ravan Ahmadov
    • , Robert M. Banta
    • , Joost A. deGouw
    • , William P. Dubé
    • , Jessica B. Gilman
    • , Martin Graus
    • , Abigail Koss
    • , Andrew O. Langford
    • , Brian M. Lerner
    • , Rui Li
    • , Stuart A. McKeen
    • , David D. Parrish
    • , Christoph J. Senff
    • , Colm Sweeney
    • , Michael K. Trainer
    • , Patrick R. Veres
    • , Rebecca A. Washenfelder
    • , Carsten Warneke
    • , Robert J. Wild
    • , Cora J. Young
    • , Bin Yuan
    •  & Robert Zamora
  2. Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, Colorado 80309, USA

    • Peter M. Edwards
    • , Ravan Ahmadov
    • , Joost A. deGouw
    • , William P. Dubé
    • , Jessica B. Gilman
    • , Martin Graus
    • , Abigail Koss
    • , Brian M. Lerner
    • , Rui Li
    • , Stuart A. McKeen
    • , Christoph J. Senff
    • , Colm Sweeney
    • , Patrick R. Veres
    • , Rebecca A. Washenfelder
    • , Carsten Warneke
    • , Robert J. Wild
    •  & Bin Yuan
  3. Department of Atmospheric Science, University of Wyoming, Larmie, Wyoming 82070, USA

    • Robert A. Field
    • , Shane M. Murphy
    •  & Jeffrey Soltis
  4. Department of Earth and Atmospheric Sciences, University of Houston, Houston, Texas 77204, USA

    • James H. Flynn
    •  & Barry L. Lefer
  5. Institute of Arctic and Alpine Research, University of Colorado, Boulder, Colorado 80309, USA

    • Detlev Helmig
    •  & Chelsea R. Thompson
  6. Air Quality Research Division, Environment Canada, Toronto, Ontario M3H 5T4, Canada

    • Shao-Meng Li
  7. Department of Oceanic and Atmospheric Sciences, University of California, Los Angeles, Los Angeles, California 90095, USA

    • Jochen Stutz
    •  & Catalina Tsai


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All authors contributed to the collection of observations or the development of models for the UBWOS campaigns. P.M.E. conducted all of the modelling work using the Master Chemical Mechanism. P.M.E. and S.S.B. wrote the paper with input from all co-authors, especially J.M.R., J.A.deG. and D.D.P.

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to Steven S. Brown.

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