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Environmental Chemistry Environmental Chemistry Society
Environmental problems - Chemical approaches
RESEARCH ARTICLE

The effect of anthropogenic volatile organic compound sources on ozone in Boise, Idaho

Victor Vargas A , Marie-Cecile Chalbot A , Robert O’Brien B , George Nikolich C , David W. Dubois C D , Vic Etyemezian C and Ilias G. Kavouras A C E
+ Author Affiliations
- Author Affiliations

A Department of Environmental and Occupational Health, University of Arkansas for Medical Sciences, 4301 West Markham Street, Little Rock, AR 72205, USA.

B VOC Technologies, Inc., 19251 Se Highway 224, Damascus, OR 97089, USA.

C Division of Atmospheric Sciences, Desert Research Institute, 755 E. Flamingo Road, Las Vegas, NV 89119, USA.

D Department of Plant and Environmental Sciences, Box 30003 MSC 3Q, Las Cruces, NM 88003, USA.

E Corresponding author. Email: ikavouras@uams.edu

Environmental Chemistry 11(4) 445-458 https://doi.org/10.1071/EN13150
Submitted: 7 August 2013  Accepted: 10 April 2014   Published: 30 July 2014

Environmental context. Volatile organic compounds are precursors of ozone, a pollutant with adverse environmental effects. It is important to determine the associations between the various sources of volatile organic compounds and ozone levels because emission controls are based on sources. We estimated the contributions of specific sources of volatile organic compounds on ozone levels using both measurements and statistical models, and found that traffic is the largest source even in events when wildfire smoke is present.

Abstract. Here, we present the application of a tiered approach to apportion the contributions of volatile organic compound (VOC) sources on ozone (O3) concentrations. VOCs from acetylene to n-propylbenzene were measured at two sites at Boise, Idaho, using an online pneumatically focussed gas chromatography system. The mean 24-h concentrations of individual VOCs varied from 0.4 ppb C (parts per billion carbon) for 1-butene to 23.2 ppb C for m- and p-xylene. The VOC sources at the two monitoring sites were determined by positive matrix factorisation. They were attributed to: (i) liquefied petroleum and natural gas (LPG/NG) emissions; (ii) fugitive emissions of olefins from fuel and solvents; (iii) fugitive emissions of aromatic VOCs from area sources and (iv) vehicular emissions. Vehicle exhausts accounted for 36 to 45 % of VOCs followed by LPG/NG and fugitive emissions of aromatic VOCs. Evaluation of photochemical changes showed that the four separate VOC sources were identified by PMF rather than different stages of photochemical processing of fresh emissions. The contributions of VOC sources on daily 8-h maximum O3 concentrations measured at seven locations in the metropolitan urban area were identified by regression analysis. The four VOC sources added, on average, 6.4 to 16.5 parts per billion by volume (ppbv) O3, whereas the unexplained (i.e. intercept) O3 was comparable to non-wildfire policy-relevant background O3 levels in the absence of all anthropogenic emissions of VOC precursors in North America for the region. Traffic was the most significant source influencing O3 levels contributing up to 32 ppbv for days with O3 concentrations higher than 75 ppbv.

Additional keywords: benzene, positive matrix factorisation, regression analysis, traffic emissions.


References

[1]  C. Cai, J. T. Kelly, J. C. Avise, A. P. Kaduwela, W. R. Stockwell, Photochemical modeling in California with two chemical mechanisms: model intercomparison and response to emission reductions. J. Air Waste Manag. Assoc. 2011, 61, 559.
Photochemical modeling in California with two chemical mechanisms: model intercomparison and response to emission reductions.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BC3MXntlyisbo%3D&md5=bec5e9d66f34dc87e3fbc51f54874b86CAS | 21608496PubMed |

[2]  J. Fuhrer, F. Booker, Ecological issues related to ozone: agricultural issues. Environ. Int. 2003, 29, 141.
Ecological issues related to ozone: agricultural issues.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BD3sXis1artbg%3D&md5=c1dc28380420ede4e4f2d5afa4858273CAS | 12676202PubMed |

[3]  N. A. Clark, P. A. Demers, C. J. Karr, M. Koehoorn, C. Lencar, L. Tamburic, M. Brauer, Effect of early life exposure to air pollution on development of childhood asthma. Environ. Health Perspect. 2009, 118, 284.
Effect of early life exposure to air pollution on development of childhood asthma.Crossref | GoogleScholarGoogle Scholar |

[4]  M. Jerrett, R. T. Burnett, C. A. Pope, K. Ito, G. Thurston, D. Krewski, Y.-L. Shi, E. Calle, M. Thun, Long-term ozone exposure and mortality. N. Engl. J. Med. 2009, 360, 1085.
Long-term ozone exposure and mortality.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BD1MXjtFyisLc%3D&md5=468af0b9cdf6bed632ea84ca1e3691d6CAS | 19279340PubMed |

[5]  A. H. Goldstein, C. D. Koven, C. L. Heald, I. Y. Fung, Biogenic carbon and anthropogenic pollutants combine to form a cooling haze over the southeastern United States. Proc. Natl. Acad. Sci. USA 2009, 106, 8835.
Biogenic carbon and anthropogenic pollutants combine to form a cooling haze over the southeastern United States.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BD1MXnsVant78%3D&md5=f052036530df26a4ed3e8f2941eef671CAS | 19451635PubMed |

[6]  C. Warneke, S. A. McKeen, J. A. deGouw, P. D. Goldan, W. C. Kuster, J. S. Holloway, E. J. Williams, B. M. Lerner, D. D. Parrish, M. Trainer, F. C. Fehsenfeld, S. Kato, E. L. Atlas, A. Baker, D. L. Blake, Determination of urban volatile organic compound emission ratios and comparison with an emissions database. J. Geophys. Res. – Atmos. 2007, 112, D10S47.
Determination of urban volatile organic compound emission ratios and comparison with an emissions database.Crossref | GoogleScholarGoogle Scholar |

[7]  V. Junquera, M. M. Russell, W. Vizuete, Y. Kimura, D. Allen, Wildfires in eastern Texas in August and September 2000: emissions, aircraft measurements, and impact on photochemistry. Atmos. Environ. 2005, 39, 4983.
Wildfires in eastern Texas in August and September 2000: emissions, aircraft measurements, and impact on photochemistry.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BD2MXntlSnsLw%3D&md5=fd721a9d46a0e5e09f930798824a0339CAS |

[8]  J. R. Arnold, R. L. Dennis, G. S. Tonnesen, Diagnostic evaluation of numerical air quality models with specialized ambient observations: testing the Community Multiscale Air Quality modeling system (CMAQ) at selected SOS 95 ground sites. Atmos. Environ. 2003, 37, 1185.
Diagnostic evaluation of numerical air quality models with specialized ambient observations: testing the Community Multiscale Air Quality modeling system (CMAQ) at selected SOS 95 ground sites.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BD3sXhslGqsbs%3D&md5=2e11114b0e040b09335929c696811d71CAS |

[9]  S. Arunachalam, B. Wang, N. Davis, B. Baek, H. J. I. Levy, Effect of chemistry-transport model scale and resolution on population exposure to PM2.5 from aircraft emissions during landing and takeoff. Atmos. Environ. 2011, 45, 3294.
Effect of chemistry-transport model scale and resolution on population exposure to PM2.5 from aircraft emissions during landing and takeoff.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BC3MXlslWqsbc%3D&md5=bd4df33333c024bf5f3361f75565fdcdCAS |

[10]  X. Tie, G. Brasseur, Z. Ying, Impact of model resolution on chemical ozone formation in Mexico City: application of the WRF-Chem model. Atmos. Chem. Phys. 2010, 10, 8983.
Impact of model resolution on chemical ozone formation in Mexico City: application of the WRF-Chem model.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BC3MXktlant7c%3D&md5=cd963265a0c085d811ca0e5a7870e370CAS |

[11]  L. C. Valin, A. R. Russell, R. C. Hudman, R. C. Cohen, Effects of model resolution on the interpretation of satellite NO2 observations. Atmos. Chem. Phys. 2011, 11, 11 647.
Effects of model resolution on the interpretation of satellite NO2 observations.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BC38Xis1Kktrk%3D&md5=0a0952971e9c4474d4d0e761a054c3bbCAS |

[12]  H. Cheng, H. Guo, X. M. Wang, S. M. Saunders, S. H. M. Lam, F. Jiang, T. J. Wang, A. J. Ding, S. C. Lee, K. F. Ho, On the relationship between ozone and its precursors in the Pearl River Delta: application of an observation-based model (OBM). Environ. Sci. Poll. Res. 2010, 17, 547.
On the relationship between ozone and its precursors in the Pearl River Delta: application of an observation-based model (OBM).Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BC3cXitVSis7w%3D&md5=f7708fae04698af7fb4899acc7cf4a96CAS |

[13]  H. R. Cheng, H. Guo, S. M. Saunders, S. H. M. Lam, F. Jiang, X. M. Wang, I. J. Simpson, D. R. Blake, P. K. K. Louie, T. J. Wang, Assessing photochemical ozone formation in the Pearl River Delta with a photochemical trajectory model. Atmos. Environ. 2010, 44, 4199.
Assessing photochemical ozone formation in the Pearl River Delta with a photochemical trajectory model.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BC3cXhtFChsL%2FF&md5=adfaf3c5dab307d2ef70d429a6019c3aCAS |

[14]  Z. H. Ling, H. Guo, H. R. Cheng, Y. F. Yu, Sources of ambient volatile organic compounds and their contributions to photochemical ozone formation at a site in the Pearl River Delta, southern China. Environ. Pollut. 2011, 159, 2310.
Sources of ambient volatile organic compounds and their contributions to photochemical ozone formation at a site in the Pearl River Delta, southern China.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BC3MXhtFeht7nP&md5=58d16190b59fe17bacf3c3224a60ae76CAS | 21616570PubMed |

[15]  W. P. L. Carter, Development of ozone reactivity scales for volatile organic compounds. J. Air Waste Manag. Assoc. 1994, 44, 881.
Development of ozone reactivity scales for volatile organic compounds.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DyaK2MXlvVKmurw%3D&md5=e8806064480e1b856d961de401738635CAS |

[16]  L. H. Wang, J. B. Milford, W. P. L. Carter, Reactivity estimates for aromatic compounds. Part 2. Uncertainty in incremental reactivities. Atmos. Environ. 2000, 34, 4349.
Reactivity estimates for aromatic compounds. Part 2. Uncertainty in incremental reactivities.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BD3cXlsVOktb4%3D&md5=659979f0631c6de325754a96d4ceecaeCAS |

[17]  B. H. Czader, D. W. Byun, S. T. Kim, W. P. L. Carter, A study of VOC reactivity in the Houston–Galveston air mixture utilizing an extended version of SAPRC-99 chemical mechanism. Atmos. Environ. 2008, 42, 5733.
A study of VOC reactivity in the Houston–Galveston air mixture utilizing an extended version of SAPRC-99 chemical mechanism.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BD1cXosVaisLs%3D&md5=d172f764306a400696f46294953674f7CAS |

[18]  W. P. L. Carter, J. H. Seinfeld, Winter ozone formation and VOC incremental reactivities in the Upper Green River Basin of Wyoming. Atmos. Environ. 2012, 50, 255.
Winter ozone formation and VOC incremental reactivities in the Upper Green River Basin of Wyoming.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BC38XitFWrsro%3D&md5=9ffd858149e454aa928d0e97021005f3CAS |

[19]  M. Barna, B. Lamb, S. O’Neil, B. Westberg, C. Figueroa-Kaminsky, S. Otterson, C. Bowman, J. DeMay, Modeling ozone formation and transport in the Cascadia region of the Pacific Northwest. J. Appl. Meteorol. 2000, 39, 349.
Modeling ozone formation and transport in the Cascadia region of the Pacific Northwest.Crossref | GoogleScholarGoogle Scholar |

[20]  J. J. Carroll, A. J. Dixon, Regional scale transport over complex terrain, a case study: tracing the Sacramento plume in the Sierra Nevada of California. Atmos. Environ. 2002, 36, 3745.
Regional scale transport over complex terrain, a case study: tracing the Sacramento plume in the Sierra Nevada of California.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BD38Xms1Gqs7o%3D&md5=a2d97856dc882516d476bf26f71b90b6CAS |

[21]  I. G. Kavouras, D. W. DuBois, V. Etyemezian, G. Nikolich, G. Spatiotemporal variability of ground-level ozone and influence of smoke in Treasure Valley, Idaho. Atmos. Res. 2013, 124, 44.
G. Spatiotemporal variability of ground-level ozone and influence of smoke in Treasure Valley, Idaho.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BC3sXjs1Cjurc%3D&md5=1a77c2db2381c4fd077a6e3b663b7e94CAS |

[22]  M. Leuchner, B. Rappengluck, VOC source-receptor relationships in Houston during TexAQS-II. Atmos. Environ. 2010, 44, 4056.
VOC source-receptor relationships in Houston during TexAQS-II.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BC3cXhtFCnsLbE&md5=ea6e0223bd21feba9b12a43b775de52eCAS |

[23]  S. G. Brown, A. Frankel, H. R. Hafner, Source apportionment of VOC in the Los Angeles area using positive matrix factorization. Atmos. Environ. 2007, 41, 227.
Source apportionment of VOC in the Los Angeles area using positive matrix factorization.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BD28XhtlajsrzP&md5=6c9abf59e7edc5ef1fc8da905c7dfa67CAS |

[24]  D. M. Bon, I. M. Ulbrich, J. A. de Gouw, C. Warneke, W. C. Kuster, M. L. Alexander, A. Baker, A. J. Beyersdorf, D. Blake, R. Fall, J. L. Jimenez, S. C. Herndon, L. G. Huey, W. B. Knighton, J. Ortega, S. Springston, O. Vargas, Measurements of volatile organic compounds at a suburban ground site (T1) in Mexico City during the MILAGRO 2006 campaign: measurement comparison, emission ratios and source attribution. Atmos. Chem. Phys. 2011, 11, 2399.
Measurements of volatile organic compounds at a suburban ground site (T1) in Mexico City during the MILAGRO 2006 campaign: measurement comparison, emission ratios and source attribution.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BC3MXnvFajsrw%3D&md5=d149f5dbf62de2d806d0352610b2b90eCAS |

[25]  Z. B. Yuan, A. K. H. Lau, M. Shao, P. K. K. Louie, S. C. Liu, T. Zhu, Source analysis of volatile organic compounds by positive matrix factorization in urban and rural environments in Beijing. J. Geophys. Res. – Atmos. 2009, 114, D00G15.
Source analysis of volatile organic compounds by positive matrix factorization in urban and rural environments in Beijing.Crossref | GoogleScholarGoogle Scholar |

[26]  C. Gaimoz, S. Sauvage, V. Gros, F. Hermann, J. Williams, N. Locoge, O. Perrussel, B. Bonsang, O. d’Argouges, R. Sarda-Esteve, J. Sciare, Volatile organic compounds sources in Paris in spring 2007. Part II: sources apportionment using positive matrix factorization. Environ. Chem. 2011, 8, 91.
Volatile organic compounds sources in Paris in spring 2007. Part II: sources apportionment using positive matrix factorization.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BC3MXjs1Glsb0%3D&md5=d8888e9a3fcffdefa756f91e0251982dCAS |

[27]  Y. Morino, T. Ohara, Y. Yokouchi, Comprehensive source apportionment of volatile organic compounds using observational data, two receptor models and an emission inventory in Tokyo metropolitan area. . J. Geophys. Res. – Atmos. 2011, 116, D02311.
Comprehensive source apportionment of volatile organic compounds using observational data, two receptor models and an emission inventory in Tokyo metropolitan area. .Crossref | GoogleScholarGoogle Scholar |

[28]  H. Jorquera, B. Rappengluck, Receptor modeling of ambient VOC at Santiago, Chile. Atmos. Environ. 2004, 38, 4243.
Receptor modeling of ambient VOC at Santiago, Chile.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BD2cXltlyhsLs%3D&md5=1181afe60d507d054bef3a69f44cfae4CAS |

[29]  B. Yuan, M. Shao, J. deGouw, D. D. Parrish, S. Lu, M. Wang, L. Zeng, Q. Zhang, Y. Song, J. Zhang, M. Hu, Volatile organic compounds (VOCs) in urban area: how chemistry affects the interpretation of positive matrix factorization (PMF) analysis. J. Geophys. Res. – Atmos. 2012, 117, D24302.
Volatile organic compounds (VOCs) in urban area: how chemistry affects the interpretation of positive matrix factorization (PMF) analysis.Crossref | GoogleScholarGoogle Scholar |

[30]  R. J. O’Brien, T. R. Smith, U.S. Patent 6 865 926. Method and apparatus for sample analysis 2005.

[31]  R. J. O’Brien, U.S. Patent 6 952 945. Method and apparatus for concentrating samples for analysis 2005.

[32]  R. O’Brien, The GC-in-a-PC: real-time Web-based monitoring of VOC and air toxics, Proceedings of the Annual Air & Waste Management Association Conference, 20–23 June 2006, New Orleans, LA, 2006 (Air and Wastes Management Association, Pittsburgh, PA).

[33]  R. O’Brien, K. Percy, A. Legge, Co-measurement of volatile organic and sulphur compounds in the athabasca oil sands region by dual detector pneumatic focusing gas chromatography (PFGC), in Development in Environmental Science II, Alberta Oil Sands, Energy, Industry and the Environment (Ed. K. Percy), 2012, Ch 6, pp. 113–144 (Elsevier: Amsterdam, the Netherlands).

[34]  EPA Positive Matrix Factorization (PMF) 3.0 Fundamentals and User Guide. EPA 600/R-08/108 2008 (US Environmental Protection Agency, Office of Research and Development: Washington, DC).

[35]  P. Paatero, P. K. Hopke, X.-H. Song, Z. Ramadan, Understanding and controlling rotation in factor analytic models. Chemom. Intell. Lab. Syst. 2002, 60, 253.
Understanding and controlling rotation in factor analytic models.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BD38XksVyhuw%3D%3D&md5=180d945c862296d9d378a5c5f7148c48CAS |

[36]  P. Paatero, U. Tapper, Positive matrix factorization: a non-negative factor model with optimal utilization of error estimates of data values. Environmetrics 1994, 5, 111.
Positive matrix factorization: a non-negative factor model with optimal utilization of error estimates of data values.Crossref | GoogleScholarGoogle Scholar |

[37]  A. V. Polissar, P. K. Hopke, W. C. Malm, F. Sisler, The ratio of aerosol optical absorption coefficients to sulfur concentrations, as an indicator of smoke from forest fires when sampling in polar regions. Atmos. Environ. 1996, 30, 1147.
The ratio of aerosol optical absorption coefficients to sulfur concentrations, as an indicator of smoke from forest fires when sampling in polar regions.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DyaK28XhslGmurY%3D&md5=98164e7770dd9b96bbcd7c8979f88362CAS |

[38]  S. Juntto, P. Paatero, Analysis of daily precipitation data by positive matrix factorization. Environmetrics 1994, 5, 127.
Analysis of daily precipitation data by positive matrix factorization.Crossref | GoogleScholarGoogle Scholar |

[39]  Locating and Estimating Air Emissions from Sources of Styrene, EPA-454-R-93-011 1993 (US Environmental Protection Agency, Office of Air Quality, Planning and Standards: Research Triangle Park, NC).

[40]  Asphalt Emulsion Technology, Number E-C102 2006 (Transportation Research Board of the National Academies: Washington, DC).

[41]  P. Paatero, P. K. Hopke, B. A. Begum, S. K. Biswas, A graphical diagnostic method for assessing the rotation in factor analysitcal models of atmospheric pollution. Atmos. Environ. 2005, 39, 193.
A graphical diagnostic method for assessing the rotation in factor analysitcal models of atmospheric pollution.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BD2cXhtVaisb%2FP&md5=ab31d63e433d4701eb7d873ac505a76eCAS |

[42]  P. Paatero, Least-squares formulation of robust non-negative factor analysis. Chemom. Intell. Lab. Syst. 1997, 37, 23.
Least-squares formulation of robust non-negative factor analysis.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DyaK2sXivFKgtLc%3D&md5=58aa60df74b28edc0b98a5a66775f61cCAS |

[43]  X.-H. Song, A. V. Polissar, P. K. Hopke, Sources of fine particle composition in the northeastern US. Atmos. Environ. 2001, 35, 5277.
Sources of fine particle composition in the northeastern US.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BD3MXmvVGgtbY%3D&md5=ec099e46ec59742f2a75633ccf6d510fCAS |

[44]  Idaho Roads – 2007 Annual Average Daily Traffic 2007 (Idaho Transportation Department). Available at http://www.itd.idaho.gov/planning/gis/maps/spatialdata/AADT2007.zip [Verified 4 February 2013].

[45]  EMFAC2011 2011 (California Air Resources Board: Sacramento, CA). [Updated January 2013].

[46]  T. Schmitz, D. Hassel, F. J. Weber, Determination of VOC-component in the exhaust of gasoline and diesel passenger cars. Atmos. Environ. 2000, 34, 4639.
Determination of VOC-component in the exhaust of gasoline and diesel passenger cars.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BD3cXmtVCguro%3D&md5=631c313a70aa18e9b67cb4857c54eec7CAS |

[47]  S. Liu, X.-Z. Liang, Observed diurnal cycle climatology of planter boundary layer height. J. Clim. 2010, 23, 5790.
Observed diurnal cycle climatology of planter boundary layer height.Crossref | GoogleScholarGoogle Scholar |

[48]  Z. J. Zhao, S. Husainy, G. D. Smith, Kinetic studies of the gas-phase reactions of NO3 radicals with series of 1-alkenes, dienes, cycloalkenes, alkenols and alkenals. J. Phys. Chem. 2011, 115, 12 161.
Kinetic studies of the gas-phase reactions of NO3 radicals with series of 1-alkenes, dienes, cycloalkenes, alkenols and alkenals.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BC3MXhtlWjt7%2FJ&md5=dfa2cc34bdf45a07c6860ce4e8dd726fCAS |

[49]  Rethinking the Ozone Problem in Urban and Regional Air Pollution 1991 (National Research Council, National Academy Press: Washington, DC).

[50]  H. Simon, L. Beck, P. V. Bhave, F. Divita, Y. Hsu, D. Luecken, J. D. Mobley, G. A. Pouliot, A. Reff, G. Sarwar, M. Strum, The development and uses of EPA’s SPECIATE database. Atmos. Poll. Res. – Atmos. 2010, 1, 196.
The development and uses of EPA’s SPECIATE database.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BC3cXhtlelsL7I&md5=d83c082270436b454ec06137d633e4deCAS |

[51]  D. R. Blake, F. S. Rowland, Urban leakage of liquefied petroleum gas and its impact on Mexico City air quality. Science 1995, 269, 953.
Urban leakage of liquefied petroleum gas and its impact on Mexico City air quality.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DyaK2MXnsFOmtL4%3D&md5=f73484cba40d5ce0de8031efffba9487CAS | 17807730PubMed |

[52]  Northern Ada County Air Quality Maintenance Area Second 10-Year Carbon Monoxide Limited Maintenance Plan. Appendix C 2011 (Idaho Department of Environmental Quality: Meridian, ID). Available at http://www.deq.idaho.gov/media/909870-ada-county-co-maintenance-plan-2011-appendices.pdf [Verified January 2013].

[53]  Final Comformity of the FY2008–2012 Northern Ada County Transportation Improvement Program. Report number 11-2007 2007 (Community Planning Association of Southwest Idaho: Meridian, ID).

[54]  J. A. de Gouw, A. M. Middlebrook, C. Warneke, P. D. Goldan, W. C. Kuster, J. M. Roberts, F. C. Fehsenfeld, D. R. Worsnop, M. R. Canagaratna, A. A. P. Pszenny, W. C. Keene, M. Marchewka, S. B. Bertman, T. S. Bates, Budget of organic carbon in a polluted atmosphere: results from the New England Air Quality Study in 2002. J. Geophys. Res. – Atmos. 2005, 110, D16305.
Budget of organic carbon in a polluted atmosphere: results from the New England Air Quality Study in 2002.Crossref | GoogleScholarGoogle Scholar |

[55]  I. G. Kavouras, B. Zielisnka, The effect of fuel evaporation and biomass burning on toluene concentrations in an urban area. Water Air Soil Pollut. 2012, 223, 5931.
The effect of fuel evaporation and biomass burning on toluene concentrations in an urban area.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BC38Xhs1Sru7jN&md5=126a5cb3f245fd525905571f17626660CAS |

[56]  R. Atkinson, Gas phase tropospheric chemistry of volatile organic compounds. I. Alkanes and alkenes. J. Phys. Chem. Ref. Data 1997, 26, 521.
Gas phase tropospheric chemistry of volatile organic compounds. I. Alkanes and alkenes.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DyaK2sXjsFGhsb8%3D&md5=da27ccc3028cf950279828482e91ae53CAS |

[57]  C. Warneke, S. A. McKeen, J. A. de Gouw, P. D. Goldan, W. C. Kuster, J. S. Holloway, E. J. Williams, B. M. Lerner, D. D. Parrish, M. Trainer, F. C. Fehsenfeld, S. Kato, E. L. Atlas, A. Baker, D. R. Blake, Determination of urban volatile organic compound emission ratios and comparison with an emissions database. J. Geophys. Res. – Atmos. 2007, 112, D10S47.
Determination of urban volatile organic compound emission ratios and comparison with an emissions database.Crossref | GoogleScholarGoogle Scholar |

[58]  C. Emery, J. Jung, N. Downey, J. Johnson, M. Jimenez, G. Yarwood, R. Morris, Regional and global modeling estimates of policy relevant background ozone over the United States. Atmos. Environ. 2012, 47, 206.
Regional and global modeling estimates of policy relevant background ozone over the United States.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BC3MXhs1Krtb3O&md5=e4e7930a94c556d234cf9895cac661faCAS |