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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.


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