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. 2019 May 10;16(9):1632.
doi: 10.3390/ijerph16091632.

Quantifying Urban Spatial Variations of Anthropogenic VOC Concentrations and Source Contributions with a Mobile Sampling Platform

Peishi Gu  1 , Timothy R Dallmann  2 , Hugh Z Li  3 , Yi Tan  4 , Albert A Presto  5
Affiliations

Quantifying Urban Spatial Variations of Anthropogenic VOC Concentrations and Source Contributions with a Mobile Sampling Platform

Peishi Gu et al. Int J Environ Res Public Health. .

Abstract

Volatile organic compounds (VOCs) are important atmospheric constituents because they contribute to formation of ozone and secondary aerosols, and because some VOCs are toxic air pollutants. We measured concentrations of a suite of anthropogenic VOCs during summer and winter at 70 locations representing different microenvironments around Pittsburgh, PA. The sampling sites were classified both by land use (e.g., high versus low traffic) and grouped based on geographic similarity and proximity. There was roughly a factor of two variation in both total VOC and single-ring aromatic VOC concentrations across the site groups. Concentrations were roughly 25% higher in winter than summer. Source apportionment with positive matrix factorization reveals that the major VOC sources are gasoline vehicles, solvent evaporation, diesel vehicles, and two factors attributed to industrial emissions. While we expected to observe significant spatial variability in the source impacts across the sampling domain, we instead found that source impacts were relatively homogeneous.

Keywords: BTEX; air toxics; mobile sampling; source apportionment.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Location of each sampling site and the boundary of each group of sites defined based on proximity and geography. Sites from the two phases of measurement are separated by color. The outer boundary is the political boundary of Allegheny County, PA.
Figure 2
Figure 2
Example chromatogram. Speciated VOC compounds are marked at their peaks. Total VOC concentrations are calculated based on the area between the chromatogram signal and the fitted baseline, starting from i-pentane to everything before nonane.
Figure 3
Figure 3
Map of elevation above sea level (in feet), major roads and major VOC point source facilities in Allegheny County. AADT = Annual Average Daily Traffic counts.
Figure 4
Figure 4
The average concentration of total VOC, speciated VOC (sum of 13 species identified in Figure 2), and BTEX for each group of sites, ranked based on the order of total VOC concentrations. Error bars show one standard deviation.
Figure 5
Figure 5
The average concentration of total VOC, speciated VOC and BTEX for each type of site when classified by land use. Error bars show one standard deviation.
Figure 6
Figure 6
Seasonal variation of total VOC, speciated VOC and BTEX concentrations for Phase I dataset. Error bars show one standard deviation.
Figure 7
Figure 7
Ratio-ratio plot with benzene and toluene concentrations normalized by Black Carbon (BC). (a) All samples (white dots) and samples from Downtown/North Shore (cyan squares) are plotted on a log scale. (b) Top 10% highest total VOC concentrations are plotted as magenta circles and lowest 10% total VOC concentrations are plotted as green circles. Gasoline vehicle (large circles) and diesel vehicle (large squares) emission profiles, as well as industrial emission profiles in Pittsburgh (diamonds) are overlaid to visualize the source impacts.
Figure 8
Figure 8
Ratio-ratio plot with toluene and n+i-pentane concentrations normalized by benzene concentrations. (a) Phase I winter data are plotted in blue circles and Phase I summer data are plotted in orange circles. The distribution of these ambient data on two axes are also shown in boxplots, with lines representing medians, boxes representing interquartile range, and whiskers representing 5th and 95th percentiles. (b) Data with the highest and lowest 10% of total VOC concentrations. Gasoline vehicle (circles) and diesel vehicle (squares) emission profiles, as well as evaporative fuel and solvent emission profiles (grey triangles) are overlaid to visualize the source impacts.
Figure 9
Figure 9
Factor profiles for the five-factor solution of the Positive Matrix Factorization (PMF) model based on the speciated VOC concentrations along with BC concentrations.
Figure 10
Figure 10
The concentrations and fractions of each PMF factor in each geographic group of sites.
Figure 11
Figure 11
The concentrations and fractions of each factor in each type of site. The source mix is similar across the various land uses.
See this image and copyright information in PMC

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