Research Article

Volatile chemical products emerging as largest petrochemical source of urban organic emissions

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Science  16 Feb 2018:
Vol. 359, Issue 6377, pp. 760-764
DOI: 10.1126/science.aaq0524
  • Fig. 1 Mass balance of organic compounds through the U.S. petrochemical industry in 2012, from crude oil and natural gas production to resulting VOC emissions.

    (A to E) Within the chemical manufacturing sector, orange sections of boxes track hydrocarbon feedstocks (A), the fraction used for production of organic solvents [(B) and (C)], organic solvents consumed domestically for chemical products (D), and resulting emissions from use of volatile chemical products (E). Emissions from plastic, rubber, and other chemical products are not considered here. All units are in Tg; boxes are sized proportionally among (B), (C), and (D) (17).

  • Fig. 2 Total VOC emission factors for end uses of petrochemical sources considered in this study, including from mobile sources and volatile chemical products.

    Shown in the bottom row are sales data of fuels for mobile sources (from Fig. 1A) and sales data of volatile chemical products (from Fig. 1D). The green symbol and dashed arrow illustrate the large reductions in tailpipe VOC emission factors as precatalyst on-road gasoline vehicles were replaced by present-day vehicle fleets. Error bars reflect the 95% confidence interval of the mean or expert judgment (17).

  • Fig. 3 Box modeling of petrochemical VOC emissions in outdoor Los Angeles air and in buildings.

    (A and B) Evaluations of our two-compartment box model with ambient observations of individual VOCs measured at Pasadena, CA, in 2010. In (A), we input only emissions from fossil fuels (mobile + upstream sources) into the model and evaluate against outdoor data under “no chemistry” conditions; (B) is the same as (A) but with the addition of VCP emissions. (C and D) Comparison of our box model against indoor observations of residential/commercial buildings. In (C) we allow outdoor VOCs to age by 3 hours at [OH] = 1.5 × 106 molecules cm−3 in the model, typical of ambient conditions at the ground site; (D) is the same as (C) but with the addition of VCP emissions indoors. For all panels, points below the 1:1 line indicate that the box model underpredicts ambient or indoor concentrations relative to observations. Shown at the lower right of each panel is the mean relative bias and R2 of the model calculated in log space. Model statistics exclude aldehydes, which appear to be from other emission sources.

  • Fig. 4 Contributors to ambient air pollution in Los Angeles.

    (A to D) Distribution of (A) petrochemical product use, (B) VOC emissions, (C) VOC reactivity with OH, and (D) SOA formation potential across petrochemical sources only. Contributions from nonfossil sources are not shown. Uncertainties in source apportionment were determined by Monte Carlo analysis.

Supplementary Materials

  • Volatile chemical products emerging as largest petrochemical source of urban organic emissions

    Brian C. McDonald, Joost A. de Gouw, Jessica B. Gilman, Shantanu H. Jathar, Ali Akherati, Christopher D. Cappa, Jose L. Jimenez, Julia Lee-Taylor, Patrick L. Hayes, Stuart A. McKeen, Yu Yan Cui, Si-Wan Kim, Drew R. Gentner, Gabriel Isaacman-VanWertz, Allen H. Goldstein, Robert A. Harley, Gregory J. Frost, James M. Roberts, Thomas B. Ryerson, Michael Trainer

    Materials/Methods, Supplementary Text, Tables, Figures, and/or References

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    • Materials and Methods 
    • Figs. S1 to S7
    • Tables S1 to S12
    • References 

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