CaltechAUTHORS
Published February 18, 2020 | Version Supplemental Material + Published
Journal Article Open

Remarkable nucleation and growth of ultrafine particles from vehicular exhaust

Creators

  • 1. ROR icon Peking University
  • 2. ROR icon State Key Joint Laboratory of Environment Simulation and Pollution Control
  • 3. ROR icon Texas A&M University
  • 4. ROR icon Tsinghua University
  • 5. ROR icon California Institute of Technology
  • 6. ROR icon Guangdong University of Technology
  • 7. ROR icon The University of Texas at Austin
  • 8. ROR icon Institute of Chemistry
  • 9. ROR icon Beijing Normal University
  • 10. ROR icon Hangzhou Dianzi University
  • 11. ROR icon University of Science and Technology of China
  • 12. ROR icon University of California, San Diego

Abstract

High levels of ultrafine particles (UFPs; diameter of less than 50 nm) are frequently produced from new particle formation under urban conditions, with profound implications on human health, weather, and climate. However, the fundamental mechanisms of new particle formation remain elusive, and few experimental studies have realistically replicated the relevant atmospheric conditions. Previous experimental studies simulated oxidation of one compound or a mixture of a few compounds, and extrapolation of the laboratory results to chemically complex air was uncertain. Here, we show striking formation of UFPs in urban air from combining ambient and chamber measurements. By capturing the ambient conditions (i.e., temperature, relative humidity, sunlight, and the types and abundances of chemical species), we elucidate the roles of existing particles, photochemistry, and synergy of multipollutants in new particle formation. Aerosol nucleation in urban air is limited by existing particles but negligibly by nitrogen oxides. Photooxidation of vehicular exhaust yields abundant precursors, and organics, rather than sulfuric acid or base species, dominate formation of UFPs under urban conditions. Recognition of this source of UFPs is essential to assessing their impacts and developing mitigation policies. Our results imply that reduction of primary particles or removal of existing particles without simultaneously limiting organics from automobile emissions is ineffective and can even exacerbate this problem.

Additional Information

© 2020 the Author(s). Published by PNAS. This open access article is distributed under Creative Commons Attribution-NonCommercial-NoDerivatives License 4.0 (CC BY-NC-ND). Contributed by Mario J. Molina, December 19, 2019 (sent for review September 23, 2019; reviewed by Robert L. McGraw and Fangqun Yu). PNAS first published February 3, 2020. This work was supported by National Natural Science Foundation of China Grants 91544214 and 21677002; National Key Research and Development Program of China Grant 2016YFC0202000: Task 3; National Research Program for Key Issues in Air Pollution Control Grant DQGG0103; and Robert A. Welch Foundation Grant A-1417. We thank Don Collins for the application of the QUALITY chamber. Data and Materials Availability: All data are available in the text or SI Appendix. S.G., M.H., J.P., and M.L.Z. contributed equally to this work. Author contributions: S.G., M.H., and R.Z. designed research; S.G., M.H., J.P., Z.W., M.L.Z., D.S., Z.D., J. Zheng, X.F., R.T., Y.W., S.S., W.Z., Y.W., Y.J., Y.L., W.W., F.Z., J. Zhao, X.G., C.W., and R.Z. performed research; S.S., M.J.M., and R.Z. contributed new reagents/analytic tools; S.G., M.H., J.P., Z.W., M.L.Z., L.Z., S.S., Y.W., A.L.Z., M.J.M., and R.Z. analyzed data; and S.G., M.H., A.L.Z., and R.Z. wrote the paper. Reviewers: R.L.M., Brookhaven National Laboratory; and F.Y., State University of New York at Albany. The authors declare no competing interest.

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Additional details

Identifiers

PMCID
PMC7035480
Eprint ID
101098
DOI
10.1073/pnas.1916366117
Resolver ID
CaltechAUTHORS:20200204-080030144

Related works

Describes
10.1073/pnas.1916366117 (DOI)

Funding

National Natural Science Foundation of China
91544214
National Natural Science Foundation of China
21677002
National Key Research and Development Program of China
2016YFC0202000
National Research Program for Key Issues in Air Pollution Control
DQGG0103
Robert A. Welch Foundation
A-1417

Dates

Created
2020-02-04
Created from EPrint's datestamp field
Updated
2022-02-16
Created from EPrint's last_modified field