Journal
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
Volume 112, Issue 1, Pages 37-42Publisher
NATL ACAD SCIENCES
DOI: 10.1073/pnas.1417609112
Keywords
fine particulate matter; biogenic secondary organic aerosol; anthropogenic emissions; sulfate; organic nitrates
Categories
Funding
- National Science Foundation (NSF) Grant [1242258, R835410]
- National Oceanic and Atmospheric Administration Climate Program Office Award [NA10OAR4310102]
- US EPA Grant [R834799]
- NSF Graduate Research Fellowship [DGE 1106400]
- NSF Grant [1250569]
- NSF [AGS-1241498]
- NCAR's Computational and Information Systems Laboratory [ark:/85065/d7wd3xhc]
- NSF
- Southern Co.
- Electric Power Research Institute
- European Social Fund
- Greek State
- EPA [150148, R834799] Funding Source: Federal RePORTER
- Directorate For Geosciences
- Div Atmospheric & Geospace Sciences [1242258, 1250569] Funding Source: National Science Foundation
- Div Atmospheric & Geospace Sciences
- Directorate For Geosciences [1241498] Funding Source: National Science Foundation
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Secondary organic aerosol (SOA) constitutes a substantial fraction of fine particulate matter and has important impacts on climate and human health. The extent to which human activities alter SOA formation from biogenic emissions in the atmosphere is largely undetermined. Here, we present direct observational evidence on the magnitude of anthropogenic influence on biogenic SOA formation based on comprehensive ambient measurements in the southeastern United States (US). Multiple high-time-resolution mass spectrometry organic aerosol measurements were made during different seasons at various locations, including urban and rural sites in the greater Atlanta area and Centreville in rural Alabama. Our results provide a quantitative understanding of the roles of anthropogenic SO2 and NOx in ambient SOA formation. We show that isoprene-derived SOA is directly mediated by the abundance of sulfate, instead of the particle water content and/or particle acidity as suggested by prior laboratory studies. Anthropogenic NOx is shown to enhance nighttime SOA formation via nitrate radical oxidation of monoterpenes, resulting in the formation of condensable organic nitrates. Together, anthropogenic sulfate and NOx can mediate 43-70% of total measured organic aerosol (29-49% of sub-micron particulate matter, PM1) in the southeastern US during summer. These measurements imply that future reduction in SO2 and NOx emissions can considerably reduce the SOA burden in the southeastern US. Updating current modeling frameworks with these observational constraints will also lead to more accurate treatment of aerosol formation for regions with substantial anthropogenic-biogenic interactions and consequently improve air quality and climate simulations.
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