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Diurnal cycle of fossil and nonfossil carbon using radiocarbon analyses during CalNex
Author(s) -
Zotter Peter,
ElHaddad Imad,
Zhang Yanlin,
Hayes Patrick L.,
Zhang Xiaolu,
Lin YingHsuan,
Wacker Lukas,
SchnelleKreis Jürgen,
Abbaszade Gülcin,
Zimmermann Ralf,
Surratt Jason D.,
Weber Rodney,
Jimenez José L.,
Szidat Sönke,
Baltensperger Urs,
Prévôt André S. H.
Publication year - 2014
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
eISSN - 2169-8996
pISSN - 2169-897X
DOI - 10.1002/2013jd021114
Subject(s) - radiocarbon dating , plume , carbon fibers , total organic carbon , aerosol , environmental chemistry , gasoline , carbon cycle , environmental science , diurnal cycle , fossil fuel , air quality index , chemistry , atmospheric sciences , geology , meteorology , geography , ecology , paleontology , organic chemistry , ecosystem , materials science , composite number , composite material , biology
Radiocarbon ( 14 C) analysis is a unique tool to distinguish fossil/nonfossil sources of carbonaceous aerosols. We present 14 C measurements of organic carbon (OC) and total carbon (TC) on highly time resolved filters (3–4 h, typically 12 h or longer have been reported) from 7 days collected during California Research at the Nexus of Air Quality and Climate Change (CalNex) 2010 in Pasadena. Average nonfossil contributions of 58% ± 15% and 51% ± 15% were found for OC and TC, respectively. Results indicate that nonfossil carbon is a major constituent of the background aerosol, evidenced by its nearly constant concentration (2–3 μgC m −3 ). Cooking is estimated to contribute at least 25% to nonfossil OC, underlining the importance of urban nonfossil OC sources. In contrast, fossil OC concentrations have prominent and consistent diurnal profiles, with significant afternoon enhancements (~3 μgC m −3 ), following the arrival of the western Los Angeles (LA) basin plume with the sea breeze. A corresponding increase in semivolatile oxygenated OC and organic vehicular emission markers and their photochemical reaction products occurs. This suggests that the increasing OC is mostly from fresh anthropogenic secondary OC (SOC) from mainly fossil precursors formed in the western LA basin plume. We note that in several European cities where the diesel passenger car fraction is higher, SOC is 20% less fossil, despite 2–3 times higher elemental carbon concentrations, suggesting that SOC formation from gasoline emissions most likely dominates over diesel in the LA basin. This would have significant implications for our understanding of the on‐road vehicle contribution to ambient aerosols and merits further study.