In
this work, we deployed a single particle aerosol mass spectrometer
(SPAMS) at a suburban coastal site in Hong Kong from February 04 to
April 17, 2013 to study individual oxalate particles and a monitor
for aerosols and gases in ambient air (MARGA) to track the bulk oxalate
concentrations in particle matter smaller than 2.5 μm in diameter
(PM2.5). A shallow dip in the bulk oxalate concentration
was consistently observed before 10:00 am in the morning throughout
the observation campaign, corresponding to a 20% decrease in the oxalate
concentration on average during the decay process. Such a decrease
in PM oxalate was found to be coincident with a decrease in Fe-containing
oxalate particles, providing persuasive evidence of Fe-mediated photochemical
degradation of oxalate. Oxalate mixed with Fe and Fe_NaK particles,
from industry sources, were identified as the dominant factors for
oxalate decay in the early morning. We further found an increase of
sulfate intensity by a factor of 1.6 on these individual Fe-containing
particles during the oxalate decomposition process, suggesting a facilitation
of sulfur oxidation. This is the first report on the oxalate–Fe
decomposition process with individual particle level information and
provides unique evidence to advance our current understanding of oxalate
and Fe cycling. The present work also indicates the importance of
anthropogenic sourced iron in oxalate–Fe photochemical processing.
In addition, V-containing oxalate particles, from ship emissions,
also showed evidence of morning photodegradation and need further
attention since current models rarely consider photochemical processing
of oxalate_V particles.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.