Aerosol characterization for agricultural field burning smoke .

摘要

Rural communities in eastern Washington and northern Idaho have been concerned about health problems related to smoke exposure from agricultural field burning. However, pollution from field burning often does not violate air quality standards, and not much is known about community exposure to smoke from field burning. This research improves the understanding of air quality impacts from regional agricultural field burning in these communities.; PM2.5 measurements were made at a monitoring site established in Pullman, WA during the fall 2002. Two source-receptor models were used to apportion PM2.5 from vegetative burning smoke. Contributions of PM2.5 from soil (38%), vegetative burning (35%), and sulfate aerosol (20%), and much less from vehicles (2%) and cooking (1%) were found in the Pullman airshed.; However, the source profile for vegetative burning used in the previous study was not able to differentiate agricultural residue smoke versus smoke from woodstoves. Levoglucosan and 19 methoxyphenols (MPs) were evaluated as tracers for wheat and Kentucky bluegrass (KBG) stubble smoke. PM samples from wheat and KBG stubble smoke were collected from controlled chamber burns, and field burns in the region. Among the MPs analyzed in this work, syringaldehyde, acetosyringone and coniferylaldehyde were found to be the most prominent tracers for wheat smoke, and were not always present in detectable amounts in KBG smoke, while the ratio of LG/syringaldehyde found in wheat stubble (∼80) was much higher than the same ratio reported for hardwood (∼5).; During the Pullman study, the continuous PM2.5 measurements alone were not able to distinguish vegetative combustion from soil originated PM. In addition to PM2.5 monitors, an aethalometer was used to make this distinction. This instrument is a semi-continuous monitor that indirectly measures light absorbing carbon (LAC) aerosol concentrations by measuring light absorption through a quartz filter.; Evidence indicates that the aethalometer may be affected by semi-volatile organic compounds (SVOC), multiple scattering, and a non-linear response to highly absorbing particles. In order to quantify and correct for these interferences, the aethalometer was tested with a SVOC denuder at controlled conditions of PM from Diesel exhaust and a correction was proposed for measuring near-real time concentrations of BC from freshly emitted soot.