Biological input to visibility-reducing aerosol particles in the remote arid southwestern United States

Abstract

Source contributions of contemporary biological material
\nto remote airsheds of the arid southwestern United States are described. Combined inputs of epicuticular plant waxes and airborne microorganisms range from winter minimum (11.3-26.9 ng/m^3) to summer maximum ambient mass concentrations (21.2-41.4 ng/m^3). Concentrations of aromatic resin acids (Le., dehydroabietic acid and 13-isopropyl-5cu-podocarpa-6,8,11,13-tetraen-l6-oic
\nacid) plus a thermally matured wood smoke marker (i.e.,
\nretene) range from 1.2 to 9.6 ng/m^3. Minimum levels of
\nthe resin acids and wood smoke marker are observed for
\nthe sparse desert vegetation site (low elevation), and
\nmaximum levels are found for the transition site of
\nponderosa pine and pinyon/juniper forest (high elevation).
\nThe total wood smoke mass contributions were estimated
\nby using the ambient mass concentrations of both the
\naromatic resin acid and wood smoke tracers. Based on
\nthese estimates, combustion of conifer biomass (e.g.,
\nnatural wildfires, camp fires, home heating) is an important
\ncomponent of the organic emission source inventory for
\nthis desert region.