Chemical Variability of PM^sub 10^ and PM^sub 2.5^ in Southwestern Rural Nevada, USA

The levels and composition of particulate matter in Ash Meadows National Wildlife Refuge (NWR) that hosts the only population of the endangered Devil's Hole pupfish (Cyprinodon diabolis) were examined to obtain baseline air quality information. PM^sub 10^ and PM^sub 2.5^ mass concentrations were measured using continuous monitors over a period of 12 months. In addition, integrated PM^sub 10^ and PM^sub 2.5^ filter samples were collected and a subset chemically analyzed for elements, ions, elemental carbon, and organic carbon. The average filter-based PM^sub 10^ (10.9 [mu]g m^sup -3^) and PM^sub 2.5^ (5.1 [mu]g m^sup -3^) levels at Ash Meadows NWR are similar to those previously measured at rural and continental background sites in the southwestern USA. Mineral dust accounted for the largest percentage of aerosol mass, with the highest concentrations being measured during fall months of 2009. Elemental and organic carbon levels were generally low, except for August 29, 2009. During this event, transport of wildfire smoke was suggested, by the passage of air masses over wildfires in California, Utah, and Arizona. Ammonium sulfate varied with season, with the highest concentrations in spring and the lowest in fall and winter. Halite (NaCl) quantities were very low, except for the filter samples collected during a windy period on October 4, 2009 indicating the possible contribution of alkaline playa dust upwind of the site. Above average concentrations of crustal calcium compounds, including carbonates and gypsum, were measured in the PM^sub 10^ sample collected on November 9, 2009 as well as the two preceding months, ascribed to wind-driven dusty conditions prevailing throughout the late summer and fall of 2009.