In­situ monitoring of trace gases in a non-urban environment

Abstract A set of commercial instruments measuring carbon monoxide (CO), ozone (O 3 ), sulfur dioxide (SO 2 ), and nitrogen oxides [nitric oxide (NO), nitrogen dioxide (NO 2 ), and odd nitrogens (NO X )] was integrated and deployed in a non– urban environment. The deployment occurred between July 2, 2007 and August 7, 2007 in Richland, WA. The mixing ratios of all species were lower than in most rural–suburban environments, and strong diurnal patterns were observed. NO 2 was depleted by photochemically formed ozone during the day and replenished at night as ozone was destroyed. The highest ozone concentration during these episodes was 45 ppb. The overall average was 15 ppb with readings approaching near zero at times. This observation is low compared to average daytime summer readings of 60–80 ppb in highly populated and industrialized urban areas in the Pacific Northwest region. Back-trajectory analysis and prevailing weather conditions both indicated that much of the ozone was transported locally or was produced in– situ . Analysis of SO 2 as a tracer for O 3 advection further indicated lack of long–range regional transport of pollutants to Richland. We also present results of analysis of high ozone episodes and comparisons relative to other areas in the Pacific Northwest region. These results provide a useful sample data set to study the historical record of air quality in rural Eastern Washington.