Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/15/2006
Publication Date: 12/15/2006
Citation: Sharratt, B.S., Lauer, D. Particulate matter concentration and air quality affected by windblown dust in the Columbia Plateau. Journal of Environmental Quality. 35:2011-2016. 2006. Interpretive Summary: Several locations within the Columbia Plateau region of eastern Washington have failed to achieve air quality standards for PM10 (particulate matter less than or equal to 10µm in diameter) on one or more days per year due to wind blown dust. The US EPA has now proposed to regulate PMcoarse (particulate matter between 2.5 and 10 um in diameter). This is a concern for locations within the Columbia Plateau because soils prone to wind erosion in the region contain relatively large amounts of PMcoarse. A 220% increase in number of days of exceedance was observed at a location immediately downwind from a vast and highly erodible agricultural area when using the proposed PMcoarse standard (daily concentration of 70µg m-3) as compared with the level of the current PM10 standard (daily concentration of 150µg m-3). Although the EPA has proposed to exempt agricultural sources from the PMcoarse standard, future regulation of all sources of PMcoarse will necessitate agronomists and soil scientists with the USDA-ARS and USDA-NRCS to escalate efforts in developing land management practices that will reduce wind erosion and emission of PMcoarse from soils in the region.
Technical Abstract: Several locations within the Columbia Plateau region of the Pacific Northwest United States failed to achieve air quality standards for PM10 (particulate matter less than or equal to 10µm in aerodynamic diameter) in the late 1980’s and early 1990’s. Exceedance of the PM10 standard (more than one day per year with a concentration >150µg m-3) is largely associated with synoptic dust storms. The EPA has recently proposed to regulate PMcoarse (particulates 2.5-10µm in diameter); exceedance of the PMcoarse standard is expected based upon the high frequency of dust storms and the large contribution of crustal material to fugitive dust in the region. The objective of this study was to explore the implication of the proposed standard for PMcoarse on air quality exceedances. Concurrent observations of both PM10 and PM2.5 (particulate matter less than or equal to 2µm in diameter) were made at Kennewick, WA from 1999 through 2005. Daily PMcoarse concentration was determined as the difference between PM10 and PM2.5 (PMfine) concentrations. The number of days that exceed the proposed US EPA national ambient air quality standard for PMcoarse was determined for various levels of the standard (the proposed daily level of the standard is 70µg m-3). Over the seven years of this study, the level of the PM10 standard was exceeded on 16 days with the PMfine constituting 4 to 7% of PM10. The proposed level of the PMcoarse standard would have been exceeded 35 days and represents a 220% increase in the number of days that exceed the level of the current PM10 standard. Changing the level of the PMcoarse standard to that of the current PM10 standard would result in a 20% decrease in the number of days that exceed the level of the PM standard. The results of this study suggest that the proposed threshold level of the PMcoarse standard will greatly increase the number of days of exceedance in a region subject to seasonal dust storms.