Submitted to: Agriculture and Forest Meterology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/16/2004
Publication Date: 7/25/2004
Citation: Kjelgaard, J., Sharratt, B.S., Sundram, I., Lamb, B., Claiborn, C., Saxton, K.E., Chadler, D. 2004. Pm10 Emission from Agricultural Soils on the Columbia Plateau: Comparison of Dynamic and Time-Integrated Field-Scale Measurements and Entrainment Mechanisms.. Agriculture and Forest Meterology. Interpretive Summary: The Columbia Plateau of central Washington contains vast deposits of fine loess and is an active emission source of dust particulates that can impair human health. Agriculture is thought to be a primary source of dust in this region, but few techniques exist for measuring the emission of dust from agricultural lands. Excellent agreement in measuring mean dust concentrations during dust storms was found between the tapered element oscillating microbalance and High Volume sampler (both instruments approved by the US EPA). In addition, saltation did not appear to be a primary mechanism for entrainment of dust in the Columbia Plateau as evidenced elsewhere (e.g. Great Plains) in the United States. These results provide state and federal scientists and air quality personnel (US EPA and local air authorities) with confidence in using either instrument to measure dust concentrations in rural environments. In addition, the results highlight the need for USDA-ARS and other scientists to consider mechanisms other than saltation for entrainment when modeling dust emissions from agricultural sources.
Technical Abstract: The Columbia Plateau contains vast deposits of fine loess soils and is an active emission source of particulates less than 10 µm mean diameter (PM10) which can impair human health. We attempt to characterize PM10 emissions with respect to meteorological conditions and entrainment mechanisms. A fallow, dryland field in central Washington was instrumented to continuously monitor meteorological conditions and PM10 concentrations during periods of high winds in 2001 and 2002. High volume air samplers (HiVols) and BSNE sediment traps were used to measure event-based PM10 emissions and total soil movement, respectively, while tapered element oscillating microbalances (TEOMs) and wind velocity profiles were utilized to examine real-time dust emission dynamics. Particle impact sensors (Sensits®) monitored particle movement (i.e. saltation) close to the surface. TEOM data clearly identified periods of active PM10 emission. TEOM and HiVol samplers showed excellent agreement in quantifying time-integrated PM10 concentrations during high wind events. Time-integrated PM10 concentrations were well-correlated with horizontal soil mass transport. Saltation does not appear to be a primary mechanism for entrainment of PM10 in the Columbia Plateau because of lack of saltator impacts as well as lack of roughness height modification caused by saltating particles. In general, threshold friction velocity was approximately 0.4 m s-1 and threshold velocity was approximately 8 m s-1 for our field conditions. Several wind events showed evidence that PM10 concentration gradients were virtually nonexistent, the PM10 being well-mixed within 5 m of the soil surface.