Title: Estimating the saltation and suspension components from field wind erosion Authors
Submitted to: Aeolian Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 25, 2009
Publication Date: October 16, 2009
Repository URL: http://www.ars.usda.gov/SP2UserFiles/Place/54300520/421Estimatingsaltation.pdf
Citation: Hagen, L.J., Van Pelt, R.S., Sharratt, B.S. 2009. Estimating the saltation and suspension components from field wind erosion. Aeolian Research. 1:147-153. Available online: http://www.sciencedirect.com/science/journal/18759637. Interpretive Summary: During wind erosion on fields, the saltation (hopping) aggregates abrade the surface and create additional dust-size aggregates. Accurate estimates of the saltation and dust leaving fields are needed to determine the near-field sediment deposition and off-site dust impacts, as well as to improve wind erosion models. In this study, improved methodology to estimate dust and saltation fractions leaving fields was developed as follows: First, the eroded sediment trapped in passive samplers spaced vertically above the soil surface was sieved with precision sieves. Next, mathematical equations were fitted to the sieved data to determine the proportions of saltation and dust leaving fields. From analysis of 9 field studies in 4 states, the improved methodology showed estimated saltation decreased by 21% and dust increased by 42% compared with estimates using prior methodology reported in the literature.
Technical Abstract: Improving wind erosion models requires correct estimates of the suspended dust and saltation/creep components from field erosion events. Estimated dust emissions are used to quantify off-site effects ranging from visibility reductions to health assessments. Moreover, the saltation/creep discharge is often used in models to drive the generation of dust including PM10 (particles < 10 'm diameter) that are regulated as a health hazard. The objectives of this study are to a) propose an improved methodology (HPS) to estimate the proportions of saltation/creep and suspended aggregates in the soil discharge based on sieve cuts of the sediment trapped in catchers, b) compare these results to those of the prior methodology (FS), and c) determine downwind variation in horizontal discharge of the saltation/creep. The HPS provided excellent fits to the flux profiles measured from 0.0013 to 1.645 m height reported for the Wolfforth field experiment in Texas. Application of HPS to additional data from 9 field studies from 4 states showed the average saltation/creep discharge was 21% less than estimated by use of total discharge near the surface as calculated using FS methodology. Application of HPS to suspension data increased the estimated average suspension discharge by 42% compared to that using FS methodology. Estimates of saltation discharge from 6 field sites showed that, with possibly one exception, none of the fields reached saltation transport capacity within the 180 m field length. To improve prediction models, additional field measurements of distances to transport capacity of the saltation/creep discharge are needed for a variety of soils and surface conditions. Using the sieved sediment catch from passive sediment catchers appears to offer significant improvements in the accuracy of subsequent analysis to determine saltation/creep and suspension discharge.