Abstract. Off-road vehicle training can contribute to air quality degradation because of increased wind erosion as a result of soil disruption during high wind events; however, limited information exists regarding the impacts of off-road vehicle maneuvering on wind erosion potential of soils. This study was conducted to determine the effects of soil texture and intensity of training with off-road vehicles on fugitive dust emission potential due to wind erosion at military training installations. Multi-pass military vehicle trafficking experiments involving wheeled and tracked vehicles were conducted at three military training facilities with different vegetative conditions and soil textures (i.e., Fort Riley, KS; Fort Benning, GA; and Yakima Training Center, WA). The top 6 cm of soil was collected with minimum disturbance into trays and tested in a laboratory wind tunnel for dust emission potential. In wind tunnel testing, the amount of emitted dust was measured using a GRIMM aerosol spectrometer. The dust emission potential was significantly influenced by soil texture, vehicle type, and number of passes. For the light-wheeled vehicle, total dust emissions increased from 66 mg m-2 for undisturbed soil to 304 mg m-2 (357%) and 643 mg m-2 (868%) for 10 and 50 passes, respectively. For the tracked vehicle, an average increase in total dust emission of 569% was observed between undisturbed conditions and 1 pass, with no significant increase in emission potential beyond 1 pass. For the heavy-wheeled vehicle, emissions increased from 75 mg m-2 for undisturbed soil to 1,652 mg m-2 (1,369%) and 4,023 mg m-2 (5,276%) for 10 and 20 passes, respectively. Soil texture also played an important role in dust emission potential. For all treatment effects, there was a 1,369% difference in emissions between silty clay loam soil and loamy sand soil.
Abstract.The Unmix receptor model was applied to the 2002-2014 speciated PM2.5 data from the IMPROVE site at Tallgrass National Preserve near Strong City, Kansas, to investigate the contributions of prescribed rangeland burning on local air quality. This investigation found the following five source categories that contribute to annual local ambient PM2.5: nitrate/agricultural (22%), vegetative burning (5%), secondary organic aerosol (29%), sulfate/industrial (30%), and crustal/soil (14%). In the month of April, the contributions of vegetative burning and secondary organic aerosol increased to 11% and 49%, respectively, indicating the influence of the prescribed burning season. The contribution of smoke from prescribed burning was estimated to be 1.05 μg m-3 as primary aerosols and 4.03 μg m-3 as secondary aerosols, which in total accounted for 42% of the average PM2.5 concentration in April.
Abstract. Off-road vehicle training can contribute to air quality degradation because of increased wind erosion as a result of soil disruption during high wind events. However, limited information exists regarding the impacts of off-road vehicle maneuvering on wind erosion potential of soils. This study was conducted to determine the effects of soil texture and intensity of training with off-road vehicles on fugitive dust emission potential due to wind erosion at military training installations. Multi-pass military vehicle trafficking experiments involving wheeled and tracked vehicles were conducted at three military training facilities (Fort Riley, Kansas; Fort Benning, Georgia; and Yakima Training Center, Washington) with different vegetative conditions and soil textures. The top 6 cm of soil was collected with minimum disturbance into trays and tested in a laboratory wind tunnel for dust emission potential. In wind tunnel testing, the amount of emitted dust was measured using a Grimm aerosol spectrometer. The dust emission potential due to wind erosion was significantly influenced by soil texture, vehicle type, and number of passes. For the light wheeled vehicle, total dust emissions (<20 μm) increased by 357% and 868% for 10 and 50 passes, respectively, from the undisturbed soil condition. For the tracked vehicle, an average increase in total dust emissions (<20μm) of 569% was observed between undisturbed soil and one pass, with no significant increase in emission potential beyond one pass. For the heavy wheeled vehicle, evaluated only at Yakima, emissions (<20 μm) increased by 2,108% and 5,276% for 10 and 20 passes, respectively, from the undisturbed soil condition. Soil texture also played an important role in dust emission potential. For all treatment effects with the light wheeled vehicle, there was a 1,396% increase in emissions (<20 μm) on loamy sand soil over silty clay loam soil.
Reverse dispersion modeling has been used to determine air emission fluxes from ground-level area sources, including open-lot beef cattle feedlots. This research compared Gaussian-based AERMOD, the preferred regulatory dispersion model of the U.S. Environmental Protection Agency (EPA), and WindTrax, a backward Lagrangian stochastic-based dispersion model, in determining PM10 emission rates for a large beef cattle feedlot in Kansas. The effect of the type of meteorological data was also evaluated. Meteorological conditions and PM10 concentrations at the feedlot were measured with micrometeorological/eddy covariance instrumentation and tapered element oscillating microbalance (TEOM) PM10 monitors, respectively, from May 2010 through September 2011. Using the measured meteorological conditions and assuming a unit emission flux (i.e., 1 µg/m2-sec), each model was used to calculate PM10 concentrations (referred to as unit-flux concentrations). PM10 emission fluxes were then back-calculated using the measured and calculated unit-flux PM10 concentrations. For AERMOD, results showed that the PM10 emission fluxes determined using the two different meteorological data sets evaluated (eddy covariance-derived and AERMET-generated) were basically the same. For WindTrax, the two meteorological data sets (sonic anemometer data set, a three-variable data set composed of wind parameters, surface roughness, and atmospheric stability) also produced basically the same PM10 emission fluxes. Back-calculated emission fluxes from AERMOD were 32 to 69% higher than those from WindTrax. Implications This work compared the PM10 emission rates determined from a large commercial cattle feedlot in Kansas by reverse dispersion modeling using AERMOD and WindTrax. Emission fluxes derived from AERMOD were greater than those from WindTrax by mean factors of 1.3 to 1.6. Based on the high linearity observed between the two models, emission fluxes derived from one dispersion model for the purpose of simulating dispersion could be applied to the other model using appropriate conversion factors.
ABSTRACT Particulate matter (PM) emitted from cattle feedlots are thought to affect air quality in rural communities, yet little is known about factors controlling their emissions. The concentrations of PM (i.e., PM2.5, PM10, and total suspended particulates or TSP) upwind and downwind at two large cattle feedlots (KS1, KS2) in Kansas were measured with gravimetric samplers from May 2006 to October 2009 (at KS1) and from September 2007 to April 2008 (at KS2). The mean downwind and net (i.e., downwind − upwind) mass concentrations of PM2.5, PM10, and TSP varied seasonally, indicating the need for multiple-day, seasonal sampling. The downwind and net concentrations were closely related to the moisture content of the pen surface. The PM2.5/PM10 and PM2.5/TSP ratios at the downwind sampling location were also related to the moisture content of the pen surface, humidity, and temperature. Measurement of the particle size distribution downwind of the feedlot with a cascade impactor showed geometric mean diameter ranging from 7 to 18 μm, indicating that particles that were emitted from the feedlots were generally large in size. IMPLICATIONS This work characterized the total suspended particulates (TSP), PM10, and PM2.5 concentrations emitted from large cattle feedlots in Kansas, providing baseline information on concentrations and size distribution of particulates emitted from feedlots in the Great Plains. As expected, high dust events were observed during the spring and summer; dust control strategies should target those potential dust events. PM emitted from the feedlots was dominated by coarse particles; as such, development and evaluation of dust control strategies, including water sprinkling, shelterbelts, etc., might have to focus more on the coarse particles. The moisture content of the pen surface was one of the most significant factors affecting PM concentrations in cattle feedlots; by controlling the moisture content, it would be possible to control dust emissions.
Abstract. Maintaining vegetative cover on the soil surface is the most widely used method for control of soil loss by wind erosion. We numerically modeled airflow through artificial standing vegetation (i.e., simulated wheat plants) using computational fluid dynamics (CFD). A solver (simpleFoam within the OpenFOAM software architecture) was used to simulate airflow through various three-dimensional (3D) canopy structures in a wind tunnel, which were created using another open-source CAD geometry software (Salomé ver. 7.2). This study focused on two specific objectives: (1) model airflow through standing vegetation using CFD, and (2) compare the results of a previous wind tunnel study with various artificial vegetation configurations to the results of the CFD model. Wind speeds measured in the wind tunnel experiment differed slightly from the numerical simulation using CFD, especially near positions where simulated vegetation was present. Effective drag coefficients computed using wind profiles did not differ significantly (p <0.05) between the experimental and simulated results. Results of this study will provide information for research into other types of simulated stubble or sparse vegetation during wind erosion events. Highlights Measured airflow through a simulated canopy was successfully modeled using CFD software. Effective drag coefficients did not differ between the experimental and simulated results. Results of this study provide 3-D simulation data of wind flow through a plant canopy. Keywords: 3-D canopy structure, OpenFOAM, Wind erosion, Wind tunnel studies.
Abstract. Crop residues help protect topsoil from depletion and abrasion due to wind erosion. Limited studies have focused on the type and orientation of canopies that help minimize the effects of erosion by wind. In this study, a series of wind tunnel experiments was conducted to measure sand transport and abrasion energies within simulated standing vegetation. Wind speed profiles, relative abrasion energies, and rates of sand discharge were evaluated during 3 min test runs at two different vegetation heights (150 and 220 mm) for each of three densities of simulated vegetation (i.e., 100 × 200 mm, 200 × 200 mm, and 300 × 200 mm spacing). Tests were also conducted for a bare sand surface. As expected, vegetation density was directly related to threshold velocity and inversely related to sand discharge. The densest configuration (i.e., 100 × 200 mm spacing) increased the threshold velocity of bare sand from 5.9 to 10 m s -1 . The presence of vegetation was found to be effective in minimizing the abrasion experienced by the standing vegetation models by lowering the saltation of sand particles that could impact the simulated plants. The coefficient of abrasion (C an ), a measure of kinetic energy via the impact of saltating particles, was affected by saltation discharge, although this did not depend on wind speed. The values of C an for all configurations were significantly different (p < 0.05) from the bare sand surface . Keywords: Abrasion energy, Sand discharge, Standing vegetation, Threshold wind velocity, Wind erosion.
