Particulate emissions from a beef cattle feedlot using the flux-gradient technique.

Data on air emissions from open-lot beef cattle () feedlots are limited. This research was conducted to determine fluxes of particulate matter with an aerodynamic diameter ≤10 µm (PM) from a commercial beef cattle feedlot in Kansas using the flux-gradient technique, a widely used micrometeorological method for air emissions from open sources. Vertical PM concentration profiles and micrometeorological parameters were measured at the feedlot using tapered element oscillating microbalance PM samplers and eddy covariance instrumentations (i.e., sonic anemometer and infrared hygrometer), respectively, from May 2010 through September 2011, representing feedlot conditions with air temperatures ranging from -24 to 39°C. Calculated hourly PM fluxes varied diurnally and seasonally, ranging up to 272 mg m h, with an overall median of 36 mg m h. For warm conditions (air temperature of 21 ± 10°C), the highest hourly PM fluxes (range 116-146 mg m h) were observed during the early evening period, from 2000 to 2100 h. For cold conditions (air temperature of -2 ± 8°C), the highest PM fluxes (range 14-27 mg m h) were observed in the afternoon, from 1100 to 1500 h. Changes in the hourly trend of PM fluxes coincided with changes in friction velocity, air temperature, sensible heat flux, and surface roughness. The PM emission was also affected by the pen surface water content, where a water content of at least 20% (wet basis) would be sufficient to effectively reduce PM emissions from pens by as much as 60%.

Comparison of AERMOD and WindTrax dispersion models in determining PM10 emission rates from a beef cattle feedlot.

UNLABELLED: 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 US. 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 microg/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.

Particulate matter emission rates from beef cattle feedlots in Kansas-reverse dispersion modeling.

Open beef cattle feedlots emit various air pollutants, including particulate matter (PM) with equivalent aerodynamic diameter of 10 microm or less (PM10); however limited research has quantified PM10 emission rates from feedlots. This research was conducted to determine emission rates of PM10 from large cattle feedlots in Kansas. Concentrations of PM10 at the downwind and upwind edges of two large cattle feedlots (KS1 and KS2) in Kansas were measured with tapered element oscillating microbalance (TEOM) PM10 monitors from January 2007 to December 2008. Weather conditions at the feedlots were also monitored. From measured PM10 concentrations and weather conditions, PM10 emission rates were determined using reverse modeling with the American Meteorological Society/U.S. Environmental Protection Agency Regulatory Model (AERMOD). The two feedlots differed significantly in median PM10 emission flux (1.60 g/m2-day for KS1 vs. 1.10 g/m2-day for KS2) but not in PM10 emission factor (27 kg/1000 head-day for KS1 and 30 kg/1000 head-day KS2). These emission factors were smaller than published U.S. Environmental Protection Agency (EPA) emission factor for cattle feedlots.

Concentrations of particulate matter emitted from large cattle feedlots in Kansas.

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 microm, indicating that particles that were emitted from the feedlots were generally large in size.

Laboratory evaluation of dust-control effectiveness of pen surface treatments for cattle feedlots.

Emission of particulate matter (PM) is one of the major air quality concerns for large beef cattle feedlots. Effective treatments on the uncompacted soil and manure mixture of the pen surface may help in reducing PM emission from feedlots. A laboratory apparatus was developed for measuring dust-emission potential of cattle feedlot surfaces as affected by pen surface treatments. The apparatus was equipped with a simulated pen surface, four mock cattle hooves, and samplers for PM with equivalent aerodynamic diam. ≤ 10 µm (PM(10)). The simulated pen surface had a layer of dry, loose feedlot manure with a compacted soil layer underneath. Mock hooves were moved horizontally on the manure layer to simulate horizontal action of cattle hooves on the pen surface. High-volume PM samplers were used to collect emitted dust. Effects of hoof speed, depth of penetration, and surface treatments with independent candidate materials (i.e., sawdust, wheat straw, hay, rubber mulch, and surface water application) on PM(10) emission potential of the manure layer were investigated. Our laboratory study showed PM(10) emission potential increased with increasing depth of penetration and hoof speed. Of the surface treatments evaluated, application of water (6.4 mm) and hay (723 g m(-2)) exhibited the greatest percentage reduction in PM(10) emission potential (69 and 77%, respectively) compared with the untreated manure layer. This study indicated application of hay or other mulch materials on the pen surface might be good alternative methods to control dust emission from cattle feedlots.

Field comparison of inhalable and total dust samplers for assessing airborne dust in swine confinement barns.

Inhalable and total dust sampling devices were compared for evaluating airborne dust in swine confinement buildings. Measurements from three swine facilities (n = 77 paired means) were obtained by area sampling using the IOM (Institute of Occupational Medicine, Edinburgh, U.K.) inhalable dust sampler and a 37-mm closed-face total (TCF) dust sampler. The overall geometric mean IOM concentration (1.18 mg/m(3), geometric standard deviation [GSD] = 2.00) was significantly greater (P < 0.05) than the overall geometric mean TCF concentration (1.08 mg/m(3), GSD = 1.98). Regression analysis with IOM and TCF values as independent and dependent variables, respectively, yielded a factor of 0.86 (+/-0.04 95% confidence interval), which can be used to estimate TCF values from the IOM measurements. Additional paired sampling data were obtained to compare the following pairs of dust samplers: (1) IOM sampler and conical inhalable sampler (CIS) (n = 20 paired means), (2) IOM and open-face total (TOF) dust samplers (n = 14), (3) CIS and TCF samplers (n = 19), and (4) TCF and TOF samplers (n = 8). Paired t-tests showed significantly (P < 0.05) higher IOM concentrations than the CIS sampler; no significant difference (P > 0.05) was found for the other three pairs compared. It may be necessary to establish work-specific conversion coefficients to obtain a reasonable estimate of worker exposure to total dust from measurements using other types of dust sampling devices.

Assessment of bioaerosols in swine barns by filtration and impaction.

Bioaerosol concentrations inside one naturally ventilated and one mechanically ventilated swine finishing barn were assessed by sampling air using membrane filtration and impaction (six-stage Andersen sampler), and assayed by culture method. The barns, located on the same commercial farm in northeast Kansas, did not show any significant difference (p > 0.05) in concentrations of total and respirable airborne microorganisms. The overall mean total concentrations inside the two barns were 6.6 x 10(4) colony forming units (CFU)/m3 (SD = 3.8 x 10(4) CFU/m3 as measured by filtration and 8.6 x 10(4) CFU/m3 (SD = 5.1 x 10(4) CFU/m3) by impaction. The overall mean respirable concentrations were 9.0 x 10(3) CFU/m3 (SD = 4.1 x 10(3) CFU/m3) measured by filtration and 2.8 x 10(4) CFU/m3 (SD = 2.2 x 10(4) CFU/m3) by impaction. Total and respirable CFU concentrations measured by impaction were significantly (p < 0.05) higher than that by filtration. The persistent strains of microorganisms were various species of the following genera: Staphylococcus, Pseudomonas, Bacillus, Listeria, Enterococcus, Nocardia, Lactobacillus, and Penicillium. It appears that filtration sampling can be used for a qualitative survey of bioaerosols in swine barns while the Andersen sampler is suitable for both quantitative and qualitative assessments.