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Simple Protocols to Determine Dust Potentials from Cattle Feedlot Soil and Surface Samples

USDA Agricultural Research Service, U.S. Meat Animal Research Center, P.O. Box 166, Clay Center, NE 68933

View larger version (27K): [in a new window]   Fig. 1. Schematic for converting a standard laboratory blender into a dust generator. Dashed arrows indicate direction of air flow into and out of the dust generator.

View larger version (43K): [in a new window]   Fig. 2. The general protocol developed for determining the dust potential of soils and feedlot surface samples including an optional step for determining the dust potential over a range of moisture.

View larger version (23K): [in a new window]   Fig. 3. Effect of (A) cumulative blending time and (B) repeated sampling from the ditch soil on dust potential. Dust potential was measured as mass of dust collected on a glass fiber filter during 15 s of vacuum collection while blending. The period of rapid dust generation is denoted using filled circles, whereas a lower rate of dust production after 4 min is denoted by open circles. All dust samples were collected consecutively from the same ditch soil sample.

View larger version (29K): [in a new window]   Fig. 4. Effect of (A) sample mass and (B) volume on measured dust potential (mass of dust on the filter after 15 s of vacuum collection during blender operation) from four feedlot samples. The SE of the least squares mean (n = 3) for dust potential is 17.5. The range of maximum dust potential for each sample is defined as the range of masses (or volumes) that produced a dust potential that did not differ (P > 0.01) from the maximum dust potential measurement.

View larger version (31K): [in a new window]   Fig. 5. Effect of vacuum collection time on the amount of dust collected on the glass fiber filter and on air flow through the dust generator. The SE of the least squares mean (n = 3) for dust potential is 25.8.

View larger version (32K): [in a new window]   Fig. 6. Effect of sample moisture and organic matter (OM) content on dust potential from the four feedlot samples. Moisture and OM at the time of sample collection are indicated in Table 1. Values of the maximum dust potential and moisture threshold (MT; the moisture at which dust potential is half of the maximum dust potential) were calculated using regression Eq. [1]. The SE of the least squares mean (n = 3) for dust potential is 13.8. Inset figure shows the relationship between OM content and MT. The 95% confidence interval for MT varied from ±2.04 to 2.65 g H2O kg-1 dry matter (DM) for the range of samples tested.

View larger version (24K): [in a new window]   Fig. 7. Effect of sample on the airborne dust residence time using the alternate protocol. The alternate protocol differed from the general protocol by collecting airborne material immediately after the blender was stopped. The SE of the least squares mean (n = 3) for dust potential is 2.3.