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Elemental Composition of Particulates Near a Beef Cattle Feedlot¹

ABSTRACT

The elemental compositions of dusts captured near a beef cattle feedlot were examined for the purpose of determining whether manure dusts could be identified in the presence of background dusts using alpha-excited X-rays.

Large quantities of particulates greater than 17 µm in diameter were caught within the feedlot, but concentrations of these large particulates downwind of the lot were equal to or less than upwind levels.

High ratios of P, S, Cl, K, and Ca to Si distinguished feedlot dusts to greater than 2 µm background particulates. For small particulate sizes (less than 2 µm), feedlot dusts were characterized by relatively high Cl, K, and Ca to Si ratios. On the fringe of feedlot influence, about 100 m downwind in this case, high K/Si and Ca/Si ratios were the most reliable indicators of manure dust.

For the particular environmental conditions during this study in the southern San Joaquin Valley of California, feedlot dusts were not detected at a distance of 750 m downwind. Feedlot dust consists mainly of large particulates that drop out rapidly and locally.

Key Words: alpha-excited X-ray flourescence • manure dust

¹ Research partially supported by California Air Resources Board Contract ARB-2-006.

² Staff Research Associate, Department of Soils and Plant Nutrition; Air Monitoring Group Leader, Crocker Nuclear Laboratory; Associate Professor of Physics, Crocker Nuclear Laboratory; and Professor of Soil Science, Dept. of Soils Plant Nutrition, University of California, Davis, Calif. 95616, respectively.

Received for publication July 17, 1973.