HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Denmead, O. T. Articles by Simpson, J. R. Search for Related Content PubMed Articles by Denmead, O. T. Articles by Simpson, J. R. Agricola Articles by Denmead, O. T. Articles by Simpson, J. R.

Atmospheric Dispersion of Ammonia During Application of Anhydrous Ammonia Fertilizer¹

ABSTRACT

There is a need lo develop techniques for the prediction of the aerial spread of hazardous chemicals released in agricultural operations. The dispersion of ammonia (NH₃) gas during soil injection of anhydrous NH₃ is one such example. In previous work we established that after injection NH₃ escaped from the soil to the atmosphere at a rate that decreased exponentially with time; in our study the whole process took about 2 h. In this paper we combine the dynamics of the emission process with existing micrometeorological theory for atmospheric dispersion from line sources, to predict NH₃ concentrations in the air at the downwind edge of the field. The predictions are compared with concentrations measured during an injection operation.

Although the total NH₃ emission during the operation was only 1.2 kg/ha, NH₃ concentrations up to 213 µg/m³ were recorded at the downwind edge in the early stages of injection. Wind speed and atmospheric stability had large influences on NH₃ dispersion. In light winds and stable conditions NH₃ concentrations > 100 µg/m³ were recorded when the applicator was > 200 m upwind, and some NH₃ enrichment still occurred when it was 600 m upwind.

The model underestimates NH₃ concentrations when the treated width is <30 m, but predicts them very well at greater distances in both stable and unstable conditions. The model is used to predict NH₃ concentrations downwind of the applicator for a range of wind speeds and emission strengths.

The approach should prove useful not only for estimating NH₃ pollution hazards but also for predicting dispersion in related agricultural operations where a time-dependent decay and/or a line-source analogy are appropriate.

Key Words: atmospheric diffusion • atmospheric pollution • aerial spread • nitrogen loss

¹ Contribution of CSIRO, Australia.

² Senior Principal Research Scientists, CSIRO Div. of Environmental Mechanics (P.O. Box 821), and Plant Industry (P.O. Box 1600), respectively, Canberra City, A.C.T. 2601, Australia.

Received for publication January 30, 1982.