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Atmospheric Dispersion of Ammonia During Application of Anhydrous Ammonia Fertilizer
Author(s) -
Denmead O. T.,
Freney J. R.,
Simpson J. R.
Publication year - 1982
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.2134/jeq1982.00472425001100040003x
Subject(s) - anhydrous , ammonia , dispersion (optics) , wind speed , atmospheric dispersion modeling , atmospheric instability , atmosphere (unit) , fertilizer , atmospheric sciences , wind tunnel , environmental science , chemistry , wind direction , air pollution , meteorology , mechanics , geology , physics , organic chemistry , optics
There is a need to develop techniques for the prediction of the aerial spread of hazardous chemicals released in agricultural operations. The dispersion of ammonia (NH 3 ) gas during soil injection of anhydrous NH 3 is one such example. In previous work we established that after injection NH 3 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 NH 3 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 NH 3 emission during the operation was only 1.2 kg/ha, NH 3 concentrations up to 213 µ g/m 3 were recorded at the downwind edge in the early stages of injection. Wind speed and atmospheric stability had large influences on NH 3 dispersion. In light winds and stable conditions NH 3 concentrations > 100 µ g/m 3 were recorded when the applicator was > 200 m upwind, and some NH 3 enrichment still occurred when it was 600 m upwind. The model underestimates NH 3 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 NH 3 concentrations downwind of the applicator for a range of wind speeds and emission strengths. The approach should prove useful not only for estimating NH 3 pollution hazards but also for predicting dispersion in related agricultural operations where a time‐dependent decay and/or a line‐source analogy are appropriate.