Micrometeorological Analysis of Diurnal Ammonia Emissions from Subtropical Sugarcane Production.

Atmospheric ammonia (NH₃) emission from agricultural field is a loss of nitrogen (N) nutrient from soil as well as an air quality pollutant as it is a precursor of airborne fine particulate matter of PM_2.5 (as ammonium sulfate, ammonium nitrate etc). Micrometeorological measurement of NH₃ is the study of different flux measurement techniques to calculate the vertical turbulent flow of NH₃ within atmospheric boundary layers by using different models and equations. This technique with active samplers can measure the vertical NH₃ flux very successfully. In this study, the effects of different meteorological parameters (rainfall, wind speed, wind direction, and air temperature) on vertical NH₃ emissions were evaluated. The field experiments were established in a sugarcane field at Louisiana State University AgCenter St Gabriel Research Station and field NH₃ volatilization was collected from 2011 to 2013 using two automated annual denuder systems installed in a meteorological tower at two different heights (3.65 m and 5.50 m, respectively). Collected NH₃ from citric acid coated denuders was washed off using ultrapure water and subsequently analyzed using an ion chromatography. Both day and night time NH₃ samples were taken to determine the diurnal NH₃ flux above sugarcane canopy. Results showed that average NH₃ flux for day time was 17% higher than night time NH₃ flux, indicating combined difference of soil and plant effects on NH₃ emission between day and night. Both wind speed and wind direction had significant influences on NH₃ flux. This result has significant implication in characterizing NH₃ emission from sugarcane production in the subtropical U.S.A.