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Ammonia (NH3) is the dominant gaseous base in the atmosphere and a principal neutralizing agent for atmospheric acids.
Volatilized ammonia:
- represents a reduction in fertilizer use efficiency by crops;
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acts as an atmospheric buffer by reacting with NOx and SOx from combustion.
NH4NOx and NH4SOx are components of
PM2.5, an air quality particulate problem that may require regulation.
In California, the estimated patterns of N deposition suggest that for areas close to
photochemical smog areas, concentrations of the oxidized forms of N (NO2,
HNO3) dominate, whereas in areas near agricultural activities the importance of reduced
N forms (NH3 and NH4+) increases.
The magnitude and distribution of NH3 emissions from fertilizer application and
other agricultural sources are still largely undetermined.
Objectives
Overall: To estimate NH3 emissions from a variety of major crop-fertilizer
combinations and from native soils in California.
Phase One:
- Develop a simulation model for NH3 emissions from native soils using satellite
image drivers and other spatial data.
- Evaluate an active sampler for monitoring NH3 emissions from fertilized fields and
background soil emission levels.
Modeling Methods
As a regional model application to the state of California, we built on the foundation
of the NASA-CASA ecosystem trace gas model. Vegetation greenness estimates from satellite data
were used as inputs to estimate productivity of ecosystems and associated nitrogen mineralization
rates in soils, which provide the substrate for potential NH3 volatilization.
Predicted NH3 fluxes from the model were constrained by a new series of field
measurements from cropped areas in the Central Valley.
Field Methods
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