This document presents an equation for calculating emission rates of NH3 using average concentration measurements and background levels. It describes the Backward-Lagrangian Stochastic method, which simulates NH3 transport from source to measurement location to predict the ratio of average concentration to emission rate. This method requires inputs like wind speed, direction, surface roughness, stability, measured concentrations and background levels.

1. QBLS = (CL-Cb)/(CL/Q)sim
Where
Q = emission rate of NH3
CL = average NH3 concentration
Cb = Background gas concentration
Backward-Lagrangian Stochastic (BLS)
 Simulates transport of NH3 from emitting source to
measurement location.
 Predict the ratio of average NH3 concentration (CL) to the
emission rate (Q).

2.  Wind Speed
 Wind direction
 Surface roughness length
 Atmospheric stability (Obukhor length, Friction velocity)
 Measured NH3 concentration
 Background NH3 Concentration
Why WindTrax?
 Experimental simplicity
 Absence of limitations on size and shape of emitting
source
 Flexibility in type and location of samplers