Abstract: Systems and methods for estimating an emission rate of at least one source are described. The system includes an anemometer, a gas sensor and a processor. The processor is configured to: receive a background concentration of the gas not affected by the at least one source and atmospheric stability 5 information associated with the sensing location; measure a set of parameters, including a concentration of a gas and a wind speed and wind direction; input the N sets of parameters, the position and height of the at least one source, the position and height of the gas sensor, the background concentration and dispersion parameters into a function relating the gas concentration to the wind 10 direction; and invert the function relating the gas concentration to the wind direction to obtain each source emission rate.