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Using an open-path FTIR for real-time detection of toxic gases and aerosols in the outdoor environments

Oz Kira, Yael Dubowski, Raphael Linker

This study focus on development of methodology for measurement of particulate matter using Open Path FTIR (OP-FTIR) remote sensing (applying both active and passive operation modes). In year 5 we succeeded to detect and quantify pesticide drift. In the active mode, we were able to quantify the amount of water content in the line of sight of the OP-FTIR. Additionally, we were able to detect in the open spraying tunnel experiments different concentrations of ammonium sulfate (0.5%-2.5% wt dissolved) in the sprayed water. In the passive mode, we developed a method for cloud free spectra reconstruction using meteorological conditions and past spectral measurements. Due to the lack of artificial IR source in this mode of operation, information on the cloud free spectra in passive sensing is crucial for detection and quantification of the target agent. This method allows us to detect droplet clouds under varying environmental conditions, using a statistical process control. In the real field experiments, we were able to identify, for the first time, the spectral signature of the active ingredient (i.e., the pesticide itself) in the sprayed solution. The present efforts will continue and detection and quantification of different compounds will be tested in the Technion spraying tunnel, both in active and passive modes. In the field, similar sprayings (with pesticides and ammonium sulfate) will be tested, with measurements of spray drift at different elevations (below and above the canopy) near the field border for different spraying devices. A paper describing detection and quantification of water aerosols is in review.