Extrapolation of Droplet Catch Measurements in Aerosol Application Treatments

This paper reports on the methodology to quantify remote measurements of airborne aerosols using a light detection and ranging (LIDAR) system. Calibration with both active and passive sampling techniques was examined in a field study to define the use of calibrated LIDAR to quantify spray distribution across both space and time. The LIDAR was used to scan vertical cross-sections of the spray plume downwind from a moving sprayer path. Active and passive field samplers were used to obtain the spray collection at 10 m from the sprayer path (at 500 m from LIDAR). A thermal fogger and two ultra-low-volume aerosol applicators were used to produce aerosol spray in both day and nighttime applications. The results showed linear relationships between LIDAR backscatter from the spray plume and spray tracer collection on samplers (R2 ≈ 0.77). A linear transfer function from the active samplers was applied to quantify spray plume flux across scanned cross-sections at various distances from the spray path. Plume-to-plume variability statistics were consistent with previous studies in turbulent atmospheres. Examples of LIDAR plume cross-section scans with extrapolated plume fluxing downwind are presented.