Ph.D Thesis

Ph.D StudentKira Oz
SubjectMonitoring Pesticide Drift Using Open-Path FTIR
DepartmentDepartment of Civil and Environmental Engineering
Supervisors PROF. Raphael Linker


The use of pesticides is important to unsure food security around the world. Unfortunately, exposure to pesticides can lead to cancer, Parkinson or developmental disorders. This study suggests using Open Path Fourier Transfer Infra-Red (OP-FTIR) spectroscopy for detecting, quantifying, and identifying aerosols in general and spray drift in particular. The rationale for this work is that numerous materials have distinct spectral signature in the mid-infrared range (wavelength range: 2μm-20μm). Moreover, for particles in the size range relevant to the present study, scattering is significant, which provides additional information but also makes the analysis much more complex. 

The OP-FTIR was used both in active mono-static and passive setups to measure different water-based droplets clouds in the size range of a few microns to ~500μm. Measurements were conducted in two main settings: a polyethylene tunnel at the Technion equipped with a custom spraying system similar to agricultural sprayers, which provided a semi-controlled environment, and a full scale research farm (Matityahu) with several orchards in which various types of tractor-mounted agricultural sprayers were tested.

The experiments conducted in the Technion tunnel demonstrated the ability of active-mode OP-FTIR to quantify water droplet in the line of sight (LOS). Additionally, we were able to quantify, for the first time, solutes such as ammonium sulfate (non-volatile, concentrations range of 0.25%-3.6%wt) and ethylene glycol (volatile, concentration range of 0.35%-2.38%wt).

Active-mode measurements performed at the Matityahu research orchards yielded positive results and the spectral signatures of the two fungicides tested (Impulse and Bogiron) were detected in several types of experimental setups. Additionally, several sprayers were tested and their spray drift was quantified at four different heights (3m, 4m, 5m, 6m). This kind of measurements provides basic information for comparing sprayers in terms of their environmental impact.

With respect to the passive OP-FTIR measurements, this research suggests a novel, simple way of detecting an aerosol cloud, without utilizing radiative transfer models. Meteorological measurements (temperature, relative humidity and solar irradiance) and chemometric methods (multiple linear regression and artificial neural networks) together with previous cloud-free OP-FTIR measurements were used to estimate the ambient spectrum in real-time. The cloud detection process included a statistical comparison between the estimated cloud-free signal and the measured OP-FTIR signal. The use of this approach led to successful detection of several aerosol clouds (water spray) in controlled conditions as well as during agricultural pesticide spraying in an orchard.

This work demonstrates the potential of the OP-FTIR for detecting clouds of water-based aerosols, quantifying water droplets loads, and quantifying and identifying solutes and active ingredients (pesticides) at concentrations relevant to agricultural applications.