|Ph.D Student||Segal Rosenheimer Michal|
|Subject||Environmental Fate of Semivolatile Pesticides in the|
Atmosphere: Implementation of FTIR Techniques in
the Investigation of Heterogeneous
|Department||Department of Civil and Environmental Engineering||Supervisors||Professor Yael Dubowski|
|Professor Raphael Linker|
|Full Thesis text|
Pesticides are important hazardous pollutants widely used in urban and rural areas. In fact, it has long been shown that the atmosphere is an important medium, both for transportation and chemical transformations of such materials. However, most previous studies regarding pesticides’ fate focused on the soil and water compartments. Following this, the main scope of this research was to address this gap of knowledge and to quantitatively investigate (using Infra-red spectroscopic tools) the atmospheric interactions of commonly used pesticide, including their degradation via photolysis and oxidation processes. As part of this work the photolysis and heterogeneous oxidation of selected pesticides by ozone and OH radicals was investigated, either as adsorbed on stagnant surfaces as well as in their airborne state (i.e., aerosolized). In addition, the effect of purity level of the applied pesticide (analytical vs. technical grade as used in the field) on its degradation rate was also checked. The work included the utilization of IR spectroscopy as non-invasive real-time monitoring method to determine reaction kinetics, and to characterize products in both gaseous and condensed phases. Two different experimental set-ups were established in order to separately investigate deposited and airborne phases. Off-line chromatographic analyses were used complimentarily. Specifically, we have focused on two selected semi-volatile compounds, cypermethrin and methyl parathion, from two different pesticides’ families: pyrethroids and organophosphates, respectively. The novel experimental setting we established during this work allowed us to obtain reaction rate constants and quantum yield data that can be used as an input in risk assessment analyses and environmental models. It was found that surface ozonolysis and photolysis are important degradation pathways, in comparison with previously studied media (e.g. water and soil). Photolysis will play a key role outdoors for both pesticides, while ozonolysis will be more important indoors. Under the investigated conditions, no significant difference in ozonolysis was observed between analytical and technical grade cypermethrin, and between films and airborne material for the same compound. Additional aspect of this work was to extend the use of FTIR spectroscopy to test the potential of using open path FTIR instrument for real time monitoring of airborne pesticides. Field experiments for the organophosphate pesticide surrogate (Tri-2-bis-ethyl-hexyl phosphate) were done and results have been compared to theoretical radiaitve calculations (based on laboratory derived optical constants and specific size distributions). The latter revealed the capability of the detection of airborne particles under certain conditions.