Determining the Binding Affinity of Pesticides and Dissolved Organic Matter

Pesticide is a general term used to comprise the insecticides, herbicides, and fungicides used in the environment, all of which are substances that are utilized to control unwanted elements. As these elements decay, insects, weeds, and fungi become organic material, which are composed of thousands of complex, organic compounds known as Dissolved Organic Matter (DOM). As DOM tends to bind with certain pesticides, these interactions can lead to leaching from soils into surface water and groundwater, thus altering water treatment processes and drinking water supplies. Thus, the objective of the research conducted was to determine the relationship between the complex, chemical structure of DOM and its binding affinity with pesticide chemicals utilizing the equilibrium dialysis experiment. DOM of 14 Texas locations were characterized before the dialysis experiment by taking total organic carbon (TOC) and ultraviolet (UV) measurements. The contaminant utilized in the PTFE dialysis units with the extracted DOM was the herbicide alachlor. From high performance liquid chromatography (HPLC) results, two samples exhibited significant interactions and binding with alachlor. Although the interactions correlated with either high or low levels of pH, TOC, and SUVA, the losses of total alachlor in the dialysis devices and its difficulty in replicating environmental conditions resulted in inconclusive data, as reported in prior studies. Additionally, the dialysis process demonstrated to be an inefficient method to reach equilibration and replicate environmental conditions.