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The first objective of this research was to determine if pesticides were leaching into the shallow groundwater beneath agricultural sites, and if so, to determine a correlation between soil and groundwater pesticide concentrations. The second was to examine the correlation between pesticide concentrations measured by gas chromatography with electron capture detector (GC/ECD) and an immunoassay method developed by OHMICRON Corporation. Samples from four agricultural and one reference (undeveloped) site were analyzed for pesticides over an 11 month period from April, 1992 to February, 1993. One hundred and nineteen separate groundwater samples were analyzed for: alachlor, atrazine, carbofuran, cyanazine, and metolachlor. Pesticide analysis of groundwater and seepage meter water was carried out by immunoassay and by solid phase extraction (SPE) with octadecyl bonded extraction disks followed by GC/ECD. Fifty-five soil and sediment samples were Soxhlet extracted followed by gas chromatography/mass spectrometry (GC/MS). Pesticides were detected in 13.4% groundwater samples by GC/ECD with only one detection being greater than 1 ppb. The immunoassay method detected pesticides in 32% of the groundwater samples with the majority of these detections also being below 1 ppb. Alachlor and/or metolachlor were detected in 44% of the soil samples at concentrations ranging from 7 ppb to 485 ppb. The study concluded that the majority of the target pesticides were being adsorbed by the soil and only limited amounts, less than 1 ppb, were being transported to the groundwater. It was also concluded that the immunoassay had lower limits of detection, but may yield some false positive results. / Master of Science