STUDY OF PESTICIDE IMPACTS TO THE SURFACE WATER AND SEDIMENTS IN THE NEAR SHORE ENVIRONMENTS OF OAHU AND KAUAI

This project was designed to study the potential presence and concentration of chemical pesticides and herbicides in the nearshore marine environment of Oahu and Kauai to develop an understanding of where pesticide contamination may be present.

The islands were divided into study areas for representative sampling conducted over a two-year period. Each study area included a stream, drainage, or other feature; specifically, where the surface water discharges into a marine or estuarine environment. The following criteria were applied to select the study areas: located on one of the islands in the study; located in an area which is potentially impacted by agriculture, urbanization, or recreational facilities which utilize a landscaped environment; and located in an area where recreational users may be impacted by runoff.

In general, the results of the study showed the following:

• Glyphosate and AMPA have been detected in the surface water and sediments of a significant number of the study areas. This supports the theory that Glyphosate discharge is widespread. Although the detected concentrations are significantly below the Hawaii Department of Health Environmental Action Level of 65 µg/L, there may still be implications to more sensitive organisms or with regards to bioaccumulation.

• Low concentrations of Metolachlor and Atrazine were detected at low levels in surface water samples on both Oahu and Kauai. Detections of these contaminants were inconsistent.

• Incidental other pesticides (Azoxystrobin, Carbaryl, Chlordane, DCPMU, p,p'-DDE, p,p'-DDT, Dieldrin, Diuron, Glyphosate, Imidachloprid, and Pendimethalin) have also been identified in low concentrations in sediment samples. Since sediment samples may reflect a longer duration of contaminant accumulation, some of these detections may be the result of “legacy” contaminants.

The results between sampling events were relatively consistent, indicating good usability of the data with respect to precision, accuracy, representativeness, comparability, and completeness parameters; and there was good correlation between field screening results and fixed-analytical laboratory results.