This project seeks to provide a sampling regime and analytical support for water quality assessment.
The New River and Lower Colorado River Toxicity Study evaluates the toxicity of ambient waters to growth and development, or reproductive capacity of invertebrates, plants, and fish. Water from several locations along the New River and Lower Colorado River were collected by scientists from the Palm Desert Regional Water Quality Control Board and shipped to UC Davis for analysis. The sampling was conducted over a second year and Phase I toxicant identification evaluations (TIEs) were done. Coordinating efforts with the EPA binational monitoring program for the New River and Lower Colorado River was a priority. At one location along the New River samples were collected monthly in order to assess seasonal effects on ambient toxicity. From the initial year a total of 20 TIEs were conducted. In these toxic samples, use of a solid phase (C8) column removed the toxicity in 94% of the samples. When the material was eluted from the column and added back, toxicity was returned in 88% of the samples. Use of the cytochrome p450 inhibitor, piperonyl butoxide (PBO) removed the toxicity in 92% of samples. This indicates the active agent was an organophosphate and that the toxicity resides with the oxon of the compound, formation of which is blocked by PBO addition. Second year TIE results were even more convincing in that the C8 column, toxicity add-backs and PBO worked in each of the seven samples on which TIEs were performed. One component of the toxicity is related to agricultural return waters.
This project has been completed and successfully provided a sampling regime and analytical support for water quality assessment.