New Mexico Geological Society Annual Spring Meeting — Abstracts

Copper sulfate has been commonly used as an algaecide to combat cyanobacteria blooms in municipal reservoirs. The United States EPA has classified copper sulfate as a Class I toxic substance with the potency inversely related to the alkalinity and pH of water. Copper can accumulate indefinitely and bind to reservoir sediments until disturbances favor its release into the water column. This study sought to determine the levels of copper in water, sediments, and chironomids as an indicator of reservoir water quality. Samples were collected seasonally at four sites in Peterson Reservoir near Las Vegas, New Mexico. Water was analyzed for temperature, pH, dissolved oxygen, conductivity, turbidity, light intensity, Secchi disk, chlorophyll-a, alkalinity, and total phosphorus. Chironomids, sediment, and water were analyzed for copper using Graphite Furnace Atomic Absorption Spectrometry. Reservoir sediment exhibited relatively high levels of copper (18-34 ppm). Copper concentrations in invertebrates were typically higher than sediments (14-1600 ppm) indicating a bio-accumulation rate of up to 4.5 times that of the surrounding sediment. Due to the high buffering capacity of pH (~9) and alkalinity: (~200), most copper concentrations in the water column were below USEPA MCL standards. However, four sites exceeded USEPA standards (>1.3 ppm) during summer stratification and fall turnover events.