U.S. Geological Survey Toxic Substances Hydrology Program--Proceedings of the Technical Meeting, Colorado Springs, Colorado, September 20-24, 1993, Water-Resources Investigations Report 94-4015

Processes Controlling Dissolved Copper Concentrations during an Instream pH-Modification Experiment

Abstract

Changes in dissolved copper (Cu) concentrations as a function of pH were observed during an instream pH-modification experiment conducted in St. Kevin Gulch, Colorado, a stream affected by acidic mine drainage. Understanding the processes that control dissolved Cu concentrations is important because dissolved Cu can pose health risks and contaminate receiving waters. Comparison of dissolved Cu concentrations during the instream experiment with changes in dissolved Cu concentrations in inbottle simulation experiments performed with streamwater in the absence of streambed sediment shows good agreement. These data indicate that processes controlling Cu attenuation with increasing pH occur primarily in the water column. Sorption reactions and (or) coprecipitation reactions with iron and (or) aluminum precipitates forming in the water column in response to increasing pH may be the processes controlling Cu partitioning in these systems. Predictive computer modeling of Cu sorption onto hydrous ferric oxide slightly underestimates Cu attenuation observed in the instream system.