Chemical Speciation of Dissolved Copper in Saginaw Bay, Lake Huron, with Square Wave Anodic Stripping Voltammetry

Abstract

Although chemical speciation studies of copper in sea and estuarine waters have received extensive attention, few investigations have been reported dealing with freshwater eco-systems. This work represents the first set of accurate and comprehensive data on chemical speciation of dissolved copper in Saginaw Bay, Michigan, obtained with square wave anodic stripping voltammetry (SWASV) at the hanging mercury drop electrode (HMDE). The average dissolved copper concentration in the bay was 10.1 nM (0.642 μg/L), and the complexing capacity and logK’ values ranged from 192 to 417 nM and 7.52 to 9.63, respectively, implying extensive chelation by natural organic ligands. Both parameters display seasonal and site location variations. This study shows that the total dissolved copper exists predominantly (> 98%) as strong organic complexes with the remainder (< 2%) as labile copper.