Iron in Surface and Subsurface Waters, Grizzly Bar, Southeastern Alaska

Abstract

Atomic absorption spectrophotometric measurements for total iron were made on 69 samples of water from 8 different environments in an outwash fan built by meltwater streams from the retreating Norris Glacier on granodiorite bedrock. Norris Glacier ice contained no iron (3 samples), a subglacial stream contained 5.5 ppm Fe (1 sample), and a meltwater lake fronting Norris Glacier contained 0.7 ppm Fe (3 samples). Iron content of ground water from outwash ranged between 0.0 and 17.0 ppm (6 samples); surface streams fed by emergent ground water on the fan periphery contained 0.0 to 0.2 ppm Fe (13 samples). Taku Inlet waters contained 6.4 ppm Fe (3 samples). Subsurface water from an intertidal mud flat contained between 0.0 and 27.0, X 5.9, ppm Fe (31 samples). Surface and subsurface water from a bog and associated stream contained 1 ppm Fe (12 samples). Little exchangeable Fe was found. In situ measurements in water for Eh showed large positive values (+0.30 to +0.50 volts) and pH was slightly alkaline. The single most important source of iron was vermiculitized biotite. Iron was transported in water in the particulate state, except in outwash ground water where particulate Fe+3 was reduced to dissolved Fe+2. Iron deposits of Fe(OH)3 were found near the top of the outwash water table.