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The fate of geothermal arsenic in the Madison and Missouri Rivers, Montana and Wyoming
Author(s) -
Nimick David A.,
Moore Johnnie N.,
Dalby Charles E.,
Savka Michael W.
Publication year - 1998
Publication title -
water resources research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.863
H-Index - 217
eISSN - 1944-7973
pISSN - 0043-1397
DOI - 10.1029/98wr01704
Subject(s) - tributary , geothermal gradient , hydrology (agriculture) , sorption , geology , sediment , arsenic , drainage basin , environmental science , structural basin , geochemistry , geomorphology , chemistry , adsorption , geography , cartography , geotechnical engineering , organic chemistry , geophysics
Geothermal As from Yellowstone National Park causes high As concentrations (10–370 μ g/L) in the Madison and Missouri Rivers in Montana and Wyoming. Arsenic transport is largely conservative in the upper basin as demonstrated by the near equivalence of dissolved and total‐recoverable As concentrations, the constancy of As loads, and consistent ratios of concentrations of As to conservative geothermal tracers. Diurnal cycling of As between aqueous and solid phases in response to p H‐induced changes in sorption equilibria causes small variations of about 10–20% in dissolved As concentrations. HCl‐extractable As concentrations in river and lake sediment in the upper basin are variable depending on position relative to the As‐rich headwaters and geochemical and physical processes associated with lakes. In the lower Missouri River, large quantities of suspended sediment from tributaries provide sufficient sorption sites for substantial conversion of As from the aqueous phase to the solid phase.