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The interaction of natural organic matter with iron in a wetland (Tennessee Park, Colorado) receiving acid mine drainage

January 1, 1999

Pore water from a wetland receiving acid mine drainage was studied for its iron and natural organic matter (NOM) geochemistry on three different sampling dates during summer 1994. Samples were obtained using a new sampling technique that is based on screened pipes of varying length (several centimeters), into which dialysis vessels can be placed and that can be screwed together to allow for vertical pore-water sampling. The iron concentration increased with time (through the summer) and had distinct peaks in the subsurface. Iron was mainly in the ferrous form; however, close to the surface, significant amounts of ferric iron (up to 40% of 2 mmol L-1 total iron concentration) were observed. In all samples studied, iron was strongly associated with NOM. Results from laboratory experiments indicate that the NOM stabilizes the ferric iron as small iron oxide colloids (able to pass a 0.45μm dialysis membrane). We hypothesize that, in the pore water of the wetland, the high NOM concentrations (>100 mg C L-1) allow formation of such colloids at the redoxcline close to the surface and at the contact zone to the adjacent oxic aquifer. Therefore, particle transport along flow paths and resultant export of ferric iron from the wetland into ground water might be possible.

Publication Year 1999
Title The interaction of natural organic matter with iron in a wetland (Tennessee Park, Colorado) receiving acid mine drainage
DOI 10.1023/A:1009617925959
Authors Stefan Peiffer, Katherine Walton-Day, Donald L. Macalady
Publication Type Article
Publication Subtype Journal Article
Series Title Aquatic Geochemistry
Index ID 70185254
Record Source USGS Publications Warehouse
USGS Organization Toxic Substances Hydrology Program