Geochemical Behavior of Dissolved Iron in the Danshuei River Watershed
Date Issued
2008
Date
2008
Author(s)
Fong, Ying-Che
Abstract
Using physical (0.1 and 0.45 μm cut-off filters) and ion exchange (Chelex-100 and AG MP-1 resins) separation techniques, detailed distribution patterns and chemical affinities of Fe were investigated under different redox conditions in the watershed of the Danshuei River, a macro-tidal, temporally anoxic estuary, passing though the metropolitan area of Taipei. Concentrations of dissolved Fe in the Danshuei River tributary/estuary ranged from 9 to 1543 nM, with the majority residing in the 1 kDa~0.1 μm fraction (~50%), in which the largest fraction occurred as cation-exchanged species (~47%). Concentrations of truly dissolved Fe (≦1kDa) showed almost at constant fraction (~6%) in the whole watershed, except in the estuary where it was lower (~15%). Furthermore, the results indicated that ~9% dissolved Fe showed zwitterionic behavior. Concentrations of dissolved iron in the upstream Keelung River were significantly higher than in the other rivers. Results obtained in this study clearly demonstrate that under different flow and redox conditions in estuarine waters, iron remaining in the water column during the removal process had a distinct pattern of size distribution and chemical affinity. Geochemical factors, including salinity, pH, dissolved oxygen and suspended particulate matter concentrations, control concentrations and distributions of the different fractions for the physical and chemical speciation scheme.
Subjects
iron
speciation
Danshuei River
ion exchange
Chelex-100
AG MP-1
Type
thesis
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