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Factors influencing stream chemistry in catchments on Prince of Wales Island, Alaska
Author(s) -
WISSMAR ROBERT,
SWANSTON DOUGLAS,
BRYANT MASON,
McGEE KATHERINE
Publication year - 1997
Publication title -
freshwater biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.297
H-Index - 156
eISSN - 1365-2427
pISSN - 0046-5070
DOI - 10.1046/j.1365-2427.1997.00216.x
Subject(s) - weathering , alkalinity , geology , streams , cave , geochemistry , karst , acid rain , environmental chemistry , hydrology (agriculture) , mineralogy , chemistry , ecology , computer network , paleontology , geotechnical engineering , organic chemistry , computer science , biology
1. Factors influencing the water chemistry of streams were evaluated for remote catchments on Prince of Wales Island, Alaska, a high‐latitude geologically diverse landscape. 2. We evaluated the hypothesis that weathering rates of dominant geological formations of catchments would be the major factor influencing the water chemistry of streams. 3. Catchments were compared by synoptic sampling of stream and cave waters, mapping to define the distribution of geological formations, and laboratory studies of rock weathering. 4. Carbonation was identified as the major mechanism influencing the weathering of rocks. High P co 2 levels of cave and upwelling waters in streams suggested CO 2 , supplied by soil respiratory processes, was the major factor controlling the concentration of dissolved CO 2 , carbonic acid dissociation, and H + replacement of cations on rock surfaces. 5. Additional evidence of carbonation included the relationship between HCO 3 1– and Ca 2+ + Mg 2+ ( r 2 = 0.95) for low‐ and high‐alkalinity waters. The relationship suggested that the high‐alkalinity waters were associated with the weathering of calcareous rocks. Waters with high alkalinities (> 1254 μeq l –1 ), pH (> 7.0), Ca : Mg ratios (> 6.0.) and saturation values for Ca 2+ (SI c = –0.59–0.06) indicated that karst (limestone) formations with calcite minerals were the major sources of calcium (> 1266 μeq l –1 ). Waters with the lowest alkalinity, pH, HCO 3 1– and cation concentrations were associated with granodiorite (igneous) rocks. Laboratory studies substantiated these findings, with weathering being highest when waters contacted Heceta and Bay of Pillars limestone formations and lowest with igneous rocks. 6. Weathering of rocks, and possibly soils, appeared to be facilitated by surface and subsurface movements of CO 2 and water through fractured karst formations, and water availability in rain‐dominated forests. The proximity of the sea and sulphur in marine aerosols and rainfall, and sulphate reacting with water, may also supply hydrogen ions to weathering reactions. 7. This study provides a basis for developing a better understanding of the influences of surface–subsurface geological and hydrological factors, and climatic conditions, on stream chemistry and biota in high‐latitude ecosystems.