Formation and evolution of soils from an acidified watershed: Plastic Lake, Ontario, Canada

Journal Article · Wed May 01 04:00:00 EDT 1991 · Geochimica et Cosmochimica Acta; (United States)

DOI:https://doi.org/10.1016/0016-7037(91)90308-R· OSTI ID:6063860

Kirkwood, D E; Nesbitt, H W ^[1]

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1. Univ. of Western Ontario, London (Canada)

The Plastic Lake watershed contains podzols developed on glacial tills deposited 12,000 years ago. Present-day, cationic fluxes from the soils are greater by a factor of 2 than long-term fluxes averaged over the age of the tills. The high rates of present-day chemical weathering may be a result of increased input of anthropogenic acids into the Plastic Lake watershed. Time-averaged proportions of cations leached from the soils are strikingly different from the proportions of cations now being leached, indicating that the character of chemical weathering has changed over time. Weathering was and is dominated by mineral dissolution, but cation exchange has become increasingly important as the soils have matured. Bulk composition analyses of soil profiles demonstrate that feldspars of the AE horizon release base cations (Na, K, Ca) and Al to solution in near-stoichiometric proportions, just as is observed experimentally for feldspar dissolution in acidic solutions. Surface area-normalized, time-averaged, dissolution rates of primary minerals of Plastic Lake soils are significantly greater than present-day rates measured for mature soil profiles. Time-averaged concentrations of elements removed from the soil, recast into essential mineralogy, indicate that vermiculite weathers most rapidly, followed closely by plagioclase. K-feldspar weathers less rapidly than plagioclase but more rapidly than quartz or hornblende. The combination of high abundance and dissolution rate results in large amounts of quartz being dissolved from the soils of Plastic Lake; it may also contribute significantly to total elemental fluxes from other catchments.

• OSTI ID: 6063860
• Journal Information: Geochimica et Cosmochimica Acta; (United States), Journal Name: Geochimica et Cosmochimica Acta; (United States) Vol. 55:5; ISSN GCACA; ISSN 0016-7037
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
540220* -- Environment
Terrestrial-- Chemicals Monitoring & Transport-- (1990-)
58 GEOSCIENCES
580000 -- Geosciences
ACID RAIN
ACIDIFICATION
ATMOSPHERIC PRECIPITATIONS
CANADA
CATIONS
CHARGED PARTICLES
CHEMICAL COMPOSITION
CHEMISTRY
DEVELOPED COUNTRIES
DISSOLUTION
ENVIRONMENTAL EFFECTS
FELDSPARS
GEOCHEMISTRY
GEOLOGIC HISTORY
ION EXCHANGE
IONS
LAKES
LAND POLLUTION
LEACHING
MINERALOGY
MINERALS
NORTH AMERICA
ONTARIO
POLLUTION
RAIN
SEPARATION PROCESSES
SILICATE MINERALS
SOIL CHEMISTRY
SOILS
SURFACE WATERS
WATERSHEDS
WEATHERING