Carbonic Acid Weathering Research Articles

Effect of Permafrost and Palaeo-Environmental History on Soil Formation in the lower Kolyma Lowland, Siberia

Abstract Danish Journal of Geography 96: 40–50, 1996. The Geography of soils has been studied in the tundra of the sandy Kolyma Lowland between latitudes 69 ° and 70 ° N. Generally, soils show characteristics indicative of variable intensity of previous fossil Podzol formation in the present day cryoturbated active layer. Hence, the transformation, transfer and segregation of chemical substances in the soil profile can be interpreted as evidence of palaeo-climate changes. Fossil soil features indicate horizon differentiating processes active in a former warmer and wetter climate. The chemical composition reflects a general sequence of pedogenetic translocation processes. Early stages of soil formation primarily involved translocation of weathering products from a carbonic acid weathering system. Inorganic Al-Fe silicate and phosphate materials were translocated into B horizons as the A horizon became more acid. At a later stage the increasing activity of simple organic acids in the A horizons caused a mig...

Mineralogy and weathering processes in Recent and Holocene tephra deposits of the Pacific Northwest, USA

Weathering and evolution of minerals in tephra deposits in the Cascade Range of Washington State, USA, are influenced by climate, vegetation, time, microtopography, and in the vicinity of Mt. St. Helens, naturally acidic precipitation. We have observed the interaction of these factors in Spodosols developed on Holocene tephra in the central Cascades, and in Entisols formed on the 1980 pyroclastic flow of Mt. St. Helens. Weathering regimens in these tephritic soils can be qualitatively characterized by the soil solution composition. Weathering reactions in the Spodosol are driven by organic acids in the upper soil horizons and by carbonic acid in the lower B and C horizons. The mineral assemblage in the Spodosol reflects, in part, the chemical regimen dictated by each proton donor. The presence of smectite in the highly acidic E horizon (pH < 4), where organic acids are the major proton donors, is perplexing. Its origin may be related to weathering of primary chlorite or inherited from the tephra. In soil horizons dominated by carbonic acid weathering (Bs, BC and C) noncrystalline substances such as imogolite and ferrihydrite are abundant, while smectite becomes interlayered with hydroxy-Al polymers. The Entisols forming in the 1980 Mt. St. Helens pyroclastic flow are strongly influenced by microtopography and naturally acidic precipitation produced by gaseous emission from the still active volcano. Smectite (saponite) and trioctahedral vermiculite are the dominant layer silicates of detrital origin. In the depressions, smectite and vermiculite have degraded into noncrystalline substances, followed by the apparent transformation of the poorly ordered materials into a more ordered kaolin mineral. We hypothesize that the kaolin mineral has resulted from acid weathering due to protons liberated by Fe hydrolysis, carbonic acid and possibly by nitrification.

Aqueous Geochemistry of the Sand‐and‐Gravel Aquifer, Northwest Florida

AbstractThe aqueous geochemistry of the sand‐and‐gravel aquifer in northwest Florida was characterized as part of the Florida Ground‐Water Quality Monitoring Network Program, a multiagency cooperative study delineating baseline and/or background water quality for the major aquifer systems throughout the State. The aquifer is the principal source of water in northwest Florida and consists predominantly of quartz sand with smaller amounts of andesine, chlorite, calcite, kaolinite, and illite. Water from 42 wells in the sand‐and‐gravel aquifer sampled during 1986 and 1987 was characteristically low in dissolved solids (median value of 72 milligrams per liter) and of nondistinct water type, although relative concentrations of magnesium and sulfate tended to be lower than those of other major ions. Nonparametric statistical tests of major‐ion concentration variations with depth and relative distance along flow paths indicate that the water chemistry does not change significantly (0.05 significance level) as the water moves vertically and laterally through the aquifer. Mass‐balance calculations indicate that dissolved solids from rainfall and saline‐water sources each account for 13 percent of the concentration of dissolved solids in ground water. Incongruent dissolution of andesine, chlorite, and muscovite to form kaolinite accounts for 94 percent of the neutralization of the total hydrogen ion input from rainfall and from carbonic acid weathering in the subsurface. The remaining neutralization is accounted for by the dissolution of calcite.

Acidification of aquatic systems: A critique of chemical approaches

The basic hypotheses are described that are required to develop chemical acidification models and their suitability for predicting anthropogenic acidification is considered. In addition, the ability to assess old chemical data is evaluated relative to the sampling containers and the analytical techniques that were used. Historical trends are especially considered. The discussion attempts to define a rigorous basis for the development of models and analysis and for the interpretation of pH and alkalinity data. Acidification models are based upon the electroneutrality condition and carbonic acid weathering. Whenever data are available, all major ions (Na/sup +/, K/sup +/, Ca/sup +2/, Mg/sup +2/) should be considered; (Ca/sup +2/) must be regarded as an approximate substitute for ..sigma..z/sub i/(M/sub i/). 44 references, 4 figures, 2 tables.