The weathering of a late Tertiary volcanic ash: Importance of organic solutes
- 31 March 1983
- journal article
- Published by Elsevier BV in Geochimica et Cosmochimica Acta
- Vol. 47 (3), 623-629
- https://doi.org/10.1016/0016-7037(83)90283-1
Abstract
The weathering of a late Tertiary volcanic ash near Jackson, Wyoming, was studied by sampling water percolating through the ash with suction lysimeters, and by examination of the associated solid phases. Soluble organic compounds derived from vegetation control the release and transport of solutes by complexing Al and Fe, and by causing low pH values. The concentrations of Na, K, Ca, and Mg, as well as those of Al and Fe correlate with the dissolved organic carbon concentrations (DOC) and follow an annual cycle with a maximum in spring. DOC concentrations averaged 5O mg C per liter, and values as high as 260 mg/l were observed. Al and Fe concentrations ranged as high as 5 mg/l. The dissolved organic matter was largely in the form of humic acids, although minor amounts of oxalate, acetate, and formate were also present. The pH of the percolating waters ranged from 4.3 to 6.5 with a mean of 5.2. During laboratory weathering experiments with the same ash in the absence of dissolved organic compounds, pH values ranged from 7.3 to 9.5, dissolved Al and Fe concentrations were below the detection limit, and there was little resemblance between the compositions of the solutions and the compositions observed in the field. Any model attempting to describe weathering in a comparable setting must incorporate biological mechanisms as the dominant controls.Keywords
This publication has 15 references indexed in Scilit:
- Hydrogeochemistry of the New Jersey Coastal Plain: 2. Transport and deposition of iron, aluminum, dissolved organic matter, and selected trace elements in stream, ground- and estuary waterChemical Geology, 1981
- Sorption of metals on humic acidGeochimica et Cosmochimica Acta, 1980
- Comparison of XAD macroporous resins for the concentration of fulvic acid from aqueous solutionAnalytical Chemistry, 1979
- Mechanism of feldspar weathering—II. Observations of feldspars from soilsGeochimica et Cosmochimica Acta, 1979
- Mechanism of feldspar weathering—I. Experimental studiesGeochimica et Cosmochimica Acta, 1979
- Calcium Oxalate: Occurrence in Soils and Effect on Nutrient and Geochemical CyclesScience, 1977
- Mechanism of feldspar weathering: Some observational evidenceGeology, 1977
- The dissolution kinetics of feldspars at 25°C and 1 atm CO2 partial pressureGeochimica et Cosmochimica Acta, 1976
- Development of fluxes for the analysis of ceramic materials by X-ray fluorescence spectrometryThe Analyst, 1976
- Determination of Oxalate Ion and Calcium Ion by Indirect ColorimetryAnalytical Chemistry, 1953