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Marrett, D.J., 1988

Acid soil processes in the Okpilak Valley, Arctic Alaska

Bibliographic Reference

Marrett, D.J., 1988, Acid soil processes in the Okpilak Valley, Arctic Alaska: University of Washington, Seattle, Ph.D. dissertation, 177 p., illust.


Field relationships suggested clearly differentiated pedogenic processes analogous to those found in temperate forests operating in two adjacent arctic soils. It was thought that podzolization affected arctic Spodosols (Pergelic Cryorthods), and either lower intensity podzolization or brunification affected Inceptisols (Pergelic Cryochrepts). The concentration and mobility of dissolved organic carbon (DOC) compounds in soil solutions were hypothesized to drive pedogenesis and differentiate pedogenic pathways. Correlations between DOC and: pH, major cations, metals, and charge deficits in soil solutions collected in situ indicated organic acids controlled leaching in both soils. Organics appeared to control pH, and elemental leaching by acting as proton donors, complexing agents and mobile anions. Concentrations of DOC, metals and cations were much higher ($\cong$5X) in Spodosol solutions. The major difference between arctic and temperate processes was high elemental mobility in arctic soils. Immobilization of DOC, Ca, Fe, and Al in arctic B horizons was much lower (20-40%) than for analagous temperate soils ($\cong$85%). High DOC mobility was simulated under laboratory conditions, and verified that field results were not primarily a function of rapid macro pore flow. Inceptisol DOC levels were low and similar in all horizons and in: (1) field, (2) laboratory simulations, and (3) water extraction solutions, without evidence of intensified leaching driven by surficial DOC. In situ C solubility relationships control Inceptisol DOC. The major factor affecting DOC mobility was DOC concentration; immobilization was greatest at high concentrations. Steady state DOC concentrations were approached rapidly (<4 hr) in sorption rate studies. Sorption of DOC was much weaker for arctic B horizons that for analogous temperate soils. Immobilization of DOC was modeled with sorption isotherms. The high DOC mobility found for arctic soils was attributed to solid phase properties poorly predicted by pedologic theory. Podzolization with low immobilization in B horizons was the dominant process in arctic Spodosols. Inceptisols showed aspects of podzolization and brunification but neither model adequately described the overall processes. While under pristine conditions DOC driven leaching losses were much higher for Spodosols, both soils appear to be very sensitive to pollution.

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