PM12 Metals in the Environment
Exhibit Hall
8:00 AM - Monday
(PM210A) Effect of moisture content on organic matter and copper release to soil solution.
Metzler, D, Ackerman, A, Ponizovsky, A, Allen, H,
ABSTRACT- The effect of moisture content on organic matter and copper release to soil solution was studied to evaluate how data on chemical equilibrium in soil suspensions can be applied to predict phenomena in soils at relatively low moisture content. Seven soils sampled from the surface layer with the pH range 4.2 to 7.5 were spiked with CuCl2. CaCl2. solution (10 mM) was added to the soils up to the 'field moisture content' (pF=1.9) (FMC), 0.8×FMC, 1.2×FMC, and to obtain soil suspensions with soil:water ratio 1:1, 1:5, and 1:10. The liquid phase was separated with centrifuge 'double chamber' method after 3-days incubation at 20.0±0.5 °C and analyzed to measure dissolved organic carbon (DOC), dissolved Cu, pH, and Cu2+ activity. DOC concentration decreased 6- to 19-fold with 22 to 67-fold increase in moisture content. The decrease followed Langmuir-type desorption isotherm. Calculated total amount of potentially soluble organic matter comprised 0.009 to 0.32% of soil organic carbon. Copper concentration decreased and Cu distribution coefficient (Kd) increased (∼4-fold) while Cu2+ activity in non-calcareous soils did not change (standard deviation ±0.1 to ±0.2 pCu with no trend) with the increase in moisture content. In calcareous soils Cu2+ activity increased with an increase in moisture content up to 1 g g-1 soil. Dissolved Cu correlated with DOC at DOC concentrations below 100 mg L-1 and did not correlate with DOC at higher concentrations. In non-calcareous soils the same value of Kd can be used over a wide range of moisture content if it is calculated based not on dissolved Cu concentration but on Cu2+ activity.
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