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Abstract
Sephadex size exclusion chromatography was used to prepare molecular size fractions from liquid pig slurry, before and after aerobic interaction with a loamy-sand soil. In the liquid fractions organic matter was characterized and some components were identified.
The distribution of zinc and copper over MW-classes was determined. In pig slurry-liquid one third of the copper and zinc was found in the mass range > 50,000. After 3 days contact with soil, copper concentration increased and 10 % was found in the nominal molecular mass range 50,000. The zinc concentration did not change, but the MW distribution had shifted in favor of higher molecular masses.
Cation exchange experiments (4 hours) with the above fractions showed a zinc exchange rate of 50 % per hour, typically. Copper complexes in HMW-fractions did not exchange, which was tentatively explained by the measured high thermodynamic complex stability. Copper in pig slurry-liquid LMW-fractions showed an exchange rate of 25 % per hour; the reaction stopped when 50 % was left, indicating the presence of stable LMW copper species. After incubation with soil the LMW copper showed a constant dissociation rate of 20 % per hour.