Alkaline humic substances and the amelioration of an acid sulphate soil and copper-contaminated mine tailings

Soil obtained from the Keld Series is acidic and its B horizon demonstrates acid sulphate soil characteristics and high levels of exchangeable aluminum. In addition, mine tailings from an abandoned gold mining site were found to be hazardous to the surrounding environment due to high acidity and often toxic levels of heavy metals.; Liming is the conventional method of improving acid soils by addition of acid-consuming material such as calcium carbonate. A new product, an alkaline humic substances extract (HS) from the waste material of coal mining, was produced and made available. Its use as an organic amendment for acid degraded lands was assessed in comparison to calcium carbonate.; Three laboratory studies were completed. The first was an evaluation of the acidity of the Keld Series soil by determination of its lime requirement.; The second study was a 9-week incubation of soil from the Ah and Bmg horizons of the Keld Series Pedon.; Finally, the alkaline HS extract was applied to acid, copper-contaminated mine tailings. The total copper content of the tailings was above 2000 mg · kg-1, approximately a third of which was in the water-soluble and exchangeable forms. Lime produced the highest increase in pH. The alkaline HS raised the pH of the tailings and altered the distribution of copper among six fractions; the free, toxic copper pool was greatly reduced and was redistributed to more tightly-bound and plant-unavailable pools such as organically-bound and precipitated fractions. These observations were more pronounced when the humic substances were added in combination with wheat straw. (Abstract shortened by UMI.)...