Submitted to: Plant and Soil
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/1/2002
Publication Date: N/A
Citation: Interpretive Summary: At many historic lead-zinc mines and smelters, soils were contaminated by dispersal of mine wastes and smelter fumes. At one location, Bunker Hill, ID, over 1500 ha remain barren and toxic to plants 30 years after closing the smelter. Methods to revegetate sloping contaminated soils at this site were needed to reduce costs of a Superfund site remediation. EPA asked ARS to cooperate in testing the use of biosolids plus alkaline byproducts on these contaminated soils to see what treatments could effectively revegetate these soils. Soils contained total Zn, Pb and Cd ranging from 6,000-14,700, 2100-27,000, and 9-28 mg/kg, respectively, and were acidic to strongly acidic. Surface application of certain amendment mixtures (organic matter plus alkalinity) including biosolids mixed with wood ash was sufficient to restore plant cover to the contaminated soils while simple chemical fertilizer plus limestone did not support revegetation. Further, the mixture of biosolids plus wood ash resulted in significant increase in subsoil pH and reduction in soluble Zn (adsorption is more effective at higher pH). This mixture maintained good plant cover for two years following amendment application; dry biomass yield in 1999 was 0.01 t/ha on the control versus a mean of 3.4 t/ha on the amended plots. Zn, Pb and Cd in the vegetation were at normal levels (below phytotoxic). Results indicate that surface application of biosolids plus woodash to make soils calcareous is sufficient to restore a vegetative cover to high metal soils.
Technical Abstract: High metal waste materials from historic mining at the Bunker Hill, Idaho (ID) Superfund site was amended with a range of materials including municipal biosolids, woody debris, wood ash, pulp and paper sludge, and compost. The existing soil or waste material has elevated metal concentrations with total Zn, Pb and Cd ranging from 6,000-14,700, 2100-27,000, and 9-28 mg kg-1, respectively. Surface application of certain amendments including biosolids mixed with wood ash resulted in significant decreases in subsoil acidity as well as subsoil extractable metals. This mixture was sufficient to restore a plant cover to the contaminated areas. At the Bunker Hill site, a surface application of high N biosolids (44 or 66 Tons ha-1) in combination with wood ash (220 Tons ha-1) with or without logyard debris (20% by volume) or pulp and paper sludge (44 Tons ha-1) was able to restore a vegetative cover to the metal contaminated materials for two years following amendment application. Plant biomass in 1999 was 0.01 Mg ha-1 in the control versus a mean of 3.4 Tons ha-1 in the residual amended plots. Metal concentrations of the vegetation indicated that plants were within normal concentrations for the 2 years that data were collected. Surface application of amendments was also able to reduce Ca(NO3)2 extractable Zn in the subsoil from about 50 mg kg-1 in the control to less than 4 mg kg-1 in two of the treatments. Use of conventional amendments including lime alone and microbial stimulants were not sufficient to support plant growth. These results indicate that surface application of biosolids in combination with other residuals is sufficient to restore a vegetative cover to high metal mine wastes.