THE EXPERIMENTAL USE OF VARIOUS COVERS AND NATIVE TRANSPLANTS FOR THE REVEGETATION OF THE KAM-KOTIA TAILINGS SITE, TIMMINS, ONTARI01 by Keith Winterhalder2 Abstract. The Kam-Katia mine/mill complex was closed in 1972, leaving 275 hectares of sulphide-rich, acid-generating tailings. Surface tailings have a pH of around 2.5, and contain elevated levels of arsenic, zinc and copper. Preliminary revegetation field trials have investigated the effectiveness of covers such as gravel, loam and peat, at different depths and in different combinations, and of locally available neutralizing agents such as ground dolomitic limestone, marl and sewage incinerator ash. The survival and growth of a seeded grass-legume mixture on replicated 2 m x 2 m plots has been monitored for a one-year period, as has the surface moisture regime and the capillary rise of acid ground-water. Plant biomass data show that a loam covering or a gravel covering topped with loam are the most effective, but at least one more season of observation will be required to determine the relative vulnerability of different cover combinations to upward movement of acids. A second approach to revegetation has been the transplanting of metal-tolerant ecotypes of native species from acid, metal- contaminated soils of the Sudbury mining area such as Oeschampsia caespitosa (Tufted Hairgrass}, Agrostis gigantea (Redtop}, Scirpus cyperinus (Wool Sedge} and Betula pumila (Dwarf Birch}. Tufted Hairgrass, Redtop and Dwarf Birch proved to be most successful on well-drained microsites, the Wool Sedge doing better on moist sites. A third approach involved the transplantation of whole sods of peat and associated plants from a nearby bog, with considerable success. While this approach may not be feasible on an operational scale under current circumstances, in view of the expense and the concomitant destruction of a natural bog community, the situation will change if current plans to develop the horticultural peat industry in Northern Ontario come to fruition. ------------ .------------------------- Introduction requires a more complex solution. Revegetation leads to the interception of a portion of the Sulphide-bearing tailings can be the source precipitation by plants, to be evaporated or of two distinct types of environmental problem. transpired back into the atmosphere, while the Firstly, the oxidation of sulphides near the presence of vegetation will, to some degree, surface leads to highly acidic pore water, and to reduce oxygen penetration into the tailings a substrate that is unsuitable for plant growth. surface, thereby reducing sulphide oxidation. This creates an aesthetic problem, and a surface Nevertheless, revegetation rarely reduces acid that is susceptible to erosion by wind and water. mine drainage by more than a small percentage, Secondly, the oxidation of sulphides leads to acid especially if ferric-iron-rich ground water mine drainage. The aesthetic and stability with a pH below 4.0 flows through the system, aspects of the tailings can be solved by allowing for the oxidation of sulphides by the revegetation, but the acid mine drainage bacterium Thiobacillus ferrooxidans. The study described below addresses only revegetation aspects of the problem; the use of a I Paper presented at the 9th Annual National constructed wetland for effluent polishing will Meeting of the American Society for Surface be investigated at a later time. Mining and Reclamation, June 14-18, 1992, Duluth, Minnesota. The Kam-Katia mine/mill complex, located at 2 Keith Winterhalder is Associate Professor of Kamiskotia, 24 km northwest of Timmins Biology, Laurentian University, Sudbury, (48°36' N 81037' W}. began operation in Ontario, Canada P3E 2C6. 1943. The ore was rich in chalcopyrite, 385 sphalerite, pyrrhotite and pyrite, and was usefulness of locally-available materials, alone mined primarily for its copper and zinc content. and in combination. A rather special case of a Following closure in 1972, the property locally-available covering material is that of reverted to the Crown without rehabilitation. intact bog peat, which is not only intended as an The area. requiring revegetation is a sulphide- oxygen barrier, but is potentially self- rich, acid-generating tailings deposit covering maintaining, provided that an adequate moisture 275 hectares, including impounded areas where level and vegetation survival can be maintained. the tailings form a consistently deep layer and non-impounded areas where the thickness of son as a covering material. Soil is often used tailings is highly variable. Acid mine drainage as a covering material in revegetating pyritic from the tailings has a pH of around 2.5, and is wastes. In this context, the soil acts as a growth high in arsenic, zinc and copper. medium, controls infiltration and runoff, and serves as a barrier to oxygen. Although the Prior studies (e.g that by the D. Comrie recommended thickness of the layer is often Consulting Ltd., 1987) recommended great (e.g. the Illinois Pollution Control sophisticated and costly solutions. In 1990, the Regulations require that coal gob piles be present author was funded by the Kam-Kotia covered with a minimum of 1.3 metres of Steering Committee to carry out a number of nontoxic material), Hoving & Hood (1984) have small-scale trials employing varied "low-tech", shown that 30 cm of soil is sufficient to impede low-cost revegetation techniques. pyrite oxidation. They also concluded, however, that whereas the use of a soil cover as an oxygen The approach to the problem was three- barrier is effective on fresh pyritic material, pronged, investigating: oxidation is difficult to stop once it has started. a. the use of a covering-material, Gravel as a covering material. The rationale for the use of coarse gravel as a covering for b. the transplanting of potentially tailings is based on its porosity. Gemmell tolerant plant material, and (1977) stresses the need for physical isolation between plant growth medium and toxic c. the transplantation of intact bog-sods material, to prevent the contamination of the rooting zone by upward diffusion of toxic ions, The use of covering materials such as that reported by Breeze (1973) for chromate ions. The rate of upward movement of Several different functions can be served by acid ground-water by capillary action in a covering materials, alternatively referred to as gravel is low, and acid ground-waters are easily "covering systems" (Parry & Bell 1985). They washed out by rain. Gravel can be placed on top can serve as growth media for vegetation. They of tailings, and in turn covered with a finer can act, if coarse-grained, as "valves", or what material, the objective being the reduction of Parry & Bell (1985) refer to as "break upward capillary movement of acid tailings pore layers", allowing the free. downward percolation water by the gravel, combined with the of precipitation, but reducing the upward maintenance of a moisture-retaining layer on movement of acid pore-water by capillary top, which will act as a partial oxygen barrier · action. They can also serve, if fine-grained, as and as a plant growth medium (Spires 1975). oxygen barriers, especially if they remain in a Nicholson et al. (1989) support the use of the wet condition for long periods of the year textured layering of fine materials over coarse (Nicholson et al. 1989, Barbour 1990). The materials to improve moisture retention in the most important characteristic of potential cover fine layer, thereby reducing oxygen diffusion materials· intended as oxygen-barriers is the coefficients. Furthermore, a well-drained proportion of fines; clays are subject to surface material underlying a fine-grained upper layer cracking, and the ideal material is high in the can actually impede downward movement of medium to fine silt range (Nicholson et al. water (Nicholson et al. 1991). 1989)., However, availability and cost- effectiveness are overriding factors, and the current ··study investigates the potential 386 The transplanting of potentially tolerant Bog peat served both as an oxygen-barrier and plant material. as a base for living bog-sods collected at the same bog. A number of native. acid-tolerant plant species growing in the Sudbury area have been shown to have evolved ecotypes that are tolerant Neutralizing agents of copper and nickel, e.g. Agrastis gigantea (Hogan et al. 1977). A. scabra (Archambault Ground Dolomitic Limestone containing 2% 1991 ), Betula pumila (Roshon 1988), calcium and 12% magnesium, and having a Deschampsia caespitasa (Cox & Hutchinson CaC03-equivalent of 101 %, was ground such 1979), 0. f/exuasa (Archambault 1989), Paa that 5.4% passed a 100 mesh screen and 100% campressa (Rauser & Winterhalder 1985). passed a 1 o mesh screen. Unless stated Although the spectrum of potentially toxic otherwise, the application rate was 4 I/ha (1.6 metals in the pore water of the Kam-Kotia kg per 4 m2 plot). tailings is different from that in the acid, metal-contaminated soils of the Sudbury area, it Sewage Incinerator Ash is a bottom ash from has been shown by Cox & Hutchinson (1979) the Ashbridges Bay Sewage Treatment Plant in that, at least in the case of Deschampsia Toronto. The material had been transported by caespitasa, ecotypes can be tolerant towards truck and stock-piled in Timmins for possible metals other than those which are elevated in the future precious metal recovery. The major soil in which they grow. It therefore seemed constituent of the ash (38%) is a calcium worth investigating the possibility that such magnesium phosphate (Ca7Mg2P5024), with plants might be at least partially pre-adapted to the acid tailings growth medium. Gadgil (1969) 30% Si02, 15% Fe203 and 9% Al203. Unless has cautioned against an assumption that the stated otherwise, the application rate was 2 I/ha results of metal tolerance tests can be used with (0.8 kg per 4 m2 plot). confidence to select plants for reclamation, but it seems reasonable to assume that any internal Marl was obtained from the Pup lakes (formerly factor that ameliorates the stress to which a Twin lakes) area in west-central Thorneloe plant is exposed will improve its chance of township, District of Temiskaming.