BIOCHAR FOR SOIL REMEDIATION ON ABANDONED MINE LANDS

Some of the most significant and enduring problems associated with waste rock piles and mine tailings include the erosion of contaminated soils due to lack of vegetative cover, the redistribution of mineralized soils through Aeolian processes, and the difficulty and long return interval of re-colonizing vegetation. The problems associated with vegetation re-colonization are due to highly acidic soil conditions and adverse physical conditions associated with soil compaction and low water retention. To address the problems of unvegetated mine sites, we sought to determine the suitability of biochar as a soil remediation tool for re-vegetating abandoned mine lands in San Juan County, Colorado. Our study assessed the effects of biochar and straw compost amendments on the mobility, bioavailability, and toxicity of inorganic and organic contaminants in soils at abandoned mine sites. To examine biochar as a soil amendment, we conducted field trials to test for restoration potential, and container trials to examine specific physical and chemical properties of biochar treatments. The biochar field sites were located at elevations between 2,800 and 3,700 meters; site soils conditions ranged from pure waste rock to partially reclaimed forest soils. The field trial segment utilized a randomized block design of three blocks consisting of 2 x 1 meter plots with one seed-only control and three treatments: (1) biochar (30% by volume); (2) biochar and straw mulch; and, (3) straw mulch. The container trials, which were conducted at the Mountain Studies Institute field station, consisted of a seed emergence test, a vegetation biomass accumulation test, and a soil leachate test. Preliminary results suggest that biochar, in conjunction with organic mulch, may increase vegetative response in both rates of re-colonization and growth vigor by up to 50%. Confirmation of these results suggests that biochar, when combined with organic mulch, may be a useful tool for soil restoration at abandoned mine sites, or at other locations with severely degraded soils.