Abstract
Re-vegetation on closed mining-sites for carbon sequestration and/or bio-energy production is one of the strategies of addressing the world-wide issues of energy crisis and global warming. However, mine soils including coal-mining refuse usually have poor quality and are unfavorable to plant growth. Thus, the major objective of this study was to improve quality of coal-mining refuse under laboratory conditions using zeolite, flue gas desulfurization gypsum (FGD), flyash, and biosolids at 10% (w/w) rate. Chemical analysis did not indicate any significantly high concentrations of toxins in the solid or the solution phase, suggesting that soil acidity was the principal chemical constraint hindering re-vegetation. In this context, FGD was the best among the tested materials for increasing soil pH and improving lettuce (Lactuca sativa) seed germination, while application of biosolids significantly enhanced soil aggregate stability. Specifically, laboratory tests showed that application of FGD increased pH of the acidic coal refuse samples from initial 3.80-4.66 to 5.70-6.60 and enhanced the growth of germinated lettuce seedlings in mine soil solution from 2.9-4.4 cm to 5.9-8.6 cm. The biosolids amendment increased the geometric mean diameter of the mine soil aggregates from the antecedent 0.93-0.99 mm to 1.13-1.25 mm. However, use of zeolite and fly-ash did not significantly improve the soil quality.
Highlights
Minesoils are formed on landscapes altered by mining processes, by the surface mining operations
Only a negligible amount of the Be (< 0.01 mg L-1) was monitored in the mine soil solutions in the present study, suggesting that Be in these mine soils was strongly bound to the soil matrix and would not be toxic to plant growth under normal conditions
The mine soils contained relatively higher amounts of Cu, Cr, Pb, Se, and Zn compared with those in agricultural soils (Table 1), the levels are lower than those in soils impacted by metal ore mining and related processing operations (Dudka & Adriano, 1997)
Summary
Minesoils are formed on landscapes altered by mining processes, by the surface mining operations. Mine soils include ore waste and coal refuse. Coal refuse is regarded as the low-grade coal material extracted along with the coal ore. The former is separated from the latter through coal processing and discarded. The refuse is usually composed of rock fragments derived from interseam shale or siltstone partings and waste rock materials from above or below the coal seam. The refuse shares many properties with the associated coal seam and still contains a certain amount of coal (or energy). Besides occupying lands for its disposal, the potential hazards of improperly reclaimed refuse include contamination of surface and groundwater by acidic leachates and runoff, erosion and sedimentation into nearby water bodies, spontaneous combustion, and damage from landslides (Daniels & Stewart, 2000; Daniels et al, 2010)
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