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Abstract:In order to better understand the role of coal gangue in potential environmental and ecological risks, the leaching behavior of trace elements from coal gangue has been investigated in an open-cast coal mine, Inner Mongolia, China. Four comparative column leaching experiments were conducted to investigate the impacts of leaching time, pH values and sample amount on the leaching behavior of trace elements. Enrichment factors (EF), maximum leached amount (L am ), maximum leachability (L rm ), effects range low (ERL) and effects range median (ERM) were employed to evaluate potential environmental and ecological hazards resulting from the leaching behavior of environment-sensitive trace elements from coal gangue. Leaching time and sample amount display important effects on trace element concentrations, leached amounts and leachability. The pH values exhibit a weak influence on the leaching behavior of the selected trace elements (e.g., As, V, Cr, Co, Ni, Cu, Zn, Se, Cd, Sn, Pb and Hg). The coal gangue are enriched in As, Co, Se and Pb and, in particular, show higher environmental pollution levels of As and Se (EF > 2). L am values suggest that all of the elements investigated do not show potential risk to soils and vegetation, but have a high hazard risk for ground water. Elements including Ni, As, Cr and Zn are inclined to show high or moderate biological toxicity.

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To determine litter decomposition rates at different elevations in the alpine forest-tundra ecotone under climate change scenarios in which woody plants shift their ranges upward, litterbags containing foliar litter were incubated on the surface of forest, tree line, and alpine meadow soils (3900, 4000, and 4200 m above sea level, respectively) in the eastern Tibet Plateau of China in October 2012. The selected woody plant species were Abies faxoniana, Betula albosinensis, Sorbus rufopilosa, Rhododendron taliense, Lonicera lanceolata, and L. myrtillus. Mass loss, carbon (C), nitrogen (N), and phosphorus (P) release, and cellulose and lignin degradation in litter were examined from retrieved litterbags over a 6 month period at the end of one snow-covered season. The results showed that the mass loss of A. faxoniana, L. lanceolata, and S. rufopilosa litter, but not that of the other species, was accelerated at higher elevations. Abies faxoniana, B. albosinensis, and S. rufopilosa C release, A. faxoniana and S. rufopilosa N release, L. myrtillus, L. lanceolata, and S. rufopilosa P release, B. albosinensis, S. rufopilosa, and R. taliense cellulose degradation, and L. myrtillus lignin degradation significantly increased with increasing elevation. These results imply that changes in foliar litter decomposition with elevation, although species-specific, could indicate a possible shift in woody plant composition in the alpine forest-tundra ecotone under climate change scenarios. Thus, further studies regarding how elevation shifts could alter litter decomposition and ecosystem sustainability are warranted.