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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.

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.

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Natural secondary succession of degraded soil has improved the ecological environment of the Loess Plateau, profoundly influencing the succession and dynamics of soil fungal communities restored grasslands in particular. This chronosequence and the varied topography of the Loess Plateau thus provide a unique opportunity to synchronously investigate the variation of soil quality and fungal communities as they develop over time and space. Here, we used high-throughput sequencing of the ITS rRNA gene region to analyze the fungal community at a local scale. Edaphic variables and fungal community characteristics were compared among three restoration durations (5, 20, and 30 years), two soil layers (topsoil and subsoil), and different topographic factors (slope positions and aspects). Edaphic variables displayed varying patterns with significant differences among restoration durations and soil layers, but no such topographic patterns were found. As succession proceeded, alpha and beta diversities of fungal communities changed as space changed; whereas, over time, the discrepancy in community composition between the two soil layers declined.Constructed co-occurrence networks of edaphic variables combined with fungal community composition and distribution patterns based on indicator and keystone species also varied among three durations. Fungal trophic guilds showed a contrasting distribution between the two soil layers, but they closely followed the soil nutrient conditions and metabolic characteristics of keystone species. Our results demonstrated that predictable spatial variation occurs in soil fungal communities in tandem with temporal succession and dynamics of indicator and keystone species in restored grassland on the Loess Plateau.

Nano-ZnS particles are newly developed alternatives to activated carbons for Hg0 removal from flue gas. We investigated the Hg0 oxidation mechanisms in the presence of chlorine (Cl2) on the (110) surface of ZnS by first-principles calculations. The results show that the Cl2 molecule can dissociate into two Cl ions on the ZnS(110) surface, forming chlorinated ZnS surfaces. Compared to the clean ZnS surface, the chlorinated ZnS surface with dissociated Cl ions exhibit enhanced binding affinity over Hg0 with promoted Hg0 oxidation efficiency (Hg0 → HgCl2). The active Cl ions on ZnS surface can directly interact with Hg0 to form HgCl2, following the typical Eley–Rideal mechanism rather than the Langmuir–Hinshelwood mechanism.

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