Abstract:[Objective] A design scheme was proposed involving the addition of hydrophilic polyurethane (W-OH, a highly water-resistant material) under disturbed soil conditions to reconstruct a bottom water-resistant layer (approximately seamless impervious layer) in order to alleviate the adverse effects of water factors on the failure of disturbed soil to form frozen soil in a high cold mining area. Changes in slope infiltration, flow production, and sediment production of weathered coal gangue after the reconstruction of a water-blocking layer in an alpine mining area were studied to provide theoretical support for the recurrence of frozen soil on a disturbed slope and the prevention and control of soil erosion on a slope after the reconstruction of a water-blocking layer. [Methods] Simulated artificial rainfall was applied at rates of 60 mm/h and 90 mm/h to reconstructed water-blocking layers having W-OH concentrations of 0%, 1.5%, 2.5%, 3.5%, and 4.5%. Infiltration characteristics and soil and water loss changes of the weathered coal gangue slope under three different slope conditions (5°, 15°, 25°) were obtained. [Results] ① The stable infiltration rate of the coal gangue slope after application of a reconstructed water-blocking layer was significantly lower than that of natural slope, and was negatively correlated with W-OH concentration. ② The flow yield of the coal gangue slope showed a trend of rapid increase at first and then gradually becoming stable over time, and the average flow yield showed a positive correlation with the W-OH addition concentration. The average runoff yield of coal gangue slopes with 1.5%, 2.5%, 3.5%, and 4.5% W-OH increased by 26.75%, 38.02%, 46.90%, and 63.23%, respectively, compared with the natural state. ③ The average slope velocity was positively correlated with rainfall intensity, W-OH addition concentration, and slope, and the influence degree followed the order of rainfall intensity＞slope addition concentration＞W-OH addition concentration. ④ The variation curve of slope sediment yield over time was mostly a “unimodal” curve, which showed a rapid rise at first, then a slow decline and finally tends to be stable. The average sediment yield of coal gangue slopes with 1.5%, 2.5%, 3.5%, and 4.5% W-OH increased by 26.98%, 49.48%, 71.64%, and 94.01% compared with the natural state. [Conclusion] The reconstructed water-blocking layer significantly reduced the permeability of weathered coal gangue on the slope, thereby effectively helping the recovery and formation of frozen soil on disturbed slopes in high, cold, mining areas. However, the decrease in infiltration rate could make the slope more prone to runoff and increases sediment production on the surface, and therefore, certain soil and water conservation measures should be applied.

Abstract:[Objective] The variation laws of community characteristics with different planting years were studied in accordance with the initial stage of vegetation restoration of the slope of a coal gangue heap in the arid area of Northwest China to provide the basis for ecological restoration in Wuhai mining area.[Methods] The Meifang coal gangue heap in Wuhai mining area was taken as the research object, and the growth status of vegetation and community stability in the initial stage of vegetation restoration were compared and analyzed by using the method of sampling and surveying the field samples.[Results] ① The number of species increased significantly during the vegetation restoration. There were only four species of natural invasive plants in the second year of restoration; then, the number increased to six in the third year. In the fourth year, the number of species increased to seven, and the dominant species were Halogeton arachnoideus. The number of natural invasive plant species increased gradually, indicating that the community was undergoing a positive succession process. ② The average vegetation coverage, superterrane biomass, and richness index increased by 1.5 times, with an increase in the restoration years from two to four, indicating that the community structure was gradually becoming stable. ③ The community of the coal gangue hill was in the initial stage of succession when the vegetation was reconstructed for two to four years. The similarity coefficient of community decreased year by year, and the community structure tended to be complicated, but it was still in an unstable state.[Conclusion] In the following vegetation restoration of coal gangue hill, naturally permanent planting of local species that are adaptive for local conditions should be properly promoted when planting typical reclamation plant species, such as Leguminosae, Gramineae, and Compositae. In addition, the local gene bank should be preserved in the coal gangue hill by planting native plant species belonging to the climax stage of succession.

Abstract:[Objective] The effects of vegetation types on the leaching and migration of Fe/Mn in coal gangue dumps under natural vegetation restoration were discussed in order to provide a scientific basis for the ecological environment management and ecological restoration of coal gangue dumps in coal mining areas.[Methods] The surface runoff of the coal gangue yard under different vegetation conditions in the abandoned coal mine area of central Guizhou Province was sampled and analyzed. At the same time, pot experiment was carried out by transplanting Masson pine, Betula luminifera and reed growing on coal gangue yard, and the samples of matrix permeate water were collected.[Results] The content of Fe or Mn in the infiltrated water of coal gangue substrates, and in the surface runoff water of coal gangue pile site grown with Masson pine, Betula luminifera and reed was significantly lower than that of gangue without plant growth. After natural recovery vegetation at coal gangue pile site, the decrease rates of Fe and Mn contents in surface runoff water were 45.27%~85.60% and 60.17%~90.13% respectively, the order of vegetation effects was Pinus massoniana young forest > Broadleaf young forest > reed grass. The sediment content of surface runoff water in the gangue pile sites grown with Pinus massoniana young forest, broad-leaved tree young forest, and reed-like grass was reduced by 40.18%, 30.67%, and 27.91%, respectively, compared with that of gangue without plant growth, and the migration of mineral particulate Fe and Mn in coal gangue was also decreased significantly.[Conclusion] Natural vegetation restoration can significantly reduce migration of Fe and Mn from the coal gangue yard to the water and improve the surface water quality in abandoned coal mines. The environmental effect of plant growth on reducing the migration of Fe from coal gangue to water was greater than that of Mn, especially the growth of Pinus massoniana.

Abstract:[Objective] The coal gangue mountains, the occupied land, and the surface vegetation destroyed by coal mining were analyzed to classify the types of coal gangue site properly. The objective of the study was to provide a basis for ecological restoration and reconstruction of mining areas.[Methods] The coal gangue in the Ningdong mining area was taken as the research object. Ten site factors were investigated and analyzed for microtopography, altitude, thickness of covering soil, and soil texture. Methods such as principal component analysis and cluster analysis were used to classify coal gangue mountain site types.[Results] The dominant factors were determined by principal component analysis as microtopography, thickness of covering soil, and soil texture. Afterwards, according to the dominant factors, the coal gangue mountains in the Ningdong mining area were classified into three site type groups, five site type subgroups, and eight site types through cluster analysis for various areas. The coal gangue platform had a large area, with slopes between 32° and 40°, and the thickness of the coal gangue overburden was > 30 cm. The soil field water capacity was between 16.82% and 34.85%, and the total K content was between 34.29 and 46.61 g/kg, which was extremely high. The total P content was between 0.31 and 0.62 g/kg, which was medium to low level. However, soil organic matter and total N content were at very low levels, and the soil of the coal gangue was more alkaline.[Conclusion] The reconstruction of gangue in Ningdong mining area should take measures according to local conditions. When gravel is less in overlaying soil, the arbor-shrub mixed pattern is selected with arbor based, or shrub pattern, or shrub grass pattern with shrub based. Whereas, the shrub grass pattern with grass based is selected when gravel is more. When the soil is light gravel, grass seeds are sown.

Abstract:Taking coal gangue mountain of Panyi coal mine in Huainan mining area as the study object, through the analysis of physicochemical properties, scanning electron microscope(SEM), energy dispersive spectrometry(EDS), total organic carbon(TOC) contents of weathered coal gangue, the authors preliminarily studied the distribution and release of organic carbon from weathered coal gangue, and the content of dissolved organic carbon(DOC) in soil, which was affected by accumulation and eluviation of coal gangue mountain. The results showed that the contents of TOC in weathered coal gangue decreased from the top of mountain to the mountainside, and to the foot, and with the increasing depth of sampling, the contents became higher. The contents of TOC in weathered coal gangue was positively related with the particle size, and negatively related with the weathering degree of weathered coal gangue. With the increase of time of leaching time, the soluble amounts of DOC leached from weathered coal gangue of different particle size reduced. In the 96 hours leachate, the soluble amounts of DOC tended to be stable, and the values were comparatively similar. Within the distance of 2~100 m to the foot of coal gangue mountain, the increasing distance of sampling, the contents of DOC in soil tended to decrease, and within the distance of 80~100 m to coal gangue mountain, the contents of DOC in soil were similar to that in normal farmland.

Abstract:Spontaneous combustion of coal gangue hill is one of the main environmental pollution sources in mining area. To seal and afforest the coal gangue, a covering layer with a certain air barrier property is needed. The covering layer is made of soil materials by rolling compaction and thus the performance of air barrier depends on rolling quality. The compaction effect in relation to rolling tool and the rolling conditions of field coal gangue was studied by combining on-site compaction test for coal gangue dump governance in the Yangquan 3rd coal mine. Based on the rolling compaction experiment on the loess of various thicknesses, soil rigidity and dry density were measured to illustrate the rolling effect and the reasonable rolling parameters were analyzed under the condition that the degree of compaction(85%) was used as the compacted quality control standard. By utilizing the self-made grinding roller(4 t) for flat rolling, results show that shallow soil was more sensitive to rolling frequency in comparison with deep soil, and its corresponding depth was about 15-25 cm. The suggested construction proposal and rolling parameters are that moisture content is close to the optimum rate of water content (between±2%), loose paving thickness is 20-40 cm, and the material is compacted by 3~5 times rolling.

Abstract:Soil respiration rates as well as soil temperature and moisture for four types of vegetation(grassland,bushes,small arbors,arbors)were monitored with Li-8100automated soil CO2flux systems at the reclamation district filled with coal gangue,which is located in Datong district of Huainan City,from July 2011to March 2012.The results indicated that diurnal variations of soil respiration for the four types of vegetationshowed a mode of single peak curve with the maximum value appearing in summer between 12:00and 16:00and the minimum value appearing in winter around 4:00AM.The soil respiration under different vegetationtypes differed significantly(p<0.05),and its rates followed a decreasing order in vegetation types as grassland,shrubs,small arbors and arbors.The annual emission of soil CO2for four types of vegetation were999.74±62.26,908.49±72.41,869.22±56.23and 726.10±63.01g/(m2·a),respectively.Consideringthe carbon emission reduction effects,arbors,small arbors and shrubs instead of grassland should be plantedin the study area.In addition to vegetation types,soil respiration of the area were affected by soil temperature at the depth of 10cm.The relationship between soil respiration and soil temperature was described well by anexponential equation,which explains more than 88%of the variance of soil respiration.The Q10(index of sensitvity)values of grassland,bushes,small arbors and arbors were 2.57,2.71,2.96and 3.67respectively.

Abstract:Soil and water conservation benefits and vegetation growth in selected plots with different coverswere analyzed based on the observed data on the No 280spontaneous combustion gangue slope in the CoalMine III,Yangquan Coal Industry Group,Shanxi Province.Results indicate that the plots covered by mixedmaterial of gangue with loess have significant soil and water conservation benefits,accompanying favorablevegetation recovery.Meanwhile,soil moisture content in the coal gangue plots is accumulated with the increased gangue cover.Among the selected plots covered by the mixed gangue with loess,the one with thegangue cover intervals of 0.15～0.25mand gangue cover degrees of 35%～45%is the optimal cover measurefor soil and water conservation and vegetation restoration.

Abstract:Research on soil contamination and plant absorption of toxic elements at coal gangue site can provide a scientific basis for pollution control and vegetation restoration.Soil pollution and heavy metal content in herbaceous plants are studied at Sanlidong coal gangue site in Tongchuan City.Moreover,soil pollution and the enrichment capacity of heavy metals in herbaceous species are analyzed and evaluated using geo-accumulation index and complex accumulation coefficient.Results show that all the elements of Cu,Cd,Zn,Mn,Ni,Pb and Crin both of the soil and plants obviously exceed their background values and the Cu,Cd and Ni elements in herbaceous species are beyond their normal range.Heavy metal element Cd in soil is in the most serious pollution grade and the elements of Ni,Cu,Zn,Pb and Cr are in the slight pollution grade.For the different plants,the heavy metal enrichment capacities of Conyza canadensis（L.）Cronq.,Artemisia sacrorum Ledeb.and Artemisia lavandulaefolia D.C.are the strongest,followed by Artemisia scoparia Waldst.et Kit and Datura Stramonium Linn.The enrichment capacity of Cynodon dactylon（Linn.）Pers.is the worst.

Abstract:Water dynamics of the 280 coal gangue dumps in Yangquan City,Shanxi Province was preliminarily studied by the analyses of physical properties,water infiltration characteristics,and water contentof the weathered gangue. Results showed thatcoal gangue texture was poor and the average contentof gravel and boulder was as high as 86. 07 %. The coal gangue dumps were dominated by non-capillary pore and the aver age values of capillary pore atthe four depths (15,30,45,and 60 cm) in the profile were 1. 40 %,1. 36 %,1. 32 %,and 1. 17 %,respectively. This caused soil water2holding capacity maintaining ata low-level throughoutthe year and the average water-holding capacity at60 cm depth was 19. 7 t/hm2. Kostiakov infil tration model can well describe the infiltration process of weathered gangue. During the infiltration process,weathered gangue had higher infiltration rate. The seasonal change in water contentof weathered gangue was mainly influenced by the amountof rainfall and its distribution. With the increasing seasonal rainfall,the av erage water contentof weathered gangue rose correspondingly. Water storage of gangue dump was linearly related with the amountof rainfall. When the amountof rainfall was low,or rainfall eventwas highly fre quent,water storage of exposed gangue was more than thatof the gangue dump covered with soil. Generally speaking,there was a dry layer between 30 and 40 cm in gangue dump,which made the lower layers of gangue dump keeping more moisture in dry season.