Experimental study and numerical simulation of soil water and salt transport under dry drainage conditions

Coal mining has serious impacts on local environment, including damage to the land and soil by subsidence, damage to ground-water systems through the fracturing and subsiding of overlying rocks, contamination of surface waters with acid mine drainage, and pollution of the atmosphere by release of toxic gases. The damage to ground water and its consequent impacts on the regional environment is the core of research of the coal mining from the perspective of environment protection. The present paper focuses on the changes of surface vegetation coverage, the pollutants released from pit coal power plants, and the damages to the ground aquifers induced by mining activities in arid Eastern Junggar coalfield of China. At first, the authors investigated the changes of surface vegetation coverage, since mining began in the 2000s using Landsat data. Results show that the low surface vegetation coverage (grade 1 plus grade 2) in the southern part of the region decreased from 11.62?×?10⁸ m² in 2003 to 9.57?×?10⁸ m² in 2017 (?17.6%), while it increased from 11.58?×?10⁸ m² in 2003 to 12.70?×?10⁸ m² in 2017 (+?9.7%) in the eastern part. The high surface vegetation coverage (grade 3 plus grade 4) in the southern part increased from 1.94?×?10⁸ m² in 2003 to 4.00?×?10⁸ m² in 2017 (+?106.2%), while it decreased from 4.39?×?10⁸ m² in 2003 to 3.26?×?10⁸ m² in 2017 (?25.74%) in the eastern part. The data of annual precipitation during the same period in this area show that the changes of surface vegetation coverage have less relationship with the annual precipitation, which indicates that the mining activities is probably the major factor for that. Second, a statistic of air pollutants generated from pit coal power plants was made based on data of references. Results show that the estimated gaseous pollutant emissions increased as 865.23 tons of smoke particles, 5940.73 tons of SO₂, and 7584.48 tons of NO₂ in 2013, which increased rapidly with 9.73 times the smoke particle, 21.69 times the SO₂, and 9.24 times the NO₂ than that of 2007. And then, the physical and numerical simulation of the damage of mining activities to aquifers was made to show the permeability of the reference points of overlying aquifers varies associated with mining activities. Results show that the porous rock matrix permeability has a negative relationship with fluctuation during mining, while the fracture permeability shows a positive one. Finally, a case investigation in southern area surrounding this coalfield was illustrated. Result shows that the local ground-water level decreased by 16 m difference from the altitude level of?+?774 m in 2003 to?+?758 m in 2013. Data and results from this study presented the already and the potential pollutions and damages to local environment induced by the mining activities in this region.