Effects of mining on the quality of soil and water in the coal mining areas of Assam.

摘要

Effects of mining on the quality of soil and water in the coal mining areas of Assam. Environmental pollution due to industrialization has now become a serious international problem. Coal mining is such an industry. Coal is essential and a very important natural resource for energy production. On a worldwide basis, coal is substantially more abundant than oil or gas, the total coal reserves being estimated at about 7.4 x 1012 MT (metric tones), which is equivalent to 4.7 x 1022 calories of energy. This may be compared to the total world energy consumption from all fuels of 6.0 x 1019 calories. It is the major fuel used worldwide for generating electricity.;Coal mining causes a great devastation of both terrestrial and aquatic environments on a local and a regional scale. It generates two major types of wastes namely acid mine drainage (AMD) and coal washeries. AMD is one of the most serious environmental problems faced by coal mining industry and is a major cause of water contamination near the coal mining area. It is generated from the oxidation of sulphur bearing minerals like pyrites in coalmines. Thus, all the sulphur present in the coal wastes as insoluble sulphate is converted to soluble from in the form of sulphuric acid. Pyrites often exist in association with other metallic elements such as As, Cd, Cu, Co, Pb, Hg, Zn. Mobilization of the trace metals like Arsenic (As), Lead (Pb), Mercury (Hg), Zinc (Zn), Copper (Cu), Cadmium (Cd), Cobalt (Co) occurs as a result of low pH (due to AMD), thus enhancing the concentration of these metals in the receiving water bodies and in many cases leading to the heavy metal toxicity. Common characteristics of AMD is low pH, sometimes less than 2, high sulphate content, high iron and manganese content and the formation of a yellow orange precipitate of Fe, Fe(OH)3 called yellow boy, that coats the bottom of stream and obstructs the biological activities.;Coal production in India has increased by about seven times in the past 40 years. Nearly 50 coalfields, ranging in size from a few square kilometers to greater than 1500 square kilometers, have been found in India. Coal mining by both opencast and underground methods affects the environment of the area. In the process of mining. huge amount of water is discharged on surface to facilitate the mining operations. The discharged water often contains high load of TSS, TDS, hardness and heavy metals, which contaminate the surface and ground water. Sometimes, the water is acidic in nature and pollutes the water regime.