Mangkolemba is one of the regions blessed with rich natural resources and biodiversity. Bounded by rivers and mountains, the valley is also noted for its rice production. Of late, coal is one of the extensively utilized minerals in the region. The usual method of coal extraction is predominantly rat-hole mining while open cast mining is employed to a lesser extent. Mining operation undoubtedly has brought wealth and employment opportunity in the area but simultaneously has led to environmental degradation and disruption of traditional values in the society.Large scale denudation of forest cover, removal of top soil, scarcity and contamination of surface water, disruption of ecosystem and biodiversity are some of the conspicuous environmental implications of coal mining. Environmental problem associated with mining is of great concern, especially the water bodies which are the greatest victims of coal mining. Clean water is critical to the health, economic and social well-being, and quality of life. Any undesirable change in water quality affects not only the human beings and their activities but also the flora and fauna of the regions. The degradation of water quality and declining trend of biodiversity in the water bodies of the mining area is primarily attributed to the Acid Mine Drainage (AMD). AMD is formed by a series of complex geochemical reactions when water comes in contact with pyrite (iron sulfide) present in coal. When pyrite is in contact with oxygen and water, highly concentrated sulfuric acid is produced which dissolves metals. And during the process of pyrite oxidation, dissolved Fe2+, SO42- and H+, followed by the further oxidation of the Fe2+ to Fe3+ are formed. Some or all of this iron can precipitate to cause turbidity of water in the form of red, orange or yellowish colour and sedimentation at the bottom of streams. The acid runoff or AMD aggravates the problem further by dissolving heavy metals such as aluminum, arsenic, copper, lead, mercury, etc. found in rocks and soil. As a result, the AMD contaminated surface water is not only acidic but also rich in dissolved metals. Consequently, the same rivers and streams that supported human life and activities, the rich biodiversity including many species of fish, amphibians, aquatic insects etc gradually lose their life sustaining role and become nearly devoid of aquatic life.
Preliminary study revealed that many water sources in and around the mining area is affected by Acid Mines Drainage (AMD). Contamination of surface water by AMD is evident by its colour which appears reddish to brownish. Low pH (high acidity), high ionic conductivity, high total dissolved solid, high sulphate content, high turbidity, moderately hard, low dissolved oxygen are some of the physicochemical parameters which characterize the degradation of water quality.
Under prevailing conditions, there is a need for initiating activities for eco restoration of the affected areas. Filling of abandoned mines, conservation of top soil, shifting of coal depot from the nearby river bank, afforestation, scientific management of AMD and water resources etc. will go a long way in restoration of the lost environmental glory of the area.
