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Mine Land and its Environmental Impacts

Abstract

Exploration of mineral resources and mining is indispensable for the economic development of any nation, but its ruinous impact on environment is inevitable. Though mining sector significantly contributes to gross domestic product (GDP) and employment of workforce in any nation, it causes irreversible harm to the environment. This sector is known to afflict environment by causing disturbance in air quality, pollution of water bodies, depletion of soil fertility, desertification, deforestation, endangerment of wildlife, etc. Therefore, any mining project must necessarily include a mine reclamation closure plan in order to exploit resources judiciously, not at the cost of environment. This chapter highlights the environmental impacts of mining and presents the solutions that can be adopted with mining to protect the environment.

Keywords: Mining; pollution; ecological disruption; acid mine drainage; reclamation;

CONTENTS

• 1.1 Introduction
• 1.2 Environmental Impacts of Mine Land and Ecological Disruption
  • 1.2.1 Soil Erosion
  • 1.2.2 Loss of Soil Fertility and Desertification
  • 1.2.3 Loss of Biodiversity
  • 1.2.4 Air Quality
  • 1.2.5 Emission of Greenhouse Gas and Climate Change
  • 1.2.6 Water Quality Deterioration
  • 1.2.7 Sedimentation in Streams and Rivers
  • 1.2.8 Groundwater Regime
  • 1.2.9 Noise Pollution
  • 1.2.10 Human Health
  • 1.2.11 Formation of Mine Dumps
  • 1.2.12 Visual Impacts
  • 1.2.13 Social Impacts
  • 1.2.14 Other Issues
• 1.3 Economic Valuation of Impacts on Environment
• 1.4 Environment Protection and Policy Implication
• 1.5 Management and Reclamation
• 1.6 Progressive Reclamation
• 1.7 Conclusion
• References

1.1 Introduction

Mineral wealth accounts to more than 70% of resources required worldwide (Pashkevich 2017). Mining activities pertain to extraction of nonrenewable resources (fuels, metallic, nonmetallic, and minor minerals) from a resource-rich ore. Mining resources are pivotal to promote economic growth and expansion of any nation. In India, mining industry contributes around 10-11% to gross domestic product (GDP) of total industrial sector. Around 80% of mining in India pertains to coal, and the rest is related to remaining minerals. India is the largest producer of mica blocks and mica splitting and produces ~60% of world's mica. As of 2019, India was fourth largest producer of iron ore and chromium; fifth largest producer of bauxite, zinc, and graphite; seventh largest producer of manganese, lead, and sulfur; and eleventh largest producer of titanium and uranium worldwide (Corporate Catalyst India [CCI] 2010). Post announcement of New Mineral Policy in 1993, mining sector in India was opened to foreign direct investment (FDI), but the investment remained low due to restrictions in obtaining approvals (Mehta 2002). Since then the FDI policy in the mining sector has been gradually liberalized, for example, by introducing automatic approval route, and has remained successful to attract FDI. However, there are certain challenges that need to be addressed in mining sector such as upgrading and adapting to eco-friendly technologies, curtailing environmental degradation and post-mine rehabilitation, and addressing social issues dealing with displacement and marginalization of native dwellers and its economic consequences. In India, premier organizations such as Geological Survey of India (GSI) and Mineral Exploration Corporation Ltd (MECL) carry out survey and mineral exploration activities, while Indian Bureau of Mines (IBM) is engaged in regulation and conservation. Though IBM updates the inventory of mineral deposits every five years, immense research and exploration still need to be carried as India has diverse mineral deposits yet to be discovered (Kumar 2019).

Environmental damage and mining scale do have an unequivocal relationship (Li et al. 2016). Around 90-95% of extracted mineral resources are lost as wastes, which result in the formation of technogenic dumps (Pashkevich and Petrova 2015). It is well documented that both active and abandoned mine sites affect terrestrial (soil fertility and erosion), aquatic (water quality and biota), and atmospheric (air quality) components of ecosystem adversely (Favas et al. 2018). It becomes alarming when active mine sites or abandoned mine lands are categorized as devastated landscape, where the natural tendency of auto regeneration is lost and only human intervention can lead to reclamation. Large-scale mining projects involve more technology, generate more wastes, and run for longer time, i.e. exposing environment to more damaging effects. Moreover, the topography and climate of a mine site also govern the level of environmental damage that is bound to occur. The mobilization of heavy metals (such as Cd, Cu, Hg, Mn, Ni, Pb, and Zn) and metalloids (As and Sb) during mining through extraction from ores and processing releases these toxic elements into the environment. Precipitation, temperature, wind flow, humidity, and other factors strongly determine the extent of diffusion of pollutants to surrounding environment. The atmosphere plays key roles in dispersion of air pollutants, whereas precipitation influences spread of water pollutants (Li et al. 2016).

Different mining projects vary in their plan according to the physical and chemical properties of the ore being mined. A proposed mining project begins with an explorative phase whereby the extent and value of the ore are evaluated via surveys, field studies, test drillings, and excavations and concludes with a post-closure phase. Each of these phases can be held responsible for a range of outcomes on environmental health. Even if the findings of explorative phase render the mining project unsuitable, the area is already de-vegetated and profoundly disturbed in the name of exploration. Whereas if the exploration proves that the ore is of sufficient grade and the mining project is economical, further developments (not without adverse impacts) are made including clearing of vast areas and construction of access roads. Thereafter, the active mining phase, i.e. extraction and beneficiation of target metal from its ore, begins. Metallic ores are generally buried under huge amount of waste rock or overburden, which needs to be removed by any of the processes depending on the type of ore. Strip ratio, i.e. the ratio between the amount of overburden generated and the mineral ore, is generally more than one or much higher. The overburden may contain toxic elements which either get deposited on-site or dumped into a landfill. If the ore is buried very deep in the ground, it is accessed through open-pit mining which results in high volume of overburden removal. Environmentally, it is the most destructive mining process especially in tropical forests, as it involves clearing of vegetated areas by cutting or burning native vegetation. Moreover, the constant increase in demand for minerals can be met from open cast mines ultimately leading to massive deforestation. But it is lower in cost and suitable for lower-grade ore mining (Environmental Law Alliance Worldwide 2010).

In another technique, placer mining is used if the metal is associated with stream sediments or floodplains, e.g. gold. Since it takes place within a streambed, it discharges high load of sediments which adversely affect surface water to great extent. An environmentally less destructive way to access ore is through underground mining as it minimally affects landscape, but it is costlier and poses safety risks as compared to open-pit mining. It can affect hydrogeological conditions and may induce earthquakes (Li et al. 2016).

After successful removal of overburden, the ore is extracted using heavy machinery and transported to processing units for beneficiation. Beneficiation includes physical and/or chemical processes to separate metals from nonmetallic components of ore. Even high-grade ores often contain toxic metal(loid)s such as lead, cadmium, and arsenic. Techniques such as milling, magnetic separation, solvent extraction, and leaching are employed for this purpose. However, these processes generate waste in the form of dumps, tailings, and leach materials. Exploitation of different types of minerals results in divergent environmental impacts. Combustible organic materials generate solid wastes and emit toxic gases. Mining of metallic ores leads to heavy metal(loid) pollution (Li et al. 2016). Beneficiation of gold and silver ores requires spraying of cyanide solution over finely milled ore to dissolve target metals and collected thereafter. Likewise, leaching of copper requires sulfuric acid and releases high-volume waste in the form of tailings which need to be addressed for proper disposal in order to prevent mobilization and release of toxic compounds into the environment. The involvement of cyanide calls for special attention for its fate and impact on environment, since it disrupts oxygen metabolism and causes acute toxicity at all trophic levels even at low concentrations and for over long periods (González-Valoys et al. 2022).

Post-mining, the ultimate aim of any mining project should be to reclaim the mining site almost to its...