How Mining Pollutes Waterways And Oceans

Mining is a highly invasive process that often has a devastating impact on the natural environment, causing water pollution that can severely affect water quality in surrounding areas. Water is essential to the extraction and processing of mined materials, and large-scale mining uses water at an industrial scale, straining water supplies in already water-stressed regions. The water used in mining can also become contaminated with chemicals and heavy metals, which can then be discharged into the surrounding environment, polluting water sources and causing long-term damage to ecosystems and human health.

Acid mine drainage

AMD is considered one of the most serious threats to water, as it can devastate rivers, streams, and aquatic life for hundreds, and under the right conditions, thousands of years. The acid can dissolve other harmful metals and metalloids such as arsenic from the surrounding rock. It can be released anywhere on the mine where sulphides are exposed to air and water, including waste rock piles, tailings, open pits, underground tunnels, and leach pads.

AMD is usually associated with currently active mining and abandoned coal mines. It is considered one of the most significant water contaminants in the mid-Atlantic region. It is also a common form of water pollution in areas where mining took place in the past. The liquid that drains from coal stocks, coal handling facilities, coal washeries, and coal waste tips can be highly acidic and is treated as acid rock drainage.

Heavy metal contamination

The Canadian mineral industry, for example, generates one million tonnes of waste rock and 950,000 tonnes of tailings per day. The waste rock, often containing acid-generating sulphides, heavy metals, and other contaminants, is typically stored above ground in large piles. This waste, along with exposed bedrock walls, is a significant source of metal pollution in waterways in British Columbia. Similarly, in the mid-Atlantic region of the United States, abandoned coal mines are a major source of heavy metal contamination of water.

The impact of heavy metal pollution on water quality is severe. It can lead to the physical and chemical degradation of surface and groundwater, including sediment discharge and deposition in rivers and lakes. The contaminated water often contains dissolved metals and other toxic constituents, rendering it unsafe for human consumption and harmful to aquatic life. Even trace amounts of heavy metals in water sources can pose serious health risks to humans and aquatic organisms, as these metals can accumulate in the food chain.

The problem is exacerbated by the non-biodegradable nature of most heavy metals, leading to their persistence in the environment for extended periods. They may be transported through soils to groundwater and eventually enter the food chain through uptake by crops. Phytoremediation, the use of plants to remediate contaminated sites, has been suggested as a potential solution. Approximately 450 plant species have been identified as hyperaccumulators of heavy metals, particularly nickel and zinc.

While modern mining practices have improved, with regulatory agencies requiring careful analysis and planning during the project design phase to minimise water pollution, the legacy of historic mining activities remains a challenge. The impact of heavy metal contamination from mining on water sources underscores the importance of implementing sound water management practices and adopting remediation technologies to protect the environment and human health.

Pollution from processing chemicals

Processing minerals and ores require the use of water, which is often sourced from freshwater supplies. The extraction and processing of ores and minerals also require the use of chemicals, which can contaminate water supplies.

Mining companies generally use chemical compounds such as sulphuric acid or cyanide to separate their respective target minerals from the ore. Contamination occurs when these chemicals are leached, leaked, or spilled from the mining area into the nearby bodies of water. These chemicals are highly toxic and could lead to loss of life in wildlife species and severe health concerns in humans.

The chemicals used in the extraction and processing of ores can also present water quality issues. Although large-scale modern mines carefully manage on-site chemical usage, historic and artisanal mines can release these compounds, such as mercury and cyanide from gold processing.

Mineral processing, also known as beneficiation, aims to physically separate and concentrate the ore mineral(s) using physical, chemical, and sometimes microbiological techniques. The use of chemicals in this process can result in the contamination of water supplies.

Acid mine drainage (AMD) is a significant environmental concern where waste materials containing metal-rich sulphides from mining activity have been stored or abandoned. AMD is caused by the infiltration of water through sulphide-containing tailings piles and ponds, surface and underground workings, waste, and development rock. This leads to the leaching of large volumes of metals into stream and river ecosystems, severely degrading water quality and making it unusable for recreation, drinking, or industrial use.

Erosion and sedimentation

Mining is a highly invasive process that often has a devastating impact on the environment and natural ecosystems. One of the key ways in which mining causes water pollution is through erosion and sedimentation.

Mineral development disturbs soil and rock layers during the construction and maintenance of roads, open pits, and waste impoundments. This disturbance of the earth's surface leaves it vulnerable to erosion by wind and water. When heavy rain falls, loosened topsoil is washed away, carrying sediments with it. These sediments are then deposited into nearby streams, rivers, and lakes.

Excessive sediment can clog riverbeds and smother vegetation, wildlife habitats, and aquatic organisms. This can lead to disfiguration of streams and river channels, resulting in flooding. The increased levels of suspended solids in the water can also affect its clarity, harming aquatic life by disrupting their feeding and breeding patterns.

In addition, the construction of roads during the exploration phase of mining can result in sedimentation if they are poorly built. This sedimentation can further disturb water sources during mine construction.

The impact of erosion and sedimentation caused by mining operations can be mitigated through the implementation of adequate prevention and control strategies. This includes ensuring proper waste management, utilizing safer mining methods, and establishing robust regulatory frameworks.

Water consumption

The water consumption patterns in mining can have far-reaching consequences, especially in areas already facing high water stress. Global data reveals that at least 16% of critical mineral mines, deposits, and districts are located in regions with high or extremely high water stress. In these areas, agriculture, industry, and households heavily rely on limited water resources. The competition for water between mining activities and other sectors exacerbates the strain on freshwater supplies, highlighting the need for sustainable water management practices in the industry.

The impact of mining on water consumption extends beyond the immediate extraction processes. The legacy of historic mining practices, particularly in the United States, has resulted in more than 500,000 abandoned or inactive mines. These sites often lack modern environmental controls, leading to long-term water quality issues. The management and treatment of water in post-closure phases can be costly and require significant long-term commitments.

Furthermore, mining activities can indirectly contribute to increased water consumption in affected regions. For instance, the physical transport of sediments and the creation of suspended solids in water bodies can render the water less suitable for on-site reuse. This, in turn, drives a higher demand for freshwater resources, further straining local water supplies.

While there have been improvements in mining practices to reduce environmental risks, the water consumption patterns in mining continue to be a critical area of focus. Sustainable water management strategies, regulatory oversight, and financial assurances are essential to mitigating the industry's impact on water consumption and ensuring the protection of this precious resource for future generations.

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