Factors Affecting Water Quality in Pit Lakes Across the USA
Mentor 1
Phillip Owens
Start Date
28-4-2023 12:00 AM
Description
Open pit mining is a widespread practice. Many pit mines flood after mining operations end, becoming pit lakes. In the USA, water quality of pit lakes varies considerably. Some can be used for recreation, aquaculture, and drinking water, while others are so toxic they can kill birds. Research shows that several factors determine water quality of these lakes. Because of their unusual distinctive vertical profile, pit lakes usually become meromictic. This means that the water becomes permanently stratified. The top two layers of water do not mix with the bottom layer. This bottom layer of pit lake water is generally viscous and has a high concentration of heavy metals. Water acidity in meromictic pit lakes is affected by oxidation of minerals dissolved in the lake water. Different minerals react differently in water. For example, oxidation of iron and copper in water usually consumes hydrogen ions. This reduces water acidity. However, when zinc, aluminum, arsenic, phosphorus, or calcium oxidize in water, hydrogen ions are produced, which increases the acidity of water. The method of pit flooding also affects water quality. Many pits are allowed to flood naturally, filling with rainwater and surface runoff that can contain dissolved fertilizers, pesticides, and other industrial chemicals. Also, the walls of open pit mines often collapse once flooded. This exposes a larger surface area to water and allows more minerals to dissolve and oxidize. Further research is expected to lead to better regulation of pit mine closure management. With proper restrictions, pit lakes can have good water quality. They can be a valuable community asset if not damaging to the environment.
Factors Affecting Water Quality in Pit Lakes Across the USA
Open pit mining is a widespread practice. Many pit mines flood after mining operations end, becoming pit lakes. In the USA, water quality of pit lakes varies considerably. Some can be used for recreation, aquaculture, and drinking water, while others are so toxic they can kill birds. Research shows that several factors determine water quality of these lakes. Because of their unusual distinctive vertical profile, pit lakes usually become meromictic. This means that the water becomes permanently stratified. The top two layers of water do not mix with the bottom layer. This bottom layer of pit lake water is generally viscous and has a high concentration of heavy metals. Water acidity in meromictic pit lakes is affected by oxidation of minerals dissolved in the lake water. Different minerals react differently in water. For example, oxidation of iron and copper in water usually consumes hydrogen ions. This reduces water acidity. However, when zinc, aluminum, arsenic, phosphorus, or calcium oxidize in water, hydrogen ions are produced, which increases the acidity of water. The method of pit flooding also affects water quality. Many pits are allowed to flood naturally, filling with rainwater and surface runoff that can contain dissolved fertilizers, pesticides, and other industrial chemicals. Also, the walls of open pit mines often collapse once flooded. This exposes a larger surface area to water and allows more minerals to dissolve and oxidize. Further research is expected to lead to better regulation of pit mine closure management. With proper restrictions, pit lakes can have good water quality. They can be a valuable community asset if not damaging to the environment.
