Aquifer Pollution: Understanding The Impact Of Contamination

Groundwater pollution, also known as groundwater contamination, occurs when pollutants are released into the ground and make their way into aquifers. This can happen through surface contamination, where pollutants are carried by surface water into the groundwater, or through subsurface contamination, where pollutants come from buried or drilled sources. Groundwater pollution can also occur naturally due to the presence of unwanted constituents, contaminants, or impurities in the groundwater. In this case, it is referred to as contamination rather than pollution.

Groundwater pollution can have significant impacts on public health, causing hazards through poisoning or the spread of waterborne diseases. It can also harm plants, domestic animals, and wildlife.

Industrial discharges, urban activities, and agricultural pollution

Industrial Discharges

Industrial wastewater discharges can contain high levels of pollutants, including Per- and Polyfluoroalkyl Substances (PFAS). These discharges can affect the quality of receiving waters and interfere with treatment processes. Mining operations, for example, can release large volumes of wastewater containing dissolved solids, radionuclides, and metals, impacting both surface and groundwater quality.

Urban Activities

Urban development and land use practices have significant effects on aquifer pollution. Urban streams, for instance, are often overlooked but play a crucial role in reducing contamination and improving the livability of urban areas. Contaminants from urban runoff, such as chemical pollutants and sediments, can degrade water quality downstream, harming aquatic ecosystems and economically valuable resources. Additionally, urban infrastructure, such as parking lots, can contribute to pollution by allowing oil, sediments, and heavy metals to accumulate and eventually flush into nearby water bodies during rainfall.

Agricultural Pollution

Agriculture is a major contributor to water pollution, accounting for 70% of water withdrawals worldwide. Agricultural activities introduce various contaminants into water bodies, including agrochemicals, organic matter, drug residues, sediments, and saline drainage. The intensive use of pesticides, chemical fertilizers, and antibiotics in livestock farming further exacerbates water pollution. Nitrate from agriculture is now the most common chemical contaminant in groundwater aquifers globally, posing risks to both aquatic ecosystems and human health.

Landfills and waste disposal

Landfills are one of the most common methods of waste management and are used in countries regardless of their developmental status. The improper disposal of waste in landfills can lead to the pollution of aquifers.

The three most common types of landfills are:

• Municipal solid waste landfill
• Industrial waste landfill
• Hazardous waste landfill

There is also an emerging type of landfill called a "green waste landfill" that is occasionally used.

Landfills can affect aquifers in several ways. One of the main ways is through the leaching of organic and inorganic substances, as well as other substances of concern (SoC) contained in the waste. This can result in the contamination of groundwater, which can have serious health implications for humans. The age of the waste is the most determining factor in the degree of groundwater pollution.

Another way that landfills can impact aquifers is through air pollution. The decomposition of waste in landfills releases gases such as carbon dioxide (CO2) and carbon IV oxide, which can pollute the air and contribute to global warming. In addition, landfills can also be a source of odour pollution, which can affect the surrounding environment and cause discomfort to nearby residents.

To prevent the pollution of aquifers, it is important to have proper waste management practices in place. This includes the use of liners to prevent waste from leaking into the groundwater and the collection of leachate to minimize the impact on the surrounding environment. However, even with these measures in place, there is still a risk of aquifer pollution, especially if the landfill is not properly maintained or regulated.

Overall, while landfills are a necessary part of waste management, they can have significant impacts on aquifers and the environment as a whole. It is important to carefully consider the potential risks and impacts when deciding on the location and management of landfills to minimize any negative consequences.

Atmospheric contamination

The interaction between groundwater and surface water is complex. Surface water seeps into the ground and becomes groundwater, while groundwater can also feed surface water sources. This means that damage to groundwater aquifers, such as through fracking or over-abstraction, can have knock-on effects on rivers and lakes.

Additionally, atmospheric deposition of pollutants can result in chemical changes in the soil, which can then leach into groundwater. Atmospheric contamination can also be a source of saltwater intrusion in coastal areas, as over-abstraction of groundwater can cause saltwater to flow in and contaminate freshwater sources, rendering wells unusable.

Furthermore, atmospheric deposition of pesticides and fertilisers can accumulate and migrate to the water table, leading to groundwater pollution. Atmospheric contamination, therefore, plays a crucial role in the degradation of groundwater quality and highlights the interconnectedness of Earth's systems.

Saltwater contamination

Sources of Saltwater Contamination

• Excess salinity in groundwater from irrigation water, wastewater contamination, road salt, and other sources.
• Oil-field brine and salt-mine waste, which can result in highly concentrated salt contamination.
• Natural sources such as salt-bearing and saltwater-bearing bedrock formations.
• Sea level rise, which reduces the hydraulic gradient between freshwater and seawater, allowing seawater to migrate inland.
• Groundwater over-pumping, which can reduce freshwater flow toward coastal areas and draw saltwater toward freshwater zones.

On-site sanitation systems

A study in the city of Agra in India assessed the impact of on-site sanitation systems on groundwater sources in quaternary sediments (sand, silt, clay, and canker). The results showed that the contamination of groundwater in alluvial settings is less compared to hard rock settings where on-site sanitation systems have been implemented. However, the presence of faecal coliform in the majority of the samples indicated pollution from the on-site sanitation system. The nitrate concentration in the groundwater samples also exceeded the permissible limits, posing a health risk to the population.

Another study in the coastal city of Chennai, India, examined the impact of on-site sanitation systems on groundwater sources in a coastal aquifer. The results showed that key parameters such as Na2+, Cl-, NO3-, faecal coliform, and total dissolved solids exceeded the concentration limits recommended by the Bureau of Indian Standards. Elevated levels of faecal coliform in all samples confirmed significant groundwater pollution from the on-site sanitation systems.

The implementation of on-site sanitation systems requires careful consideration of the hydrogeological conditions to ensure the protection of groundwater sources. In areas with multiple aquifers, drinking water should be sourced from deeper aquifers rather than shallow ones. Additionally, mandatory monitoring of faecal coliforms and critical parameters like nitrate should be carried out regularly to detect any potential contamination incidents.

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