Land Pollution's Journey To Water: Understanding The Transition

Land pollution occurs when solid or liquid waste materials contaminate the soil and groundwater. These waste materials are often referred to as municipal solid waste (MSW) and can include hazardous and non-hazardous substances such as heavy metals, pesticides, fertilisers, litter, and pharmaceuticals. Land pollution can have detrimental effects on both the environment and human health, including contaminated drinking water, reduced air quality, and the endangerment and extinction of species.

Water pollution, on the other hand, occurs when harmful substances contaminate bodies of water such as streams, rivers, lakes, and oceans, degrading water quality and rendering it toxic to humans and the environment. Water is particularly vulnerable to pollution due to its ability to dissolve more substances than any other liquid on Earth.

So, how exactly does pollution travel from land to water?

Fertilisers and pesticides from farming

Fertilisers and pesticides are essential in farming to increase crop yields and protect crops from harmful pests and diseases. However, their excessive use can have detrimental effects on the environment, especially water bodies. When it rains, excess fertilisers and pesticides are washed off from farmlands into nearby streams, rivers, or other water bodies, becoming water pollutants.

Fertilisers are made of nutrients such as nitrogen and phosphorus. When these nutrients reach water bodies, they cause an excessive growth of algae, which uses up the oxygen in the water. This reduction in oxygen levels can hurt aquatic wildlife and even lead to fish kills. This process is known as eutrophication, which can lead to hypoxia or "dead zones" in the water. Additionally, excess nutrients in water can cause harmful algal blooms (HABs), which not only disrupt aquatic ecosystems but also produce toxins harmful to humans.

Pesticides, on the other hand, are designed to kill pests and insects. However, when they enter water bodies, they can have similar detrimental effects on aquatic life. Pesticides can accumulate in the bodies of aquatic organisms and sediment soil, posing health risks to humans who consume them. Chronic exposure to pesticides through water ingestion can interfere with the human body's hormones, reduce immunity, disrupt hormone balance, trigger reproductive issues, and even have carcinogenic effects.

The use of fertilisers and pesticides in farming is a significant contributor to water pollution. To mitigate their impact on water bodies, it is essential to adopt sustainable farming practices. This includes adopting nutrient management techniques, using conservation drainage practices, ensuring year-round ground cover, implementing conservation tillage, and engaging in watershed efforts to reduce nutrient losses and prevent excess nutrients from entering water bodies.

Septic tanks, vehicles and boats

Septic tanks, vehicles, and boats can all contribute to water pollution in various ways.

Septic Tanks

Septic systems are a potential source of water pollution, particularly in areas with high water tables or shallow impermeable layers. Contaminated effluent from septic tanks can pollute nearby water bodies if the tank is not functioning properly or is located too close to a water source. This can lead to the spread of diseases such as typhoid, gastrointestinal illness, hepatitis A, and cholera, as well as cause "blue baby syndrome" in infants due to excess nitrate consumption. Poor maintenance, improper design and construction, and the use of harmful products can also contribute to septic system pollution.

Vehicles

The increase in vehicle usage has led to the creation of more roads, parking lots, and driveways, reducing habitats for wildlife and natural filters for pollution. Vehicle emissions release pollutants into the air, which eventually find their way into water sources through rainfall and groundwater. Stormwater runoff from paved surfaces is a significant contributor to water pollution, as it carries pollutants directly into nearby streams and rivers.

Boats

Motorized boats can impact water quality by adding metals and chemicals to the water. Two-stroke boat motors can emit up to 30% of their unburned fuel and oil mixture into the water, affecting pH levels and dissolved oxygen, which in turn influences aquatic life. Additionally, boat motors can churn up the lake bottom in shallow areas, stirring up sediments and releasing nutrients that promote algal growth, reducing water clarity and potentially leading to algal blooms.

Air pollution

One of the primary ways air pollution affects water is through acid rain. Sulfur dioxide (SO2) and nitrogen oxides (NOx), which are emitted from the burning of fossil fuels, can mix with water vapour in the atmosphere to form acid rain. Acid rain has a detrimental effect on both aquatic and terrestrial ecosystems, altering the chemical composition of water bodies and soils, and making it difficult for plants, fish, and other wildlife to survive. For instance, increased soil acidity can cause leaching of essential nutrients and minerals, such as calcium, magnesium, and potassium, making them less available for land organisms. Soils with higher calcium carbonate content, such as limestone and dolomite, are more resistant to acid rain due to their ability to neutralise acids.

In addition to acid rain, air pollution can also lead to eutrophication of water bodies. Nitrogen oxides and ammonia (NH3) in the air can be deposited into water bodies, leading to an excess of nitrogen. This contributes to eutrophication, where algal blooms thrive and deplete the oxygen available for other organisms, creating "dead zones".

Furthermore, air pollution can affect the oceans' ability to absorb carbon dioxide. While the oceans act as a carbon sink, absorbing carbon dioxide and reducing greenhouse gases in the atmosphere, the resulting increase in ocean acidity can have complex effects on marine life.

It is worth noting that natural sources, such as volcanoes and forest fires, also contribute to air pollution. However, human activities remain the primary source of air pollution, and it is crucial to implement measures to reduce air pollution and improve air quality, such as transitioning to cleaner energy sources and improving fuel efficiency.

Poor waste management

Firstly, municipal solid waste (MSW) is often disposed of in open dumps, which can contaminate nearby water sources. Open dumping was once a common practice, and while it is now banned in many countries, old dumps continue to cause water pollution. Decomposing garbage produces a highly contaminated liquid called leachate, which can infiltrate and percolate through waste material, eventually mixing with groundwater or seeping into nearby bodies of surface water. Leachate jeopardizes both public health and environmental quality.

Another issue with poor waste management is that it can lead to the contamination of soil, which in turn can pollute water sources. Soil is particularly vulnerable to contamination from hazardous waste, which includes harmful substances produced by chemical manufacturing companies, petroleum refineries, paper mills, smelters, machine shops, dry cleaners, and automobile repair shops.

In addition, poor waste management can result in the open burning or incineration of waste, which contributes to air pollution. This has knock-on effects on water sources, as toxic substances from the air can mix with water, causing further pollution.

Furthermore, poor waste management can lead to the mixing of household garbage with hazardous waste, which can then be transported and released into water sources. This can happen due to deficient transportation systems and informal disposal methods, such as uncontrolled dumping and open-air incinerators.

Finally, poor waste management can result in the discharge of untreated wastewater directly into water sources. This is a particular issue in poorer urban areas, where a large proportion of wastewater may be discharged untreated. This wastewater can contain household effluent, human waste, toxic chemicals, and medical waste, all of which can contaminate the water environment and pose risks to human health.

Mining and mineral extraction

The first is through acid mine drainage (AMD). AMD is a natural process in which sulphuric acid is produced when sulphides in rocks are exposed to air and water. When large quantities of rock containing sulphides are excavated, it can react with water and oxygen to create sulphuric acid. This acid then leaches from the rock and is carried off the mine site by rainwater or surface drainage, eventually being deposited into nearby streams, rivers, lakes, and groundwater. AMD severely degrades water quality and can kill aquatic life, making water virtually unusable.

The second is through heavy metal contamination and leaching. Heavy metal pollution occurs when metals such as arsenic, cobalt, copper, cadmium, lead, silver, and zinc, which are contained in excavated rock or exposed in an underground mine, come into contact with water. Metals are leached out and carried downstream as water washes over the rock surface. Leaching is particularly accelerated in the low pH conditions created by acid mine drainage.

The third is through the use of processing chemicals. This kind of pollution occurs when chemical agents, such as cyanide or sulphuric acid (used by mining companies to separate the target mineral from the ore), spill, leak, or leach from the mine site into nearby water bodies. These chemicals can be highly toxic to humans and wildlife.

The fourth is through erosion and sedimentation. Mineral development disturbs soil and rock in the course of constructing and maintaining roads, open pits, and waste impoundments. In the absence of adequate prevention and control strategies, erosion of the exposed earth may carry substantial amounts of sediment into streams, rivers, and lakes. Excessive sediment can clog riverbeds and smother watershed vegetation, wildlife habitats, and aquatic organisms.

Additionally, mining operations require large amounts of water for processing ore, and this can affect freshwater sources. For example, in Chile's Salar de Atacama, lithium and copper extraction have consumed over 65% of the local water supply, depleting water available for Indigenous farming communities in an already water-scarce region.

Furthermore, waste from mining and processing, including residual minerals and chemicals, can contaminate water in nearby communities. This is particularly true for lithium mining, which uses an evaporation method that can cause the salinization of freshwater and deplete nearby surface and groundwater supplies.

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