Water Pollution: Can It Kill A Lake?

Water pollution is a pressing issue that affects lakes, rivers, and other bodies of water worldwide. It occurs when harmful substances, often chemicals or microorganisms, contaminate water sources, degrading water quality and rendering it toxic to humans and the environment. One of the consequences of water pollution is the creation of dead zones in lakes, where most marine life dies or leaves due to a lack of oxygen. This can happen when excess nutrients from human activity, such as agricultural runoff or sewage, stimulate an overgrowth of algae, which then sinks and decomposes, depleting the oxygen available to healthy marine life. This process, known as eutrophication, has been observed in lakes such as Lake Erie, one of the Great Lakes in North America, where industrial pollution and agricultural runoff have led to severe algal fouling and fish die-offs.

Eutrophication

The accumulation of nutrients in the water, most commonly phosphates and nitrates, leads to excessive plant and algal growth. This growth reduces water clarity, light levels, and oxygen levels, which can have negative consequences for organisms living in the lake. In extreme cases, anaerobic conditions may develop, promoting the growth of bacteria. These zones are known as dead zones, where fish and other aquatic organisms suffocate due to lack of oxygen.

To address eutrophication, it is crucial to minimise pollution from sewage and agriculture, which are major contributors to nutrient loading in water bodies. This can be achieved through improved sewage treatment processes and the implementation of buffer zones near farms and waterways. Additionally, the introduction of bacteria and algae-inhibiting organisms, such as shellfish and seaweed, can help control the growth of harmful algae.

The management of eutrophication requires ongoing cooperation between citizens, scientists, managers, and policymakers. By reducing nutrient inputs and implementing effective remediation techniques, it is possible to restore aquatic ecosystems and improve water quality.

Point source vs. non-point source pollution

Water pollution can indeed cause a lake to be biologically dead. This can happen through the dumping of industrial waste, sewage, and other chemicals, as well as agricultural and urban runoff.

Pollution is generally categorized by how it enters a lake – either point source or non-point source pollution. Point-source pollution is easier to identify and manage, whereas non-point source pollution is harder to address as it comes from multiple places at once.

Point Source Pollution

Point source pollution comes from a single, identifiable place, such as a factory, power plant, or sewage treatment plant. It is defined as any contaminant that enters the environment from a confined place. Examples include smokestacks, discharge pipes, and drainage ditches. Factories and power plants can affect both air and water quality. Smokestacks may release carbon monoxide, heavy metals, sulfur dioxide, nitrogen dioxide, and particulate matter into the air. Oil refineries, paper mills, and auto plants may discharge effluent—wastewater containing harmful chemical pollutants—into bodies of water.

Municipal wastewater treatment plants are another common source of point-source pollution. Effluent from these plants can introduce harmful nutrients and microbes into waterways, causing rampant growths of algae.

Non-Point Source Pollution

Non-point source pollution comes from multiple diffuse sources and often enters bodies of water in small amounts. However, it can become concentrated in lakes and other freshwater resources. Examples include agricultural runoff (pesticides, fertilizers, manure), acid rain, nitrate deposition, and leaching from septic tanks. Non-point source pollution includes many activities that occur around lakes and can be extremely harmful to water quality.

Runoff is generally associated with non-point source pollution, as water accumulates contaminants from sources like gardens, parking lots, or construction sites before being emptied into streams or rivers. In urban areas, rainwater can wash away oil leaked from car engines, tire rubber, dog waste, and trash, which then ends up in nearby rivers.

Airborne pollutants are another major contributor to non-point source pollution, as they can result in acid rain. This is formed when sulfur dioxide and nitrogen oxides from factories and power plants combine with water.

Preventing and Managing Pollution

To prevent and manage pollution, several questions must be answered:

• What is the source of the pollution?
• How much pollution is occurring?
• What is the projected lifetime of the pollution?
• What are the expected effects of the pollution?

Point source pollution is generally easier to manage than non-point source pollution because the source, volume, and impact can be easily identified, and the impacts are often concentrated in one location.

To reduce pollution, individuals can dispose of waste properly, plant trees to reduce sediment runoff, promote water filtration, and reduce fertilizer and pesticide usage. At the community, state, and federal levels, policies and regulations can be implemented to enforce water quality standards and reduce pollution from industries and agriculture.

Sewage and wastewater

Sewage is often contaminated with chemicals, toxins, and heavy metals, such as mercury, lead, and chromium. These contaminants can have a range of harmful effects on aquatic life and ecosystems. For example, they can cause changes in pH levels, hypoxia or anoxia, increased water temperatures, and excessive turbidity.

One of the most significant issues with sewage is the release of nutrients, particularly nitrogen and phosphorus, into water bodies. This nutrient enrichment, known as eutrophication, leads to excessive growth of algae and bacterial growth, resulting in the depletion of dissolved oxygen in the water. This process can cause substantial environmental degradation and harm aquatic life.

In addition to the ecological impacts, sewage pollution also poses risks to human health. Treated wastewater can still contain contaminants that affect fish, which then enter the food chain when consumed by humans. Furthermore, inadequate sewage treatment can lead to the spread of water-borne diseases when people use polluted water for drinking or irrigation.

To mitigate the negative impacts of sewage and wastewater, proper sanitation and sewage treatment are crucial. Well-designed and operated sewage treatment systems can remove a large proportion of pollutants. However, in some cases, even treated sewage may still contain harmful substances.

It is important to note that sewage pollution is not limited to a single source but can come from various point sources and non-point sources. Point sources include discharges from wastewater treatment plants, factories, or storm drains. Non-point sources include agricultural runoff, atmospheric deposition, and sewage overflow during heavy rainfall or storms.

To effectively manage sewage and wastewater pollution, a combination of infrastructure improvements, management plans, and legislation is required. This includes improving sanitation, sewage treatment technologies, and implementing measures to control urban runoff and agricultural wastewater.

Oil spills

Water pollution can indeed cause a lake to be biologically dead. This can occur through eutrophication, which is the process of excessive nutrients accumulating in a body of water, resulting in increased growth of organisms that deplete the oxygen in the water. This can be caused by human activities such as industrial waste, sewage, and agricultural runoff, leading to harmful algal blooms and the depletion of oxygen levels, causing the death of aquatic life. Oil spills are a significant contributor to water pollution and can have devastating effects on lakes and rivers.

• Density and Movement: Oil typically floats on water due to its lower density. However, some very heavy oils with densities close to that of freshwater (around 1 gram per cubic centimeter) may sink in lakes or rivers. The movement of oil in rivers is generally downstream, influenced by currents and wind, and it may move along the river underwater before refloating when it reaches the ocean.
• Dams and Locks: The presence of dams or locks in rivers can slow down or divert water flow, causing oil to collect in specific areas. This can make it easier for responders to use skimmers, sorbent pads, or booms to remove the oil from the water surface.
• Vegetation: Unlike open coasts, many rivers have vegetation and trees growing along their edges. Cleaning oil from vegetation is more challenging than cleaning sandy beaches, and responders may have to cut, burn, or flush the affected plants.
• Sediment Interaction: Rivers often carry sediment in their currents, and oil droplets can combine with this sediment, eventually settling on the river or lake bed, especially near the mouth as the water slows down.
• Containment and Cleanup: In the event of an oil spill in a lake or river, containing and cleaning up the oil can be difficult. Booms can be used to contain the oil, and skimmers or sorbent materials can remove it from the surface. If oil sinks and pools on the bottom, vacuum devices may be used, but they may also capture a lot of water and sand.

To prevent and mitigate the impacts of oil spills in lakes, it is crucial to have effective measures in place, such as regular maintenance of equipment, swift response protocols, and collaboration between government agencies, companies, and environmental organizations.

Radioactive substances

Radioactive pollution of water is an emerging issue that poses a grave threat to water quality and human health. Radioactive contamination has been reported in many parts of the world. Radioactivity is the spontaneous emission of particles or waves from the unstable nuclei of some elements. There are three types of radioactive emissions: alpha, beta, and gamma. Alpha particles are positively charged helium atoms, beta particles are negatively charged electrons, and gamma rays are neutral electromagnetic radiations.

Radioactive elements are naturally found in the earth's crust. The percolation of naturally occurring radioactive materials (NORM) from soil sediments to the aquifer causes groundwater contamination. Nuclear weapons, nuclear disasters, nuclear power plants, and the dumping of radioactive waste are significant anthropogenic sources of radioactive pollution. The application of radioactive elements in industries and scientific laboratories is a minor source.

Nuclear reactors and nuclear warhead experiments are the key sources of human-induced radionuclides discharge. Nuclear reactors produce radioisotopes that are used as sources of gamma radiation in radiotherapy and other industrial applications. Strontium-90, Caesium-137, and other unnecessary radioactive wastes are also formed by nuclear reactors.

Radioactive contamination is more prevalent in groundwater than in surface water since groundwater is more exposed to the radioactive elements found in rocks. Magma can also release radioactive gases into the environment, and the deposition of these gases in water bodies can cause radioactive contamination. Atmospheric deposition (both dry and wet) of cosmogenic radionuclides also contributes to radioactive nuclei in surface water.

Radioactive pollution in water can have severe consequences for human health. High doses of radiation can cause acute radiation syndrome or cutaneous radiation injury. Exposure to radiation can cause various disorders, including cancer, leukaemia, genetic mutations, osteonecrosis, cataracts, and chromosomal disruption.

Radioactive pollution can also have immediate and long-term effects. The immediate consequences include skin, lung, and genital distress, as well as hair loss. The long-term outcomes include various infections, such as radiation damage, bone marrow death, cataract formation, cancer stimulation, cholera, dysentery, tuberculosis, and pneumonia, which can sometimes be fatal.

Furthermore, genetic effects of ionizing radiation can induce mutations in germ cells, resulting in structural alterations in germ cell DNA that are passed on to offspring. Hereditary disorders can lead to premature death and severe mental illness.

To ensure a safe water supply, proper analysis and monitoring of radioactive pollutants are necessary. Prevention and precaution measures can help control anthropogenic sources of radioactive contamination in water resources. Various treatment methods, such as aeration, reverse osmosis, ion exchange, and granular carbon adsorption, are effective remedial measures for treating radioactive contaminated water.

Frequently asked questions