Lakes Under Threat: Sources Of Pollution

Lakes can get polluted in a variety of ways, and human activities are often to blame. From turning forests into farms to burning coal for energy, human actions can have a detrimental impact on the health of lakes. Nutrient pollution, caused by excess nitrogen and phosphorus in water or air, is the number-one threat to water quality worldwide and can lead to harmful algal blooms. Other sources of lake pollution include sewage and wastewater, oil spills, and radioactive substances. Urban development, including the expansion of residential areas and roads, can also contribute to lake pollution as rainwater carrying pollutants is redirected towards waterways instead of draining into the ground.

Agricultural pollution

Fertilizers, pesticides, and animal waste from farms and livestock operations contain high levels of nutrients such as nitrogen and phosphorus. When it rains, these chemicals are washed into lakes and streams, causing nutrient pollution. This type of pollution is the number-one threat to water quality worldwide and can lead to algal blooms, which are toxic to people and wildlife.

In the United States, agricultural pollution is the top source of contamination in rivers and streams, the second-biggest source in wetlands, and the third main source in lakes. It is also a major contributor to contamination in estuaries and groundwater. In 2014, nearly half a million people in western Lake Erie lost access to safe tap water for two days, and in some cases, more than a week, due to toxic algae contamination caused by agricultural pollution.

To prevent agricultural pollution from reaching lakes and other water sources, measures such as vegetative buffer strips planted alongside farmland and waterways have been proposed. These natural buffers can help capture and filter pollutants before they reach the water. However, many large farms do not utilize these buffers, and special interests have opposed making them a requirement.

Sewage and wastewater

Wastewater from sinks, showers, and toilets (sewage) and from commercial, industrial, and agricultural activities can contain metals, solvents, toxic sludge, and other pollutants. In the United States, wastewater treatment facilities process about 34 billion gallons of wastewater per day. These facilities reduce the amount of pollutants such as pathogens, phosphorus, and nitrogen in sewage, as well as heavy metals and toxic chemicals in industrial waste. However, aging and overwhelmed sewage treatment systems can also release untreated wastewater into lakes and other waterways.

Motor vehicles are another source of sewage and wastewater pollution. They distribute dirt, oil, road salts, and other debris that can be swept away by rainwater or snowmelt into storm drains, eventually making their way into lakes and other water bodies.

The impact of sewage and wastewater pollution on lakes is significant. High levels of nitrogen and phosphorus in wastewater can contribute to nutrient pollution, leading to the growth of harmful algal blooms. These blooms can reduce water clarity, make it difficult for other water plants to survive, and deplete oxygen levels in lakes, creating a hostile environment for deep-water fish.

To reduce sewage and wastewater pollution in lakes, proper management and treatment of wastewater are crucial. This includes advocating for improved wastewater treatment processes and reducing the use of polluting chemicals in commercial and industrial activities. Additionally, individuals can play a role by properly disposing of chemicals, oils, and other waste, and by supporting initiatives that protect and preserve water resources.

Oil pollution

Oil has unique chemical properties that make it particularly harmful to aquatic ecosystems when spilled. Due to its buoyancy, oil tends to rise to the surface and disperse over large areas of water. This can smother fish and impede the movement of marine birds, leading to fatal consequences. Oil also blocks light from reaching photosynthetic aquatic plants, disrupting the entire food web.

The density of oil determines whether it will float, semi-submerge, or sink in freshwater. Heavier oils are more likely to sink or partially submerge, making their containment and cleanup more complex. Quick response is crucial in addressing oil spills, as oil can quickly soak into soil and rock, contaminating groundwater and drinking water sources.

In addition to spills, routine shipping, run-offs, and dumping are other ways oil enters lakes and oceans. Oil pollution from shipping travel, drains, and dumping accounts for about 88% of the oil that enters the ocean. While oil spills are a more localized problem, they can still have catastrophic consequences for the affected areas.

The effects of oil pollution on aquatic ecosystems are wide-ranging. Some organisms, such as certain bacteria, may experience population growth due to their ability to break down hydrocarbons in crude oil. However, the overall impact on the food web is detrimental. Phytoplankton and zooplankton, which form the base of the food chain, have been observed to decrease by up to 70% following oil spills.

Radioactive substances

Lake Karachay was used as a dumping ground for radioactive waste by the nearby Mayak nuclear weapons laboratory and fuel reprocessing plant. The facility, built in the late 1940s, was kept secret by the Soviet government until 1990. During this period, it is believed that numerous nuclear-related accidents occurred, resulting in the contamination of the lake and the surrounding area. The lake began to dry out in the 1960s, and the wind carried radioactive dust from its bed, irradiating half a million people in the region.

The effects of the pollution on the local population were devastating. The Techa River, which provided water to nearby villages, became contaminated, and about 65% of local residents suffered from radiation sickness. The Chelyabinsk region reported a 21% increase in cancer cases, a 25% increase in congenital disabilities, and a 41% increase in leukemia. The radioactive pollution was so severe that just standing on the shore of Lake Karachay for an hour in 1990 would have exposed a person to a lethal dose of radiation.

To address the contamination, the lake has been completely filled in with special concrete blocks, rock, and dirt, effectively turning it into a permanent nuclear waste storage facility. However, the surrounding area will remain dangerous for hundreds of years, and the impact of the pollution on the environment and public health will be felt for generations to come.

Nonpoint sources of pollution

Nonpoint source pollution is contamination that comes from diffuse sources, such as agricultural runoff, precipitation, drainage, or seepage. When rain or snowmelt moves over and through the ground, it absorbs and assimilates any pollutants it encounters, such as pesticides, fertilizers, sediment, and oil, and deposits them into a stream, which eventually deposits them into a lake.

Nonpoint source pollution is challenging to manage because it comes from multiple sources and is difficult to trace back to a specific location or offender. It often enters water bodies in small amounts but can become concentrated in lakes and other freshwater resources. Examples of nonpoint source pollution include:

• Agricultural runoff: Pesticides, fertilizers, and manure from farms can wash into lakes during rain or snowmelt, contributing to nutrient pollution and harmful algal blooms.
• Acid rain: Atmospheric pollutants from car exhaust pipes or industrial power generation can turn into acid rain or other forms of acidic precipitation, which can alter the pH of lakes and harm aquatic life.
• Nitrate deposition: Excess nitrogen in the water or air can come from agricultural activities and contribute to nutrient pollution, leading to algal blooms and reduced oxygen levels in lakes.
• Septic tank leaching: Bacteria and nutrients from failing or substandard septic systems can contaminate lakes, leading to swimming beach closures and other recreational use impairments.
• Sediment runoff: Soil erosion from construction activities, urban development, or agricultural practices can wash sediment into lakes, reducing water clarity and quality and smothering aquatic habitats.

Nonpoint source pollution is the leading cause of water pollution in U.S. waters, and it is essential to address this issue through proper land management practices, such as minimizing runoff, reducing chemical usage, and implementing effective waste disposal methods, to protect the health of lakes and other freshwater ecosystems.

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