How Bodies Of Water Absorb And Filter Pollutants

Water pollution is a pressing issue that poses a threat to human health, the environment, and the economy. It occurs when harmful substances contaminate bodies of water, degrading water quality and rendering it toxic or unsafe for human use. These harmful substances can include chemicals, waste, plastic, oil spills, and disease-causing microorganisms. With water being a universal solvent, it is vulnerable to pollution from various sources, and this has contributed to a freshwater crisis. Understanding the sources of pollution, such as point source and nonpoint source pollution, is crucial for addressing this issue and protecting our valuable water resources.

Point-source pollution

Water pollution is a widespread problem that jeopardizes human health. It occurs when harmful substances contaminate a body of water, degrading water quality and rendering it toxic. These harmful substances can be chemicals, waste, plastic, or other pollutants.

The Environmental Protection Agency (EPA) in the United States regulates point-source pollution by establishing limits on what can be discharged directly into a body of water. While point-source pollution comes from a specific place, it can affect miles of waterways and oceans. For example, sewage treatment plants, while considered point sources, are not the original source of pollution as they treat human waste. However, the treated effluent from these plants can still contain pollutants and be discharged into streams or rivers, impacting the surrounding aquatic ecosystems.

Another example of point-source pollution is combined sewer overflow (CSO). In older cities, sanitary and stormwater systems may be combined. During heavy rains or excessive rainfall, these combined sewer systems can become overwhelmed, causing raw sewage and rainwater runoff to mix and discharge directly into nearby water bodies without treatment. This can have severe consequences for human health and the environment, including restricting activities like fishing and swimming due to unsafe water conditions.

While point-source pollution is easier to control compared to non-point source pollution, it still contributes significantly to the degradation of water quality. Understanding and addressing point-source pollution are crucial steps in protecting our valuable water resources and ensuring safe and healthy aquatic ecosystems.

Nonpoint-source pollution

Water pollution occurs when harmful substances contaminate a body of water, degrading water quality and rendering it toxic to humans or the environment. Nonpoint-source (NPS) pollution is the nation's largest water quality problem and is the leading remaining cause of water quality issues. Unlike pollution from industrial and sewage treatment plants, NPS pollution comes from many diffuse sources.

NPS pollution generally results from land runoff, precipitation, atmospheric deposition, drainage, seepage, or hydrologic modification. Rainfall or snowmelt moves over and through the ground, picking up and carrying away natural and human-made pollutants, which are eventually deposited into lakes, rivers, wetlands, coastal waters, and groundwater.

Sources of NPS pollution include agricultural land, urban areas, forests, wetlands, and minelands. In agricultural settings, NPS pollution can come from farm fields, livestock facilities, construction sites, lawns and gardens, surface coal mines, and forestry. The major NPS pollutants in this category are nutrients and sediment. Nutrients, such as fertilizers and animal waste, can cause excessive algae growth, leading to eutrophic "dead zones" where aquatic life cannot survive due to a lack of oxygen. Sediment, which is soil that has eroded from farm fields, construction sites, and streambanks, can make the water cloudy, hindering the ability of aquatic organisms to see and feed properly. It can also damage fish gills and the breathing of aquatic insects, cover fish spawning habitats, and reduce sunlight penetration, affecting plant growth. Additionally, sediment can carry other pollutants like metals and toxic chemicals.

In urban settings, NPS pollution can come from city streets, parking lots, and storm drains. Oil, pet waste, pesticides, herbicides, road salt, bacteria, and other contaminants that end up on the ground can be picked up by rainwater and snowmelt, eventually making their way into bodies of water.

The effects of NPS pollutants on specific waters can vary and may not always be fully assessed. However, it is known that these pollutants can have harmful impacts on drinking water supplies, recreation, fisheries, and wildlife.

Oil spills

The impact of an oil spill depends on various factors, including the type and amount of oil spilled, the affected environment, and the plants, animals, and habitats in the area. Oil spills can occur in oceans, rivers, lakes, and coastal areas, with thousands of spills happening in US waters annually. Large oil spills are major disasters that often result from broken pipelines, sunken oil tanker ships, or drilling operation mishaps. The consequences of these large spills can persist for decades, affecting ecosystems and local economies.

Cleaning up oil spills requires specialised equipment and training. The process involves containing and absorbing the spilled oil, followed by proper disposal of the oil and any materials used in the cleanup process. Protective clothing and gear are crucial to safeguard the health of individuals involved in the cleanup efforts, as exposure to oil and solvents can lead to serious health issues.

To address oil spills and their environmental impacts, it is essential to understand their sources and the types of water bodies affected. Oil spills can originate from point sources, such as leaks or discharges from oil refineries or wastewater treatment facilities, or nonpoint sources, like agricultural runoff or marine debris. By identifying the sources and implementing preventive measures, we can better protect our water resources and mitigate the harmful effects of oil spills on the environment and human health.

Solid waste

The improper disposal of solid waste can have severe environmental and health consequences. When solid waste is dumped near water sources or directly into them, it can contaminate both surface water and groundwater. This is known as "point source pollution" and has deadly impacts on aquatic ecosystems. Municipal solid waste, such as plastic waste, litter, and sludge, can cause physical and chemical impacts on aquatic organisms and ecosystems. For example, plastic waste can strangle, suffocate, and starve animals, while electronic waste can break down and leach harmful chemicals into the water.

In addition to direct dumping, solid waste can also indirectly pollute water bodies through leachate and gaseous emissions from landfills. When solid waste is disposed of in landfills, it undergoes complicated biochemical and physical procedures that produce leachate and gaseous emissions. Leachate can migrate from landfills and reach water resources, leading to surface water and groundwater pollution. Gaseous emissions, such as volatile organic compounds, can also have environmental and health impacts.

Furthermore, solid waste can contribute to water pollution through the overuse or improper use of agricultural and industrial chemicals. Agricultural fertilizers, pesticides, and organic matter can enter water bodies and cause nutrient overload, eutrophication, and redox imbalance. Industrial activities can release heavy metals, organics, and chemicals into water bodies through wastewater discharges, which can have toxic effects on aquatic life and humans.

The pollution caused by solid waste has severe consequences for aquatic ecosystems and human health. It can lead to the accumulation of toxic substances in the food chain, reducing biodiversity and disrupting the balance of ecosystems. It can also result in waterborne diseases and chemical poisoning in humans, with children being particularly susceptible to these pollutants. Therefore, it is crucial to address the improper disposal of solid waste and implement effective solid waste management practices to protect water bodies and safeguard human health.

Microplastics

The presence of microplastics in bodies of water has raised concerns about their impact on the environment and human health. While the World Health Organization (WHO) has stated that there is currently no evidence that microplastics in drinking water pose significant health hazards, more research is needed to fully understand their effects. Microplastics can be consumed by marine wildlife, and through the process of biomagnification, they can become concentrated in humans who consume seafood.

The issue of microplastics in bodies of water is a global concern. They have been found in various water systems, including rivers in India, China, and Korea, where the concentration tends to increase downstream due to urban population growth and anthropogenic activities. The dark-coloured microplastics deposited in snowfields, ice caps, and glaciers in the polar regions contribute to global warming by absorbing sunlight and enhancing local heating.

To address the issue of microplastics in bodies of water, preventive and removal measures are essential. Wastewater and drinking water treatment systems have been effective in removing more than 90% of microplastics from wastewater and are expected to have similar success in treating drinking water. Additionally, reducing plastic waste and improving solid waste management practices can help minimise the discharge of microplastics into water bodies.

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