Nutrient Pollution: Water Quality Impacts And Solutions

Nutrient pollution is a pressing issue in the United States, threatening drinking water sources, human health, and the environment. It occurs when excessive amounts of nutrients, primarily nitrogen and phosphorus, are introduced into water bodies, acting as fertilisers and causing rapid algae growth, known as eutrophication. This process disrupts aquatic ecosystems, leading to reduced oxygen levels and the death of fish and other aquatic organisms. The main sources of nutrient pollution include agricultural practices, wastewater discharge, fossil fuel usage, and stormwater runoff. While it is a challenging problem to address, states are implementing various measures to reduce nutrient pollution and protect water quality.

Nitrogen and phosphorus in water

Nitrogen and phosphorus are essential nutritional elements for life processes in water bodies. They are nutrients that are natural parts of aquatic ecosystems. Nitrogen is also the most abundant element in the air we breathe.

However, when there is an excess of these nutrients in the water, they can cause water pollution. Nitrogen and phosphorus occur naturally, but most of the nutrients in our waterways come from human activities and sources—fertilizers, wastewater, automobile exhaust, animal waste, and fossil fuel burning.

An overabundance of nitrogen and phosphorus in water can lead to eutrophication, a process where they act like fertilizer, causing excessive growth of algae. This is known as an algal bloom and can smell bad, block sunlight, and even release toxins in some cases. When the algae die, they are decomposed by bacteria, which consumes the oxygen dissolved in the water and is needed by fish and other aquatic life to breathe. If enough oxygen is removed, the water can become hypoxic, creating a "dead zone" where there is not enough oxygen to sustain life.

Nitrogen and phosphorus can enter water bodies through runoff from farm fields and pastures, discharges from septic tanks and feedlots, emissions from combustion, and wastewater treatment facilities. They can also come from natural sources such as weathering of rocks and soil in the watershed and ocean currents.

The effects of nitrogen and phosphorus pollution in water can be harmful to both the environment and human health. It can lead to biodiversity loss, food web changes, dissolved oxygen deficits, toxin production, and economic impacts due to increasing water treatment costs and losses in commercial fishing, shellfish harvesting, and tourism.

To address this issue, mitigation approaches such as nutrient remediation, nutrient trading, and nutrient source apportionment can be implemented. Additionally, states are working to support and recognize farmers who are taking steps to address discharge from fertilizer use and reduce nutrient pollution.

Algal blooms

The potential for algal blooms comes from nutrient pollution, specifically an excess of nitrogen and phosphorus, which are essential plant nutrients. These elements enter waterways from a variety of sources, including point sources such as industrial and wastewater treatment plant discharges, and nonpoint sources such as septic tanks and stormwater runoff from urban areas, farms, and residential areas. When the concentrations of nitrogen and phosphorus increase in a body of water, the right combination of temperature, sunlight, and low flow can trigger an algal bloom.

In addition, some algal blooms can produce toxins that are harmful to humans and other organisms. Exposure to these toxins can cause a range of health issues, including skin rashes, liver and kidney damage, neurological issues, and respiratory problems.

Eutrophication

Human activities that contribute to eutrophication include agricultural practices, such as the use of fertilisers, and concentrated animal feeding operations (CAFOs). When excess nutrients from fertilisers are washed by surface runoff into bodies of water, they act as fertilisers, causing excessive growth of algae and other aquatic plants. This process is known as nutrient pollution. CAFOs discharge high concentrations of nutrients, such as phosphorus and nitrogen, into rivers, streams, lakes, and oceans, leading to recurring cyanobacterial blooms and algal blooms.

Another contributor to eutrophication is direct sewage discharge and industrial waste disposal into water bodies. Sewage water, even after treatment, can introduce high amounts of chemical nutrients that stimulate the dense growth of algal blooms and other aquatic plants, threatening the survival of aquatic life. Industrial wastewater discharges also contribute to eutrophication.

Natural events, such as floods and the natural flow of rivers and streams, can also contribute to eutrophication by washing excess nutrients into water systems. As lakes age naturally, they accumulate sediments, phosphorus, and nitrogen nutrients, which contribute to the explosive growth of phytoplankton and cyanobacterial blooms.

The consequences of eutrophication include the destruction of aquatic systems and a reduction in water quality. Dense algal blooms limit light penetration, reducing the growth of plants in littoral zones and impacting predators that rely on light to catch prey. High rates of photosynthesis associated with eutrophication can deplete dissolved inorganic carbon and raise pH levels to extremes. When these dense algal blooms die, microbial decomposition depletes dissolved oxygen, creating a 'dead zone' lacking sufficient oxygen to support most organisms. This process, known as hypoxia, can lead to the death of aquatic animals and the creation of aquatic dead zones.

Sources of nutrient pollution

Nutrient pollution is caused by an excess of nutrients, usually nitrogen and phosphorus, which act as fertilisers and cause the overgrowth of algae. This process is called eutrophication and can lead to severe problems such as low oxygen levels in the water, which can kill fish and other aquatic animals.

Agriculture:

Animal manure and chemical fertilisers are essential for crop growth, but when plants cannot fully utilise these nutrients, they can be lost from farm fields, impacting the quality of air and water. This is especially true for nitrogen and phosphorus, which are the primary nutrients in commercial fertilisers. Animal production and crop farming are both contributors to nutrient pollution.

Stormwater:

Precipitation in urban areas can carry pollutants, including nitrogen and phosphorus, from hard surfaces like roads and rooftops into local waterways.

Wastewater:

Sewer and septic systems may not adequately remove nitrogen and phosphorus before discharging into waterways, contributing to nutrient pollution.

Fossil Fuels:

The use of fossil fuels by electric power generation, industry, transportation, and agriculture has increased nitrogen levels in the air and contributed to nutrient pollution.

Residential:

Fertilisers, yard and pet waste, and certain soaps and detergents can contain nitrogen and phosphorus. If not properly used or disposed of, these can contribute to nutrient pollution, especially during wet weather when runoff is more likely to occur.

Natural Sources:

Nutrients can also come from natural sources, such as the weathering of rocks and soil in watersheds, or the mixing of ocean currents. However, human-related inputs are of greater concern to scientists due to their impact on coastal waters.

Effects of nutrient pollution

Nutrient pollution is a widespread issue that poses a threat to drinking water sources, human health, outdoor recreation, and ecosystem health. It is caused by the introduction of excess nitrogen and phosphorus into the air and water, which are natural parts of aquatic ecosystems. However, when too much of these nutrients enter the environment, it can lead to serious problems. Here are some of the effects of nutrient pollution:

• Excessive Algal Growth: Nitrogen and phosphorus act as fertilizers, causing excessive growth of algae. This process is known as eutrophication. The rapid growth of algae can block light, hindering the growth of other plants like seagrasses. When the algae and seagrass die, they decompose, depleting the oxygen levels in the water and leading to the death of aquatic animals such as fish, crabs, and oysters.
• Water Quality Degradation: The significant increase in algae harms water quality, food resources, and habitats for other organisms. The presence of algal blooms can severely reduce or eliminate oxygen in the water, leading to illnesses and deaths in fish populations.
• Human Health Risks: Some algal blooms produce elevated toxins and bacterial growth that can make people sick. Exposure to harmful algal blooms (HABs) can occur through eating contaminated fish, swimming in affected water, or drinking contaminated water. This exposure can cause skin rashes, liver and kidney damage, neurological issues, and respiratory problems. Additionally, nitrate, a form of nitrogen found in fertilizers, can enter drinking water sources in high concentrations, posing serious health risks, especially to infants.
• Economic Impacts: Nutrient pollution can have economic consequences, including increased water treatment costs, losses in commercial fishing and shellfish industries, reduced tourism income, and recreational fishing losses.
• Environmental Concerns: Excess nitrogen in the atmosphere can produce pollutants such as ammonia and ozone, which can impair respiratory functions, limit visibility, and alter plant growth. When excess nitrogen returns to Earth, it can harm forests, soils, and waterways.

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