Nitrogen Water Pollution: Understanding Its Human-Made Sources

Nitrogen is a nutrient that is essential for the growth of plants and animals. However, an excess of nitrogen in water can lead to nitrogen pollution, which has serious environmental, economic, and health consequences. Nitrogen pollution in water can come from a variety of sources, both natural and human-related. Natural sources include the weathering of rocks and soil, while human-related sources include agricultural runoff, sewage, and the burning of fossil fuels. Human activities, such as the use of fertilizers and the modification of landscapes for agriculture, have led to an increase in nitrogen levels in water, causing adverse effects on aquatic ecosystems and human health.

Agriculture and fertilizers

Agriculture is a major contributor to nitrogen water pollution. This is largely due to the use of fertilizers, which provide crops with the nitrogen they need to grow. However, when nitrogen is not fully utilized by plants, it can be washed from fields into waterways during rain and snowmelt or leach into groundwater over time. This excess nitrogen in water can cause a range of adverse health and ecological effects.

Fertilizers are applied to crop fields worldwide to increase crop yields and meet the growing global demand for food. While nitrogen is a key component in fertilizer, helping plants grow, it is also highly water-soluble. When too much fertilizer is applied and not fully absorbed by crops, irrigation and rainwater wash the excess nitrogen into groundwater and waterways. This process is known as agricultural runoff.

Agricultural runoff is a significant contributor to nitrogen water pollution. In the United States, two-thirds of nitrogen pollution is caused by agricultural runoff, according to one source. Another source states that 80% of fertilizer used for agriculture worldwide is lost to the environment. This excess fertilizer ends up in water sources, challenging water quality and requiring nitrate removal solutions to make water safe for drinking.

The overabundance of nitrogen in water can lead to a range of problems. Excess nitrogen can cause overstimulation of the growth of aquatic plants and algae, leading to harmful algal blooms (HABs). These blooms can be toxic to fish, wildlife, and people. HABs can also result in eutrophication, which can lead to hypoxia or "dead zones" in water, causing fish kills and a decrease in aquatic life. Additionally, high levels of nitrogen in drinking water sources have been linked to health concerns, including an increased risk of cancer.

To reduce nitrogen water pollution from agriculture and fertilizers, proper nutrient management practices are essential. Farmers can play a crucial role in reducing nutrient loss by adopting techniques such as applying the right amount of fertilizer at the appropriate time of year and using the correct method and placement. Additionally, keeping livestock and their waste away from streams and rivers can help prevent excess nitrogen from entering water sources.

Sewage and septic systems

In the United States, about 20% of homes, or approximately 30% in the case of Michigan, use septic systems to treat their wastewater. Septic systems are recognized as one of the top 5 sources of pollutants in surface water bodies. When a septic system is improperly managed, it can release elevated levels of nitrogen and phosphorus into local water bodies or groundwater.

An estimated 10 to 20% of septic systems fail at some point in their operational lifetimes due to aging infrastructure, inappropriate design, overloading with too much wastewater in too little time, and poor maintenance. Homeowners are responsible for maintaining their septic systems in most cases. To protect and maintain their systems, they should have their systems inspected regularly and pump their tanks as necessary.

In certain parts of the country, wastewater treatment plants are a large source of nitrogen pollution. For example, the Fairhaven treatment plant has historically discharged into inner New Bedford Harbor, where nitrogen pollution gets trapped inside the hurricane barrier. At the Marion Wastewater Treatment Plant, 20 acres of unlined sewage lagoons leaked nitrogen directly into the ground for nearly 50 years.

In Florida, groundwater is vulnerable to nitrogen pollution in many areas because of limited confining layers, shallow water tables, and numerous sinkholes and caves that can rapidly transport nitrogen and other contaminants to groundwater. Nearly 40% of Florida's septic systems are located in coastal areas, where the wet season water table is likely to be shallow, and porous sandy soils allow rapid transport of contaminants to groundwater.

In Long Island, nitrogen pollution from outdated septic systems has resulted in algae blooms and rust tides. Even when working properly, traditional Long Island cesspools and septic systems are not designed to keep reactive nitrogen from entering groundwater aquifers.

Fossil fuels

Nitrogen water pollution is a direct result of human activities, including fossil fuel use. When fossil fuels are burned, they release nitrogen oxides into the atmosphere, which contribute to the formation of smog and acid rain. The combustion of fossil fuels by power plants, large industries, and automobiles is a major source of nutrients in the atmosphere.

The nitrogen oxides released from burning fossil fuels can be deposited back onto land and wash into nearby water bodies. This excess nitrogen contributes to water pollution, harmful algal blooms, and oxygen-deprived aquatic zones. This process is known as eutrophication.

The combustion of fossil fuels releases nitrogen oxides and ammonia, which are deposited into water bodies through precipitation or dry deposition. This atmospheric deposition of nitrogen is greatest in areas with high precipitation, such as the Northeast region of the United States. The excess nitrogen from fossil fuel combustion can have adverse health and ecological effects, impacting the quality of water and the survival of aquatic organisms.

To reduce nitrogen water pollution from fossil fuels, businesses can take steps to manage and reduce emissions, increase energy efficiency, and promote the use of alternative energy sources. Conserving energy and minimizing vehicle miles traveled can also help reduce nitrogen oxide emissions from fossil fuel combustion.

Atmospheric deposition

Natural sources of atmospheric nitrogen deposition include chemical reactions and the weathering of rocks and soil. For example, nitrogen can be derived from the oxidation of other nitrogen compounds such as nitrite, ammonia, and organic nitrogen compounds.

However, human activities have significantly increased the amount of nitrogen in the atmosphere, particularly through the combustion of fossil fuels, such as coal and gasoline, used for electric power generation, industry, transportation, and agriculture. The burning of fossil fuels has led to increased levels of nitrogen compounds in the air, which contribute to air pollution and subsequently, water pollution when deposited back on Earth.

Additionally, human activities such as agriculture also play a role in atmospheric nitrogen deposition. The use of chemical fertilizers and animal manure in farming can result in nitrogen runoff during heavy rains, leading to nitrogen-containing compounds being deposited into nearby water bodies. Inefficient wastewater treatment facilities that do not effectively remove nitrogen can further contribute to elevated nitrogen levels in surface and groundwater.

Stormwater runoff

The impact of stormwater runoff on nitrogen pollution is significant. As the water flows over impervious surfaces, it can pick up excess nitrogen from the atmosphere that has accumulated on these surfaces. This excess nitrogen, in the form of compounds like ammonia and ozone, can then be washed into local water bodies, leading to nitrogen pollution.

In addition to atmospheric nitrogen, stormwater runoff can also pick up nitrogen from other sources. For example, outdated septic systems can contribute to nitrogen pollution, as the excess nitrogen washes into nearby water bodies. This excess nitrogen fuels the growth of invasive plants and toxic algae, which can have devastating effects on aquatic ecosystems, including fish and wildlife populations.

The consequences of nitrogen pollution from stormwater runoff are far-reaching. It can impair water quality, harm aquatic life, and even pose risks to human health. High levels of nitrogen in drinking water sources can be harmful to infants, and the growth of toxic algae can make recreational areas unsafe.

To mitigate the impact of stormwater runoff on nitrogen pollution, communities and local governments can employ various management practices. Public education and outreach are crucial to help homeowners and businesses understand the proper use and storage of household toxic materials and responsible lawn care practices. Additionally, erosion and sediment control measures can help prevent pollutants from washing off construction sites. Implementing incentives or controls on land use can also help limit impervious surfaces, encourage open spaces, and promote the use of natural landscape features to slow down and filter contaminants from stormwater.

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