How Nitrate Fertilizers Pollute The Air

Nitrogen is an essential element for the growth of agricultural crops, but its overuse through synthetic fertilizers causes damage to both health and the environment. Nitrate pollution of ground and surface water bodies worldwide is generally linked to the increasing use of fertilizer nitrogen. Excess nitrogen in the atmosphere can produce pollutants such as ammonia and ozone, which impair our ability to breathe, limit visibility, and alter plant growth. This excess nitrogen can also contribute to the formation of climate-changing greenhouse gases and the thinning of the protective ozone layer in the Earth's atmosphere.

Excess nitrogen in the atmosphere

Nitrogen is one of the most important nutrients in the environment, and it exists in many different forms. It is a major component of the atmosphere, making up 78-79% of it in the form of N2 gas. However, this form of nitrogen is unreactive, and therefore insufficient to sustain human life. To address this, humans have developed technologies to convert N2 to reactive nitrogen compounds, enriching the soil that crops grow on.

The biggest human source of reactive nitrogen is nitrogen fertilizer. The Haber-Bosch process, which converts atmospheric nitrogen to ammonia, has allowed humans to produce nitrogen-based fertilizers on an industrial scale. While nitrogen is vital as an energy supply to grow food for the growing human population, its uneven distribution causes food shortages in some parts of the world, while other places have too much nitrogen.

To address the issue of excess nitrogen, it is important to reuse nitrogen and convert it back into unreactive nitrogen (N2) as soon as possible. Individuals can also reduce their nitrogen footprint by decreasing fertilizer use, consuming less animal meat, properly maintaining septic tanks, and minimizing food waste.

Nitrogen-based fertilisers and infant health

Nitrogen-based fertilisers are a major source of nitrate leaching pollution, which affects both surface and groundwater bodies worldwide. This pollution is linked to the increasing global use of fertiliser nitrogen, with consumption in developing countries now surpassing that of industrialised nations. The issue is particularly acute in East and South Asia.

Nitrogen-based fertilisers have been widely used in US agriculture since WWII, providing an inexpensive source of nitrogen and other plant nutrients, leading to significant increases in agricultural productivity. However, it is estimated that only about 50% of the nitrogen fertiliser applied to crops is directly utilised, with the rest being lost to the environment through gas emissions or water pollution. This pollution has severe consequences for human health, especially for infants.

Infants are vulnerable to a nitrogen-based compound called nitrates found in drinking water. High levels of nitrate in drinking water can cause methemoglobinemia, also known as "blue baby syndrome," which infants are especially susceptible to. This condition inhibits the oxygen-carrying capacity of the blood by converting nitrate to nitrite, which binds to haemoglobin. In addition to methemoglobinemia, ingesting nitrate-contaminated water has been associated with various cancers, adverse reproductive outcomes, diabetes, and thyroid conditions.

Furthermore, excess nitrogen in the atmosphere, which can be attributed to nitrogen-based fertilisers, can produce air pollutants such as ammonia and ozone. These pollutants can impair respiratory functions, limit visibility, and alter plant growth.

To address these issues, restrictions on fertiliser nitrogen use and improved soil and water management practices have been proposed. Additionally, public water utilities are mandated to maintain nitrate levels below the Maximum Contaminant Level (MCL) of 10 mg/L nitrate-nitrogen to protect human health, especially that of infants.

Water pollution from nitrate-based fertilisers

Nitrate pollution of groundwater and surface water bodies is a pervasive global problem that is generally linked to the increasing use of nitrogen (N) in fertilisers. Nitrates are compounds that form naturally when nitrogen combines with oxygen, and they exist naturally in soil and water. Plants absorb nitrates from the soil to make amino acids, and farmers use fertilisers to increase the level of nitrates in the soil to help crops grow. However, agricultural practices that overuse chemical fertilisers and manure cause an excess of nitrates in the soil.

Research has shown that more than 50% of the nitrogen in fertiliser is not used by the crops to which it is applied. While a small portion may directly leach down and reach groundwater and surface water bodies, a large proportion ends up in the soil organic nitrogen pool. From here, nitrogen is mineralised and is taken up by plants and/or lost via leaching over several decades. This leaching of nitrogen from soil layers in farmlands, grasslands, and natural lands contributes to N loading in rivers, which is proportional to the size of the watershed and the level of nitrate-N pollution in the catchment area.

The use of nitrate-based fertilisers in agriculture has led to water pollution and health issues. For example, the Yangtze or Chang Jiang, one of the world's three largest rivers, has become one of the most polluted rivers due to industrial waste and the application of large amounts of fertilisers in farming in its catchment area. Similarly, in Denmark, a national nitrate management plan has been in place since the 1990s to address the issue of nitrate pollution, and the country has seen a 40% reduction in surplus nitrogen between 1985 and 2010.

To reduce water pollution from nitrate-based fertilisers, various measures have been proposed, including restrictions on fertiliser N use, amount of fertiliser, time of application, source modification, and proper coordination with soil and water management. Additionally, technology can help by using sensors or lasers to measure nitrogen loss from agricultural land, allowing for more targeted fertiliser application. Implementing proactive policies and governance arrangements at the national and international levels is crucial to address this global issue effectively.

Mitigating the environmental impact of fertilisers

Fertilisers are essential for modern agriculture, providing crops with the nutrients needed to grow efficiently and produce higher yields. However, their environmental impact is becoming increasingly difficult to ignore. The overuse and mismanagement of fertilisers have led to water pollution, soil degradation, and air pollution.

To mitigate these impacts, a range of diversification and innovation in fertiliser use can be implemented. Firstly, the use of renewable resources for artificial fertiliser production can reduce the environmental footprint of fertiliser manufacturing. For example, green ammonia is emerging as a cleaner alternative to traditional ammonia, a key component of nitrogen fertilisers.

Secondly, improving soil health can help mitigate the environmental impact of fertilisers. This can be achieved through the use of organic and mineral fertilisers, which provide nutrients to plants and improve agricultural crops in a more balanced way for the soil. Organic farming methods also encourage crops free of fertiliser residues, such as nitrates, and promote sustainable agricultural practices such as crop rotation.

Thirdly, precision application technologies and nutrient planning can improve the efficiency of fertiliser usage. Precision agriculture, enabled by technologies like soil sensors, GPS mapping, and data analytics, allows farmers to apply fertilisers exactly where and in the quantities needed. This minimises waste, reduces runoff, and lowers costs, all while maintaining yields.

Finally, addressing the over-reliance on synthetic fertilisers can help mitigate their environmental impact. Excess nitrogen in the atmosphere from synthetic fertilisers can produce pollutants such as ammonia and ozone, impairing our ability to breathe, limiting visibility, and altering plant growth. By reducing the use of synthetic fertilisers and encouraging the use of less polluting alternatives, such as organic and bio-fertilisers, the environmental impact of fertilisers can be significantly reduced.

The economic impact of air pollution

Nitrogen-based fertilisers contribute to nitrate pollution in water bodies worldwide. This type of pollution is linked to increasing global consumption of fertiliser nitrogen (N), particularly in developing countries in East and South Asia. While nitrate pollution primarily affects water, excess nitrogen in the atmosphere can produce pollutants such as ammonia and ozone, which have adverse effects on human health and the environment.

Excess nitrogen in the air can impair our ability to breathe, limit visibility, and alter plant growth. It is also associated with significant economic costs. For example, the burning of fossil fuels, which releases excess nitrogen into the atmosphere, costs each average American around $2,500 in additional medical bills. When coupled with higher temperatures, fossil fuel emissions can cause increased ozone pollution, leading to even higher health costs.

Air pollution, including that caused by excess nitrogen, has a significant economic impact. It hampers workforce productivity, with 1.2 billion workdays lost globally each year, resulting in a substantial economic burden. The health impacts of air pollution also contribute to economic costs, with the World Bank estimating that the health damage caused by air pollution costs $6 trillion annually, equivalent to a 5% reduction in global GDP.

The economic effects of air pollution extend beyond healthcare expenditures. Environmental damage, lost ecosystem services, and decreased tourism also contribute to the economic burden. Furthermore, certain economic sectors bear higher costs related to air pollution. For example, agriculture, utilities, manufacturing, and transportation contribute to a significant portion of air pollution-related damages while comprising a smaller percentage of GDP.

However, addressing air pollution can have economic benefits. Clean air initiatives have boosted the EU economy by €50-60 billion annually since 2014. Additionally, studies show that the economic benefits of air pollution mitigation can outweigh the costs, providing a strong case for investing in cleaner technology and green industry development.

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