1. Introduction
Nitrogen pollution, a problem that has reached alarming proportions worldwide, is the direct result of human actions that trigger the excessive release of nitrogen compounds, such as ammonia and nitrogen oxides, into our environment. This introduction seeks to delve deeper into the seriousness of this situation that transcends geographical borders and affects the health of our planet in a comprehensive manner. The United Nations Environment Programme (UNEP) 2018-2019 Borders Report classified nitrogen pollution as one of the most important pollution problems facing humanity.
"Nitrogen is a primary nutrient essential for the survival of all living organisms on Earth."
We live in an era where the demands of the world's population have led to unsustainable practices in agriculture, industry and energy. The constant increase in the use of nitrogen fertilizers to boost agricultural production, uncontrolled emissions from industry and the massive burning of fossil fuels all contribute to the excessive emission of nitrogen into the atmosphere and land. This phenomenon, seemingly invisible but with devastating consequences, has become a global problem that demands immediate attention.
The sources of nitrogen pollution are as diverse as the impacts they generate. A thorough understanding of this phenomenon is essential to address its consequences, which range from the degradation of water and soil quality to critical alterations in terrestrial and aquatic ecosystems.
It is important to emphasize that, while nitrogen is essential for the growth of plants and animals, its excess triggers a series of events that are detrimental to life on Earth. The accelerated expansion of intensive agriculture, the lack of effective industrial regulation and the continued dependence on fossil fuels are exacerbating this problem at an unprecedented rate. The harmful effects of nitrogen pollution know no borders, affecting both industrialized and developing nations. From the loss of biodiversity to the direct threat to food security and human health, the ravages of this pollution are multiple and complex.
2. Sources of pollution
Every year, 200 million tons of reactive nitrogen (80 percent of the total) are lost to the environment.
2.1 Agricultural Practices
Agricultural practices, while essential to meet growing food demand, have become one of the main sources of nitrogen pollution. The excessive and inappropriate use of nitrogen fertilizers, rich in compounds such as nitrate and ammonium, contribute significantly to the uncontrolled release of nitrogen into soil and water.
The intensification of modern agriculture has led to the massive adoption of fertilizers to increase crop productivity. However, this practice, while beneficial to agricultural production, has serious environmental consequences. The leaching of nitrates into groundwater contaminates water resources, affecting the quality of drinking water and generating ecological problems in aquatic ecosystems.
Excessive application of nitrogen-rich animal manure also contributes to soil and air pollution. Ammonia emissions during manure decomposition not only affect air quality, but can also be deposited in the soil, contributing to the overall problem of nitrogen pollution.
When nitrogen in its active form, such as in fertilizers, is exposed to soil, microbial reactions occur that release nitrous oxide. This gas is 300 times more potent at warming the atmosphere than carbon dioxide. It also remains active in the atmosphere for more than 100 years.
2.2 Industrial Emissions
Industrial emissions represent another major source of nitrogen pollution. Various industries, such as chemical and manufacturing, release nitrogen oxides (NOx) into the atmosphere as a byproduct of certain processes. These NOx contribute to the formation of fine particulate matter and ground-level ozone, affecting air quality and having direct consequences for human health.
The lack of clean industrial technologies and practices has led to the excessive release of NOx, which, in addition to contributing to air pollution, can be deposited in soil and water during rainfall. This nitrogen deposit can alter terrestrial and aquatic ecosystems, affecting biodiversity and generating adverse effects on soil quality.
2.3 Combustion of Fossil Fuels
The combustion of fossil fuels, such as coal, oil and natural gas, is a significant source of nitrogen pollution. During this process, nitrogen oxides are released into the atmosphere, contributing to the formation of smog and affecting air quality.
These emissions, in addition to being harmful to human health, have global implications. Nitrogen oxides contribute to global warming and climate change by influencing solar radiation and the formation of atmospheric aerosols.
Modern society's continued reliance on fossil fuel-derived energy makes this source of nitrogen pollution persistent. Addressing this crucial issue involves transitions to cleaner and more sustainable energy sources, thereby reducing the nitrogen load on our environment.
3. Water and its quality
3.1 Impact on Aquatic Ecosystems
Nitrogen pollution has a devastating impact on aquatic ecosystems, triggering a series of events that alter the natural balance of these vital habitats. Excess nitrogen, mainly from agriculture and industrial emissions, seeps into rivers, lakes and oceans, triggering negative consequences.
Algal blooms are one of the most obvious effects of nitrogen pollution in aquatic environments. These massive algal blooms are fueled by excess nutrients, especially nitrogen, and can create “dead zones” by depleting oxygen in the water. As a result, aquatic organisms, such as fish and other marine life, suffer from a lack of oxygen, leading to biodiversity loss and ecosystem destabilization.
The excessive introduction of nitrogen also affects the chemical composition of the water, altering its pH and contributing to acidification. This has direct consequences for sensitive aquatic organisms, such as molluscs and certain types of fish, which may experience changes in their behaviour, development and reproduction.
3.2 Drinking Water Pollution
Nitrogen pollution represents a direct threat to drinking water quality, affecting supply sources that rely on groundwater and surface water. Nitrate leaching from agricultural fields and surface runoff carry these compounds into water bodies used for human consumption.
High levels of nitrates in drinking water can have serious consequences for human health, especially for vulnerable groups such as pregnant women and infants. Ingestion of nitrates can lead to the formation of nitrosamines, potentially carcinogenic compounds. Furthermore, the presence of nitrates in drinking water has been associated with health problems such as methemoglobinemia or "blue baby syndrome", a condition that affects the blood's ability to carry oxygen.
Nitrogen pollution of drinking water underscores the urgent need to adopt effective measures to reduce nitrate emissions and runoff. Implementing sustainable agricultural practices and efficient water management systems becomes essential to preserve the integrity of our drinking water sources and safeguard the health of the communities that depend on them.
4. Effects on air quality
4.1 Nitrogen Oxides and Atmospheric Impact
Nitrogen pollution has a significant impact on air quality, with nitrogen oxides (NOx) being the main cause of these atmospheric consequences. These compounds, generated mainly by the combustion of fossil fuels and industrial emissions, trigger a series of events that affect both the composition of the air and the global climate.
The presence of NOx in the atmosphere contributes to the formation of tropospheric ozone and fine particles, elements that constitute air pollution. Tropospheric ozone, at ground level, not only negatively affects human health and the health of ecosystems, but also contributes to global warming by being a potent greenhouse gas.
The formation of fine particles, also influenced by nitrogen oxides, has direct consequences for air quality. These particles can penetrate deep into the lungs, affecting respiratory health and exacerbating pre-existing medical conditions. In addition, fine particles contribute to the formation of haze and reduce visibility, affecting road safety and quality of life in urban environments.
4.2 Health Consequences of Poor Air Quality
Poor air quality, a direct result of nitrogen pollution, has adverse consequences for human health. Continuous exposure to high levels of nitrogen oxides and fine particulate matter is associated with a variety of health problems, affecting both the respiratory and cardiovascular systems.
In respiratory terms, inhaling polluted air can cause or worsen diseases such as asthma and chronic bronchitis. Fine particles can penetrate the lungs and trigger inflammation, making breathing difficult and reducing lung function. In addition, chronic exposure to nitrogen pollution has been linked to an increased risk of long-term respiratory diseases.
At the cardiovascular level, poor air quality contributes to the development and worsening of heart disease. Inhalation of nitrogen oxides can trigger inflammatory responses that affect blood vessels and the heart. Long-term exposure to nitrogen pollution has been shown to be associated with an increased risk of heart disease, stroke, and other cardiovascular problems.
Addressing nitrogen pollution and improving air quality is essential to protecting public health. Implementing effective environmental policies and transitioning to cleaner energy sources are crucial steps to mitigate these negative impacts and ensure healthier air for present and future generations.
5. Nitrogen pollution and soil health
5.1 The Supposed Ecological Advantage of Synthetic Nitrogen: Basis and Challenges
The common hypothesis holds that by applying synthetic nitrogen to crop fields, plant growth is stimulated, which in turn boosts the absorption of atmospheric carbon dioxide. The harvested plant part is removed, but the residue, in the form of plant remains, remains in the soil and eventually becomes organic matter. This process, according to accepted theory, would contribute to the accumulation of carbon in the soil and would therefore be seen as a significant environmental benefit.
5.2 The Alarming Counterpart: Loss of Organic Matter and Harmful Effects
However, recent studies by this research team question this optimistic outlook. They argue that, contrary to common belief, the use of synthetic nitrogen has a net negative effect on soil organic matter. The reason behind this lies in the fact that nitrogen fertilizer stimulates soil microorganisms, which, by feeding on organic matter, counteract the benefits of additional crop residues.
The scenario becomes even more alarming when it is suggested that the use of synthetic nitrogen creates a “treadmill” effect. As organic matter decreases, the soil’s capacity to retain organic nitrogen is also reduced. As a result, large amounts of nitrogen leach into groundwater as nitrates, contaminating the water supply, and are released into the atmosphere as nitrous oxide (N2O), a potent greenhouse gas.
5.3 Consequences for Long-Term Productivity and Soil Sustainability
The loss of organic matter not only affects the soil's ability to store carbon, but also has adverse consequences. Soil compaction, vulnerability to runoff and erosion, limitation of stabilizing root growth, and decreased water retention are some of the detrimental effects identified by researchers.
If the Illinois team’s claim is accurate, the supposed ecological advantage of nitrogen fertilizers would turn out to be their biggest disadvantage. Instead of contributing to climate change mitigation, these fertilizers could be exacerbating the problem and undermining the long-term productivity of soil. The idea, while challenging, is not entirely new, having been found in academic literature from the 1920s and 1930s, and in seminal 20th-century works on soil health.
The research of this team of renowned scientists raises the need to review current agricultural practices and consider more sustainable approaches that preserve soil health and mitigate environmental impacts.
5.4 Degradation of agricultural soil
Nitrogen pollution poses significant challenges to the health and quality of agricultural soils, which are critical to sustaining global food production. Primary sources of this pollution include the intensive use of nitrogen fertilizers and the indiscriminate application of animal manure.
Excess nitrogen in the soil causes changes in the chemical and biological composition of the soil. The leaching of nitrates into deeper soil layers contaminates groundwater, affecting not only water quality, as mentioned above, but also soil structure. This process can result in the loss of essential plant nutrients and, consequently, in a decrease in soil fertility.
Degradation of agricultural soil due to nitrogen pollution not only reduces its capacity to efficiently support crops, but also contributes to the loss of fertile soil. Soil compaction and erosion are additional consequences that negatively impact long-term productivity.
5.1 Impact on Plant Growth
Although plants require nitrogen for growth and development, an excess of this element can be harmful. Nitrogen pollution directly affects the nutrient balance in the soil, which can result in uneven availability of essential elements for plants.
Excessive growth of certain types of plants, known as eutrophication, is a common consequence of nitrogen pollution. This phenomenon, fueled by an abundance of nitrogenous nutrients, can lead to the proliferation of undesirable plant species and compete with agricultural crops, affecting the production and diversity of desirable plants.
Furthermore, nitrogen pollution can have a negative impact on the mutualistic symbiosis between plants and soil microorganisms. Disruption of this relationship can affect the ability of plants to obtain essential nutrients, such as phosphorus, through natural processes.
Addressing nitrogen pollution and its effects on soil health requires the implementation of sustainable agricultural practices, careful management of fertilizers, and a deeper understanding of nutrient cycles in agricultural ecosystems. Preserving soil health is essential to ensuring food security and the long-term sustainability of agriculture.
6. Global Impact of Nitrogen Pollution
Nitrogen pollution, originating mainly from human activities, transcends local and national borders to become a global phenomenon. The ramifications that this form of pollution has in the global context, highlighting two crucial aspects: its interconnection with climate change and its impact on biodiversity loss.
6.1 Connection with Climate Change: Beyond Common Emissions
The relationship between nitrogen pollution and climate change is complex and interdependent. Although air pollution by nitrogen oxides has traditionally been linked to greenhouse gas emissions, understanding this connection goes beyond common emissions.
The massive use of nitrogen fertilizers and industrial emissions contribute to the increase of nitrogen oxides in the atmosphere. This presence not only affects air quality and human health, but also amplifies climate problems. Nitrogen oxides not only act as precursors of tropospheric ozone, a key component of air pollution, but also trigger the emission of nitrous oxide (N2O), a potent greenhouse gas that contributes significantly to global warming.
This complex link between nitrogen pollution and climate change poses significant challenges to effectively addressing both problems.
6.2 Biodiversity Loss: An Inestimable Global Cost
Biodiversity, essential for the balance of ecosystems, is threatened by nitrogen pollution on a global scale. Excess nitrogen in soils and water bodies alters natural patterns, affecting a wide variety of species and their habitats.
The direct consequences of nitrogen pollution on biodiversity loss are evident in phenomena such as toxic algal blooms, which deplete oxygen in the water and threaten aquatic life. In addition, the modification of the chemical composition of the soil affects plants and animals that depend on specific conditions to thrive.
Nitrogen pollution becomes a stressor for global biodiversity, examining specific cases and assessing the urgent need for conservation and restoration strategies.
There is a need to provide a holistic view of the global impact of nitrogen pollution, understanding that its influence goes beyond geographical borders and addressing fundamental issues for the health of the planet and future generations.
Last year, at the resumed fifth session of the United Nations Environment Assembly, governments adopted a resolution on sustainable nitrogen management. While the first UNEA resolution on Sustainable Nitrogen Management, adopted at UNEA4 in March 2019, laid the groundwork for urgent work on nitrogen, this second resolution is important because it includes both an ambition to “significantly reduce nitrogen waste globally” and a timeline “for 2030 and beyond.”
Full article, website: (24) Nitrogen…the forgotten pollution problem? | LinkedIn
References
- UN Environment Programme, https://www.unep.org/news-and-stories/story/four-reasons-why-world-needs-limit-nitrogen-pollution
- UN Environment Programmme, What is nitrogen pollution? https://www.unep.org/interactives/beat-nitrogen-pollution/
- UN Environment Program Frontiers 2018/19 Emerging Issues of Environmental Concern, The nitrogen fix: from nitrogen cycle pollution to nitrogen circular economy: https://wedocs.unep.org/bitstream/handle/20.500.11822/27543/Frontiers1819_ch4.pdf? sequence=11
- UNEA resolution 4/14 and 5/2: Sustainable Nitrogen Management
- US EPA Nutrient Pullution https://www.epa.gov/nutrientpollution/problem
- UNEP Beat Nitrogen Pillution https://www.unep.org/beatpollution/nitrogen