Topics Covered:
- Conservation, environmental pollution and degradation, environmental impact assessment.
Nitrogen pollution
What to study?
For Prelims and Mains: Nitrogen- natural cycle, pollution and ways to prevent it.
Context: The annual Frontiers Report 2019 published by the United Nations (UN), has included a chapter on nitrogen pollution in its latest edition. The report was released by the United Nations Environmental Assembly (UNEA) in Nairobi.
Highlights of the Frontiers Report 2019:
- Pollution caused by the reactive forms of nitrogen is now being recognised as a grave environmental concern on a global level.
- It highlights that growing demand on the livestock, agriculture, transport, industry and energy sector has led to a sharp growth of the levels of reactive nitrogen — ammonia, nitrate, nitric oxide (NO), nitrous oxide (N2O) — in our ecosystems.
- The report claims that the total annual cost of nitrogen pollution to eco system and healthcare services in the world is around $340 billion.
- The report also warns that the scale of the problem remains largely unknown and unacknowledged outside scientific circles.
Nitrogen as an essential nutrient:
Nitrogen, which is a vital macronutrient for most plants, is the most abundant element in the atmosphere.
A little over 78% of dry air on Earth is nitrogen. But atmospheric nitrogen, or dinitrogen, is unreactive and cannot be utilised by plants directly.
Until the beginning of the 20th century, farmers depended on a natural process called nitrogen fixation for the conversion of atmospheric nitrogen into reactive nitrogen in the soil: nitrogen-fixing bacteria like rhizobia live symbiotically with leguminous plants, providing nitrogen to the plant and soil in the form of reactive compounds like ammonia and nitrate.
But the natural nitrogen cycle was inadequate to feed the growing population. Scientists Fritz Haber and Carl Bosch solved this problem by producing ammonia by combining atmospheric nitrogen with hydrogen gas at high temperature and pressure—known as the Haber-Bosch process. The Green Revolution, which was instrumental in establishing food security in the developing countries in the 1960s, was driven by artificial nitrogen-fixation. Today, about half of the world’s population depends on this process for its nutrition.
How Nitrogen turned into pollutant from nutrient how it is affecting health and environment?
- Nitrogen is an inert gas that’s necessary for life. But we’re changing it into forms that are harmful, overloading the environment with it, and throwing the natural nitrogen cycle out of whack.
- Nitrogen compounds running off farmland have led to water pollution problems around the world, while nitrogen emissions from industry, agriculture and vehicles make a big contribution to air pollution.
- Over 80% of the nitrogen in soil is not utilised by humans. While over four-fifths of the nitrogen is used to feed livestock, only about six per cent reaches humans in case of non-vegetarian diet, as compared to the 20% that reaches the plate of a vegetarian.
- Nitrogen becomes a pollutant when it escapes into the environment and reacts with other organic compounds. It is either released into the atmosphere, gets dissolved in water sources such as rivers, lakes or groundwater, or remains in the soil. While it might lead to favourable growth of species that can utilise this nutrient, nitrogen as a pollutant is often detrimental to the environment and health.
Effects on health:
According to the World Health Organization, nitrate-contaminated drinking water can cause reduced blood function, cancer and endemic goiters. Surplus inputs of nitrogen compounds have been found to cause soil acidification. The lowering pH, as a result of the acidification, can lead to nutrient disorders and increased toxicity in plants. It may also affect natural soil decomposition.
Nitrogen pollution has a significant impact on the environment:
- It creates of harmful algal blooms and dead zones in our waterways and oceans; the algae produce toxins which are harmful to human and aquatic organisms (and indirectly affects fisheries and biodiversity in coastal areas).
- Contamination of drinking water. 10 million people in Europe are potentially exposed to drinking water with nitrate concentrations above recommended levels. This can have an adverse effect on human health.
- Food Security: Excessive nitrogen fertiliser application contributes to soil nutrient depletion. As the world needs to feed an ever growing population loss of arable land is major global problem.
- The release of Nitrous Oxide is essentially a greenhouse gas which is harmful to the environment.
Sources: the hindu.
