Context: The latest report of the Central Ground Water Board finds the presence of excessive nitrates (defined as more than 45 mg per litre) in groundwater in 440 districts as of 2023, an increase from 359 such districts in 2017. Other major chemical contaminants affecting groundwater quality are Fluoride and Uranium.
Relevance of the Topic: Prelims: Nitrate Contamination; Methemoglobinemia; Eutrophication.
Major Highlights:
- About 56% of India’s districts face the problem largely due to subsidised synthetic nitrogenous fertiliser, a key input for farming. This is a health hazard, particularly for young children, and a source of environmental toxicity.
- Rajasthan, Karnataka, and Tamil Nadu reported the highest nitrate contamination problem, with 49%, 48%, and 37%, respectively, of their tested samples reporting numbers beyond the safe limit.
What is Nitrate Contamination?
- Nitrate (NO3) is a compound of Nitrogen and Oxygen naturally found in air, soil, water, and some foods.
- Utility of Nitrates:
- Plants require nitrates for their survival and growth. It occurs naturally in soil and dissipates when the soil is extensively farmed. Thus, nitrogen fertilizers are applied to replenish the soil.
- In Agriculture, nitrate is used as fertiliser for crops and lawns.
- In Industry, nitrates are used in food preservation, certain pharmaceutical medications, as well as the manufacture of munitions and explosives.
- Sources of Nitrates:
- Natural sources: Igneous rocks, atmospheric deposition and symbioses of some plants, along with cyanobacteria and some heterotrophs.
- Anthropogenic sources: Nitrogen-rich fertilisers used for agricultural purposes, discharge of poorly treated domestic, and industrial wastewaters, livestock manure, and leachate from landfill sites.
- Nitrate Pollution:
- Nitrogen (N) in the form of nitrate is a common pollutant in both surface and ground water. Nitrates are highly soluble in water and have no taste or smell.
- It can be highly toxic as they can enter the food chain via groundwater and surface water.
- High Nitrate levels can harm the respiratory and reproductive system, kidney, spleen and thyroid in children and adults. It is particularly harmful to infants, causing Methemoglobinemia (or blue-baby syndrome).
- Together with phosphorus, Nitrates in excess amounts can accelerate Eutrophication, causing dramatic increases in aquatic plant growth.
What is Methemoglobinemia?
- Methemoglobinemia is a blood disorder which occurs due to an abnormal amount of methemoglobin in the blood.
- Hemoglobin is the protein in red blood cells (RBCs) that carries and distributes oxygen to the body.
- Methemoglobin is a form of hemoglobin that cannot carry oxygen (due to its lower tendency to bind with Oxygen).
- Due to higher Methemoglobin concentration in blood, the Red Blood Cells’ Oxygen carrying capacity becomes low. Thus, body tissues do not receive enough Oxygen, which gives it a bluish appearance (blue-baby syndrome).
What is Eutrophication?
- Eutrophication is a natural or human-induced process in which bodies of water become overly enriched with nutrients, particularly Nitrogen and Phosphorus.
- This nutrient enrichment leads to excessive growth of algae and aquatic plants, known as an algal bloom.
- As the algae die and decompose, the oxygen in the water is depleted (due to High Biological Oxygen Demand), causing hypoxia or even anoxic conditions. This can harm fish and other aquatic organisms, leading to ecosystem imbalances.
