Acid Rain Alert: IMD-IITM Study Reveals India's Downpour Chemistry Changing

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A 34-year-long India Meteorological Department (IMD) and Indian Institute of Tropical Meteorology (IITM) study has found a worrying trend towards rising acidity in the rainfall of India. The study from 1987 to 2021 documents a remarkable decline in the pH levels of rainwater at various sites, especially in industrial and urban areas. The process, fueled by heightened pollution rates, threatens to bring risks to ecosystems, infrastructure, and human health if the trend persists.

Study Overview:

Spanning 34 years (1987–2021) and carried out by IMD and IITM.
Observed rainwater chemistry at 10 Global Atmosphere Watch (GAW) stations in India, covering cities such as Visakhapatnam, Prayagraj, Mohanbari, Pune, and Srinagar.

Results on Acidity:

Substantial reduction in rainwater pH levels at the majority of sites.
Rainwater with a pH value less than 5.65 is considered acidic; some sites had pH as low as 4.77–5.32 in previous studies.
Cities such as Prayagraj demonstrated steep decreases in pH (-0.74 units/decade in wet months).

Sources of Pollution:

Major contributors towards acidity are emissions from cars, industries, thermal power plants, agriculture residue burning, and domestic sources.
In Visakhapatnam, oil refinery, power plant, fertilizer plant, and shipping terminal emissions were reported to be major drivers.

Regional Patterns:

Urban and industrial zones such as Visakhapatnam and Pune demonstrated increased trends of acidity.
Natural dust particles in areas such as Jodhpur and Srinagar assisted in the neutralization of acid components.

Effect on Neutralizing Agents:

Decrease in calcium particles (which counteracts acidity) seen in areas such as Prayagraj and Nagpur.
Rise in ammonium particles recorded but considered to be insufficient to reverse escalating acidity.

Likely Hazards:

Acid rain may result in deterioration of historical monuments (such as marble structures), corrosion of infrastructures, and leaching of poisonous heavy metals into water bodies.
Long-term effects may include health hazards from heavy metals entering the food chain.

Current Status and Warnings:

While current pH levels are not critically low, scientists warn that continued acidification could have severe future implications.
Monitoring and mitigation efforts are essential to address this growing concern.

Sources: Economic Times, Times of India