Short notes on estuaries and on the Bhopal gas tragedy

The question asks for any two of the three notes. Notes (i) and (iii) are answered.

(i) Estuaries

Meaning. An estuary is the partly enclosed mouth of a river where its fresh water meets and mixes with the sea. It is an aquatic ecosystem of brackish water, less salty than the sea but saltier than the river, as in river deltas.

Features

• Changing salinity. The salt content rises and falls with the tides and with the river's flow, high in the dry season and low in the monsoon.
• Rich in nutrients. Rivers bring down silt and nutrients that settle in the calm water, so estuaries and the brackish deltas around them are among the world's most productive ecosystems in biomass; their shores are often covered by mangrove forests.
• Specially adapted life. Plants and animals here must tolerate changing salt and water levels: mangroves, crabs, prawns, oysters, mudskippers and many fish.

Importance

• Breeding and nursery grounds for many sea fish and prawns, which supports coastal fisheries.
• Feeding grounds for wading and migratory birds.
• Natural buffers that absorb floods and storm surges, and ports and harbours for trade.

Threats. Sewage and industrial waste from cities on their banks, dams upstream that cut the flow of fresh water and silt, and clearing of mangroves for prawn ponds. India's estuaries include the Hooghly, the Mahanadi and the Godavari.

(iii) Bhopal gas tragedy

The event. In December 1984 a pesticide factory of Union Carbide at Bhopal accidentally released methyl isocyanate, a highly poisonous gas used in making pesticides; the textbook puts the release at about 30 tonnes.

Effects

• Loss of life and health. The textbook records about 3,330 deaths and 1.5 lakh people injured in the surrounding area; survivors suffered damage to the eyes, lungs and other organs.
• Lasting damage. Many survivors still live with chronic illness, and the contaminated site long remained a hazard to the soil and groundwater around it.
• Social cost. The worst affected were poor families living in crowded settlements next to the plant.

Causes and lessons

• Industry sited close to homes, with poor regulatory control, endangers urban health.
• Stronger law. The Air Act of 1981 was found too weak to prevent or correct such hazards; after Bhopal the more comprehensive Environment (Protection) Act of 1986 was passed, giving enforcement agencies punitive powers for the first time.
• Hazardous plants need safety systems, emergency plans and a buffer zone between the factory and homes.