Why hill and southern states have cleaner air, and why Delhi faces a pollution crisis
New Delhi. Air in the country’s hill states and in several cities of South India has remained relatively clean, while pollution levels in Delhi-NCR continue to raise concern. Every year, from October through winter, the capital’s air begins turning toxic. The reason is not only vehicle emissions or stubble burning, but also Delhi’s geographical location, weather conditions and pollution coming from surrounding areas.
Delhi’s geographical position is a major factor. Delhi is located in the vast Indo-Gangetic plain of north India. It is surrounded by densely populated cities and industrial areas. Because of the Himalayas to the north and the geographical structure of the surrounding plains, the spread of polluted air becomes limited in winter. In contrast, in many South Indian cities located close to the sea, sea winds help disperse pollutants. In hill regions, relatively lower industrial activity and better air flow also help keep the air clean.
Pollutants get trapped in the air during winter. In cold weather, changes in temperature create a condition known as temperature inversion. In this, cold air remains close to the ground and a layer of warm air forms above it. As a result, pollutants cannot rise upward and begin accumulating near the lower surface. Low wind speed and the lack of vertical mixing in the atmosphere make the problem more severe.
Stubble burning and vehicle emissions are also responsible. Both local and regional sources contribute to Delhi’s pollution. Vehicle emissions, dust from construction work, industrial emissions, waste burning and biomass burning increase pollution. In October-November, smoke from stubble burning in nearby areas including Punjab and Haryana also affects air quality. North-westerly winds can carry this smoke to Delhi.
Efforts across the entire region are necessary for a solution. According to experts, Delhi’s pollution cannot be controlled only through measures within the capital’s boundaries. A shared strategy is needed across Delhi-NCR and neighbouring states to control vehicles, industries, construction activities and stubble burning. To improve air quality, sustained efforts will be needed at the regional level along with local action.
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