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The city of Delhi, India's national capital, recently experienced a paradoxical situation: despite persistent rainfall, the air quality remained severely compromised, shrouded in a thick blanket of smog. This perplexing phenomenon, a consequence of meteorological conditions interacting with existing pollution, underscores the complexities of combating air pollution in densely populated urban centers. The rain, while seemingly beneficial, actually exacerbated the problem by trapping pollutants within a layer of condensed moisture. This created a 'fog' effect, significantly reducing visibility and further deteriorating the air quality index (AQI). The AQI, a crucial indicator of air quality, hovered around the 'very poor' category, indicating a severe health risk to the city's residents. This situation highlights the limitations of relying solely on natural mechanisms, such as rainfall, to cleanse the air. The intricate interplay between meteorological factors, pollution sources, and urban infrastructure necessitates a more holistic approach to address the persistent air pollution challenges faced by Delhi.
Experts attribute the trapped pollution to a combination of factors. The cold weather conditions caused increased condensation of moisture in the air, forming a dense fog. This fog layer acted as a lid, trapping existing pollutants and preventing their dispersal. Anumita Roychowdhury, executive director of the Centre for Science and Environment (CSE), explained this phenomenon, noting that the inefficient natural ventilation processes within the city further contributed to the poor air quality. The inversion layer, a meteorological condition where warmer air sits above cooler air, prevents the pollutants from rising and dispersing, thereby exacerbating the situation. While the rain might have had a slight 'washout' effect, removing some pollutants through precipitation, the increased moisture and condensation ultimately counteracted this benefit, leading to a net worsening of air quality. The uncertainty surrounding whether the continued rain would effectively improve air quality in the long term highlights the unpredictable nature of this environmental challenge.
In response to the severe air pollution, the Delhi-National Capital Region (NCR) implemented GRAP stage 4, the strictest level of its graded response action plan. This plan, enacted when the AQI surpasses 400, includes measures such as a ban on the entry of trucks (except those carrying essential commodities) and a halt to construction and demolition activities. However, the limitations of GRAP stage 4 become apparent when considering its incomplete address of the issue. The plan notably lacks measures to control private vehicle usage, a significant contributor to Delhi's air pollution. Furthermore, the impact of construction activities on PM2.5 levels on December 17th was only around 2%, suggesting that other sources deserve greater attention in the anti-pollution strategy. The insufficient focus on comprehensive transport management and the reliance on measures with limited immediate impact point to the need for more effective and far-reaching strategies to combat Delhi's chronic air pollution problem. The existing measures, though important, may not be sufficient to create sustainable improvements in air quality given the complexity of the sources and dynamics of pollution.
The recurring nature of Delhi's air pollution problem is rooted in the combination of seasonal factors and anthropogenic activities. Studies indicate two major peaks in air pollution: one related to stubble burning during the agricultural season, and another occurring during December and January, primarily due to meteorological conditions. The December-January peak, as explained by Professor Sagnik Dey of IIT Delhi, is weather-driven, with cold temperatures and low wind speeds contributing to the accumulation of pollutants. While progress has been made in addressing Delhi's air quality, the pace is slow, highlighting the ongoing need for effective strategies. The lack of updated emission data at the time of reporting further limits a thorough assessment of the current situation and a detailed comparison to past periods. A comprehensive understanding of the emission sources, combined with the implementation of robust and sustainable mitigation strategies, is crucial to effectively tackle this persistent environmental challenge faced by the city of Delhi.
Source: Delhi’s air quality deteriorates despite rains as toxic smog blankets city