Delhi’s air quality around Diwali has often been under scrutiny, but this year, despite a high pollution spike during the festival, the city witnessed a noticeable improvement in air quality the day after. This shift, marking one of the lowest post-Diwali AQI levels in recent years, brings into focus a broader set of factors influencing Delhi’s pollution beyond Diwali-related activities. Let’s explore why the air was cleaner this year and how other factors contribute to Delhi’s pollution levels.
Understanding AQI
The Air Quality Index (AQI) is a system that simplifies complex air quality data into a single, easy-to-understand number and color code. It measures the concentration of key pollutants like PM10, PM2.5, Nitrogen Dioxide (NO₂), Ozone (O₃), and Carbon Monoxide (CO) in the air. Each pollutant’s impact on health is weighted, and the highest-impact pollutant determines the AQI value.
Key Points about AQI:
- Purpose: Provides the public with a clear view of air pollution levels and associated health risks.
- Pollutants Measured: Focuses on pollutants that pose health risks, especially PM2.5, which can penetrate the lungs and bloodstream.
- Health Guidance: Different AQI ranges indicate levels of pollution from “Good” to “Hazardous,” helping individuals take appropriate precautions.
Introduced by the Indian government in 2014, the AQI is a critical tool for public awareness and helps guide pollution control measures and policies.
Why Was Delhi’s Post-Diwali Air Cleaner This Year?
While Diwali celebrations did lead to a temporary increase in pollution levels, the city’s air quality significantly improved shortly after due to natural and climatic factors. Let’s examine the two main reasons for this year’s improvement.
1. Unusually Warm Temperatures
- Record-High October Temperatures: October 2024 was the warmest October in 73 years, with average highs reaching 35.1°C and lows around 21.2°C. Such high temperatures helped prevent pollutants from getting trapped close to the ground.
- Temperature Inversion Dynamics: Cooler temperatures often lead to temperature inversions, where a layer of warmer air traps cooler air beneath it, keeping pollutants near the surface. This year’s warm October reduced the chance of such inversions, enabling better air circulation and dispersal of pollutants, leading to a quicker post-Diwali AQI recovery.
2. Strong Winds That Facilitated Pollution Dispersal
- High Wind Speeds: The day after Diwali, westerly winds moved in, reaching speeds of up to 15 km/h. These winds effectively dispersed particulate matter, such as PM2.5 and PM10, that had accumulated due to Diwali festivities and agricultural stubble burning from neighboring states.
- Impact of Winds on AQI: Wind speed is crucial in clearing pollutants from the atmosphere. Strong winds allow pollutants to be carried away from ground level, improving air quality in heavily populated areas like Delhi.
How Does Delhi’s AQI This Year Compare with Previous Years?
This year’s post-Diwali AQI was recorded at 339, which, while still categorized as “very poor,” is a clear improvement over previous years:
- 2023: AQI was 358 post-Diwali
- 2022: Exceptionally low AQI due to favorable weather patterns and reduced firecracker usage
- 2021: AQI reached an alarming 462 post-Diwali, indicating severe pollution and health risks
These fluctuations reflect how weather and environmental factors can significantly impact air quality.
Understanding Broader Sources of Delhi’s Pollution
Delhi’s pollution problem is a year-round issue, influenced by a variety of sources that go beyond Diwali festivities. Here’s a look at some of the persistent contributors to Delhi’s air pollution:
1. Agricultural Stubble Burning in Neighboring States
- Seasonal Impact: In autumn, farmers in states like Punjab and Haryana burn crop residue, producing smoke that drifts into Delhi. This practice, known as stubble burning, leads to sharp spikes in particulate matter, especially PM2.5.
- Measures Being Taken: To combat this, government efforts focus on promoting alternative crop management techniques, though these initiatives are still evolving and require widespread adoption to reduce the impact on air quality.
2. Vehicle Emissions and Industrial Activity
- Traffic Pollution: Vehicle emissions are a constant source of pollution in Delhi. With the city’s high vehicle density, exhaust fumes contribute significantly to NO₂ and CO levels, which worsen air quality.
- Industrial Sources: Factories and industrial areas around Delhi release large quantities of pollutants. Diesel generators, often used as backups, also add to the pollution load, especially during power shortages.
3. Construction Dust and Urban Infrastructure
- Construction Activities: Delhi’s continuous construction projects generate dust, which increases PM10 levels in the air. Without effective dust control measures, this becomes a persistent issue.
- Mitigation Efforts: Various restrictions, including construction bans and dust control regulations, are periodically imposed to curb construction-related pollution. However, enforcing these regulations consistently remains a challenge.
Government Measures and AQI-Driven Actions
Delhi’s government has implemented several measures aimed at reducing pollution levels, especially during high-risk periods like the post-monsoon season. These actions include:
- Graded Response Action Plan (GRAP): Based on AQI readings, GRAP involves staged responses, such as restricting vehicle use, imposing construction bans, and enforcing limits on industrial emissions.
- Firecracker Bans and Traffic Restrictions: Although firecrackers are often cited as contributors to Diwali-related pollution spikes, they are just one factor among many. Temporary bans aim to reduce their impact, but broader, year-round policies targeting major pollution sources are essential for meaningful improvement.
Conclusion: A Holistic Approach to Improving Delhi’s Air Quality
While Diwali often brings a temporary spike in pollution, broader factors like weather conditions, agricultural practices, vehicular emissions, and industrial pollutants are the year-round culprits behind Delhi’s air quality issues. This year’s improved post-Diwali air quality highlights how natural factors, such as warm temperatures and strong winds, play a significant role in air quality. These elements helped counteract pollution from multiple sources, underscoring that a comprehensive approach to pollution management—beyond single events like Diwali—is needed.
Achieving sustained improvements in Delhi’s air quality will require continued efforts from government, industry, and the public. Implementing and enforcing policies that address primary pollution sources, encouraging cleaner agricultural practices, and promoting sustainable urban planning are all steps in the right direction. By recognizing the multifaceted nature of Delhi’s pollution, we can work toward creating a healthier environment for all.