Stubble Burning’s Impact on Delhi-NCR Air Quality

Recent research has revealed vital information about the relationship between stubble burning in Punjab and Haryana and air quality in the Delhi-NCR region. A study published in January 2025 found no direct correlation between stubble-burning events and fine particulate matter (PM2.5) levels in Delhi. Despite a notable reduction in stubble burning, PM2.5 levels have remained high. This indicates that other sources contribute more to air pollution in the area.

Study Overview

• The study analysed data from a network of sensors across Punjab, Haryana, and Delhi, alongside chemical transport models.
• It concluded that stubble burning accounts for only about 14% of PM2.5 in Delhi-NCR.
• The research brought into light that PM2.5 levels remained stable, even as stubble-burning incidents dropped from 2015 to 2023.

Stubble Burning Trends

Between 2022 and 2024, stubble burning events in Punjab and Haryana decreased sharply. In Punjab, incidents fell from 48,489 in 2022 to 9,655 in 2024. In Haryana, the number dropped from 3,380 to 1,118 in the same period. Despite this decline, PM2.5 levels in Delhi-NCR increased by 20% in 2023.

Role of Meteorological Factors

The study emphasised that meteorological conditions influence PM2.5 levels. Low wind speeds and temperature inversions trap pollutants near the surface, contributing to poor air quality. Wind patterns can transport pollutants but do not solely determine PM2.5 levels.

Local Emissions and Pollution Sources

Data indicated a persistent increase in carbon monoxide (CO) levels during the night in Delhi, suggesting emissions from local sources like transport and industry. The study found that CO emissions in Delhi-NCR are primarily due to fossil fuel combustion and not linked to stubble burning.

Contributions to PM2.5 Levels

The major contributors to PM2.5 in Delhi-NCR include the transport sector (30%), local biomass burning (23%), and construction activities (10%). In contrast, stubble burning contributes only about 13% during peak seasons.

Impact of Regulatory Measures

The implementation of the Graded Response Action Plan (GRAP) showed reduction in PM2.5 levels during strict enforcement periods. However, pollution levels surged again once the measures were lifted, denoting the importance of local regulations in air quality management.

Questions for UPSC:

1. Critically analyse the impact of stubble burning on air quality in urban areas, with suitable examples.
2. What are the primary sources of PM2.5 in metropolitan regions? How do they compare with rural sources?
3. Estimate the effectiveness of regulatory measures like the Graded Response Action Plan in improving air quality.
4. Point out the relationship between meteorological conditions and pollutant dispersion in urban environments.

Answer Hints:

1. Critically analyse the impact of stubble burning on air quality in urban areas, with suitable examples.

1. Recent studies show stubble burning contributes only about 14% of PM2.5 in Delhi-NCR.
2. Despite reduction in stubble-burning events, PM2.5 levels have remained high.
3. Other sources, such as transport and local industries, play a more critical role in urban air pollution.
4. For example, PM2.5 levels increased by 20% in 2023 despite a drop in stubble burning.
5. Regulatory measures like the Graded Response Action Plan have shown effectiveness but need consistent enforcement.

2. What are the primary sources of PM2.5 in metropolitan regions? How do they compare with rural sources?

1. In metropolitan regions, primary sources include transport (30%), local biomass burning (23%), and construction activities (10%).
2. In contrast, rural areas may experience higher contributions from agricultural practices, including stubble burning.
3. Stubble burning contributes only about 13% to PM2.5 during peak seasons in urban areas.
4. Local emissions, such as from industries and waste management, impact urban air quality.
5. Rural sources tend to have a more seasonal impact, while urban sources are more consistent year-round.

3. Estimate the effectiveness of regulatory measures like the Graded Response Action Plan in improving air quality.

1. The Graded Response Action Plan (GRAP) has led to reductions in PM2.5 levels during strict enforcement periods.
2. For instance, PM2.5 dropped during GRAP stages III and IV when measures were implemented.
3. However, pollution levels surged back once these measures were lifted, indicating a lack of long-term effectiveness.
4. Continuous enforcement and adaptation of regulations are necessary to maintain air quality improvements.
5. Local sources, including transport and industry, must be targeted for sustained air quality management.

4. Point out the relationship between meteorological conditions and pollutant dispersion in urban environments.

1. Meteorological conditions, such as low wind speeds and temperature inversions, trap pollutants near the surface.
2. These conditions can lead to poor air quality, especially during winter months in urban areas.
3. Wind patterns can transport pollutants but are not the sole determinant of PM2.5 levels.
4. Stagnant air prevents effective dispersion, exacerbating pollution levels in densely populated areas.
5. About these relationships is crucial for developing strategies to mitigate air pollution in urban environments.