Environmental Threats to Delhi

What is the issue?

• Haze loomed over Delhi and its adjoining areas for over a week.
• The causes and consequences of it demand a more holistic approach in responding to this environmental problem.

How is the dust pollution scenario in Delhi?

• Air quality - For over five days, a thick layer of dust hung over Delhi.
• It kept the air quality ‘severe’, the worst category in the pollution index.
• It was odd because it happened in the peak summer.
• Summer is generally considered the off-season for air pollution in Delhi.
• Pollutant - The major air pollution threat in Delhi is from the tiny PM2.5 particles.
• However, during the summer, PM10 is found to be the primary pollutant.
• The summer average for PM10 in Delhi was found to be 5 times the national average.
• About 40% of PM10 particles (with diameter less than 10 micron) was dust.  
• Dust - Windblown dust consists of soil, sand and rock particles.
• Besides, it also contains “re-suspended” dust kicked up by vehicles, digging or construction.
• The dust hosts toxic materials, including, heavy metals such as lead, chromium and nickel.

What are the causes?

• The recent phenomenon was triggered by a dust storm that began over Rajasthan.
• It was carried by strong westerly wind.

• The dusty blanket spread itself over Punjab, Haryana, Delhi and western UP.
• It was kept close to the surface by the anticyclonic flow of winds.
• Anti-cyclones swirl clockwise in the northern hemisphere.
• It pushes the local air down and prevents outside air from entering the region.

What are the changing conditions?

• The recent dust haze is notably not a one time incident resulting just from desert storm.

• The phenomenon could be aggravated by

1. desertification around Delhi
2. the uncontrolled urban development
3. climate change

• Delhi’s summer aandhis, like Kolkata’s kaalbaisakhis, are localised events.
• However, the recent development is different in scale and impact.
• Strangely, all of North India was enveloped.
• These climatic conditions cannot any longer be seen in isolation.

Why is desertification a serious issue?

• What - Desertification is the process of relatively dry land becoming increasingly arid.
• It refers to a condition of reduction of water supplies and lowering of water table in the soil.

• The factors range from loss of vegetation and overexploitation of soil to climate change.
• Scale - The rate of desertification in India is said to be at 23 hectares of dryland per minute.
• Nearly 70% of India’s area is dryland.
• A third of this is affected by degradation and a quarter by desertification.
• Rajasthan and Delhi were among the worst affected.
• Impact - Delhi has historically had a barrier of trees.
• This exists in the form of the Delhi Ridge and the linked Aravalli range.
• But nearly 12 vegetative gaps in southern Haryana are increasingly prone to desertification.
• The forest cover in Haryana, UP and Rajasthan is also found to be declining.
• Significance - Preventing desertification is crucial because failing on this would result in more dust.

How to address this?

• Preparing for more climate related incidents in the future should be a priority.
• Australia and several countries in sub-Saharan Africa and West Asia carry out dustfall monitoring.
• Measuring dust deposits in the air alongside ambient air monitoring can be done.
• The data would help in the mitigation processes.
• Projects like the African Union-led “Great Green Wall for the Sahara and Sahel Initiative” could be taken up.
• It aims to create a mosaic of trees across North Africa, Sahel and the Horn.
• Vegetation buffers could be positioned between residential and industrial areas or roads.
• The urban design of Delhi should be rethought.
• Greening has to be done intelligently; roads need to be designed with tree cover.
• The Aravalli and the Ridge need to be protected.
• This in turn will protect the water table and benefit the city throughout the year.

Source: Indian Express