Thread by @ParveenKaswan

City of Delhi:
Pic 1 - 1991
Pic 2 - 2016

There are many reasons behind air pollution in NCR. Let me add 'geographical factors' also for prolonged pollution exposure here. The Indo Gangetic plain, sandwiched between Himalayas & Vindhya, home to 600 million people. 1/n

The rainfall is less with alluvial soil. Historically also the ganga plain is used for wheat cultivation & true now also. Surrounding region Haryana, W. UP, Punjab etc region grows both Rice & Wheat, alternate. Stubble burning takes place in both, but more prevalent in Rice. 2/n

Here in winter winds blow from north-west to east which carry pollutants from other regions to NCR, western disturbances also provide winter rains. The season coincides with Temperature inversion, longer the inversion lasts, higher the levels of pollution trapped under it. 3/n

Since the big cities are in valley the pollution has less space to expand. Addition is urban heat island with local vehicular pollution & construction debris. Due to continental location no mixture of air like in Chennai or Bombay by sea breeze. 4/n

Stubble burning has increased due to mechanisation bcz machine leaves larger part of stubble, to save time/money they burn them. But its not only stubble. A number of factors including vehicles, construction debris are behind it. Sand storms from thar due to loss of Aravali. 5/n

There are many causative factors but geography is a limiting factor.

We need to check causative factors. N/n

Punjab has more stubble burning. Because of simple reason. This is Kharif season, paddy is the main crop. And also rice stubble is burnt. Paddy cultivation in Punjab is 2.6 million hectares whereas in Hartana it is 1 million hectares.

Limiting factor for reducing pollution.

Mechanisation is one of biggest reason; earlier rice is being cut from below, made bundles & rice was seperated manually. Now harvester cut it from above, leaving large stubble, this then cut by another machine in field only. Then it is burned for saving labour/money/time.

This picture shows the expansion of city. With geographical expansion the infrastructure & vehicles are also increasing. Construction debris & industrial pollution are also rising. The valley houses one of the biggest urban conglomerate.

adding all factors we have a peak of pollution & PM2.5 in this season.

200-300 (AQI of expanding city) + 100 (after effect of diwali) + 200-300 (stubble burning ) + winter & geographical factor = AQI of 500-700.

to solve also we need multiple solutios.

Source: berkeleyearth