October - The Month Delhi Sees A Rise In Air Pollution

Every year in October, Delhi sees a sharp rise in its air pollution. The reasons are below.

Delhi’s air quality starts to dip every year in October.
On October 15, the Air Quality Index touched ‘very poor’ for the first time this season.
Air pollution in the whole Indo-Gangetic plains and Delhi is a complex phenomenon.
The weather during October, the input of pollutants and the local conditions play a part in the rise of air pollution in Delhi in October.
In 2015, a study conducted by IIT-Kanpur states that 17-26% of all particulate matter in Delhi air pollution in winter is biogas burning.
The System Air Quality and Weather Forecasting And Research (SAFAR) developed a system to calculate the contribution of stubble burning.
The stubble burning season is around 45 days long and in the beginning of October it has been 2%-4%.

In northwest India, October marks the withdrawal of monsoons.
The direction of the wind is towards the east during monsoons.
These winds carry moisture which travels from over the Bay of Bengal and brings rain to this region.
When the monsoon has withdrawn the direction of the wind changes to northwesterly.
During summer the storms carry dust from Rajasthan, Pakistan and Afghanistan and the direction of the wind is also to north westerly.
The scientists from the National Physical Laboratory conducted a study and reviewed that the winter winds of Delhi, which is of 72% comes from northwest and the remaining 28% from the Indo-Gangetic plains.
In 2017, a far off storm in in Iraq, Saudi Arabia and Kuwait led to a drastic dip in air quality in Delhi, showing the impact of the northwest winds on the Capital city’s air.
The increased pollution is also due to the dip in the temperatures.
As the temperature dips, the inversion height is lowered where the concentration of pollutants in the air increases.
Inversion height is the layer beyond which the pollutants cannot move into the upper layer of the atmosphere.
For dispersing pollutants, high speed winds are very effective but winters bring a dip in wind speed.
The combination of these meteorological factors make the region prone to pollution and other factors such as farm fires, dust storms add a high base to pollution.

The easiest and low cost method to get rid of paddy stubble is the farm fire.
With the use of combine harvesters, the practice became more common.
The Farm fire practice gained acceptance from 2009 when the Punjab and Haryana government passed laws delaying the sowing of paddy.
This law allows conserving groundwater as the new sowing cycle will coincide with monsoons and less water extraction.
This will make farmers to have little time for sowing for the next time.
The paddy straw and stalk have high silica content which is not suitable for livestock. So, the best way to get rid of it is to set fire to it.
The smoke residues from the fires, due to the northwesterly movement of the winds travel to Delhi during the winter leading to an increase in pollution in the city.

In winter, the two biggest causes of dipping air quality in Delhi are dust and vehicular emissions.
The top contributor for air pollutionduring the season is dust pollution which contributes 56% of PM 10 and PM 2.5load at 59t/d. The major source for dust pollution is roads at 38% of PM 2.5 concentration.
Between October and June, there won’t be much rain due to which dust seems prevalent in the entire region.
The second contributor to air pollution is vehicular pollution – 20% PM 2.5 in winters.
Government has taken several steps to reduce pollution such as introducing BS VI cleaner fuel, push for electric vehicles, odd-even as an emergency measure and construction of Eastern and Western Peripheral Expressways.
Still, Delhi is reeling under severe air pollution every year.