While particulate matter levels in Delhi continued to spike after implementation of the odd-even policy, the levels of PM 10 (particles of diameter less than 10 microns) were generally the highest in east and northeast Delhi, data released by the government showed.
The smaller PM 2.5 particles (of size less than 2.5 microns) were highest in border areas of South Delhi, and relatively high in other areas of South Delhi.
According to data collected from mobile monitoring vans at over 65 locations in Delhi between January 1 and 5, PM 10 levels in many parts of northeast and south Delhi are over 900 micrograms per cubic metre (µg/m³), against a safe limit of 100 µg/m³.
In comparison, south and southeast Delhi have reported high PM 2.5 levels of 300 µg/m³ against a safe limit of 60 µg/m³.
The government is yet to share data on PM 1, the ultra fine particles of size less than 1 micron, which is being collected for the first time in Delhi.
Sources said though these are early trends, the major cause of PM 10 at this time of the year is construction dust and wind blown dust.
According to a scientist in Delhi Pollution Control Committee, “PM 10 particles are comparatively large-sized particles that are related to construction and factories, rather than vehicular pollution. Northeast and east Delhi are close to ongoing construction sites in Noida, Greater Noida and Ghaziabad. Factories are also located in these areas. Exhaust fumes from the bus depot in Anand Vihar is also a factor.” He added that the finer PM 2.5 vehicles are “more directly attributable” to the combustion of vehicular pollution.”
Dr M P George, senior scientist at DPCC said high particulate matter was “generally observed” in different parts of outer Delhi, and a further analysis of this was yet to be done. “We associate vehicular pollution more with PM 2.5 levels and PM 10 with other sources. Both are high in different parts of outer Delhi.”
Here is what the average of 20 minutes recorded by DPCC for each location showed.
> On January 5, PM 2.5 levels touched 426 µg/m³ in Harikesh Nagar. Gokalpur in Northeast Delhi recorded high PM 10 levels of between 680-883 µg/m³.
> On January 4, In Gorakh Park west in Babarpur, a PM 10 level of 924 µg/m³ was reported. In Raju Park in Ambedkar Nagar, a PM 2.5 level of 429 µg/m³ was recorded.
> On January 2 data, Babarpur again recorded the highest PM 10 data out of 15 locations at 734 µg/m³, over seven times that in South Delhi border areas. PM 2.5 values were among the highest at 150-177 µg/m³ in parts of South Delhi.
Anumita Roychowdhury from the Centre for Science and Environment said PM 2.5 was more associated with combustion. “We are yet to study this data, but it is safe to say that areas which have high PM 10 levels are generally associated with heavily populated, visibly dusty areas, where there is a high truck traffic congestion, trash burning and construction dust. For High PM 2.5 levels, while there may not be so much of visible dust, they indicate a proximity to combustion sources like vehicles which release finer particles,” said Roychowdhury.
Dr R.K. Jenamani, head of IGI airport Met office said meteorological factors could also be contributing to these trends. “High temperatures and wind speeds and low humidity help disperse pollutants and reduce smog cover composed of particulates. Wind speeds and directions… vary largely in different areas and have a great role in dispersing particles of different sizes.”