Possible Reasons behind the high RSPM levels:

     Crop Harvesting Seasons: 

Located nearby the agricultural hubs (Punjab/Haryana), city received a lot RSPM from the wheat harvesting, stubble burning and field ploughing/preparation for the next crop during summers (April - June); whereas the repetition same activities for rice cultivation takes place during winters (Oct-Nov).

     Effect of Pollens:

Plants and Trees used to propagate their seeds through air by the process of Pollination. Almost all the flowering plants distribute their seeds through air to the nearby area. In the process, as the size of these pollens lie within the limits of RSPM (less than 10 µm) therefore pollens counts for the major part in the RSPM level of any city. Chandigarh, a green city, also has very high density planted series of different trees, which consists of a major fraction of flowering trees. List of flowering (pollinating) trees in Chandigarh is given below:

Source: An Inventory of Multipurpose Avenue Trees of Urban Chandigarh, India

Temperature Effect: 

 Diagrams shows the rising RSPM levels during the low temperature seasons because when temperature      declines, the air masses gets denser and settle down causing the phenomenon of “Inversions”.

 The cold and humid air traps the pollutants to the lower heights and prevent their dilution in environment  thus one of the main reason behind the high RSPM.

 In hot days the vehicular emission also increases due to the air conditioner load.

During the winter season, average mixing height is lower as compared to other seasons and atmospheric dispersion is typically at a minimum and therefore the pollutants will not be as widely dispersed. Lower

   average mixing height in winter season results in less volume of troposphere available for mixing and hence higher concentrations. Calm conditions in winter season result in less dispersion of pollutants resulting in building up their levels. The monsoons results in large amount of precipitation, high wind velocities and changes in general wind direction. The large amounts of precipitation reduce atmospheric pollution via associated wet deposition processes. Further wind velocities will allow for pollutant transport away from sources and increase mixing processes, thereby resulting in lower levels.

However in the rest of the period the low RSPM is controlled by the rainfall (monsoon/western disturbances) and spreading due to heated air masses & wind speed.


  Location of the city & Industrial surroundings:

 Chandigarh is surrounded by the Industrial hubs such as Baddi, Mohali, Zirakpur, Derabassi and Panchkula. Chandigarh too has a vast number of Industrial setups. As observed, the RSPM level of these cities is usually remains higher than that of the Chandigarh; therefore it can contribute to the RSPM of the city.


 RSPM levels in air also increases due to the operation season of brick kilns (Oct  May) and sugar mills (Oct - March) located at the surroundings of Chandigarh. Their continuous exhaust releases enormous amounts of SPM/RSPM, which can travel tens of kilometers to the nearby areas.


 Human Activities:

 High RSPM levels in the months of winter may also be attributed to the shooting of fire crackers due to number of festivals like Diwali (Nearly Rs. 10 Crores), Guruparav and New  Year eves; moreover it's the season when most of the marriages happen in the north region.


 Falling of leaves and their illegal burning in autumn season i.e November to January (winters) is also one of the main reason behind high RSPM in winters as green leaves exhibits a ultimate property of adsorbing the suspended particulates and purifying air.


 Population & Vehicle density:

As per the census 2011, the population of city has crossed the mark of 10 Lakh. The population density during the last 5 decades (1961-2011) has increased 9 fold, from 1051 to 9252 persons per sq. Km. Due to the high economic status; the city has the largest density of vehicles (878 vehicles/1000 people) also, which is one of the main contributors to the RSPM level. Frequent braking and idling at light points; resulting in higher emission of pollutants. Moreover unmanaged diesel auto rickshaw and buses also adding up to the problem.

 Transportation Load in the city: 

With the increase in population the need of travel facilities has also been increasing. People used to travel daily to the city from adjoining Haryana, Himachal and Punjab and enter Chandigarh from Zirakpur, Panchkula, Mullanpur, and Mohali. It was estimated that Chandigarh has nearly 5471 registered and about 3000 unregistered auto-rickshaws (including LPG/CNG) running daily throughout the city. It was estimated that nearly 5000 diesel auto-rickshaws join the city traffic daily including the auto from the neighbouring Haryana and Punjab. 

As per the information obtained from the RLA department, Chandigarh; more than 3,18,000 four wheelers, 4494 buses, 8243 goods vehicle and more than 6,05,800 two wheelers were registered with the city till year 2013. 

The Govt. Road transport is also packed with a huge vehicular load, as the CTU only has around 417 buses (209 on local route) running around 16 hrs/day throughout the city. Whereas the total bus movement in the city (including other sate transport) is about 1900 per day. The distribution of buses coming from the other states is as below:

Transport All State Buses


ISBT Sector 17

ISBT Sector 43

Total No of Buses

AC Private Integral Buses












J & K




























As per the national summary report 2010 (CPCB) the total contribution of vehicular exhaust of any city adds up 15  70% of the total PM10 level, depending upon the density of vehicles and weather conditions, out of which the main contributors (56%) are diesel vehicles including buses, trucks and auto-rickshaws. (Bangalore is the only city with highest PM contribution coming from vehicular sector with 41%. Pune with 61 % and Chennai with 72 % show the highest percent contribution from road dust. Pune has the lowest industrial contribution (1-3%) as it has mainly engineering industries and also most of them are outside the city boundary).  

Source: SoER-2014, Chandigarh