This present study addresses the relationship between Particulate Matter (PM) and meteorological parameters over two metropolitan cities in India (Delhi and Pune) together with the Potential sources contribution function (PSCF) in order to understand the role of the transport on the variability of PM for a period of one year. To examine the variations of PM, over different time scales (diurnal and seasonal), at different observational locations, diurnal scales, are shown that maximum values of standard deviations (SD) are found in early hours of morning around 10AM, and later hours in the night over Delhi, however, the maximum values of SD are found in the morning hours around 8 to 10 AM over Pune. The relationship between PM and meteorological parameters is studied and explains a positive relationship between wind speed and planetary boundary layer height (PBLH), with a PM. Also, analyses on the Potential source contributions function (PSCF) over Delhi show that higher source contributions are observed during months of November, December and January over the region of Indo Gangetic Plain (IGP) plane north and Eastward of Delhi. Similarly, over Pune, most of the time, the source contribution in terms of pollution in Pune is coming from the south-east and eastern part of India, except in the winter season in the months of (December, January, and February). This analysis clearly suggests that the orography is played a pivotal role over the variations of PM over Pune.
Over last several decades, environmental chemistry and climate are major issues due to the drastic change in the levels of particulate matters (PM) and gaseous components in the metropolitan cities of all over the world [
Delhi is located at (28.37˚N; 77.12˚E, 216 m above mean sea level-MSL) and covers ~1500 km2 of the industrial area including the suburban towns of Ghaziabad, Noida Faridabad, and Gurgaon. According to 2011 census, Delhi is the second highest populous (~11 million population) city in India, as well as it is one of the most polluted urban environments over the globe. Delhi climate is humid subtropical climate and hot semi-arid with high temperatures of 40˚C - 45˚C in pre-monsoon (warm) season while lowest of 13˚C - 15˚C during in winter period. The monsoon arrives at the end of June, along with an increase in humidity.
Pune is located at (18.5˚N; 73.8˚E) an altitude of about 550 m above the MSLs, it is situated in the western zone of the Deccan plateau and covers an area of ~700 km2. It is one of the most rapidly developing cities in India in terms of industries as well as vehicular population and also urbanization [
Continuous measurements of PM2.5 and PM10 with meteorological parameters were carried out from the System of Air Quality Forecasting and Research (SAFAR) network of the year of January-December, 2015. It consists of eight Air Quality Monitoring Stations (AQMS) and Automatic Weather Stations (AWS) set up across Delhi and Pune. PM2.5 and PM10 mass concentrations were observed using the Beta Attenuation Monitor (BAM-1020; Met One Instruments, Inc., USA). The BAM-1020 measures the mass concentrations of airborne particulate matters in (µg/m3) using the principle of beta ray attenuation. A small Carbon-14 (14C) element provides a constant source of high energy electrons known as beta rays. The beta particles are detected and counted by a sensitive scintillation counter. Detailed information of BAM-1020 has been reported in a study by [
The potential source contribution function (PSCF) is used to calculate the possible source locations using back trajectories [
The analysis was begun from the annual variations of PM at all the observational locations over Delhi and Pune. The higher values of PM10 were observed over Delhi as compared to Pune (it was the same case for PM2.5). All the stations over Delhi were having the same amount of PM in all the seasons with the higher values are found during the pre and post monsoon seasons, and the lower values are observed during the monsoon months due to the settling of pollutants by rainout and washout mechanism. And the same is the case for Pune with the higher values were found during the pre-monsoon and the lower is observed during the summer monsoon season (
On the other hand, IMD Lodhi road is recorded the maximum (minimum) values of PM10 with 644.25 (42.85) μg/m3. On the overall statistics of PM10 has shown the higher variability in terms of their standard deviation with 89.31 μg/m3 while the lower Standard Deviation (SD) is observed over IITM Delhi with the values of 72.06 μg/m3. On an average, all the stations over Delhi have the SD of more 90 ug/m3 except single station IMD Aya Nagar. Also, it is the
Site | Mean | Max | Min | Std | Mean | Max | Min | Std |
---|---|---|---|---|---|---|---|---|
PM10 Concentration(μg/m3) - 2015 | PM2.5 Concentration(μg/m3) - 2015 | |||||||
CRRI | 91.76 | 683.41 | 53.73 | 95.29 | 110.36 | 430.65 | 9.37 | 57.46 |
C V Raman | 229.15 | 711.03 | 28.01 | 115.61 | 127.38 | 412.93 | 17.91 | 65.56 |
Delhi University | 209.80 | 662.05 | 66.16 | 97.53 | 136.16 | 421.06 | 46.78 | 60.25 |
IITM Delhi | 165.08 | 526.41 | 25.51 | 72.06 | 96.64 | 318.35 | 16.91 | 44.95 |
IGI Airport | 198.31 | 796.67 | 38.46 | 112.27 | 135.09 | 600.03 | 14.85 | 82.87 |
IMD Aya Nagar | 164.69 | 761.97 | 27.02 | 78.70 | 93.85 | 459.98 | 13.65 | 46.30 |
IMD Lodhi Road | 185.88 | 644.25 | 42.85 | 89.31 | 78.28 | 238.40 | 25.57 | 34.82 |
Site | Mean | Max | Min | Std | Mean | Max | Min | Std |
---|---|---|---|---|---|---|---|---|
PM10 Concentration(μg/m3) - 2015 | PM2.5 Concentration(μg/m3) - 2015 | |||||||
IITM | 91.66 | 428.04 | 25.86 | 34.44 | 41.18 | 106.36 | 10.26 | 14.75 |
IMD | 105.99 | 386.53 | 16.66 | 50.62 | 51.82 | 171.30 | 8.43 | 23.19 |
Airport | 105.08 | 360.83 | 20.74 | 35.48 | 53.93 | 153.57 | 5.36 | 22.49 |
Alandi | 81.51 | 418.41 | 14.32 | 51.32 | 34.93 | 112.60 | 6.78 | 18.37 |
Katraj | 116.90 | 343.72 | 3.05 | 47.10 | 60.04 | 180.81 | 1.34 | 28.43 |
Bhosari | 117.12 | 333.39 | 4.34 | 58.98 | 46.93 | 131.07 | 1.05 | 25.68 |
Nigadi | 69.78 | 231.08 | 14.15 | 28.04 | 31.58 | 88.25 | 4.35 | 16.11 |
Manjri | 95.72 | 313.60 | 14.72 | 49.31 | 46.85 | 154.37 | 4.65 | 31.23 |
same case for PM2.5 with the higher values of maximum values are recorded over IGI airport and IMD ayanagar with the minimum values of 14.85 (13.65) μg/m3 with SD of 82.87 (46.30) μg/m3 for the above two stations. From the statistical calculation, IMD Lodhi road recorded the lower values of both PM10 and PM2.5.
Both PM2.5 and PM10 concentrations are lower over Pune as compared to Delhi. Within Pune, overall results have shown the higher maximum values over IITM, Pune with Alandi is followed to IITM with the values of 428.04 for IITM and 418.41 μg/m3 for Alandi. Despite their maximum values, Alandi has shown higher variability of 51.32 μg/m3 than the IITM with a lesser value of about 34.44 μg/m3. Further analysis infers the minimum values over Katraj (Bhosari) as 3.05 (4.34) μg/m3 with higher SD values 47.10 (58.98). While it is the same case for the PM2.5 over these locations following the minimum values as 1.34 (1.05) μg/m3 and higher SD as 28.43 (25.68) μg/m3. Over Pune, Nigidi observational locations have recorded the lowest variability in both PM10 and PM2.5 among all the other nine stations. However, the overall variations of PM10 and PM2.5 over Pune is 2 and 3 times lesser than that of the Delhi respectively, and the annual mean mass concentration of PM10 and PM2.5 over Delhi is varied from 27.02 μg/m3 to 796.67 μg/m3 and 9.37 μg/m3 to 600.03 μg/m3 respectively as well as in Pune the annual mean mass concentration of PM10 and PM2.5 is varied from 3.05 μg/m3 to 428.04 μg/m3 and 1.05 μg/m3 to 180.81 μg/m3 as recorded in the year 2015. The observed values of PM10 and PM2.5 over Delhi have substantially exceeded the standards of their annual averages with reference to Indian National Ambient Air Quality Standards (NAAQS) i.e. 100 μg/m3 and 60 μg/m3 for 24 hours average. But over Pune observed values of PM10 and PM2.5 exceeds in winter and Pre-monsoon seasons only and rest of the period maintains the standard levels. According to previous studies over Delhi, the transport sector has contributed 45% to total PM2.5 concentrations, 27% of PM2.5 is contributed from industrial sector, 24% from industries and 4% from power sector [
The average diurnal variations in PM10, PM2.5 and their ratio concentration at Pune and Delhi are shown in
was found in the early hours of the morning and later hours in the night over Delhi with also peak in the morning hours around 10 AM, on the other hand, the maximum values of SD are found in the morning hours around 8 to 10 am over different locations over Pune. These higher deviations are mainly attributed due to the usage of a high number of vehicles which cause the higher emissions in the observed values. In the Metro area, PM2.5 concentrations are observed low at early morning hours to 8:00 am, followed by increase around 2:00 pm, and after which rises up to midnight 12:00 am. The metro area, therefore, displays a bimodal pattern with a weak signal. Whereas the Metropolitan cities are showing the strong bimodal pattern which is showing an almost similar pattern. The metro area has a dense traffic and huge pollution will lead to the high concentration of particulate matter as well as low diurnal variation. The morning peak is due to enhanced anthropogenic activity during rush hour. The condition is more or less same for both PM10 and PM2.5 with the less SD values over Pune as compared to Delhi. Interestingly the ratio of PM10 and PM2.5 has shown the higher values especially during the hours between 10 to 2 PM whereas it is more is less similar pattern over Delhi with higher deviations.
Further, we have analyzed the diurnal variations of PM10, PM2.5 and their ratio patterns during different seasons are shown in
value of around 285 μg/m3 during the winter season in Delhi while the minimum is observed around 16:00 PM with a value of 200 μg/m3, however, their high deviations are also observed around same time with 115 μg/m3 while the minimum is observed as ~65 μg/m3. In case of Pune, it is observed that the maximum is around morning 10:00 AM with a value of about 200 μg/m3 and the minimum is same as Delhi at 16:00 PM with a value of 90 μg/m3. It is interesting to note that the variability is found to be higher during the midnight with a value around 40 μg/m3 while the minimum variability is observed in the afternoon hours with a value as low as 13 μg/m3. The mean and SD values over Pune are below the half of the values Delhi during the winter season. During the pre-monsoon season in the PM10, the concentrations shows maximum in the early hours of the morning around 5:00 PM which is about 230 μg/m3 while the minimum is observed around 18:00 PM with a value of 150 μg/m3 over Delhi. As it is mentioned, the higher variability is reported during the winter season, and pre-monsoon also follows the winter season, showing the same pattern of variability in terms of their SD, on the other hand, minimum variability is observed at 18:00 PM. But in the case of Pune, PM10 has shown two peaks in its diurnal time scale, one of the maximum is observed around 10:00 AM in the morning with a value of about 125 μg/m3 and the second peak is observed with the same magnitude at midnight 12:00 PM. Interestingly the diurnal scale of variability is more or less similar of a value of about approximately 50 ug/mg except for few hours between 14:00 PM to 20:00 PM with minimum variability. But it is clearly seen there is a diurnal variability in terms of their SD over Delhi that is observed with mean values showing two peaks with lesser amplitude difference between 10:00 AM to 16:00 PM during the summer monsoon season. Minimum values are observed during the early hours in the morning.
Higher SDs is observed in the morning hours while the lesser SDs is observed during the night hours over Delhi region in
Ambient conditions of air pollution distribution will mainly depend on local meteorological conditions as well as long-range transport; Strong seasonality will lead to modulating the air quality levels [
Time series of particulate pollutants and meteorological variables are shown in
and downward air motion which favors the accumulation of PM2.5 and PM10 that emitted from local sources [
On the other hand, the relationship between PM and meteorological parameters were further analyzed, as shown in
Further, in order to see the contribution from both PM10 and PM2.5, we have shown the scatter plot in
Long-range transport of particulate matter is important to understand the direct emissions from local sources.
are carried out from the ocean with the strong winds called jet streams bring the particulate matter pollution toward the western ghat region of India, where Pune is located.
During the winter, temperatures are very low due to the topographical structure of the city, so planetary boundary is low and the winds are very calm. Hence in Pune, long-range transport occurs only in the Pre-monsoon and Monsoon periods, remaining Post Monsoon and Winter Periods are dominated by the local pollution events. As observed from
In this study the variability of PM over two metropolitan cities in India was studied using the ground-based observational datasets for the period of one year. In addition to this variability, we have also done the analysis on the source contributory function in order to understand the long-range transport of particulate matter; this will provide the information on the source regions from the emission points. Initially, we begin our analysis on variability by presenting the variations in diurnal and annual means along with their standard deviations. Analysis indicated that the higher values of PM10 are observed over Delhi as compared to Pune and also it is the same for PM2.5. Higher values were found during the pre and post monsoon with the lower values during the monsoon months due to settling of pollutants by rainout and washout mechanism at all the stations over Delhi. On the other hand, over Pune, higher concentrations are found during the pre-monsoon and lower values were observed during the summer monsoon season. The analysis is also based on different observational locations over Pune and Delhi by presenting the variations in terms of the means and standard deviations at all the observational locations. Overall analysis of the variations of PM10 and PM2.5 over Pune is 2 and 3 times lesser than the Delhi respectively and the annual mean mass concentration of PM10 and PM2.5 over Delhi is varied from 27 - 796 (μg/m3) and 9 - 600 (μg/m3), respectively. However, in Pune PM2.5 and PM10 were found in the ranges of 3 - 428 (μg/m3) and 1 - 180 (μg/m3), respectively in the year 2015. The variations at diurnal scales during the different seasons over both metropolitan cities over India also were studied by using the hourly values. The variability over different locations over Delhi was higher in terms of their SD than the locations over Pune. However, the maximum values of SD have found in the early hours of the morning and later hours in the night over Delhi with also peak in the morning hours around 10 AM, on the other hand, the maximum values of SD are found in the morning hours around 8 to 10 am over different locations over Pune. The reason for the higher concentrations of SD is mainly attributed due to the usage of a high number of vehicles which cause the higher during the observational period. In the diurnal cycle of PM10 is maximum in the midnight time around 12:00 AM with a value of around 285 μg/m3 during the winter in Delhi while the minimum is observed around 16:00 PM with a value of 200 μg/m3, however, their high deviations are also observed around same time with 115 μg/m3 while it is the minimum observed as ~65 μg/m3. On the other hand, over Pune, it is observed that the maximum (minimum) is around in the morning 10:00 AM (at around 16:00 PM) with a value of about 200 μg/m3 (90 μg/m3). The Metropolitan cities are showing the strong bimodal pattern which is showing an almost similar pattern. The metro area has a dense traffic and huge pollution will lead to the high concentration of particulate matter as well as low diurnal variation. Enhanced anthropogenic activities are a major source of the higher values in the diurnal. The condition is more or less same for both PM10 and PM2.5 with the less SD values over Pune as compared to Delhi. One interesting point here is to notice that the values are lesser in both amplitude and as well as the standard deviations which are almost half of its values over Pune as compared to Delhi.
Further, the relationship between the PM and meteorological parameters also were analyzed in order to see the roles on the maximum and minimum concentrations over both metropolitan cities. A positive relationship has been found t between wind speed and PM. It indicates that when there is a higher value of winds causes the higher values of PM which is obvious reasons for a positive relationship and it is the same relationship for the case also for the planetary boundary layer height (PBLH). But it is interesting to note that there is a negative relationship is observed between wind speed and PM values especially during monsoon season over Pune, which is opposite to Delhi. This analysis will provide with the distinct meteorological systems which control the variability in different seasons at different time scales over both metropolitan cities.
In addition to above analysis, in order to see the long-range transport, i the Potential source contributions function (PSCF) over both metropolitan cities also were analyzed. Higher source contributions were observed during the November, December, and January over the region of IGP plane north and Eastward of Delhi. This is mainly attributed to the heavy dust loading in the pre-monsoon months and stagnant of winds in the winter months the pollution accumulates in Delhi. The lowest values of PSCF within range of 0.1- 0.3 is observed in remaining all the months which appeared to be cleaner. On the other hand, over Pune, most of the time the source contribution in terms of pollution in Pune was coming from the south-east and Eastern part of India, except in the winter season in the months of (December, January, and February). Due to fact that the large temperature contrast, there are processes viz., land and sea breeze circulation over the Indian region and southern Indian Ocean, South West winds were carried out from the ocean with the strong winds called jet streams bring the particulate matter pollution toward the western ghats region of India, where Pune is located. This analysis clearly suggests that the orography is also played a pivotal over the variations of PM. And long-range transport occurs in the Pre-monsoon and monsoon periods, with remaining post-Monsoon and Winter Periods, are dominated by the local pollution events. This analysis is an insightful to understand the transport mechanism through the source contribution for the PM variations together with the aid of meteorological parameters over metropolitan cities. Long-term data sets further help to assess the variability at different time scales over different parts of India in order to understand the air quality standards and mitigation processes.
The authors are grateful to the Director, Indian Institute of Tropical Meteorology, Pune for their encouragement and support during the preparation of this manuscript. Authors also thank SAFAR and India Meteorological Department for data generation. Authors also thank HySPLIT to get the back trajectories data. Also authors would like to thank the anonymous reviewers for their valuable comments and suggestions to improve the quality of the paper.
The authors declare no conflicts of interest regarding the publication of this paper.
Krishna, K.R. and Beig, G. (2018) Influence of Meteorology on Particulate Matter (PM) and Vice-Versa over Two Indian Metropolitan Cities. Open Journal of Air Pollution, 7, 244-262. https://doi.org/10.4236/ojap.2018.73012