Impact of anthropogenic activity and cyclonic storm on black carbon during winter at a tropical urban city, Pune
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- Raju, M.P., Safai, P.D., Rao, P.S.P. et al. Nat Hazards (2014) 71: 881. doi:10.1007/s11069-013-0937-y
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Black carbon (BC) aerosols are emitted into the atmosphere as a byproduct of different combustion processes and are reported to be a very strong absorber of solar radiation. In this paper, we present results on BC aerosols over Pune, a tropical urban city in south west India during Diwali festival in the month of November 2010. Daily mean BC showed about 5 % increase on Diwali day compared with preceding and succeeding period with concentrations reaching as high as about 21 μg/m3 in the morning on Diwali day, mainly due to the influence of extensive fireworks. However, the strong winds accompanied by occasional rainfall due to severe cyclonic storm “Jal” formed in the Bay of Bengal on the same day dampened this effect and reduced BC to about 2 μg/m3 within 6 h. There was only 5 % increase in mean BC concentration on Diwali day during 2010 as compared to the average increase of about 17 % during preceding 4 years on Diwali day, mainly due to the impact of weather conditions induced by Jal.
KeywordsBC aerosolsDiwali festivalDiurnal variationLong-range transportSevere cyclonic storm “Jal”
Black carbon (BC), the light absorbing fraction of carbonaceous aerosols, mainly originates from combustion sources, has complex climatic implications involving atmospheric heating and surface cooling (Ramanathan et al. 2001). The main sources of BC in the atmosphere are forest fires and anthropogenic combustion processes such as power generation, vehicular emission, residential heating and biomass burning for agricultural or domestic purposes. The total amount of BC released into the atmosphere from all sources is estimated to be around 6–30 × 1012 g/year (Crutzen and Andreae 1990). Freshly emitted BC is mostly hydrophobic and eventually becomes hydrophilic by oxidation or coating with sulfate and organics (Liousse et al. 1993). It has become evident that BC aerosols, emitted from combustion, can be carried far away to thousands of kilometers from source regions. Typical concentrations of BC range from 3 to 10 μg/m3 in urban areas, 0.1–1 μg/m3 in rural areas and 0.001–0.1 μg/m3 in remote regions. The highest concentrations (>10 μg/m3) occur over densely populated continental regions, and the mass fraction of BC in urban aerosols is typically a few percent (Heintzenberg and Winkler 1984). Due to its high absorbing potential, BC is reported to be the second largest contributor to global warming, after green house gas CO2 (Jacobson 2002).
Normally, BC is inert in ambient atmosphere as it is insoluble in polar and non-polar solvents and is stable in air or oxygen at temperatures up to approximately 350–400 °C. However, due to its great porosity, it has the ability to adsorb other species from the vapor phase, especially organics. BC particles are usually small enough (≤1 μm size) to be readily inhaled and further get deposited in the lungs or other airways. They may act as vehicles for the transport and localized deposition of harmful compounds to the human pulmonary system. Epidemiological studies provide sufficient evidence of the association of cardiopulmonary morbidity and mortality with BC exposure. The review of the toxicological studies suggested that BC may not be directly a major toxic component of fine particulate matter, but it may operate as a universal carrier of a wide variety of chemicals of varying toxicity to the lungs, the body’s major defense cells and possibly the systemic blood circulation (WHO 2012).
Several studies on BC aerosols over the Indian region have been reported in the recent years (Babu and Moorthy 2002; Badarinath et al. 2009; Pant et al. 2006; Tiwari et al. 2012; Ram et al. 2010; Ramachandran and Rajesh 2007; Safai et al. 2007, 2008, 2010; Dumka et al. 2010; Das et al. 2009; Raghavendra Kumar et al. 2011; Beegum et al. 2009; Raju et al. 2011). However, studies on BC emissions during intense combustion activities like burning of crackers, especially during Diwali festival are very few (Babu and Moorthy 2001; Tiwari et al. 2009). Diwali/Deepawali, also known as the “Festival of Lights” is a major Indian festival. It usually falls in the post-monsoon/winter period in the months of October/November, and is one of the most popular and widely celebrated festivals in India. During this festival, extensive display of fireworks is observed. High concentrations of anthropogenic particulate and gaseous components are injected into the atmosphere due to burning of crackers and fireworks. Fireworks mainly contain chemicals such as arsenic, sulfur, manganese, sodium oxalate, aluminum and iron dust powder, potassium perchlorate, strontium nitrate, barium nitrate and charcoal (Mclain 1980; Wang et al. 2007). In addition, burning of fireworks releases pollutants such as sulfur dioxide (SO2), carbon dioxide (CO2), carbon monoxide (CO), suspended particles (including particles below 10 μm in diameter, i.e., PM10) and several metals such as aluminum, manganese and cadmium, which are associated with serious health hazards (Hirai et al. 2000). Bach et al. (1975) reported an increase in total suspended particulate matter (TSPM) on an average of 300 % at 14 locations and by 700 % in the lung penetrating size ranges at one location due to fireworks on New Year’s Eve. Increase in particle number is witnessed in the accumulation mode range (100 nm) during the millennium fireworks in Leipzig, Germany (Wehner et al. 2000). Liu et al. (1997) reported the chemical composition and particle size of typical firework mixtures. BC increased by a factor of three (Babu and Moorthy 2001), and SO2, NO2, PM10 and TSP showed an increase by 2–10 times (Ravindra et al. 2003) during Diwali. Several interesting results are reported in literature related to Diwali fireworks over different parts of India (Ravindra et al. 2003; Agarwal et al. 2006; Barman et al. 2008; Kakoli and Gupta 2007; Singh et al. 2003). Babu and Moorthy (2001) observed a large increase in carbon particles after Diwali festival in Thiruvananthapuram. Tiwari et al. (2012) have reported the impact of firecracker burning on aerosol and gaseous pollutants in Delhi. Mass ratios of BC and aromatic organic carbon are reported to be highest on the day of Diwali and a day before Diwali event, proving the festival to be a major carbon intensive event (Agrawal et al. 2011). However, all the above-mentioned studies report excess BC concentrations during Diwali, whereas the present study reports both enhancement and reduction in BC at Pune during Diwali (except on Diwali day) due to the effect of a cyclonic storm over this region during the Diwali period of 2010.
2 Location of the experimental site
The city of Pune is situated in the leeward side of the Western Ghats. It is about 100 km to the east of Arabian Sea. BC mass concentrations were monitored during Diwali festival from November 1–10, 2010 at Pashan, a semi-urban region in Pune city. Anthropogenic activities, such as brick making in the nearby surroundings, are also one of the causes of pollution. The current population of Pune urban agglomerate is over 4 million. Pune receives annual rainfall at an average of 76 cm. Almost 80 % of the annual rainfall takes place during monsoon (June–September). During post-monsoon/winter, winds are normally from east-north-east crossing across the northeast and central India, and dispersion of particulate pollutants is comparatively less due to the low ventilation coefficients.
3 Methodology of BC sampling
BC observations during the period of 10 days (November 1–10, 2010) are studied at Pune (18°32′N, 73°51′E, 559 m AMSL). Also for the sake of comparison, past BC observations from the same location during Diwali period have been used. Continuous observations of BC were carried out using an aethalometer (Magee Sci., Inc., USA, Model AE-42). The principle of aethalometer is to measure the attenuation of light beam at 880 nm wavelength (Hansen et al. 1984). In this method, atmospheric air is pumped through an inlet with a flow rate set for 3 LPM, which impinges on a quartz microfiber strip. The light beam from a high-intensity LED lamp is then transmitted through the sample deposit on the filter strip. The measurement of the attenuation (ATN) of light beam is linearly proportional to the amount of BC deposited on filter strip. The time base for each observation was set at 5 min. The filter-based absorption technique used in aethalometer is reported to have shown good comparison with the other methods used for monitoring of BC particles (Allen et al. 1999; Babich et al. 2000). Operational principal and detailed description of the instrument can be found at www.mageesci.com.
It is observed that the BC concentrations obtained using an aethalometer apparently rise after the filter tape advances, and therefore, the relationship between ATN change and BC concentration is not linear, and as the ATN increases, the measured BC concentration becomes underestimated (Weingartner et al. 2003; Arnott et al. 2005). This loading effect should be taken into account when using empirical correction algorithms. In order to account for this effect, we have used the correction algorithm presented by Virkkula et al. (2007) and also employed by Park et al. (2010) and Raju et al. (2011).
4 Results and discussions
4.1 Temporal variations in BC during Diwali festival and effects of severe cyclone “Jal”
Statistical details of BC mass concentration (μg/m3) before, during and after Diwali day and during Diwali Month at Pune during 2010 as compared with earlier years
BC before Diwali
BC on Diwali
BC after Diwali
BC in Diwali Month
4.83 ± 2.05
6.15 ± 2.88
5.85 ± 3.14
7.86 ± 2.55
2.80 ± 1.85
3.14 ± 1.62
2.94 ± 2.14
3.57 ± 1.38
4.35 ± 2.88
4.95 ± 2.56
4.47 ± 2.33
5.11 ± 2.18
1.10 ± 0.83
2.86 ± 1.56
2.70 ± 1.94
3.38 ± 1.33
7.30 ± 3.31
7.45 ± 4.30
6.81 ± 2.48
8.25 ± 2.90
4.2 Diurnal variation in BC during Diwali
Thus, Diwali day during 2010 experienced impact of burning of fire crackers as well as wet deposition due to rains that resulted from severe cyclonic storm Jal over BoB. This is clearly demonstrated in Fig. 5b, which shows hourly BC variation on Diwali day (5 November) in comparison with that observed before Diwali day (1–4 November) and after Diwali day (6–9 November). BC concentrations were significantly high on Diwali day in the morning hours due to extensive burning of fire crackers but on the same day due to combined effect of high winds and rains; concentrations of BC sharply decreased after morning peak and were persistently low till the end of the day, though BC concentrations showed increase after 1500 hours and reached to another peak in the late night hours (the second peak on Diwali day was comparatively low by about 2 μg/m3 than that observed on preceding and succeeding days).
4.3 Comparative study of BC with earlier observations at Pune during Diwali
One would expect less BC concentrations during Diwali 2010 compared to earlier year Diwali days due to Jal effect; however, the mean BC during 2010 was observed to be more in before, during and after Diwali as compared to earlier years. In fact, as seen from Table 1, mean BC during Diwali month was also more in 2010 as compared to earlier years. This indicates that not only the increase in fireworks activity in 2010 (which could not be quantified due to lack of data on fireworks burning activity for these all years) but also the increase in vehicular emissions due to increase in number of vehicles in Pune city could have contributed to the mean BC concentration during this period. Incomplete combustion in vehicular emissions is reported to be a major local source for BC, and the number of two wheelers is ever increasing in Pune (Safai et al. 2013).
Concentrations of BC aerosols were studied over Pune during the Diwali festival in 2010. Normally, BC concentrations are observed to be high during Diwali or on increasing trend during this period because of transition from post-monsoon to winter season. The daily mean BC concentration on Diwali day was 5 % more than preceding and succeeding days in 2010, whereas in earlier years, this increase was observed to be around 17 %. The dilution of BC concentration during the Diwali week in 2010 was mainly attributed to the high winds and occasional rains due to the severe cyclonic system Jal. In spite of the unfavorable meteorological conditions due to the cyclonic storm, the effect of cracker-burning was observed to overcome it, especially during the period when the fireworks activity was intensive in the night preceding Diwali day through the morning on the Diwali day. Thus, the Diwali day in 2010 witnessed effects of both source and sink mechanism on BC over Pune.
Authors are thankful to the Director, Indian Institute of Tropical Meteorology, Pune for encouragement to undertake this work. Authors are also thankful to the ISRO-GBP/ARFI, Department of Space, Government of India for providing financial support.