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Trend of atmospheric aerosols over the north western Himalayan region, India
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Atmospheric Environment 39 (2005) 4817–4825 www.elsevier.com/locate/atmosenv
Trend of atmospheric aerosols over the north western Himalayan region, India Khwairakpam Gajanandaa, Jagdish C. Kuniyalb,, G.A. Mominc, P.S.P. Raoc, P.D. Safaic, S. Tiwaric, K. Alic a Environment Protection Division, Shriram Institute for Industrial Research, 19, University Road, Delhi-110 007, India G.B. Pant Institute of Himalayan Environment and Development, Himachal Unit, Mohal-Kullu, Himachal Pradesh-175 126, India c Indian Institute of Tropical Meteorology, Dr. Homi Bhabha Road, Pashan, Pune-411 008, India
b
Received 2 June 2004; accepted 10 January 2005
Abstract Total suspended particulate (TSP), size-separated atmospheric aerosols and aitken nuclei (AN) were monitored at Mohal (Kullu) and Manali tourist complex, in the northwestern part of the Himalayas from 1996 and onwards. Longterm trend analysis for TSP indicated a significant increase since January 1996 to December 2003 at Mohal (Po0:05) and at Manali there is no increase in the TSP level (P ¼ 0:9). The results indicate that the eight years average concentration of TSP at Mohal is 78.4 mg m3 and 66.9 mg m3 at Manali. Seasonal average shows that the TSP is highest during summer (Mohal 90.3 mg m3, P ¼ 0:2; and Manali 74.1 mg m3, P ¼ 0:5) followed by winter season (Mohal 84.3 mg m3, Po0:05; and Manali 71.0 mg m3, P ¼ 0:7). The mass size distribution of aerosols showed bimodal distribution having one peak in fine mode (0.08–2.1 mm) and the other in coarse mode (3.3–10 mm) at both the locations. The highest value of fine size separated aerosol showed the maximum values at 0.43 mm mode. AN (0.001–0.1 mm) density shows fine particles of air pollutants more at low altitude as compared to high altitude. The diurnal variation of AN showed maximum values between 1100 and 1400 h. The daily average concentration of AN at Mohal, Manali and Kothi was found to be 3990, 3200 and 1350 N cm3, respectively. The increasing trend of TSP, high value of size separated aerosols in the fine mode and the peaking of fine particles during noontime are the indication of rising air pollution due to anthropogenic activities in this region. r 2005 Elsevier Ltd. All rights reserved. Keywords: Total suspended particulate; Size-separated aerosols; Aitken nuclei; Air pollution; Kullu
1. Introduction The potential influences of atmospheric pollution on the ecosystems have been recognized long ago (McLaughlin, 1985). Because of the rising anthropoCorresponding author. Tel.: +91 1902 225329; fax: +91 1902 222720. E-mail address: [email protected] (J.C. Kuniyal).
genic interferences for development in the Himalaya, not only the immediate landscape environment, but also the atmospheric environment is adversely affected (Safai et al., 1995; Momin et al., 1999). Aerosols, the major air pollutants, are colloid systems in which matter in liquid or solid phase lies suspended in the gaseous phase of matter called the carrier gas (Kourti and Schatz, 1998). Trace elements released to the atmosphere from anthropogenic sources are the
1352-2310/$ - see front matter r 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.atmosenv.2005.01.038
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prime pollutants that worsen the quality of air and increase the risks to public health (Schroeder et al., 1987; Rizzio et al., 1999). Increasing concentration of tourism activities with inflow of tourists in certain spots of the mountains has resulted in severe cases of localized atmospheric pollution that ultimately adds to global pollution causing many disorders to the health of world population. Nausea, vomiting, irritation in eyes, nose and throat, pains and constriction in the chest with coughing, labored breathing and severe headaches are typical symptoms of exposure to high air pollution episodes (Butler, 1979). Acute respiratory infection, the world over, is the major cause of mortality among children below 5 year of age. It kills 4.3 million children annually and 95% of these live in developing countries (Smith, 1996). The problem of air pollution is aggravated in the developing countries because wood biomass and agricultural waste are the primary sources of household fuel for cooking, heating and lighting in these countries (Caceres and Caceres, 1987; McCracken and Smith, 1998). The present study was initiated in 1994–1995, keeping in view the increasing pressure of tourists and related activities in the western Himalayan ecosystem and to formulate a sustainable tourism plan. The study area namely the Kullu valley is an important tourist destination in western Himalaya. The valley has experienced tremendous growth in tourism over the last decade. Currently, Kullu-Manali tourist complex hosts 100 thousands of tourists per annum (Kuniyal et al., 2003). High numbers of tourist vehicles in summer and biomass burning in winter have primarily influenced the level of air pollutants. As a combined impact of these activities, air pollution increases continuously and raises the concentration of TSP and fine particles (0.1o mm). TSP measurements are the basic and useful indicators to tell the general status of air pollution. Mass size distributions of aerosols unfold the emitting sources of pollution from natural as well as anthropogenic activities. Besides, aitken nuclei (AN) comprise the fine particles that directly reach up to alveoli in the lungs. AN also relates to atmospheric electricity, atmospheric chemistry, air pollution, cloud phenomena and radiative forcing (Rao et al., 1999). Thus, Sampling of TSP from 1996 to 2003, size-separated aerosols (1996, 1998 and 2000) and AN (1996, 1999 and 2000) were carried out at these areas. The present study also described the increasing trend of TSP in the region.
2. Materials and methods Sampling sites around Kullu (native population 18,306 in 2001 census) and Manali (native population 6,265 in 2001 census) tourist spots fall under the Kullu
district that comprise the Beas basin of the hill state of Himachal Pradesh in the northwestern Himalaya. The Kullu valley begins from Larji (957 m in lower Beas basin) and stretches up to Rohtang crest (4038 m under upper Beas basin). The valley is about 80 km long and 2 km wide at maximum, bisected by River Beas and the National Highway (NH)-21, which goes parallel to it. In all the seasons, Mohal has the higher frequency of vehicles due to tourism, festivals and commercial activities. All the vehicles going to Manali pass through Mohal via NH-21. Besides, Mohal experiences less rainfall since it falls in rain shadow zone in rainy season (mid June to August) as compared to Manali. Again, during winter (December to February), very high snowfall occurs at Manali and its adjoining areas, whereas at Mohal, it is negligible. The plying tourist vehicles are also low at Manali during the winter season. The festival of Kullu-Dusshera customarily is celebrated every year in the month of October whose impact remains up to November. Kullu town where Dussehra is celebrated is about 5 km from our monitoring site at Mohal. The numbers of vehicles during these months are very large. Rohtang crest is the upper most part of the Kullu valley. The air sampling locations within the Kullu valley comprise mainly Mohal (1150 m), Manali (2050 m), Jagatsukh (2040 m), Palchan (2320 m) and Kothi (2530 m) (Fig. 1). The average air temperature recorded at Mohal in the year 1 April 2003 to 31 March 2004 is 18.9 1C and the minimum and maximum temperatures recorded are 0.4 and 40.9 1C on 3 February 2004 and 7 June 2003, respectively. The average annual wind speed is 3.03 m s1 and the maximum was recorded to be 31.9 m s1 on 16 June 2003. At Mohal, the wind direction is mostly from 180–2701 sector or say from northwestern direction of the experimental site. The annual average relative humidity is around 68.2% and rainfall about 582 mm. In 1996–1997, Mohal and Manali were the monitoring sites. In 1997–1998, Palchan (2320 m) south to Kothi was the sampling site, which was again shifted to Jagatsukh (2040 m) for 1998–1999. During the years 2000–2003, Mohal and Kothi are the monitoring sites. The overall objective in shifting these sites around Manali and Kullu is to get true background concentration of particulate matters and other air pollutants. 2.1. Total suspended particulate (TSP) TSP was monitored at different altitudinal locations by using high volume air samplers (Envirotech APM415, 430 and 460NL) at a flow rate of 1.2 m3 min1 for a period of 8 to 24 h at each location. These samplings were mostly carried out away from major towns to obtain a true background concentration of aerosols in the ambient air. Minimum 8 h sampling
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Fig. 1. Map of the Kullu District of Himachal Pradesh, India. Locations of the sampling sites are given with MSL.
was set to obtain the TSP sample. The filter paper used for deriving concentration of TSP was Whatman, 20.3 25.4 cm Glass Microfibre Filters (GF/A). Experimental sites for TSP monitoring were kept on moving around major towns or major monitoring sites. For example, at Mohal, two sites were selected. One was at a distance of 100 m away from NH-21 from March 1996
to February 1998. The second monitoring site at Mohal was shifted to the G. B. Pant Institute’s campus since April 1999, which was about 200 m away from direct emission sources of vehicles plying on NH-21. Similarly, TSP experimental sites around major tourist resorts at Manali were keep on shifting at three sites from 1997 to 1999. Since March 1996 to May 1998,
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TSP was monitored within Manali at Hadimba temple and forest rest house. Palchan (2320 m), 10 km away from Manali, was the next experimental site from June 1998 to April 1999. Sampling site was again shifted in June 1999 from Palchan to Jagatsukh (2040 m). This third site is at a distance of 6 km from Manali. The last inhabitable site in the Kullu valley was Kothi, which is about 15 km from Manali and the sampling at this experimental location was done from 2000 to 2003.
2.2. Mass size distribution Sampling of size-separated aerosols was carried out using a Low Volume Air Sampler (Andersen Inc., USA, make), which collects particles on 9 different stages with sizes ranging from o0.08 to 9 mm diameter. These samples were collected on Whatman 41 filter papers of 8 cm diameter. The collections of the particle aerosols were done at the flow rate of about 28.3 L min1. The net aerosol load on the filter papers was determined by weighing the filter papers before and after sampling with a microbalance in humidity-equilibrated environment. The size distributions of the aerosols were taken into two different modes, ‘fine mode’ (0.08 to 2.10 mm diameter) and the ‘coarse mode’ (3.3–9.0 mm diameter). The sampling and analysis were carried out at our Institute’s campus-Mohal, from May to June for three years, i.e., 1996, 1999 and 2000. While the next experimental site to monitor mass size distribution was the last inhabited site of the Kullu valley at Kothi where it was measured only in May–June 2000.
2.3. Aitken nuclei (AN) A portable expansion type counter (Gardener Assoc., USA, make) was used for the measurement of AN concentration in the size range of 0.001 to 0.1 mm radius. Continuous hourly observations of AN were taken at a height of 1 m above the ground level (Momin et al., 2000). Atmospheric air is pumped into a small chamber at a pre-set pressure in ANC and slowly injected into the main chamber containing water vapor. The saturated vapor condenses on the Aitken particles present in the sampled air to form a cloud, which is illuminated by a light source. The scattered light intensity, which is proportional to the number of particles, is measured as the number of droplets per unit volume particles. It unfolds direct analogue display of AN in N cm3 (Rao et al., 1999). The AN sampling and analysis were carried out during May–June of 1996, 1999 and 2000 at Mohal. In 1996 samples were also collected from Manali. The third experimental site to monitor AN was Kothi where it was measured during May-June of 1999 and 2000.
3. Results and discussions 3.1. Total suspended particulates (TSP) Long-term trend analysis for TSP indicated a significant increase from January 1996 to December 2003 at Mohal (Po0:05), but at Manali there is no significant increase in TSP level (P ¼ 0:9) (Fig. 2). Data observed during the last eight years shows that the monthly average concentration of TSP at Mohal was 78.4 mg m3 and at Manali it was 66.9 mg m3. The average seasonal concentrations of TSP show the highest value during summer at Mohal (90.3 mg m3) and Manali (74.1 mg m3) but did not show any significant increase in both the sites (P ¼ 0:2 and P ¼ 0:5). The higher levels of TSP during summer at both the locations may be attributed to the high tourist influx passing through the NH-21. The second highest was observed during the winter season, and interestingly at Mohal (84.3 mg m3) TSP increase significantly (Po0:05). This significant increase in TSP at Mohal during winter may be due to biomass burning, festivities and trucks plying for commercial purposes. On the other hand at Manali (71.0 mg m3) there is no significant increase (P ¼ 0:7) during winter, when tourist influx are low. Also in case of Manali, as the samplings are conducted at three different low populated sites, which are from 6 to 15 km away from the main town, the winter value showed insignificant trend of TSP. In contrast to these, during spring the seasonal average value at Mohal was 61.3 mg m3 (P ¼ 0:4) and Manali 56.8 mg m3 (P ¼ 0:3) whereas during autumn the average value at Mohal was 77.6 mg m3 (P ¼ 0:4) and at Manali it was 65.8 mg m3 (P ¼ 0:09). During spring and monsoon the numbers of tourists were less and the rainfall values were high, thus the seasonal average TSP shows lesser values. TSP was found to be higher in the pre-monsoon than those in the post-monsoon season at Kosi, near a hill tourist town, Almora of Uttaranchal State, India and soil derived aerosols dominated in both the seasons (Safai et al., 1995). In another study by Shrestha et al. (2000), the aerosol concentrations at the Himalayan region of Nepal were low during the second half of the monsoon and post-monsoon seasons and gradually increased during the winter season. The regression analysis of the data for both Mohal and Manali showed that the correlation between these two areas is not so significant (R2 ¼ 0:3) but the ‘P’ value is highly significant (Po0:001), indicating the reliability of the data in both the different altitude areas. In other mountain site of India-Silent valley, core zone of the Nilgri Biosphere Reserve, during three different seasons of 1989–1990 showed 37 mg m3 (Safai et al., 1993), which is below the values reported from our present study. However, recent studies carried out by the Himachal Pradesh Environment Protection & Pollution
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y = 0.5106x - 534.16 R2 = 0.0728 y = 0.021x + 41.769 R2 = 0.0001
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Fig. 2. Long-term trend of total suspended particulate (TSP) matters observed at Mohal and Manali, 1996–2003.
Control Board (HPEPPCB) in four sensitive areas of Himachal Pradesh observed that Shimla has the SPM level of 76.42 mg m3 during November 2002; Parwanoo, 852.04 mg m3 during May 2002; Jassur, 334.40 mg m3 during May 2002; and Paonta Sahib more than 500 mg m3 during the months of April, May, September and November 2002 (Ref. http://hppcb.nic.in/am bient.htm). The inter-seasonal variations always had the high concentrations in summer, which have crossed the threshold limit in the sensitive areas such as KulluManali tourist complex except for 2002 at Manali (22.2 mg m3). The main reason for being high concentration in summer is high vehicular emissions from a large number of tourist vehicles plying on the roads of Kullu-Manali region. TSP concentration during winter is mainly affected due to biomass burning for heating and cooking. Electric supply during this period is irregular due to snowfall. As a result, TSP concentrations crossed its permissible levels at Mohal, showing 104 mg m3 in 1998 and 165.4 mg m3 in 2001. Similarly, TSP concentrations at Manali in winter crossed its threshold limit in 1998 and 2001 showing 126.8 and 164.7 mg m3, respectively. Monsoon is the season when much of the aerosols due to washout effect show low concentrations except at Mohal in 2001 registering 143.3 mg m3. The lowest ever values at Manali for monsoon period came to 25.3 mg m3 in 2003. The lowest value at Mohal during monsoon season was 49.6 mg m3 in 1996.
From the inter-annual data observation, it is observed that the year 2001 had the highest annual average of TSP in both the locations—Mohal (133.1 mg m3) and Manali (134.3 mg m3), compared to other years. These high values of TSP at Mohal and Manali in the year 2001 may be due to road and hotel construction; high vehicular movement and emission along the NH-21; rock and road blown dust; sparse vegetation resulted due to tree felling for road and hotel construction, and biomass burning for cooking and heating during winter snowfall. The SPM concentration was high due to a large number of diesel-powered vehicles plying on the road and resuspension of dust particles (Kumar and Patil, 1993). TSP is also strongly influenced by meteorological conditions like wind velocity and atmospheric stability. Stable atmospheric conditions with a low mixing layer height may result in significantly enhanced TSP concentrations (Kaupp and McLachlan, 1999). This was probably the main reason for higher TSP concentrations measured in February as compared to August. 3.2. Mass size distribution of aerosols Fig. 3 shows a mean plot of mass size distribution of aerosols collected during 1996, 1999 and 2000 for Mohal and the year 2000 only for Kothi. In this figure, the highest concentrations of the total aerosols in the fine modes are in 0.43 mm. The values of 0.43 mm size indicate 41.2 mg m3 (7.8%) at Mohal (low altitude site) and
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56.3 mg m3 (13.7%) at Kothi (high altitude site). Based on the average data of three years at Mohal, aerosols in coarse size range (4.7 mm) denoted 117.0 mg m3 (9.1%) and data for one-year at Kothi shows the value as 48.3 mg m3 (12.2%). Thus, there is a bimodal distribution of the size-separated aerosols. According to Safai et al. (1993), in the Silent valley of Nilgri hills of the Western Ghat region of India, size separated aerosols showed bimodal distribution, with one peak in the coarse mode (2.1 to 3.3 mm) and the another in the fine mode (0.08 to 2 mm), in all the three seasons. The contribution of submicron particles in the Silent valley was higher than that of coarse particles (Safai et al., 1993). The submicron particles contributed 66% and the coarse particles 34% to the total mass of aerosol at the core zone of the Nilgiri Biosphere Reserve (Momin et al., 1990). On an average, out of the total aerosols obtained in these two different modes at Mohal, 45.1% were fine particles whereas 54.9% were coarse. While at Kothi, these size-separated aerosols values remained 59.1% in fine mode and 40.9% in coarse mode. The higher percentage contribution of fine size particles at Kothi may be attributed to (i) higher human interference,
vehicular movement and emission, and higher tourism activities during the sampling months and (ii) higher altitude of Kothi (2530 m asl) than that of Mohal (1150 m asl) because the coarse particles due to their higher density may not be reaching up to the high altitude sampling site. The human interferences at Kothi remained in the form of plying tourist vehicles on the way to snow points such as Rahla Falls and Rohtang Pass during the sampling months of 2000. Fine particles (submicron mode) are produced mainly from anthropogenic sources, and the larger particles (coarse mode) from natural sources (Safai et al., 1993). In India, the mass size distribution of aerosols reveal that coarse particles (natural sources) dominate over the submicron particles (anthropogenic sources) (Khemani, 1993) as in the case of Mohal. Fine aerosols (o1.1 mm) are of main concern in aerosol studies because these aerosols are emitted from anthropogenic activities like industrial, vehicular as well as domestic combustion sources, which are rich in toxic trace metals, polycyclic aromatic hydrocarbons (PAHs) and other carcinogenic organic matters (Agrawal et al., 1990). From the present result, there is an indication that fine particles dominate the coarse mode especially during tourist season, this
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locations. Similarly, Momin et al. (1990) also observed that the diurnal variation of AN at Silent valley peaked in the afternoon period at 1400 h. The AN values at Manali was 4230 N cm3 between 700 and 1200 h during pre-noontime. Kothi has the highest concentration of 1810 N cm3 between 700 and 1300 h. It is important to note here that the concentrations of AN were the lowest between 100 and 600 h at every experimental site of sampling. The high diurnal concentration of AN at Manali and Kothi, relatively at high altitudes, was notable during pre-noontime, which is followed by afternoon and evening. Here, the morning peak is attributed to gas-to-particle conversion processes due to photochemical reactions, the noon could be higher due to high traffic movement, and the evening peak may be due to biomass burning. According to Khemani (1989) AN concentration was at its maximum when solar elevation was at the highest level. Similar behavior was also reported for the diurnal variation of AN concentration at Thumba, Pune, Delhi and Sinhagad (Khemani, 1989). Butler (1979) mentioned that particles less than 10 mm reach beyond the trachea and of these only those between 0.001 and 0.1 mm get as far as the alveoli of human lungs.
may be the sign of increasing human interference in the northwestern part of the Indian Himalayan region. 3.3. Aitken nuclei (AN) Fig. 4 shows the average diurnal variation of AN (0.001–0.1 mm radius) at Mohal (1996, 1999 and 2000), Manali (1996) and Kothi (1999 and 2000). The diurnal variations of AN concentration showed its highest density during daytime when sunshine and traffic pressures remained high. The diurnal concentration of AN at Mohal varied from 900 to 9180 N cm3 with an average of 4352 N cm3, whereas at Kothi these values varied from 370 to 2650 N cm3 with an average of 1392 N cm3. At Manali, the diurnal values showed 180–4880 N cm3. According to Momin et al. (1990), the average concentration of AN at the Silent valley was 1850 N cm3, whereas the average minimum and maximum concentrations were 650 and 5210 N cm3, respectively. However, the average concentration of AN at Thumba was reported 4100 N cm3 (Khemani, 1989). Fig. 4 also shows trimodal distributions with one peak in the morning (700–800 h) and during noontime (1200–1300 h), the other in the evening (1800–2000 h) at all the locations. The 24-h average data of AN derived from these three different locations showed that the concentration was in accordance with altitudinal variations (Fig. 4). The highest diurnal concentration is at the lowest altitude experimental site at Mohal and the lowest is at the highest altitude-sampling site, i.e., Kothi. At Mohal, AN concentrations was 4710 N cm3, which is the highest between 1300 and 1800 h, followed by morning (700–1200 h) and night (1900–2400 h); however, this pattern is slightly different at two other
4. Conclusion The foregoing discussion makes clear that long-term trend analysis of TSP at Mohal has significantly increased since January 1996. The eight years average concentration of TSP at both the observation sites— Mohal and Manali shows 78.4 and 66.9 mg m3, respectively. Average seasonal value was highest at both
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R2 = 0.1752 R2 = 0.0221 R2 = 0.1542
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Fig. 4. Diurnal variation of Aitken Nuclei (AN) at Mohal, Manali and Kothi.
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the locations during summer (Mohal 90.3 mg m3, P ¼ 0:2) followed by winter season, which shows a significant rise in the TSP level (84.3 mg m3, Po0:05) at Mohal. The eight years seasonal averaged values were within the set limit and sometimes greater than the National Ambient Air Quality Standards (NAAQS) laid down for sensitive areas by the Central Pollution Control Board (CPCB) of India and WHO Air Quality Guidelines for long-term (annual) values of 60–90 mg m3. During the year 2001 the level of TSP crossed the NAAQS limit in both the present locations (Mohal and Kothi). The mass size distribution of aerosols at Mohal and Manali showed bimodal distribution with one peak in sub-micron mode and another in coarse mode. Fine particle aerosols dominate the coarse one. This is an indication of increasing human interferences in the region because fine particles are commonly considered to be originating due to human interferences. Concentration of AN (0.001–0.1 mm) varied according to increasing altitudes of the location of experimental sites. The highest concentrations of AN were at Mohal and the lowest at Kothi indicating more respiratory pollution at the former than at the latter site. The diurnal behavior of AN indicated high concentration during daytime, particularly around noontime, when human activities remain in full swing. From the above results, it can be concluded that the level of air pollution over the sensitive area of northwestern part of the Himalaya is increasing due to high anthropogenic activities.
Acknowledgements Authors are thankful to the Directors of G.B. Pant Institute of Himalayan Environment and Development, Kosi-Katarmal, Almora (Uttaranchal) and Indian Institute of Tropical Meteorology, Pune (Maharashtra) for encouraging inter-institutional collaborative research program and providing facilities in respective institutes to complete the study successfully. The first author thanks to Dr. R.K. Khandal, Director, Shriram Institute for Industrial Research, Delhi for encouragement and moral support. The financial assistance by the Department of Science and Technology (DST), Govt. of India, New Delhi to conduct the research (from December 2002 and onwards) for three years is also acknowledged with thanks. The authors are greatly obliged and heartily thank to the anonymous referee to go through the draft manuscript honestly, diligently and critically which could further increase the quality of the scientific contents of the present article.
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Atmospheric Environment 39 (2005) 4817–4825 www.elsevier.com/locate/atmosenv
Trend of atmospheric aerosols over the north western Himalayan region, India Khwairakpam Gajanandaa, Jagdish C. Kuniyalb,, G.A. Mominc, P.S.P. Raoc, P.D. Safaic, S. Tiwaric, K. Alic a Environment Protection Division, Shriram Institute for Industrial Research, 19, University Road, Delhi-110 007, India G.B. Pant Institute of Himalayan Environment and Development, Himachal Unit, Mohal-Kullu, Himachal Pradesh-175 126, India c Indian Institute of Tropical Meteorology, Dr. Homi Bhabha Road, Pashan, Pune-411 008, India
b
Received 2 June 2004; accepted 10 January 2005
Abstract Total suspended particulate (TSP), size-separated atmospheric aerosols and aitken nuclei (AN) were monitored at Mohal (Kullu) and Manali tourist complex, in the northwestern part of the Himalayas from 1996 and onwards. Longterm trend analysis for TSP indicated a significant increase since January 1996 to December 2003 at Mohal (Po0:05) and at Manali there is no increase in the TSP level (P ¼ 0:9). The results indicate that the eight years average concentration of TSP at Mohal is 78.4 mg m3 and 66.9 mg m3 at Manali. Seasonal average shows that the TSP is highest during summer (Mohal 90.3 mg m3, P ¼ 0:2; and Manali 74.1 mg m3, P ¼ 0:5) followed by winter season (Mohal 84.3 mg m3, Po0:05; and Manali 71.0 mg m3, P ¼ 0:7). The mass size distribution of aerosols showed bimodal distribution having one peak in fine mode (0.08–2.1 mm) and the other in coarse mode (3.3–10 mm) at both the locations. The highest value of fine size separated aerosol showed the maximum values at 0.43 mm mode. AN (0.001–0.1 mm) density shows fine particles of air pollutants more at low altitude as compared to high altitude. The diurnal variation of AN showed maximum values between 1100 and 1400 h. The daily average concentration of AN at Mohal, Manali and Kothi was found to be 3990, 3200 and 1350 N cm3, respectively. The increasing trend of TSP, high value of size separated aerosols in the fine mode and the peaking of fine particles during noontime are the indication of rising air pollution due to anthropogenic activities in this region. r 2005 Elsevier Ltd. All rights reserved. Keywords: Total suspended particulate; Size-separated aerosols; Aitken nuclei; Air pollution; Kullu
1. Introduction The potential influences of atmospheric pollution on the ecosystems have been recognized long ago (McLaughlin, 1985). Because of the rising anthropoCorresponding author. Tel.: +91 1902 225329; fax: +91 1902 222720. E-mail address: [email protected] (J.C. Kuniyal).
genic interferences for development in the Himalaya, not only the immediate landscape environment, but also the atmospheric environment is adversely affected (Safai et al., 1995; Momin et al., 1999). Aerosols, the major air pollutants, are colloid systems in which matter in liquid or solid phase lies suspended in the gaseous phase of matter called the carrier gas (Kourti and Schatz, 1998). Trace elements released to the atmosphere from anthropogenic sources are the
1352-2310/$ - see front matter r 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.atmosenv.2005.01.038
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prime pollutants that worsen the quality of air and increase the risks to public health (Schroeder et al., 1987; Rizzio et al., 1999). Increasing concentration of tourism activities with inflow of tourists in certain spots of the mountains has resulted in severe cases of localized atmospheric pollution that ultimately adds to global pollution causing many disorders to the health of world population. Nausea, vomiting, irritation in eyes, nose and throat, pains and constriction in the chest with coughing, labored breathing and severe headaches are typical symptoms of exposure to high air pollution episodes (Butler, 1979). Acute respiratory infection, the world over, is the major cause of mortality among children below 5 year of age. It kills 4.3 million children annually and 95% of these live in developing countries (Smith, 1996). The problem of air pollution is aggravated in the developing countries because wood biomass and agricultural waste are the primary sources of household fuel for cooking, heating and lighting in these countries (Caceres and Caceres, 1987; McCracken and Smith, 1998). The present study was initiated in 1994–1995, keeping in view the increasing pressure of tourists and related activities in the western Himalayan ecosystem and to formulate a sustainable tourism plan. The study area namely the Kullu valley is an important tourist destination in western Himalaya. The valley has experienced tremendous growth in tourism over the last decade. Currently, Kullu-Manali tourist complex hosts 100 thousands of tourists per annum (Kuniyal et al., 2003). High numbers of tourist vehicles in summer and biomass burning in winter have primarily influenced the level of air pollutants. As a combined impact of these activities, air pollution increases continuously and raises the concentration of TSP and fine particles (0.1o mm). TSP measurements are the basic and useful indicators to tell the general status of air pollution. Mass size distributions of aerosols unfold the emitting sources of pollution from natural as well as anthropogenic activities. Besides, aitken nuclei (AN) comprise the fine particles that directly reach up to alveoli in the lungs. AN also relates to atmospheric electricity, atmospheric chemistry, air pollution, cloud phenomena and radiative forcing (Rao et al., 1999). Thus, Sampling of TSP from 1996 to 2003, size-separated aerosols (1996, 1998 and 2000) and AN (1996, 1999 and 2000) were carried out at these areas. The present study also described the increasing trend of TSP in the region.
2. Materials and methods Sampling sites around Kullu (native population 18,306 in 2001 census) and Manali (native population 6,265 in 2001 census) tourist spots fall under the Kullu
district that comprise the Beas basin of the hill state of Himachal Pradesh in the northwestern Himalaya. The Kullu valley begins from Larji (957 m in lower Beas basin) and stretches up to Rohtang crest (4038 m under upper Beas basin). The valley is about 80 km long and 2 km wide at maximum, bisected by River Beas and the National Highway (NH)-21, which goes parallel to it. In all the seasons, Mohal has the higher frequency of vehicles due to tourism, festivals and commercial activities. All the vehicles going to Manali pass through Mohal via NH-21. Besides, Mohal experiences less rainfall since it falls in rain shadow zone in rainy season (mid June to August) as compared to Manali. Again, during winter (December to February), very high snowfall occurs at Manali and its adjoining areas, whereas at Mohal, it is negligible. The plying tourist vehicles are also low at Manali during the winter season. The festival of Kullu-Dusshera customarily is celebrated every year in the month of October whose impact remains up to November. Kullu town where Dussehra is celebrated is about 5 km from our monitoring site at Mohal. The numbers of vehicles during these months are very large. Rohtang crest is the upper most part of the Kullu valley. The air sampling locations within the Kullu valley comprise mainly Mohal (1150 m), Manali (2050 m), Jagatsukh (2040 m), Palchan (2320 m) and Kothi (2530 m) (Fig. 1). The average air temperature recorded at Mohal in the year 1 April 2003 to 31 March 2004 is 18.9 1C and the minimum and maximum temperatures recorded are 0.4 and 40.9 1C on 3 February 2004 and 7 June 2003, respectively. The average annual wind speed is 3.03 m s1 and the maximum was recorded to be 31.9 m s1 on 16 June 2003. At Mohal, the wind direction is mostly from 180–2701 sector or say from northwestern direction of the experimental site. The annual average relative humidity is around 68.2% and rainfall about 582 mm. In 1996–1997, Mohal and Manali were the monitoring sites. In 1997–1998, Palchan (2320 m) south to Kothi was the sampling site, which was again shifted to Jagatsukh (2040 m) for 1998–1999. During the years 2000–2003, Mohal and Kothi are the monitoring sites. The overall objective in shifting these sites around Manali and Kullu is to get true background concentration of particulate matters and other air pollutants. 2.1. Total suspended particulate (TSP) TSP was monitored at different altitudinal locations by using high volume air samplers (Envirotech APM415, 430 and 460NL) at a flow rate of 1.2 m3 min1 for a period of 8 to 24 h at each location. These samplings were mostly carried out away from major towns to obtain a true background concentration of aerosols in the ambient air. Minimum 8 h sampling
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Fig. 1. Map of the Kullu District of Himachal Pradesh, India. Locations of the sampling sites are given with MSL.
was set to obtain the TSP sample. The filter paper used for deriving concentration of TSP was Whatman, 20.3 25.4 cm Glass Microfibre Filters (GF/A). Experimental sites for TSP monitoring were kept on moving around major towns or major monitoring sites. For example, at Mohal, two sites were selected. One was at a distance of 100 m away from NH-21 from March 1996
to February 1998. The second monitoring site at Mohal was shifted to the G. B. Pant Institute’s campus since April 1999, which was about 200 m away from direct emission sources of vehicles plying on NH-21. Similarly, TSP experimental sites around major tourist resorts at Manali were keep on shifting at three sites from 1997 to 1999. Since March 1996 to May 1998,
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TSP was monitored within Manali at Hadimba temple and forest rest house. Palchan (2320 m), 10 km away from Manali, was the next experimental site from June 1998 to April 1999. Sampling site was again shifted in June 1999 from Palchan to Jagatsukh (2040 m). This third site is at a distance of 6 km from Manali. The last inhabitable site in the Kullu valley was Kothi, which is about 15 km from Manali and the sampling at this experimental location was done from 2000 to 2003.
2.2. Mass size distribution Sampling of size-separated aerosols was carried out using a Low Volume Air Sampler (Andersen Inc., USA, make), which collects particles on 9 different stages with sizes ranging from o0.08 to 9 mm diameter. These samples were collected on Whatman 41 filter papers of 8 cm diameter. The collections of the particle aerosols were done at the flow rate of about 28.3 L min1. The net aerosol load on the filter papers was determined by weighing the filter papers before and after sampling with a microbalance in humidity-equilibrated environment. The size distributions of the aerosols were taken into two different modes, ‘fine mode’ (0.08 to 2.10 mm diameter) and the ‘coarse mode’ (3.3–9.0 mm diameter). The sampling and analysis were carried out at our Institute’s campus-Mohal, from May to June for three years, i.e., 1996, 1999 and 2000. While the next experimental site to monitor mass size distribution was the last inhabited site of the Kullu valley at Kothi where it was measured only in May–June 2000.
2.3. Aitken nuclei (AN) A portable expansion type counter (Gardener Assoc., USA, make) was used for the measurement of AN concentration in the size range of 0.001 to 0.1 mm radius. Continuous hourly observations of AN were taken at a height of 1 m above the ground level (Momin et al., 2000). Atmospheric air is pumped into a small chamber at a pre-set pressure in ANC and slowly injected into the main chamber containing water vapor. The saturated vapor condenses on the Aitken particles present in the sampled air to form a cloud, which is illuminated by a light source. The scattered light intensity, which is proportional to the number of particles, is measured as the number of droplets per unit volume particles. It unfolds direct analogue display of AN in N cm3 (Rao et al., 1999). The AN sampling and analysis were carried out during May–June of 1996, 1999 and 2000 at Mohal. In 1996 samples were also collected from Manali. The third experimental site to monitor AN was Kothi where it was measured during May-June of 1999 and 2000.
3. Results and discussions 3.1. Total suspended particulates (TSP) Long-term trend analysis for TSP indicated a significant increase from January 1996 to December 2003 at Mohal (Po0:05), but at Manali there is no significant increase in TSP level (P ¼ 0:9) (Fig. 2). Data observed during the last eight years shows that the monthly average concentration of TSP at Mohal was 78.4 mg m3 and at Manali it was 66.9 mg m3. The average seasonal concentrations of TSP show the highest value during summer at Mohal (90.3 mg m3) and Manali (74.1 mg m3) but did not show any significant increase in both the sites (P ¼ 0:2 and P ¼ 0:5). The higher levels of TSP during summer at both the locations may be attributed to the high tourist influx passing through the NH-21. The second highest was observed during the winter season, and interestingly at Mohal (84.3 mg m3) TSP increase significantly (Po0:05). This significant increase in TSP at Mohal during winter may be due to biomass burning, festivities and trucks plying for commercial purposes. On the other hand at Manali (71.0 mg m3) there is no significant increase (P ¼ 0:7) during winter, when tourist influx are low. Also in case of Manali, as the samplings are conducted at three different low populated sites, which are from 6 to 15 km away from the main town, the winter value showed insignificant trend of TSP. In contrast to these, during spring the seasonal average value at Mohal was 61.3 mg m3 (P ¼ 0:4) and Manali 56.8 mg m3 (P ¼ 0:3) whereas during autumn the average value at Mohal was 77.6 mg m3 (P ¼ 0:4) and at Manali it was 65.8 mg m3 (P ¼ 0:09). During spring and monsoon the numbers of tourists were less and the rainfall values were high, thus the seasonal average TSP shows lesser values. TSP was found to be higher in the pre-monsoon than those in the post-monsoon season at Kosi, near a hill tourist town, Almora of Uttaranchal State, India and soil derived aerosols dominated in both the seasons (Safai et al., 1995). In another study by Shrestha et al. (2000), the aerosol concentrations at the Himalayan region of Nepal were low during the second half of the monsoon and post-monsoon seasons and gradually increased during the winter season. The regression analysis of the data for both Mohal and Manali showed that the correlation between these two areas is not so significant (R2 ¼ 0:3) but the ‘P’ value is highly significant (Po0:001), indicating the reliability of the data in both the different altitude areas. In other mountain site of India-Silent valley, core zone of the Nilgri Biosphere Reserve, during three different seasons of 1989–1990 showed 37 mg m3 (Safai et al., 1993), which is below the values reported from our present study. However, recent studies carried out by the Himachal Pradesh Environment Protection & Pollution
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Fig. 2. Long-term trend of total suspended particulate (TSP) matters observed at Mohal and Manali, 1996–2003.
Control Board (HPEPPCB) in four sensitive areas of Himachal Pradesh observed that Shimla has the SPM level of 76.42 mg m3 during November 2002; Parwanoo, 852.04 mg m3 during May 2002; Jassur, 334.40 mg m3 during May 2002; and Paonta Sahib more than 500 mg m3 during the months of April, May, September and November 2002 (Ref. http://hppcb.nic.in/am bient.htm). The inter-seasonal variations always had the high concentrations in summer, which have crossed the threshold limit in the sensitive areas such as KulluManali tourist complex except for 2002 at Manali (22.2 mg m3). The main reason for being high concentration in summer is high vehicular emissions from a large number of tourist vehicles plying on the roads of Kullu-Manali region. TSP concentration during winter is mainly affected due to biomass burning for heating and cooking. Electric supply during this period is irregular due to snowfall. As a result, TSP concentrations crossed its permissible levels at Mohal, showing 104 mg m3 in 1998 and 165.4 mg m3 in 2001. Similarly, TSP concentrations at Manali in winter crossed its threshold limit in 1998 and 2001 showing 126.8 and 164.7 mg m3, respectively. Monsoon is the season when much of the aerosols due to washout effect show low concentrations except at Mohal in 2001 registering 143.3 mg m3. The lowest ever values at Manali for monsoon period came to 25.3 mg m3 in 2003. The lowest value at Mohal during monsoon season was 49.6 mg m3 in 1996.
From the inter-annual data observation, it is observed that the year 2001 had the highest annual average of TSP in both the locations—Mohal (133.1 mg m3) and Manali (134.3 mg m3), compared to other years. These high values of TSP at Mohal and Manali in the year 2001 may be due to road and hotel construction; high vehicular movement and emission along the NH-21; rock and road blown dust; sparse vegetation resulted due to tree felling for road and hotel construction, and biomass burning for cooking and heating during winter snowfall. The SPM concentration was high due to a large number of diesel-powered vehicles plying on the road and resuspension of dust particles (Kumar and Patil, 1993). TSP is also strongly influenced by meteorological conditions like wind velocity and atmospheric stability. Stable atmospheric conditions with a low mixing layer height may result in significantly enhanced TSP concentrations (Kaupp and McLachlan, 1999). This was probably the main reason for higher TSP concentrations measured in February as compared to August. 3.2. Mass size distribution of aerosols Fig. 3 shows a mean plot of mass size distribution of aerosols collected during 1996, 1999 and 2000 for Mohal and the year 2000 only for Kothi. In this figure, the highest concentrations of the total aerosols in the fine modes are in 0.43 mm. The values of 0.43 mm size indicate 41.2 mg m3 (7.8%) at Mohal (low altitude site) and
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56.3 mg m3 (13.7%) at Kothi (high altitude site). Based on the average data of three years at Mohal, aerosols in coarse size range (4.7 mm) denoted 117.0 mg m3 (9.1%) and data for one-year at Kothi shows the value as 48.3 mg m3 (12.2%). Thus, there is a bimodal distribution of the size-separated aerosols. According to Safai et al. (1993), in the Silent valley of Nilgri hills of the Western Ghat region of India, size separated aerosols showed bimodal distribution, with one peak in the coarse mode (2.1 to 3.3 mm) and the another in the fine mode (0.08 to 2 mm), in all the three seasons. The contribution of submicron particles in the Silent valley was higher than that of coarse particles (Safai et al., 1993). The submicron particles contributed 66% and the coarse particles 34% to the total mass of aerosol at the core zone of the Nilgiri Biosphere Reserve (Momin et al., 1990). On an average, out of the total aerosols obtained in these two different modes at Mohal, 45.1% were fine particles whereas 54.9% were coarse. While at Kothi, these size-separated aerosols values remained 59.1% in fine mode and 40.9% in coarse mode. The higher percentage contribution of fine size particles at Kothi may be attributed to (i) higher human interference,
vehicular movement and emission, and higher tourism activities during the sampling months and (ii) higher altitude of Kothi (2530 m asl) than that of Mohal (1150 m asl) because the coarse particles due to their higher density may not be reaching up to the high altitude sampling site. The human interferences at Kothi remained in the form of plying tourist vehicles on the way to snow points such as Rahla Falls and Rohtang Pass during the sampling months of 2000. Fine particles (submicron mode) are produced mainly from anthropogenic sources, and the larger particles (coarse mode) from natural sources (Safai et al., 1993). In India, the mass size distribution of aerosols reveal that coarse particles (natural sources) dominate over the submicron particles (anthropogenic sources) (Khemani, 1993) as in the case of Mohal. Fine aerosols (o1.1 mm) are of main concern in aerosol studies because these aerosols are emitted from anthropogenic activities like industrial, vehicular as well as domestic combustion sources, which are rich in toxic trace metals, polycyclic aromatic hydrocarbons (PAHs) and other carcinogenic organic matters (Agrawal et al., 1990). From the present result, there is an indication that fine particles dominate the coarse mode especially during tourist season, this
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locations. Similarly, Momin et al. (1990) also observed that the diurnal variation of AN at Silent valley peaked in the afternoon period at 1400 h. The AN values at Manali was 4230 N cm3 between 700 and 1200 h during pre-noontime. Kothi has the highest concentration of 1810 N cm3 between 700 and 1300 h. It is important to note here that the concentrations of AN were the lowest between 100 and 600 h at every experimental site of sampling. The high diurnal concentration of AN at Manali and Kothi, relatively at high altitudes, was notable during pre-noontime, which is followed by afternoon and evening. Here, the morning peak is attributed to gas-to-particle conversion processes due to photochemical reactions, the noon could be higher due to high traffic movement, and the evening peak may be due to biomass burning. According to Khemani (1989) AN concentration was at its maximum when solar elevation was at the highest level. Similar behavior was also reported for the diurnal variation of AN concentration at Thumba, Pune, Delhi and Sinhagad (Khemani, 1989). Butler (1979) mentioned that particles less than 10 mm reach beyond the trachea and of these only those between 0.001 and 0.1 mm get as far as the alveoli of human lungs.
may be the sign of increasing human interference in the northwestern part of the Indian Himalayan region. 3.3. Aitken nuclei (AN) Fig. 4 shows the average diurnal variation of AN (0.001–0.1 mm radius) at Mohal (1996, 1999 and 2000), Manali (1996) and Kothi (1999 and 2000). The diurnal variations of AN concentration showed its highest density during daytime when sunshine and traffic pressures remained high. The diurnal concentration of AN at Mohal varied from 900 to 9180 N cm3 with an average of 4352 N cm3, whereas at Kothi these values varied from 370 to 2650 N cm3 with an average of 1392 N cm3. At Manali, the diurnal values showed 180–4880 N cm3. According to Momin et al. (1990), the average concentration of AN at the Silent valley was 1850 N cm3, whereas the average minimum and maximum concentrations were 650 and 5210 N cm3, respectively. However, the average concentration of AN at Thumba was reported 4100 N cm3 (Khemani, 1989). Fig. 4 also shows trimodal distributions with one peak in the morning (700–800 h) and during noontime (1200–1300 h), the other in the evening (1800–2000 h) at all the locations. The 24-h average data of AN derived from these three different locations showed that the concentration was in accordance with altitudinal variations (Fig. 4). The highest diurnal concentration is at the lowest altitude experimental site at Mohal and the lowest is at the highest altitude-sampling site, i.e., Kothi. At Mohal, AN concentrations was 4710 N cm3, which is the highest between 1300 and 1800 h, followed by morning (700–1200 h) and night (1900–2400 h); however, this pattern is slightly different at two other
4. Conclusion The foregoing discussion makes clear that long-term trend analysis of TSP at Mohal has significantly increased since January 1996. The eight years average concentration of TSP at both the observation sites— Mohal and Manali shows 78.4 and 66.9 mg m3, respectively. Average seasonal value was highest at both
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the locations during summer (Mohal 90.3 mg m3, P ¼ 0:2) followed by winter season, which shows a significant rise in the TSP level (84.3 mg m3, Po0:05) at Mohal. The eight years seasonal averaged values were within the set limit and sometimes greater than the National Ambient Air Quality Standards (NAAQS) laid down for sensitive areas by the Central Pollution Control Board (CPCB) of India and WHO Air Quality Guidelines for long-term (annual) values of 60–90 mg m3. During the year 2001 the level of TSP crossed the NAAQS limit in both the present locations (Mohal and Kothi). The mass size distribution of aerosols at Mohal and Manali showed bimodal distribution with one peak in sub-micron mode and another in coarse mode. Fine particle aerosols dominate the coarse one. This is an indication of increasing human interferences in the region because fine particles are commonly considered to be originating due to human interferences. Concentration of AN (0.001–0.1 mm) varied according to increasing altitudes of the location of experimental sites. The highest concentrations of AN were at Mohal and the lowest at Kothi indicating more respiratory pollution at the former than at the latter site. The diurnal behavior of AN indicated high concentration during daytime, particularly around noontime, when human activities remain in full swing. From the above results, it can be concluded that the level of air pollution over the sensitive area of northwestern part of the Himalaya is increasing due to high anthropogenic activities.
Acknowledgements Authors are thankful to the Directors of G.B. Pant Institute of Himalayan Environment and Development, Kosi-Katarmal, Almora (Uttaranchal) and Indian Institute of Tropical Meteorology, Pune (Maharashtra) for encouraging inter-institutional collaborative research program and providing facilities in respective institutes to complete the study successfully. The first author thanks to Dr. R.K. Khandal, Director, Shriram Institute for Industrial Research, Delhi for encouragement and moral support. The financial assistance by the Department of Science and Technology (DST), Govt. of India, New Delhi to conduct the research (from December 2002 and onwards) for three years is also acknowledged with thanks. The authors are greatly obliged and heartily thank to the anonymous referee to go through the draft manuscript honestly, diligently and critically which could further increase the quality of the scientific contents of the present article.
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