Indion Journal of Radio & Space Phys ic, Vol. 34. Oc tobcr 2005. pp.:B2-340

Aerosols behaviour in sensitive areas of the northwestern Himalaya-­A case of Kullu-Manali tourist complex, India

Jagdish C Kuniyal

G. B. P~lIll Instillltt? of Himalayan Em ironmt?nt and Dl:VL'lopment. Il imClchal Unit. Mohal-Kul lu (I .JP ) 175 I ~6. Indi a

E-mails:~u ni ya ljc @yahoo.com/jckuniya l @redifTmai l.com

and

G A MOlllin. P S P Rao. PO Safai. S Tiwari & K Ali

Indian Institute of Tropi cal M eteoro logy . Dr Homi I3habha Road. Pashan. Pune 41 10m:. India

and

Khwai rakpalll Gajananda

Shriralllinstillite for Industrial Resea rch. Env ironment Protccti on Di vision. 1<). Uni versity Roaci. Delhi liD 007. India

Rel'<!il'ed.f Jlllle 2()O.f; rel'i.l'et/ 20 April 2005 ; ({('ceIJ/l'd 14 Jlllle 2005

Tota l suspended particu late (TS P) matter on fortni ght ly basis throughou t th e: year and Illass si ze: distri bution of aerosob as wel l as ultrafine: aeroso ls un week ly basis in the Illonths of May and June lVere monitored during I <)<)6-2003 at dilTerent alti tudinal locations of the Kullu-M anali touri st complex in the: nort hwestern Himalaya. Concentration of TSP ranged frolll 35.8 (August I <)l)6) to 207.3 f1,g nf-' (Julle 2003) at Mohal II 150 m from average: sea level (ASL ) I and from 31.7 (Ju ly 2003) to 23l) f1, g m'-' (April 200 I ) at Manali (2050 III ASL). The mass size di stribut ion of aeroso ls showed a bimodal distribution hav ing onc peak in the coa rse size ra nge (3.3- l) f1, m dial and the other in the finc size mnge (0.OX-2. 1 f1,1ll dial at both the locati ons. Ultrafine aerosol (UA) (O'( )OI -O.1 f1,m radius) concentrations werc found to be highest at the lowest experimental altiwde site (M ohal) and l'ice 1'1' 1'.1'0. The diurnal variati on of UA concentrati oll for three years showed lhat the concentration ranges from 2640 (at 0500 hI'S LT) to 5 160 Number (N) cm'-' (at 1300 hI'S L T) at M ohal and from 400 (at 0400 Ill'S LT) to 2 1l)O N cm'.1 (at 1300 hI'S L T) at Koth i. On an average. TSP crossed its permi ssib le limit set by National Ambielll Air Qua lit y Standard (NAAQS) leve l in the sensiti ve areas such as Kullu-Manali hill spots. Bi modal nallire r Illass size distribution indi cates two importalll sources contribu ting in total aerosols-the fine mode. primaril y due to anthropogenic act ivities and the coarse mode aeroso ls. mainl y due to natural ,ources. Large number o f' concentrati on of ultrafine parti cles indicates the presencc of air pollutants more <1 tlow altitucies as compared to high altillides.

Keywords: Aerosols' behav iour. Total suspended particulate,. Mass size distri bu ti on. Ultrafinc aerosols. Kull u-Manali touri st complex, North western Himalaya

PA CS No.: lJ2 .60. Mt: l)2 .60 Sz: lJ2.70 Cp

IPCCode: GO IJI 5106:GO IWI 1I 7

1 Introduction Aerosols, the major air pollutants, are colloid

systems in which matter in liquid or solid phase li es suspended in gaseous form ca lled the carrier gas I. Trace elements released to the atmosphere from anthropogenic sources are the prime pollutants that worsen the quality of air and increase the risks to public health2

.,. Acute respiratory in fec tion , the world over, is the major cause of mortality among children below 5 years of age. It kill s 4.3 million children annually and 95% of them live in developing countries4

The problem of air pollution is aggravated in the developing countr ies due to vehicular exhausts. burning of wood biomass and agricu l tura l waste for cooki ng, burning of fuel for heating and lighting in the households5

-7

, etc. A ir pollution levels at Kathmandu In Nepal exceeded the acceptable standard by four times ( 1,000-5,000 Ilg Ill ''), Kathmandu's air quality is comparable to Kansas. Jakarta. Beijing and Vienna, which is worst in the world8,9 .

The concentration of total suspended particulate (TSP) in coastal and forest regtons of Kerala was

KUNTY AL et 01.: AEROSOL BEHA VIOVR IN NORTHWESTERN HIMALAYA 333

found to be within permissible limit of 100 Ilg m,3 (Ref. 10). But in northwestern and central India, these values are quite large and vary from 200 to 550 Ilg m'3 (Ref. 11).

Vltrafine aerosols (VA) have an important role in atmospheric studies related to air pollution , atmos­pheric chemistry, atmospheric electricity, cloud phenomena and radiative forcing l2. Besides, UA comprises particles which directly reach up to alveoli in the lungs causing health hazards . 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 cause many disorders to the health of the natives in the areas of concerned. Nausea, vomiting, irritation in eyes, nose and throat pains and cons­triction in the chest with coughing, laboured breathing and severe headaches are typical symptoms of exposure to high air pollution episodes 13 .

A large number of studies undertaken in India reveal that aerosol concentrations are increasing '4. Reported annual average levels of suspended particulate matter (SPM) in the ambient air of four Indian metropolitan cities in 1995 showed that Chennai, Mumbai , Kolkata and New Delhi had occupied 141.8, 246.2, 344.3, 410.5 Ilg m,3, respec­tively' o. In 2002, SPM in Chennai was -88 Ilg m') (at Santhome), in Mumbai -228 Ilg m,3 (at Kalbadevi), and in Kolkata around 190 (at CESE, Mandevitle Garden, Gariahat) to 260 Il g m,3 (at Lal Bazaar), while in Delhi it ranged from 329 (at Nizamuddin) to 534 Ilg m'3 (at Town Hal\) ls. Apart from metropolitan cities, at the hill stations where the present study is carried out, also the SPM level s remarkably increased, sometimes reaching alarming values from one hill town to another. According to Central Pollution Control Board (CPCB), Shimla showed 139 Ilg m') (at Tekka Bench Ridge) in 1994 that came down to 58 Ilg m,3 at the same place '6 in 1999. According to the recent studies carried out by the Himachal Pradesh Environment Protection and Pollution Control Board (HPEPPCB) in four hill towns of Himachal Pradesh in 2002, Shimla has the average SPM level of 76.42 Ilg m,3 (in November), Jassur 334.40 Ilg m') (in May), and Paonta Sahib >500 Ilg m,3 (in April , May , September and November)' 7. In other Himalayan locations, SPM, someti mes, crosses its permissi ble limit in the residential areas (200 Ilg m,3) showing Shillong (at State Central Library), Dehradun and Parwanoo with 113,405,202 Ilg m ,3, respectively IS.

Isolated atmospheric aerosol samples have been collected on the south slopes of the Himalayas 18,20. When the towns located in the Indian Himalayan region are reviewed from SPM concentration point of view, some of the hill towns have already crossed their permissible level21. The TSP was found to be higher in the pre-monsoon than in the post-monsoon season at Kosi near a hill tourist town Almora of Vttaranchal State. Soil derived aerosols here were dominating in both the seasons22 . Fine particles « 2.1 11m dia) emitted from anthropogenic activities like industrial , vehicular and domestic combustion are of major concern in aerosol studies. Such fine particles are highly rich in toxic trace metals, polycyclic aromatic hydrocarbons (PAH1» and other carcinogenic organic matter23 .

The variation of VA concentrations in air masses from continents and oceans is very large. The average concentration of VA in the Silent valley during the period of measurement (7 days during December 1989) was 1850 N cm,3, whereas the average mini­mum and maximum concentrations were 650 and 5210 N cm,3, respectively24.25 . The diurnal variation of

VA at the Silent valley had shown its peak at 1400 hrs LT when anthropogenic activities surrounding to a certain experimental site remain at optimum level26.

Vehicular pollution during tourist season is at its peak in the hill spots of Kullu-Manali tourist complex . Aerosol studies with regard to highly sensitive areas of the Himalaya have become more important, where there has been a dearth of si milar studies in the past. So, the major aim of this study is to understand the concentration levels of TSP in topographically fragile and ecologically delicate areas in the high ranges of the Himalayas and their pollution potential.

2 Methods of sampling and analysis 2.1 Experimental locations

Kullu and Manali tourist spots fall under the Kullu district that comprises the River Beas basin of the hill State of Himachal Pradesh in the northwestern Himalaya. The Kullu valley begins from Larji (957 m in the lower River Beas basin) and stretches up to Rohtang crest (4,038 m in the upper River Beas basi n) (Fig. 1) . The valley at maximum is 80 km long and 2 km wide, Kullu town (1,219 m: sub-temperate climate) is located between 31 °38' N latitude and 77°6' E longitude with a geographical area of 7 km2

inhabited by 18,306 permanent residents in 200 I (Ref. 27). Kullu and Manal! are the major tourist spots in this valley, Mohal is 5 km before Kullu town.

334 INDIAN J RADIO & SPACE PHYS, OCTOBER 2005

To Leh N .----~

" Rohtang Pass

+ '" (3978m) Kothi "''''',

...

oe~--L ,0 ~e'l'l y

(2530 m) --, .),.

lJ.J J agatsukh

[®J Major Tourist Spots

[~J Sampling Sites

[2] Road

ctl River k.~J Kullu Valley

8 a 8

km

\

, , "

" ... \ \ ----- \ --"

\" ~ " .... f' · ... ., .... KuUu Volley in \ ....

I KuUu DiatnCl &. ·' lI . p . Ji,..

" , f '~') , r

·v.... ' .... ' . .-,( , - ... . :,

' . _ . '" '2'20

! liM

Fig. I---Geographicallocati on of the study sites

Manal i tourist resort located in mid altitude of temperate climate between 32°24'30" N latitude and 77°10'6" E longitude with a geographical area of about 3.5 km2 inhabited by 6,265 permanent residents in 200 1 (Ref. 27) . Approximately , 11 .40 lakh touri sts (I lakh= 100 thousand) visit Manali and 2.56 lakh (22 .53%) tourists to Kullu annuall/ 8

. Kothi, the last settlement of the valley, is 12 km away from Manali.

2.2 Instrumentation and sampling The TSP was monitored in and around Kullu­

Manali tourist spots fortn ightly on 8 h basis from 1996 to 200 1 and on alternate day basis (with a gap of every si ng le day) for 24 h sampling from midnight to midnight during 2003. These sampli ngs were mostly carried out away from maj or towns ' polluting activit ies. such as bus stations and roads to obtain a true background concentration of aerosols in the ambient air and to represent prevailing dust levels . At Mohal, there are two sites--one at a distance of 100 m away from National Highway-2l (NH-21) and the other at G.B . Pant Institute of Himalayan Environ-

ment and Development (GBPIHED), Himachal Unit, Mohal-Kullu (about 200 m from NH-21 ), where sampl ing were done fro m March 1996 to February 1998 and fro m April 1999 and onwards, respectively. Similarl y, TSP measurements were conducted at three sites around major tourist resorts at Mana1i from 1997 to 1999. From March 1996 to May ]998, TSP was monitored with in Manali at Hadimba temple and Forest Rest House and from June 1998 to April 1999 at Palchan (2,320 m ASL), 10 km away from Manali. Sampling site was shifted in June 1999 from Palchan to Jagatsukh (2,040 m ASL). This third site was at a distance of 6 km fro m Manali. Kothi (2 ,530 m ASL), at a distance of 12 km from Manal i, was the fourth and the last inhabitable experi mental site in the Kullu valley for TSP and UA measurements from 2000 to 2003. Hi gh Volume Samplers (Envirotech, APM 4 15 and APM 430) were used for co llection of dust samples over microfibre fi lters. The GF/A grade microfibre filters manufactured by W hatman, UK, were used to collect the TS P samples.

KUNIY AL et al.: AEROSOL BEHAVIOUR IN NORTHWESTERN HIM ALA Y A 335

Mass size distribution of aerosols , using a Low Volume Air Sampler (Andersen, 2000; Andersen Inc., USA make) which collects particles on 9 different stages with sizes ranging from 0.08 f,lm to 9 f,lm dia, was monitored during May-June for three years (1996-1999) at GBPIHED, Mohal. While the next experimental site to monitor mass size distribution was at Kothi , the last inhabited site of the Kullu valley, where the measurements were carried out during the period May-June 2000. The filter papers used for the collection of aerosols were Whatman 41 make with 8 cm dia. The particle collection was done at the flow rate of about 28 I min' ) (Ref. 29) . The filter papers were heated first to remove volatile deposits and then desiccated and weighed before and after sampling with a microbalance in humidity-equilibrated environ­ment to derive net aerosol load.

Ultrafine Aerosol Counter (UAC) works on a principle of cloud chamber. A portable expansion type counter (Gardener Assoc., USA) was used for the measurement of UA concentration in numbers per cm-3 in the size range of 0.001-0.1 f,lm . The sub­micron particles are injected into a cloud chamber containing saturated vapour. The vapour condenses on these particles and form droplets . Atmospheric air is pumped into a small chamber at a pre-set pressure in UAC and slowly injected into the main chamber containing water vapour. The saturated vapour 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 analog display of UA in N cm-3

(Ref. 12). Continuous hourly observations of UA were taken at a height of 1 m above the ground level.

2.3 Quality assessment and quality control Enough care was taken in quality assessment (QA)

and quality control (QC) in filter conditioning, storage and weighing to derive one TSP sample. Before using microfibre filters for sampling, these were condi­tioned in desiccators with active silica gel, which were initially heated to remove volatile contents, and then desiccated for about 16-24 h. Care was taken that these filters are not folded either during handling or during weighing. Weighing of filter was done on a digital balance having sensitivity of about 0.1 mg. Before weighing, the balance was calibrated. The filter was weighed by keeping the rolled one in a clean-tarred beaker over the pan of balance. Post

conditioning of filters was also done under identical conditions that followed for the pre-exposed ones. Monitoring of background dust was carried out by installing the machine at rooftop of an inhabitable house, which was quite away from the main town and located in upwind of the town from the polluting activities and road. Monitoring was done on pre­decided 8 h intervals continuously for 24 h. A day and night period of 24 h was categorized into three shi fts, namely, shift A: 0600-1400 hrs LT, shift B: 1400-2200 hrs LT and shift C: 2200-0600 hrs LT. Since electricity, usually, gets disturbed due to snowfall in winter and could not uninterruptedly available conti­nuously for 24 h, it was decided to consider any of those samples valid which are run at least for 75% of the pre-decided hours . A minimum of 6 h sampling was set to obtain a TSP sample. While monitoring, observation of climatic data and pollution activities were also noted and used during interpretation of the data.

3 Results and discussion 3.1 Total suspended particulate (TSP) matter

3. j .1 Diurnal variations in TSP concentration­Table I depicts the diurnal variations in TSP, particularly, in tourist season in two spots. It is noticed that the highest concentration reached up to 185 .5 f,lg m-3 (1000-1600 hI'S LT on 22 May 2000) at Mohal. These values are followed by 175.2 f,lg m-3

between 1200 and 1800 hrs LT on 20 May 2000. The lowest TSP concentration at Mohal was found to be 86.3 f,lg m·3 between 2200 and 0600 hrs LT on 24 May 2000.

Kothi, located at a higher altitude than Mohal, showed highest TSP levels of 240.4 f,lg m-3 between 1000 and 1800 hrs LT on 29 May 2000. However, lowest concentrations -64 f,lg m-3 was observed between 2230 and 0630 hrs L T on 31 May 2000. In essence, the average values of TSP at both the locations showing 139.2 f,lg m-3 at Mohal and 120.4 f,lg m-3 at Kothi crossed their permissible level of 100 f,lg m-3 (Ref. 10). On an average, in all the three sampling intervals (shifts A: 0600-1400 hrs LT, B: 1400-2200 hrs LT and C: 2200-0600 hrs LT), the TSP concentrations crossed the permissible limit, except during shift C at Kothi (87.8 f,lg m-\ The reason for being high TSP during shift A and shift B in a day at Mohal and Kothi is due to the presence of human as well as tourism activities that remain in full swing during the peak tourist season (May-June) (see Table 1).

336 INDIAN J RADIO & SPACE PHYS, OCTOBER 2005

Table I- Diurnal va ri ati ons in TSP concentrations (Ilg m-:1 ) in Kullu-Manali tourist complex during May 2000

Mohal (low altitude)

Date Time (hI's L T) TSP

20 1200-1 800 175.2

21 1000-1600 180.7

21 2300- 0500 141.7

22 1000-1600 185.5

22 2200- 0400 150.4

23 1000-1 800 113.6

23 2200- 0400 121.0

24 1030-1 830 148.4

24 2200- 0600 86.3

25 1030-1830 107.6

26 0900-1500 120.5

Average 139.2

NOle: na=Dala not available

In essence, diurnal pattern of TSP for the two locations are similar. However, the night values at shift C: 2200-0600 hr L T for Mohal and Kothi are comparable. There is a significant difference of TSP in the night at both the locations. The TSP at Mohal is having 37.1 Ilg m-" higher concentration as compared to Kothi during the night (2200-0600 hrs LT). Overall , seeing TSP concentration at these two locations , Mohal ranks highest in TSP concentration followed by Kothi. The major causes to affect TSP variations on diurnal basis at both the experimental sites are mainly tourism activities. From dawn, as the tourism activities start, the TSP also starts increasing and crosses its permissible level by noon.

3. 1.2 MOllthly and seasonal variations in TSP cOl1celltratiolls-The monthly highest TSP levels from 1996 to 2003 is found to be 207.3 Ilg m-3 at Mohal in June 2003 and 239 Ilg m-3 at Manali 30 in April 2001 (Fig. 2). The lowest values were 35.8 Ilg m-3 at Mohal in August 1996 and 17.8 Ilg m-3 at Manali in September 2003.

From Fig. 2, it is seen that the monthly mean TSP concentrations during eight years (1996 to 2003) is large at Mohal crossing permissible level in different occasions (one time each in January 2001, April 1999, June 2003 and two times in May 1997 and (998). While at Manali, these monthly mean TSP values during the same eight years sampling, permissible level of TSP crossed two times each in April 1999, 2001 and December 1997, 1998, and one time in May

Kothi (hi gh altitude)

Date Time (h I'S L T) TSP

27 1100-1900 125 .1

28 1000-1600 129.4

28 2200-0600 109.0

29 1000-1 800 240.4

29 2200- 0400 105.8

30 0730-1530 133.3

3 1 1200-2000 103.8

31 2000-1000 72.5

31 2230-0630 64.0

na na na

na l1a na

120.4

300 ,---------------::-------, y = 0.5106x - 534.16, R2 = 0.0728

'7E Ol

• Mohal

250 0 Manali y = 0.021x + 41 .769, R2 = 0.0001 ..... Linear (Manall) DO

200 - Linear (Mohal) • • • . ~ ~ :l. 150 octJ .J;l •

c: 0 ~ " .. 0 •• ~ rP ~~~ ••• ~ 0 ".

100 • n • • ~ .... 8~ • • ~ ••

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..., 0 ~ 0 ~ 4: .., ..., z 4: C/) u. 0

MONTHS-YEARS

Fig. 2-Lol1g-term trend of IOlal suspended particulates matterJO

observed at Mohal and Manali during 1996-2003

200 i . Thus, there are two categories of months repre­senting two seasons (summer and winter) showing the TSP above its threshold limit.

Summer season (March-June) recorded highest TSP levels at all locations in almost every year from 1996 to 2003 followed by wi nter (November­February) and monsoon (July-October) seasons. However, the year 200 1 shows highest TSP concentration during the winter (158.4 Ilg m-3)

followed by summer season ( 123.3 Il g m-3) at Mohal. The concentration of TSP in summer is partly influenced by tourism and its allied activities; and in winter partly due to biomass burning (fuel for heating

KUNIY AL el al. : AEROSOL BEHAVIOUR IN NORTHWESTERN HIM ALA Y A 337

and cooking, and accidental as well as manmade forest fires).

Burning fuel wood in hotels during electric failure due to heavy snowfall in winter, emits smoke and ash that add suspended particulate matter in the atmosphere. As a result, out of total eight years of observation, TSP levels crossed their permissible level in three years during winter season at Mohal (i.e., 105.6 f.L g m-3 in 1998, 103.9 f.Lg m·3 in 1999, and 158.4 f.L g m-3 in 2001). The lowest TSP value at Mohal was 44.8 f.Lg m-3 in December 1997. Similarly, mean TSP levels at Manali in winter also crossed its threshold limit in three years showing 104.7 f.Lg m-3 in 1997, 124.6 f.Lg m-3 in 1998 and 159.5 f.Lg m·3 in 2001. The lowest ever recorded TSP in winter at Manali was 26.5 f.Lg m-3 in February 2003 .

During monsoon as washout effect becomes significant, the aerosol concentration reaches its lowest value at Kothi. Since Mohal falls in rain shadow effect, it had relatively high mean values (104.5 f.Lg m-3 in 1999 and 117.8 f.Lg m-3 in 2001) to represent the monsoon season. The lowest value recorded at Mohal was 35.8 f.Lg m-3 in August 1996 during monsoon season . The TSP levels, on an average, are moderate at Mohal due to lesser rainfall frequency during the monsoon seasons of 1999 and 2001 as compared to Manali and its surroundings. The highest and lowest ever mean values at Manali for monsoon period were 91.1 f.Lg m-3 in 1998 and 26.9 f.Lg m-3 in 2003 , respectively. So rainfall conditions in local meteorology at every experimental location have also played an important role in determining TSP concentrations along with other human activities.

3.1.3 Trends in TSP levels--The annual mean TSP concentration was largest in 2001 [133.2 f.Lg m-3 at Mohal and 134.3 f.Lg m-3 at Manali (Jagatsukh)] . At Mohal, the annual average TSP levels were above the permissible level since 1999, while at Manali it crossed the permissible level only in two occasions, i.e. in 1998 and 2001. The lowest annual mean concentration (during the 8-yr period 1996-2003) of 63 .2 f.Lg m-3 was observed in 1996 at Mohal and that of 43.2 f.Lg m-3 in 2003 at Manali. This is mainly because the Kullu valley from Larji (from where it begins) to Katrain (mid part of the valley) within which the first sampling site Mohal exists, falls under rain shadow zone (leeward side), while north of Katrain up to Rohtang crest, where Manali and other sampling sites are located, falls under rainfall zone

(wi ndward side) where washout due to monsoon rain is significant in lowering the TSP levels.

The other factors governing TSP concentrations at Mohal are relatively high inflow of tourists, vehicles ' exhausts from the NH-21, fuel wood burning for cooking and heating, accidental and manmade forest fires, ever increasing shrinkages in forest areas due to forest clearances for timber and fuel wood, encro­achment by the villagers in the third class forest land for agricultural practices, and continual upcoming construction activities for hotels, hou"es, roads and hydropower projects. The TSP concentration is also significantly influenced by local meteorological conditions like windward and leeward side of monsoon rain, wind velocity and atmospheric stabi lity . Stable atmospheric conditions with a low mixing height layer may result in significant enhance­ment in TSP concentrations. This was probably one of the major reasons for high TSP concentrations observed in February as compared to August.

Based on the above trend found at Mohal in particular and at Kothi in general, TSP levels are expected to be higher in the following years if the tourism pressure continues at its present pace of growth in the Kullu-Manali complex. The need of the hour is to regulate tourists' inflow and their vehicles at a time, to discourage relatively a larger size hotel structures and to follow pollution norms in a cohesive way to minimize the level of TSP in these sensitive regions of the Himalaya.

3.2 Mass size distribution of aerosols Mass size distribution of aerosols at Mohal and

Kothi was found to be of bimodal type with one peak in the fine (0.08-2.1 f.Lm dia) and the other in the coarse (3. 3-9 f.Lm dia) size range (Fig. 3). At Mohal , the fine size peak was observed in 0.43 f.Lm dia and the coarse size peak at 4.7 f.Lm dia. At Kothi , though the fine size peak was found at 0.43 f.Lm dia, the coarse size peak was in 5.8 f.Lm dia. Fine size aerosols contributed about 59 % to the total aerosol load at Kothi, whereas at Mohal they contributed only about 45 %. This feature indicates towards the dominance of fine size particles at Kothi and that of coarse particles at Moha!. Generally, the fine size particles are originated from the anthropogenic sources, such as, high tourism activities, vehicular movement and consequent emissions, and biomass burning. Coarse size particles are mainly produced by natural ources like soil and sea. Crustal particles found at Mohal are mainly comprised AI, Fe and Ca (Ref. 31).

338 INDIAN J RADIO & SPACE PHYS, OCTOBER 2005

150

- . - Mohal (average of 1996,1998 and 2000)

120 -0- Kothl (2000)

.E CI :t 90

& ~. 60

-~ 30

0 0 .01 0 .1 10

PARTICLE DIAMETER, ~m

Fig. 3--Mass size distribution of aerosols at Mohal and Kothi

The dominance of fine size particles at Kothi can be attributed to higher alt(tude of this sampling site (about 2325 m ASL)3o. The vehicular exhausts in peak tourist season of summer and biomass burning throughout the year in rural houses for cooking and heating could be the other major reasons for high contributions in fine size particles at Kothi. At Mohal, significant contribution of coarse size particles is due to dominance of natural sources such as wind blown dust, sparse vegetation, bare rocks apart from comparatively a low height of this sampling site (about 1150 m ASL).

3.3 Ultrafine aerosols

Ultrafine aerosols (UAs) are mostly formed from photochemical reactions leading to gas-to-particle conversion. Anthropogenic sources such as emissions from vehicles, biomass burning and others signi­ficantly contribute UA concentration. The UA in the size range of 0.001-0.1 Jlm radius directly penetrates into the alveoli of human lungs. Measurement of the concentration of these particles at the above sites thus becomes important.

3.3. J Mean diurnal variation ill UA concen­tration-The average diurnal values of UA at these three locations show that this concentration increases with the decrease in altitude. The highest diurnal average values (3990 N cm-3) are observed at the lowest site- Mohal ; and lowest concentrations (1350 N cm-3) are observed at the highest altitude site­Kothi. Mohal has three times more UA concentrations than Kothi and Manali (mid altitude) concentrations stand in between_

The diurnal variations based on six hours average data presented in Fig. 4 show that UA concentration is

7e 6 ,

~Mohal

" 0 ~Manall

0 -tr- Kothl 0 -

~ • Z 4 iii -' 0 r/) 0 II: w « w z ii: « II: .... -' ::::>

TIME , hI'S 1ST

Fig. 4--Diurnal variation in UA concentrations based on average of six hourly data at Mohal, Manali and Kothi

largest during the pre-midday period (0700-1200 hrs L T) at Manali (4230 N cm-3) and Kothi (1810 N cm-3). At Mohal, largest UA concentrations (4710 N cm-3) are observed in the afternoon period 1300-1800 hrs LT with a lag of around 6 h. In the early morning hours tourist related activities start at the hill spots. Traffic congestion and resulting pollution potential also increase from dawn reaching its peak around noon, thus causing increased concen­trations of UA. On the basis of mean level of UA concentrations, Kothi has the lowest values followed by Manali. Highest concentrations are observed at MohaL This can be attributed to the altitude difference of these three stations. While Mohal is situated at the lowest altitude of 1150 m ASL, Manali is situated at 2050 m ASL and Kothi at 2530 m ASL. This clearly shows that the UA concentration decreases significantly with increase in station altitude. It is important to note that the concentrations of UA were lowest between 0100 and 0600 hrs L T at all the three experimental sites.

The hourly variations in the concentration of UA at the three experimental sites showed a range from 2640 N cm-3 (0500 hrs L T) to 5160 N cm-3 (1300 hrs LT) at Mohal , from 1800 N cm-3 (0400 hrs LT) to 4880 N cm-3 (1200 hrs LT) at Manali and from 400 N cm-:1 (0400 hrs LT) to 2190 N cm-3 (1300 hrs LT) at Kothi (Fig. 5)_ The UA concentrations at all the three locations remain highest between 1200 and 1300 hrs L T in a day and lowest between 0400 and 0500 hrs LT at night. During the whole study period (1996-2000), highest UA concentration at Mohal was 9180 N cm-J at 1400 hrs L Tin 1996.

KUNIY AL et al.: AEROSOL BEHA VIOUR IN NORTHWESTERN HIMALAYA 339

iii ...J o III~

~ 'E w U <I: 0 W g Z ~ u: x <I: Z II: I­...J ::J

6 ,--------------------------------,

. . .... . Mohal

5 ---fr- Manali

_Kothi l . 4

2

3 5 7 9 11 13 15 17 19 21 23

TIME, hra 1ST

Fig. 5--Diumal variation of UA concentrations on hourly basis at Mohal, Manali and Kothi

In short, the pattern of diurnal vanatlOns in UA concentration are, more or less, similar at Mohal and Manali. The amplitude of diurnal variation is largest at Manali. For the other two stations, the amplitudes of diurnal variation are comparable. The rate decrease in UA concentration in the afternoon period in Mohal and Kothi is rather low compared to that of Manali . The gas-to-particle conversion process due to photochemical reaction, high congestion due to inflow of a large number of tourists, vehicles and biomass burning would have significantly contributed for the observed daytime peak in UA concentration.

4 Summary and conclusions

(i) The TSP concentration at both the experimental sites, namely, Mohal and Kothi, was higher than the permiss ible level set for envi ronmental standards for the sensiti ve locations. The TSP is high during daytime and low during night at both the experimental sites. The range of diurnal variation from minimum to maximum in TSP concentration is largest at Kothi .

(ii) The TSP concentration is highest during summer and lowest during monsoon with winter concentration lying in between. High TSP in summer would be partly attributed to increase influx of tourists.

(iii) Of eight years measurements, the average values of TSP crossed the permissible level during three years (1999, 200 I and 2003) at Mohal and in two years (1998, 2001) at Manali . Annual average values of TSP at both the experimental sites were highest in 200 1 among the total eight

years of observation (133.2 Jlg m-3 at Mohal and 134.3 Jlg m-3 at Manali) .

(iv) The relative abundance of fine size range (0.08-2.1 Jlm dia) particles dominate at high altitude experimental location, Kothi , whereas this situation is opposite at low altitude site Mohal. The coarse size range particles (3 .3-9 Jlm dia) dominate the fine size range at Mohal. The coarse sizes at Mohal (about 55%) are mainly produced by natural sources like soil31 such as AI, Fe and Ca. A larger share of the fine particles at Kothi (about 59%) is attributed more due to anthro­pogenic sources, such as high tourism activities , emissions from plying vehicles and biomass burning.

(v) The UA (0.001-0.l Jlffi radius) particles are mainly formed from gas-to-particle conversion process due to photochemical reactions. The hourly mean UA concentration at low altitude (Mohal) was -5160 N cm-3, whereas at high altitude (Kothi ) their concentration was 2190 N cm-3. The diurnal variation of UA indicated high concentration around noon (1200 hrs LT) when the anthropogenic activities reaches a maximum. The UA concentrations are low in the early morning hours (0400-0600 hrs L T) when tourism activities reach at its lowest level. Thus, thi s study brings out the need of enforcing strict vehicle laws not only in the metros, but also in sensiti ve hill tourist spots of the country.

Acknowledgements

The authors are thankful to the Directors of GB Pant Institute of Himalayan Environment and Development, Kosi-Katarmal, Almora (Uttaranchal) and Indian Institute of Tropical Meteorology, Pune (Maharashtra), for encouraging inter-i nstitutional collaborati ve research programmes and providing fac ilities in respective institutes to complete the present study successfully. One of the authors (KG) thanks Dr R K Khandal, Director, Shriram Institute for Industri al Research , Delhi , for his constant encou­ragement and help. The financial ass istance provided by the Department of Science and Technology (DST), Govt. of India, New Delhi , to one of the authors (JC K) to conduct these research works is also highly acknowledged . The authors also thank Mr Oinam Santaram Singh, Research Scholar and Er. Samar Bhowmjck, Research Associate, of this un it of the

340 INDIAN J RADIO & SPACE PHYS. OCTOBER 2005

institute for drawing and reformatting some of the illustrations presented in this paper.

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