(Pre-draft, to be submitted to Atmospheric Environment)
Observation of Ozone, Trace Gases, UV radiation, TSP and
Aerosol, its composition and Optical Depth at Darjeeling
(27.010N, 880 15”E, msl=7204 feet) and associated places
T.K. Mandal, B.C.Arya, R.S.Tanwar, A.B.Ghosh, Suresh Kumar Yadav, Ravi Kumar, S.L.Jain, Rishal
Singh, Ranu Gadi, Shompa Das, R.S.Parmar, D.C.Parashar, S.C.Garg, A.P.Mitra
Radio and Atmospheric Sciences Division, National Physical Laboratory, New Delhi 110012, India
Prabhat Kumar Gupta, Sulochana Koul, A.K.Sarkar, Nahar Singh
Analytical Chemistry Section, Material Characterization Division, National Physical Laboratory, New
Delhi 110012, India
Sibaji Raha
Bose Institute, Kolkata
Subrata Roy,
North Bengal University, Silliguri
Abstract
For the firsttime a joint study of atmospheric and health parameters was done at Darjeeling (msl: 7204
feet) and its associated places during the period of 18-29, 2001. However, the results of atmospheric
parameters were here. Several interesting aspects were presented here. It shows that ozone
concentration has varied from 30 to 70 ppbv and GHG has shown very high value at this point.
1. Introduction
Air pollution is a serious problem in the hills due to hypoxic conditions, low temperature, extensive
use of biomass fuels and inadequate ventilation systems. Emissions from biofuels and fossil fuels and
environmental tobacco smoke constitute a complex mixture of pollutants containing CO, NOx, SO2,
volatile organic compounds, polycyclic aromatic hydrocarbons, particulate matter, elemental carbon,
soot etc. Due to inadequate ventilation systems in the hills the indoor concentration of these pollutants
are often extremely high and women and children are the most serious suffers.
These compounds acting either singly or in combination cause various acute and chronic respiratory
illness and the effects vary considerably with the concentration and duration of exposure. Moreover,
hypoxic stress related adaptations in highlanders, which are primarily meant for effective oxygen
utilization may cause additional health complications when exposed to high particulate pollutants and
gases.
With the establishment of a High Altitude Research Centre at Mayapuri, Darjeeling (msl: 7204 feet), in
the eastern region of India, multidisciplinary research activities has been strongly emphasized relating
physical, chemical, biological and environmental conditions of high altitude and/or problems of
regional interest. National Physical Laboratory, New Delhi, one of the leading organizations engaged
in atmospheric studies Chittaranjan National Research Institute, Kolkata engaged in human health may
take major initiative in explaining the health problem retaled to High Altitude. Prior to this campaign,
NPL scientists at Mayapuri in campaign mode have carried out few measurements of acid rain, aerosol
size distribution, UV-B dosage etc. In present campaign, collective measurements for environment and
health aspects are made to verify the impact of environment on health.
The advantage of this multidisciplinary study was to access the different altitude places of different
environments: e.g., Tiger Hill (msl: 8,480 feet), which is bare land with no pollution, Mayapuri,
Darjeeling (msl: approx. 7204 feet), hill station with rapidly growth of tourists and Siliguri (msl: 512
feet), a plane town with small airport nearby.
The broad objective of this campaign is to assess of the relationship between pollutant and pulmonary
responses in altered physiological and environmental conditions in the hills. The study has been carried
out in rural and urban areas at different altitudes of Darjeeling district. Emphasis has been given to
correlate the health effects with the concentration of pollutants, exposure to environmental tobacco
smoke, living conditions, socioeconomic and nutritional status in the hills. In addition concentration of
pollutants like particulate matter, CO, O3, NOx and SO2, aerosols etc has been measured at different
places. Pulmonary responses of exposed individuals have been assessed by clinical examination
mainly of the respiratory Symptom complex, lung function tests and alveolar macrophage responses.
Attempts have been made to correlate the nature and concentration of pollutants with the pulmonary
function and alveolar macrophage responses in this campaign. The clinical experiments e.g., lung
function test, collection of sputum, blood & checking of blood sugar has been done by doctors of
Chittaranjan National Cancer Institute (CNCI), Calcutta. The analysis of the samples collected by
doctors from CNCI will be reported separately
3.2 Environment
3.2.1 Instruments and Methodology
The methodologies of the instruments, which have been used for various measurements related to
atmospheric parameters have been reported here.
Measurement of surface ozone by UV-based photometric analyzer of DASIBI make of (Model 1008RS). The instrument measures the relative attenuation of a beam of an UV light of about 254 nm
between samples, free from ozone and in which ozone is present. With the knowledge of the sample
path length and the absorption coefficient of ozone at 254 nm, the ozone concentration is determined.
The data were collected at an interval of 10 seconds and averaged over every five minutes. In addition
to above the hourly and daily average values are also available.
Measurement of Trace Gases was done by Grab Sampling by flushing the air through the glass
samplers. The Glass samplers were flashed initially for ten minutes. When it is observed that glass
samplers are being completely flashed then the sampler is locked. These samples were analyzed for
GHGs viz, CH4, CO2 and N2O in the laboratory at NPL, New Delhi by gas chromatograph (model
Sigma-2000 of Perkin-Elmer, USA) with FID/ECD. FID with Methanizer was used to analyze CO2.
Measurement of Total Ozone, Water vapor Content was done by Microtop, a microprocessor-based
sun-photometer (Solar Light, USA) direct sun radiation at 305, 312, 320, 940 and 1020 nm to estimate
water vapor, total column ozone etc. The first three narrow bandwidth (2.5 nm FWHM) filter channels
are used to derive total ozone while later two filter channels having bandwidth of 10 nm (FWHM) are
used for water vapor and aerosol optical depth. The field of view of each optical channel is 2.5 0. The
input parameters such as latitude, longitude and altitude of the place of observations are obtained from
GPS receiver. On board clock and calendar keeps track of the time necessary for astronomical
calculations. A built in barometer provides atmospheric pressure for the Rayleigh scattering correction
and both raw data and calculated results are stored in an onboard non-volatile memory.
Measurement of Total Suspended Particulates (TSP) at different places e.g., Darjeeling, Siliguri was
carried out using High Volume Sampler (Vayubodhan APM-430). The suspended particulate matter
(SPM) was measured by passing ambient air at a high flow rate of 1.0 and 1.3 ug/m 3. the passage of air
reaching the filter does not allow the heavier settlable dust particles to reach the filter. The sampling of
NOx as NO2 was done by passing ambient air at the flow rate 1 l/min through the impinger having the
absorbing solution. The samples were analysed calorimetrically using a UV-VIS spectrophtometer
(Perkin Elmer Lamda 3). Chemical composition was analyzed at laboratory for Cl, SO4, NOx, Na, K,
Ca, Mg.
Measurement of Aerosol Optical Depth is done by Microtop (Solar Light, USA), which uses the direct
solar radiation. The sun photometer can scan the solar radiation from lower zenith angle to higher
zenith angle. Five interference filters with peak transmissions wavelengths at 340, 500, 675, 870 and
1020 nm are used for solar radiation measurements. The optical thickness of aerosol  was calculated
by signals of the instruments calibrated by the Langley method.
While considering the radiative equilibrium model, the solar radiation passing through the atmosphere
is absorbed and scattered by the neutral particles, aerosols, water vapor and ozone. The law of
absorption (sometimes known as Lambert’s law) states that the absorption which occurs when a
radiation of intensity I traverses an element slab of atmosphere of thickness dz is proportional to the
mass of absorber dz (being the density of absorber) and to the incident of radiation itself. Thus
dI=Ikdz
(1)
Where k is the absorption coefficient. Integrating (1) leads to
I=I0xexp[-kdz]
(2)
Where -kdz is the optical depth
Thus I=I0exp [-(R+kx+A)]
(3)
Where I= intensity of solar radiation at frequencies 340, 500, 675, 870 and 1020 nm
I0= Intensity of solar radiation at frequencies 340, 500, 675, 870 and 1020 nm at space
R=Rayleigh optical depth
K=absorption coefficient of ozone
a=aerosol optical depth
x=amount of ozone in the atmosphere
Measurement of Aerosol Optical Depth was done by another Sunphotometer, which measures the solar
radiation at 368 nm, 500nm, 675nm, 778 nm.
Measurements of UV radiation at different wavelengths were done by using UV-Biometer and
Erythemal Probe. UV-Biometer measures UV-B intensity in wide band from 280 nm to 340 nm in
terms of Minimum Erythemal Dose (MED), one MED being 5.83x1.0E-6W/cm2 and Erythemal Probe
has the special response (half power points) from 291.3 nm to 301.3 nm assuming monochromatic
irradiance at 297 nm, which is most sensitive to human skin.
4. Brief summary of the campaign sites
4.1 Primary observational Site
Dr.A.J.C Bose Institute, Mayapuri is relatively away from town. It may represent the background value
of the Darjeeling town. All equipments became operational on May 19, 2001. We had operated
continuously Surface Ozone Analyzer and High Volume Sampler and Anderson Sampler at this place
to measure surface ozone, TSP and composition of aerosol and size distribution of aerosol. Apart from
that we have measured UV-dosages, UV radiation at different wavelengths, total ozone, total water
vapor content, aerosol optical depth at different wavelengths etc for time-to-time.
4.2. Secondary observational Sites
Site -1: ManiBhajan (260 59.34”N, 880 07.20”E, msl=6578 feet)
ManiBhajan is basically a remote forest area with sparsely populated. It situated in the valley region
and position is and altitude is. Weather of that day was very cloudy with small drizzle. Total vechular
population is about 40. We measured surface ozone and Total suspended particle. Though it is very
remote area, ozone concentration shows on average. Since it was cloudy day it was not possible to
measure optical operated equipment.
Site-2: Darjeeling Govt. College (27.010N, 880 15”E, msl=7204 feet)
Darjeeling is district town of these hill area. Situated at 2134 meter it enjoys of summer of maximum
temperature of about 150C and minimum temperature of 50C. the winter temperatures range from 10C
to 60C. We measured surface ozone and TSP on May 21, 2001 at Darjeeling Govt. College campus.
This college is situated relatively in the main city.
Site-3 Darjeeling Railway Station (27.010N, 880 15”E, msl=7204 feet)
Darjeeling Railway represents one of the busiest and crowded place of Darjeeling town so far.
Moreover, railway have introduced Desiel operated engine and the charcoal operated engine in this
area. We have carried out our observation at the top of railway station. Moreover, this area is densely
crowded. Doctors measured health related parameters of student
Site-4 Kalimpong Girl School & SUMI (270 04”N, 880 28”E, msl=6424 feet)
Situated at an altitude of 1250 meter, kalimpong enjoys the best climate in the region. The hills areas
of Kalimpong are mainly an agricultural region. Kalimpong Girl school is situated in the heart of the
town. 70% of the people uses LPG as cooking gas and rest of the people use charcoal and fuel wood as
cooking purpose. With total oldest school represent the student of all parts of the Kalimpong.
Site-5 North Bengal University, Siliguri (260 42”N, 880 2.00”E, msl=488 feet)
North Bengal University situated outside of Siliguri town represents the background environment of
this area. The campus is completely crowded with green tree. We have taken measurement of 24 hours
to observe the dirunal changes in plain area. In addition, doctors, from CNCI also measured the health
parameters of the inhabitants of the campus.
Site-6 Tiger Hill (260 59”N, 380 07.00”E, msl=8480 feet)
At an elevation of 2,590 meter, it enjoys one of the highest point in the area which provides the most
exotic view of the Kanchenjunga peaks. From this place the other peaks of the Eastern Himalayas can
be seen. On a clear day, the sight of Mt. Everest is enthralling. The sight of the sun rising from over the
Tiger Hills is an unforgettable experience. The first rays of the sun on these peaks of the Great Barriers
gives an impression of molten gold having been spread. Every day, a large number of people flock to
this place to catch a glimpse of sunrise.
5. Results and Discussion
5.1 Ozone
Comparison between two Ozone analyzers
Two UV-Based Ozone analyzers (Model 1008-RS) were taken for measurement. These were operated
at the same place on May 19-20 and on May 26-27, 2001. One equipment was installed at Dr. A.J.C.
Bose Institute, Darjeeling and other equipment are taken at different places for spot measurements.
Some of the results are shown here. It represents good correlation between two equipments.
Ozone at A.J.C Bose Institute, Mayapuri
Surface ozone measurements were carried out at Bose Institute, Darjeeling during May 19-27, 2001.
The weather conditions were overcast and rainy during these measurement periods, as a result of which
no clear day was available for measurements. The predominant wind directions were South-East.
There was no clear day during these measurement periods. The relative humidity was very high, varied
from 85% to 100%. The diurnal variations of hourly average concentration of surface ozone at
different observational days are depicted in figures. The mountain site shows little diurnal variation
and maintains rather large concentrations throughout the day whereas the plain station urban location
like Delhi showed strong diurnal variation. The surface ozone was found varying from 30 ppb to 60
ppbv. During daytime up slope winds were blowing these upslope winds enhance the vertical mixing.
Sometimes in a day time non-precipitating white clouds were also touching ground like fog and were
blowing up slope with the winds. Whenever these clouds are passing through the sucking tube of
analyzer O3 concentration were observed increasing, suggest that O3 is being transported from clouds
vertically from low lying area. The ozone concentrations showed increasing behavior during nighttime
hours with a distinct preference for midnight. This may be attributed to cooling of mountain causing
down slope flow, which draws more ozone reach air from aloft and carrying, it to downward and
maintaining high O3 concentration during night. Hourly running averaged data of surface ozone is
being plotted here.
Ozone at associated places of Darjeeling
On 19/05/01 the observation were made at A.J.C. Bose Institute, Mayapuri.
On 20/05/01 the observation were made at Manebhanj, Darjeeling
On 21/05/01 the observation were made at Darjeeling Govt. College. The concentration varies from 35
ppbv to 45 ppbv.
On 22/05/01 observation were taken at Railway station of Darjeeling. It is supposed to be one of the
polluted part of this region. Ozone concentration varies 30 ppbv to 60 ppbv. This sites gives maximum
value at 15:00 hrs.
On 23/05/01 the observation were made at Kalimpong. Ozone concentration varies from 30 ppbv to 40
ppbv.
From the period of 24/05/01 to 25/05/01 observation were taken at North Bengal University, Siliguri.
This site belongs to the plane area. But the observational site is little away from the town where
maximum vehicles are available. Ozone concentration varies from 25 ppbv to 55 ppbv. This site does
not provides any clear picture of diurnal cycle.
On 26/05/01 observation were taken at Tiger Hill, highest point we could reach. Ozone concentration
varies from 25 ppbv to 70 ppbv with maximum peak at 16:00 hrs.
For the period of 26/05/01 to 27/05/01, the observation were taken at A.J.C. Bose Institute, Darjeeling.
Ozone concentration varies from 25 ppbv to 70 ppbv. Dirunal variation shows minimum at 00:00 hrs
and 19:00 hrs with maximum peak at 12:30 hrs.
5.2 GreenHouse Gases
This study shows that CO2 is within the range of 400 to 700 ppmv. This value is quite high and
generally represents the urban value. Similarly, N2O concentration is within the range of 350 to 550
ppb. Figure – shows that CH4 concentration is within the range of 1.7 to 2.5 ppmv. Darjeeling is a
tourist place, therefore, these large concentration of CH4, N2O and CO2 may be due to the large
increment of the transports. Moreover, the lower boundary layer traps these gases all the year.
5.3 TSP, NOx using High Volume Sampler
The SPM sampling was continuously carried out a Bose Institute, Darjeeling from 19 th May 2001 to
27th May 2001. It was observed that SPM varied between 16 to 66 ug/m3 as shown in the figure with
highest value 24th/25th May. This is probably due to the reason that 22nd May onwards the cloudy sky
persisted so SPM increased slowly because of trapping in the lower atmosphere and reached a high
value on 24th May. Figure 2 shows the SPM values observed at sites in and around Darjeeling. It was
observed that Tiger Hil showed the lowest value of 24 ug/m3 possibly due to the reason that it has very
less population and as such has no or very little anthropogenic activity.
The nitrogen oxides as observed in figure 3 and 4 show the highest value at Railway station, Darjeeling
due to the reason that lot of anthropogenic activity including emissions from fuel is involved there. At
Bose Institute and other sites except Railway station, Darjeeling the NOx values observed or less than
2 ug/m3.
5.4 Aerosol Optical Depth Using Microtop
5.5 Aerosol Optical Depth Using Sunphotometer
5.6 Minimum Erthymal Dose (MED)
5.7 Total Ozone, Water vapor Content by Microtop
5.8 Trajectories
After trajectory analysis it shows that the most of air flow comes from the either from Gulf countries
and from associated places.
6. Conclusion
For the first time such joint study of atmospheric and health parameters was made in this region.
Characteristics of the hilly regions are generally different from plain region. This region sites in the
Eastern Himalayas. Some important points have come from this study. Those are following:
(1) Ozone concentration at Darjeeling and its associated places was quite high than we expected.
(2) GHG also show very high value.
(3) Low concentration of SPM and NOx
7. Acknowledgement
8. References