Amongst
the inventions, the wheel is perhaps one the most utilitarian from the
point of view of human comforts and necessities! Wheels lead to
road-rail transport. A communication network became the hall mark of a
developed nation. India, since the times of Akbar, the great Moghul king
has been developing a network of roads. Today the ruling parties lose
the battles at the elections on account of poor or less roads in their
states.
Though a vital link for communication and transport, roads are also
becoming a source of pollution. An account of how the Road Deposited
Sediment (RDS) is a threat to ecosystem makes an enlightening reading.
Raza Rafiqul Hoque and Upasona Devi of Department of Environmental
Science, Tezpur University, and Ritu Thakur of Northeast Regional
Institute of Water and land Management, Tezpur, India, carried out an
interesting study of the extent of pollution and health hazard spread by
RDS in northeastern India.
Road deposited sediment is a product of interaction of solid, liquid and
gaseous material produced from different sources on the roads and has
become a valuable archive of environmental information say Raza and his
co-workers in their recently published paper in the Current Science.
Composition and concentration of RDS is a reliable indicator of the
presence of heavy metal particles in the soil due to anthropogenic
activities in a particular area. Dust as we know spreads far and wide
suspended in the atmosphere. It gets washed down to surface and travels
to subsurface with rain water. This dust when polluted by toxic metals
becomes a potential health hazard for the humans and all other biota.
With the tremendous increase on the road use assessment of RDS gains
significance. Greater the use of the road, higher is the re-suspended
RDS, which is infact a particulate matter (PM) in the air and a serious
air pollutant. Rainwater carries RDS horizontally as well as vertically
and the hazardous toxic components of the RDS pollute the surface and
reach the ground water too.
Heavy metal present in the soil surrounding the roads, slopes reaches
the road via rainwater, dry and wet atmospheric deposition, degradation
of road paint and vehicle wear and tear, vehicular fluid and particulate
emission all add to the RDS.
The toxicity of the heavy metals is well known since the historic times.
Even now they are under the scanner of the environmentalists. For
example lead is a cumulative poison and it can affect blood, kidney,
nervous system and brain. Due to ill effects lead has been phased out as
an additive from petrol. Similarly, Nickel can induce lung and sinus
cancer. Nickel particles reach the RDS via fuel combustion, smelting and
volcanic eruptions. Compared to these two, Zinc is less toxic. Particles
of zinc reach RDS via industrial processes, fuel combustion and
suspended dust. However, being a metal the tiny particles are hazardous
enough to damage the lungs.
Lead pollution and its ill effects have been drawing the attention of
the environmental scientists for the past few decades. In the 1970s it
was found that children in urban surroundings suffer the effects of lead
poisoning from the dust from the streets.
In India very few such studies have been carried out therefore, the
study carried out by Raza and his colleagues is one of the systematic
accounts of RDS quality and quantity from the northeastern region.
National Highways (NH-37) at Kaliabor, Nowgong district on the south
bank of River Brahmaputra; NH-52 at Mission Chariali, Tezpur, on the
north bank of; link highway that joins NH-37 and 52 through a bridge
over Brhamaputra and a market place in Tezpur city, Sonitpur district
were chosen as sampling locations for this study. These places have a
varied vehicular movement and density and also other anthropogenic
activities.
Tezpur is one of the most ancient settlements in the country. During the
post Independence era the city has grown along the highway continuously
over long stretches. The highways also pass through agricultural fields
and forests.
Analysis of the samples gave some alarming results. Lead levels were
found to be 241.8 ± 4.0, 177.7 ± 11.9, 495.0 ± 20.9 and 101.6 ± 8.7
µg/gm in RDS of NH-37, 52, market place and link highway respectively.
Raza et al have compared their results with Delhi (average 121-200
µg/gm) and Bursa city, Turkey (210 µg/gm). However, one sample from an
industrial area of Delhi has lead level of 3760 µg/gm. It is imperative
that such high level is because of the industrial activity. Yet RDS
being a dust can travel far and wide and the neighboring areas can have
serious repercussions. Do we care!
Their study found that near the motor and machinery repair shops on
NH-52 and link highway the Zinc content of RDS was unusually high, 1381
± 29.3 µg/gm and 994.1 ± 35.8 µg/gm respectively. Compared to Zinc, a
much lower content of Nickel 105 µg/gm was found in the rural areas.
Though a higher content of 315 µg/gm was shown by a sample from road
with heavy traffic and was 365 µg/gm in the industrial area. It is
alarming to note that RDS sample from an industrial in an industrial
site in Delhi contained Nickel as high as 1000 µg/gm.
Earlier, in 2005 S. Kar, A.C. Samal and S.C. Santra of Department of
Environmental Science, University of Kalyani, Kalyani, India and B. Nath
of Department of Geology, Jadavpur University, Kolkata, India studied
RDS from the roads of Kolkata metropolitan area. Kolkata, a town with a
history of 300 years is one the most densely populated metropolis. It
has a large number of small and big industries in the northern and
central part. Roads are always under pressure of vehicles of all kinds.
Kolkata boasts of trees almost along all major arteries of the town. The
dust generated by the vehicles rises and settles on the tree canopy.
The study by Kar and his co-workers revealed something astounding.
Leaves of the canopy of trees along the roads were found to be laden
with the dreaded, Arsenic. The highest average concentration of Arsenic
in particulates deposited on canopy leaves found in C.I.T. Road is 39
µg/gm-1, followed by Shaymbazar, M.G. Road and Sealdah showed arsenic
levels of 29, 29, and 28 respectively. Compared to these Arsenic
concentrations of other sites like Chingreghata, Maidan and Moulali
areas are much less, 22.08 ± 0.87, 17.82 ± 0.96 and 22.60 ± 1.19 µg/gm-1
respectively.
On the contrary Arsenic levels in the street dust do not vary much from
place to place, though C.I.T. road has a higher level (18.71 µg/gm-1)
of Arsenic in road dust too. This type of arsenic concentration in dust
fallout like in street dust, is less compared to the medium arsenic
concentration range 32-113 71 µg/gm-1
measured in residential roadside dust in Chihuahua, Monterry and Torren
in North Mexico, says Kar.
Lot of research is being carried out on deteriorating air quality in
urban areas, especially with reference to pollution from vehicle
exhausts. The study and analysis of RDS in India needs a wider attention
to pinpoint the culprits. The alarming levels of Lead from Delhi, Tezpur
and Arsenic from Kolkata in the RDS is enough reason for systematic
studies from all over the country and build a data base to save the
population from the fallout.
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Amongst
the inventions, the wheel is perhaps one the most utilitarian from the
point of view of human comforts and necessities! Wheels lead to
road-rail transport. A communication network became the hall mark of a
developed nation. India, since the times of Akbar, the great Moghul king
has been developing a network of roads. Today the ruling parties lose
the battles at the elections on account of poor or less roads in their
states.