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Remediation of Contaminated Sediments
Contaminated bed sediments in
rivers, streams, lakes and coastal regions all over the world, including
India, are a source of environmental concern through the
accumulation of hazardous chemicals from decades of uncontrolled industrial
and municipal discharges, combined sewer overflows, and urban and
agricultural non-point source runoff. Persistence of high concentrations of
chemicals in sediments, long after the disposal events, raises significant
concerns about potential risks to aquatic organisms, wildlife and humans,
through various pathways – including air. Contaminated sediments can
potentially serve as a long-term repository of hazardous chemicals and
hence reflect the industrial and waste history of the region. Sediments are
a complex heterogeneous biogeochemical matrix and may comprise of mineral,
inorganic, organic, biological, non-aqueous phase liquids and aqueous
phases. Chemicals of concern associated with sediments cover a wide
spectrum of hazardous materials ranging from persistent organic pollutants
such as polyaromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs),
dioxins, pesticides to heavy metals such as lead, mercury, chromium, and
arsenic.
Contaminated sediments
remediation include options such as dredging (removal or relocation of
sediments), capping (or the placement of a diffusional barrier on the
contaminated zone), active remedial techniques (such as in-situ
bioremediation) or monitored natural recovery. In-situ options for control
or remediation, such as capping or biodegradation, are widely favored since
they limit the potential disturbance caused to the eco-system through
remedial options such as dredging. Active in-situ capping is an innovative
combination of capping and in-situ remediation, in which the goal is to
develop barrier materials that are stable and can supply and sustain
reactive agents that can degrade the contaminants in the sediment. Several
options are available in designing such a cap including a mat-like
structure that is lightweight and capable of accommodating networks of
fibers that can serve several functions in the remediation and the post
remediation monitoring process. Current interests are to explore the
possibility of using UV radiation in the presence of an amended
photocatalyst for integration into such a cap-layer for the degradation of
organic contaminants. If successful, future engineering developments
include the possible use of sunlight and simultaneous sensing of
pollutants.
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Contaminant
Fate and Transport in the Environment:
The impact of a pollutant in
the environment can be evaluated from the knowledge of its interaction with
the different target compartments in the environment. In this context,
‘bioavailability’ is a term commonly used to represent the
concentration of the chemical that any biological receptor in the
environment is directly exposed to and is therefore the focus of most
contaminant fate and transport investigations. The analysis of bioavailability
involves the study of factors affecting equilibrium thermodynamics,
reaction and transport of the contaminant with respect to its environment.
Experimental data is necessary to validate predictive tools that are useful
for multimedia chemical fate and transport modeling or for the design of
remediation methods. Current interests are to experimentally characterise
the fate and transport of organic and inorganic chemicals in contaminated
sediments and dredged materials.
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Air Pollution: Processes and Control
The air pollution problem in
major cities all over the world constitutes pollutants in the gas phase as
well as the
dispersed particulate or
aerosol phase. Airborne particulate matter is among the most serious
pollutants in Indian cities and originate from various industrial and
domestic sources - large industrial plants, medium- and small-scale
industries, refuse burning, households burning biomass for cooking and
heating, vehicular exhaust, re-suspended road dust, construction, particles
migrating from other regions, and naturally occurring dust. These
particulates vary in size, structure and chemical composition depending on
their origin, transport and fate in the lower atmosphere. The organic and
inorganic particulate matter can have very grave health effects leading to
respiratory tract illnesses. It is important to understand and characterize
the problem thoroughly in order to evolve an effective remedial solution.
Current and long-term interests include the development extensive air pollution
characterization databases in urban sectors, source apportionment, study of
related gas-particle interaction in laboratory scale experiments,
development of laboratory and field instrumentation for atmospheric
pollutant monitoring and the development of personal air pollution
protection devices.
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Waste
Treatment and Sensing Methods
This research sub-division includes problems of
interest, especially in water, waste-water and solid waste management issues,
that do not fall under the above three categories. These include
biological, physical and chemical routes to accomplish remediation or
monitoring objectives.
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