Transportation ,accumulation and transformation of pollutants, Biomagnification and Transformation Processes

1. Transportation ,accumulation and
transformation of pollutants,
Biomagnification and
Transformation Processes

2. Transport
Two kinds of transport Mechanisms are distinguished
Intermedia transport
• intermedia transport, which is transport
from one environmental medium to
another.
• Intermedia transport (air-water, water-
sediment, etc.) also takes place by
advective and dispersive mechanisms.
Advective intermedia transport takes
place if a chemical is transported from
one environmental compartment to
another by a physical carrier.
• Intermedia dispersion, like intramedia
dispersion, is diffusive in nature and
follows concentration gradients.
Intramedia transport
• intramedia transport, which is transport away
from a source in one environmental medium
• Intramedia transport takes place through the
mechanisms of advection and dispersion.
Advection causes a chemical to travel from
one place to another as a result of the flow of
the medium in which it occurs; locally emitted
packages or “puffs” of a chemical are carried
as far as the wind or water current can take it
during the residence time in that medium.
Dispersion mechanisms (molecular diffusion,
eddy diffusion) make the chemical move
down concentration gradients until the
concentration gradients disappear.

3. Wet and Dry Deposition
Chemicals are transported from the atmosphere to water and soil by
atmospheric deposition
Wet and dry atmospheric deposition
mechanism.
• Wet deposition is the sum of rain-out (in-cloud
processes) and wash-out (below-cloud
processes)
• The efficiency of the wet deposition process
varies greatly. It depends on meteorological
factors such as the duration, intensity and type
of precipitation (snow, rain, hail), as well as on
the size and the number of droplets. Other
specific parameters, like solubility in rain and
snow.
• In the case of dry deposition, the main resistances
occur at the air-surface interface: transport of the
chemical from the air to the interface, diffusion
across the interface and transport from the
interface to the solid surface.

4. Bio accumulation
An important process through which chemicals can affect living organisms is
bioaccumulation. Bioaccumulation means an increase in the concentration of a chemical in a
biological organism over time, compared to the chemical's concentration in the
environment. Compounds accumulate in living things any time they are taken up and stored
faster than they are broken down (metabolized) or excreted.
UPTAKE
Uptake is a complex process which is still not fully
understood. chemicals tend to move, or diffuse,
passively from a place of high concentration to one
of low concentration. The force or pressure for
diffusion is called the chemical potential, and it
works to move a chemical from outside to inside an
organism.
STORAGE
Some chemicals are attracted to certain sites, and by binding to
proteins or dissolving in fats, they are temporarily stored. If
uptake slows or is not continued, or if the chemical is not very
tightly bound in the cell, the body can eventually eliminate the
chemical.

5. ELIMINATION
Chemicals that dissolve readily
in fat but not in water tend to
be more slowly eliminated by
the body and thus have a
greater potential to accumulate.
Many metabolic reactions
change a chemical into more
water soluble forms called
metabolites, that are readily
excreted.
Bioconcentration
Bioconcentration is the specific
bioaccumulation process by which
the concentration of a chemical in
an organism becomes higher than
its concentration in the air or water
around the organism.

6. Volatilizationo or Gas Sorbtion
Volatilization of chemicals from soil is the transfer of the chemical as a gas through the soil-air
interface under environmental conditions; volatilization from plants is the corresponding process.
• volatilization of chemicals may contribute significantly to air pollution and, thus, to the long-range
transport of chemicals by air.
• The resistance to intermedia transfer is considered to be concentrated in two thin films on either
side of the interface
• Transport through this interfacial double layer has to take place by molecular diffusion and is,
therefore, slow.
• The direction of transport depends on the concentrations in air and water.
• If the actual concentration of the chemical in water is higher than the
equilibrium concentration in water, the chemical will volatilize from the
water phase into the gas phase.
Ammonia Volatilization Loss from a Paddy Soil

7. Conceptual model of vapors migration to outdoor air
The case investigated
is a contaminated
area located in a
industial area of
Trento North
district once occupied
by Italian
Carbochimica plant
.Pollution in that area
is due to
contamination of soil
and groundwater.

8. Biomagnification
• When the concentration of a chemical becomes higher in the organism than
in its food (and the major uptake route is food) this is called
biomagnification.
• Chemicals reaching relatively high concentrations in food
• While low
concentrations in other
surrounding media,
such as water for
aquatic organisms, air
for terrestrial
organisms and soil and
sediment for soil
organisms.

9. Uptake from Food, Water & Sediment
• Uptake from food occurs in the gastrointestinal tract (GIT).
• After release of the contaminants in the GIT lumen, the chemicals may cross the lipid
membranes
• Xenobiotic compounds can be taken up by aquatic organisms from water, food or sediment
• Methods for measuring Biomagnification: Dietary tests in fishes
• The simplest measure is the Biomagnification Factor (BMF), which is described as the ratio
of the chemical concentrations in the organism (CB) and the diet of the organism (CD), i.e.,
BMF = CB/CD, where the chemical are usually expressed in units of mass of chemical per kg
of the organism (in wet weight or in a lipid basis) and mass chemical per kg of food (in wet
weight or in a lipid basis) (Gobas and Morrison 2000)

10. Food as a major source of contaminants

11. Abiotic Transformation Processes
• Degradation or transformation of a compound refers to the disappearance of the parent
compound from the environment by a change in its chemical structure
• Chemicals released into the environment gets transformed by abiotic and biotic
processes
• If the above mentioned change is brought by microorganism it is referred to as,
biodegradation or bio transformation.
• Transformation of chemicals in environment can occur by abiotic processes,
1- Hydrolysis: alteration of the chemical structure by direct reaction with water.
2- Oxidation: a transformation process in which electrons are transferred from the
chemical to a species accepting the electrons; the oxidant.
3- Reduction: the reverse of oxidation; electron transfer takes place from a reductant to
the chemical to be reduced.
4- Photochemical degradation: transformation due to interaction with sunlight

12. Abiotic Transformation
Transport and transformation
phenomena and processes in a water
system. The transformation processes,
including dissociation and degradation to
form metabolites and degradation
products (B, C, and D), simultaneously
consist of both abiotic (e.g., hydrolysis
and photolysis) and biotic (i.e.,
biodegradation). In addition to chemical
reactions, Compound A, the parent, and
its reaction products also undergo
physical changes, e.g., scouring,
molecular diffusion (usually only
important in quiescent systems, e.g.,
sediment layers), and advective
processes.

13. Biotic Transformation Processes
• Organism eat chemical, they excrete or alter it
• Biodegradation and biotransformation.
• Biotransformation influences the fate of a compound by decreasing its amount due to
conversion into a new xenobiotic compound, the metabolite
• Biotransformation requires enzymes (Biological catalyst)
• Formation of Hydrophilic compounds- Chemical structures altered then..
• Bio activation/ detoxification
• There are two types of biotransformation reactions: Phase-I non-synthetic reactions and
phase II synthetic reactions.
• Phase-I reactions include hydrolysis, reduction, and oxidation. During Phase-I reactions
the molecule is changed by the introduction of polar groups, such as hydroxy (-OH),
carboxyl (-COOH) or amino (-NH2) group
• Phase-II reactions are usually conjugation reactions. The products of Phase-I reactions
are often reactive compounds which can be easily conjugated in Phase-II reactions. The
conjugated products will then be excreted.

14. Biotransformation
a) catabolism
- degradation vs. mineralization (CO2, H2O)
- energy for growth and motility (but not always!)
b) Decomposition bacteria and fungi
. Pseudomonas, Bacillus, Arthrobacter, Actinomycetes
c) Methanogens
- strict anaerobes
- convert fermentation products (ethanol, acetate,...) to methane

15. Attenuation and degradation mechanisms in macrophytic plants.