Lecture 12: Bioaccumulation Flashcards
Ecotoxicology
is the study of the fate and
effects of toxicants in an ecosystem.
* more abt animals and how they respond to toxicants
Distribution, degradation and eventual fate
are important.
List the different matrices
4 different “matrices”: atmosphere(air),
lithosphere (land), hydrosphere (water) and biosphere (animals)
– Once in a matrix, can move between different
matrices.
Give an example of how Once in a matrix, toxicants can move between different
matrices
methylmercury goes up into the air eventually deposited on land thru atmospheric deposition, surface run off bring it into water and turns into methylmercury becoming harmful
What is a broad way of describing the sources of toxicants?
Point and Nonpoint Sources of Pollution
• Point sources
are from a discrete source * can be traced back to a single source – Discharge pipes. – Effluent. - waste water treatment
Nonpoint sources
of pollution cannot be precisely narrowed down to a
single source. Can be from numerous sources.
– Surface run-off (pesticides)
– Atmospheric deposition (volcanoes, for Hg)
– Firepits in Winnipeg
– Others?(car exhaust)
Can things be both point and
nonpoint sources of pollution?
yes
Bioaccumulation
concentration in an organism is higher than the
concentration in the environment by absorption AND ingestion
- biomagnification
Bioconcentration
= concentration in an organism is higher than the
concentration in the environment by absorption only (via water in aquatic
systems or inhalation in terrestrial systems)
Bioconcentration factor (BCF)
unitless parameter calculated from the ratio of the steady-state toxicant concentration in the whole organism or tissue to its concentration in the surrounding environment.
- way to determine whether a toxicant itself is actually bioconcentration when it gets released
BCF < 1
toxicant is actively excluded by the
organism
- not being picked up or absorbed as quickly/ high that it comes intp equ’ with the enviroment
- broken down by animal/ excreted
BCF = 1
toxicant exhibits no selectivity
- at same concentration in animal and environment
BCF > 1
toxicant is accumulated within
organism at higher quantity than in
environment
- absorbing more of toxicant so it starts to bioaccumulate
Hydrophobic compounds are more likely to bioconcentrate.
Why?
a lot of toxicants are hydrophobic/ lipophilic and will be more likely to bioconcentrate
if in an aquatic environment they won’t want to be in water so it will bind to something as quickly as possible/ absorbed by animals
biomagnify
concentration increases as it moves up the food chain
Some toxicants become increasingly concentrated (i.e., biomagnify) at successively higher trophic levels, generally via predators feeding on prey items
Trophic dilution
(also known as “biodilution”) - where concentrations decrease with increasing trophic
level
• i.e., opposite of biomagnification
- stuff that can be broken down so it won’t cause issues in humans
When does trophic dilution occur?
• Occurs when rates of
contaminant biotransformation
and elimination exceed rates of
ingestion and assimilation
List Factors that influence biomagnification
of organic contaminants:
– Degree of hydrophobicity
– Ability of animal to biotransform
– Properties of the animal.
Endotherms are more likely to
biomagnify than ectotherms.
Octanol-water partition
coefficient (Kow).
– Peak at ~7 because of limitations of bioavailability for animals.
What does a high Kow mean?
more hydrophobic
Why don’t super high Kow bioaccumulate?
super high don’t magnify bc these have a limited bioavailability, too hydrophobic that they can’t be picked up by animals
What about compounds that have high Kow?
they don’t get broken down easily and have a higher chance of biomagnification
What kow do compounds that biomagnify have?
around 7
What happens to the ability of a compound to biomagnify if we are able to metabolize it?
it decreases the chance of it to biomagnify in the food chain
