Lecture 7 - DA Flashcards
Define radiation.
Energy that can be transferred from one body to another through vacuum.
What are the two types of radiation? Give 3 examples for both.
Non-ionising - low energy photon: infrared, visible, UV, radiowaves
Ionising - high energy: alpha, beta, gamma
What happens when beta and gamma rays penetrate matter?
They dissipate their energy through collisions, and the absorbing ions become ionised, breaking molecular bonds.
Define the two sources of ionising radiation.
Natural - produced in nuclei within naturally occurring unstable atoms as they decay.
Artificial - unstable nuclei created by bombarding them with high energy particles, and which will later decay.
Define isotope.
Atoms of an element with the same proton number, but atomic mass.
Which is worse, external or internal irradiation, and why?
Internal, as external can be blocked or removed, while internal cannot. Also makes alpha radiation dangerous.
What are the two molecular impacts of radiation?
Ionisation - may cause unstable fragments - free radicals.
Excitation - elevates electrons to a higher state, causing potential dissociation or transfer of energy when it returns to the lower state.
Define the two forms of biological damage.
Direct - radiation strikes a molecule, causing damage.
Indirect - radiation strikes a molecule, causing it to release free radicals, which then cause damage.
Define a free radical.
Free uncombined atom, molecule, or atomic group, carrying an unpaired electron.
Which is worse, neutral free radicals, or charged free radicals?
Charged free radicals.
Define somatic damage and genetic damage.
Somatic - damage to enzymes, membranes, organelles, and in DNA leading to cancer.
Genetic damage - damage to DNA and chromosomes in reproductive tissue, leading to birth defects.
Most radiation damage occurs as mutations and cancers, rather than damage to proteins. Explain why.
A high dose is required for direct damage, so mostly causes mutations leading to cancer, which requires a low dose.
Name the three syndromes that collectively cause acute radiation syndrome, and describe the response for each. List them in order of the dose needed to be induced.
Haemopoietic syndrome - recovery or death
Gastrointestinal syndrome - death
Neurovascular (CNS) syndrome - death
What is the true cause of death in gastrointestinal syndrome? What is the underlying cause of this outcome?
Infection rather than gastrointestinal dysfunction. The higher chance of infection is due to the loss of the lymphocyte population from haemopoietic syndrome.
What are the two possible explanations of neurovascular (CNS) syndrome?
Leakage of blood vessels into the brain (ie a haemorrhage) causing pressure
Changes in neuronal permeability, leading to loss of action potential
What are the three pathologies of gastrointestinal syndrome and what does it lead to (4)?
Death of GIT mucosa
Increased shedding of mucosal cells
Decreased replacement of mucosal cells
Leads to a denuded GIT, starvation, water loss, and electrolyte loss.
Define alpha radiation.
Identical to a helium nuclei - 2 protons, 2 neutrons.
Define beta radiation.
Energetic electron ejected from an atom following the conversion of a neutron to a proton.
Define gamma radiation.
EM radiation ejected from a nucleus.
Describe what materials are needed to block alpha, beta, and gamma radiation.
Alpha - stopped by paper
Beta - goes through paper, stopped by 3mm Al foil
Gamma - goes through paper, Al foil, stopped by slab of lead
Define decay rate.
Number of nuclei decaying per unit time.
Define half-life.
Time taken for half the radioactive atoms to decay.
Describe the following formula:
At = Ao/2n
At=activity after time
Ao = activity at time 0
n = number of half lives
How can isotopes be differentiated? What else does this feature reveal?
Each isotope has a characteristic half-life. Also explains why some are more dangerous than others.
What can radioactive isotopes with long half-lives be likened to in terms of toxicology?
Persistent toxicants.
Name the isotopes that are used as tracers for the following elements:
H, C, Zn
H - tritium
C - C14
Zn - Zn65
What is the unit of radiation, and what does it represent?
Bq - becquerel
One transformation per second
What is equivalent dose?
Dose taking into account the type of ionising radiation, and the effect it has on living tissue.
How is equivalent dose calculated?
Equals absorbed dose by weighting factor.
What is the SI unit for equivalent dose?
Sv - sievert
What are dose rates referring to the whole body measured in?
What about rates referring to parts of the anatomy?
Whole body - measured in equivalent dose with reference to time
Partial - measured in absorbed dose with reference to time.
Is alpha radiation more dangerous than gamma radiation?
Yes, but only if alpha radiation is swallowed.
What are the sources of exposure to radiation in %?
Internal - 12% (food, water) Terrestrial - 14% Medical - 12% Cosmic - 10% Rason - 50%
What are naturally occurring isotopes called?
Cosmogenic.
Can a gieger counter distinguish between the types or energy levels of a given radiation?
No.
Whats worse, terrestrial pollution, or aquatic and why?
Aquatic, because it can be carried across the world through currents.
Name 8 types of water pollution. Give an example for each.
Organic - sewage Nutrient - phosphate/nitrate Atmospheric - chlorine Thermal - heat Metal - mercury Pesticide - self-explanatory Radioactive - isotopes Oil - spill/dispersant
Define biological oxygen demand (BOD).
Measure of pollution potential of waste water with a source of organic carbon to determine oxygen usage.
Name 3 effects pollution can have on the water column. What happens to the microbiota?
Lowers available oxygen
Increases turbidity
Decreases light availability
Organic waste settles to the bottom, where bacteria multiply
Do cleanwater fauna tolerate low oxygen well?
No.
Define indicator species.
Species that by their presence indicate condition of the habitat. Also called sentinel organisms.
what are the indicator species for the following: Sewage bacteria (2), polluted rivers, recovery zones, a region of nutrient increase, anoxic conditions.
Polluted rivers - algae
Recovery zone - diatom
Nutrient increase - filamentous greens, cyanobacteria
Anoxic conditions - tubificid worms
Whe presence of which two organisms indicated recovery?
Isopods, and amphipods
What 3 species are most sensitive to organic pollution?
Mayflies, stoneflies, and caddisfish.
What dominated polluted waters?
Protoxoa.
Define eutrophication, and its two types.
Enrichment of waters by inorganic plant nutrients like nitrates and phosphates.
Natural - occurs with ageing of the water body.
Artificial - fertiliser runoff.
What consequence can atmospheric pollution on water?
Acidification of natural waters, like acid rain.
Name a source of thermal pollution. What effect does it have on species richness? Do algae tolerate it well?
Released from power plants.
Species richness decreases.
Algal productivity increases, leading to blooms.
Are accidental oil spills a high contributor to the overall oil pollution?
No, tanker operations spill more oil than accidents.
Why are oil spills dangerous?
Because of the polycyclic aromatic hydrocarbons, and because they float and form an oil slick.
What is a consequence of the oil from spills eventually becoming emulsified and dispersed?
The more they dissolve, the more they become bioavailable.
What are two physical ways an oil spill can be cleaned?
Booms and skimmers.
What are 3 non-physical ways an oil spill can be cleaned?
Burning the oil
Adding dispersants
Bioremediation.
Seeding with oil degrading bacteria.
Define bioremediation.
Spraying with nutrients to encourage microfauna, which will break the oil down.
Are chemical dispersants of oil a good way to clean spills?
Some dispersants were found to be more toxic than the oil.
