Ch 2b & 2c Flashcards
Describe metals
Shiny, malleable, ductile & conductive
Describe metalloids
semiconductors, some metallic properties ex - arsenic, silicon
Describe Heavy metals
Originally metals with densities greater than iron, however NOW defined as metallic elements of concern regardless of density
Describe Trace elements
those present in low concentrations (less than ppm)
TRUE or FALSE
Many important contaminants have both natural & anthropogenic sources
TRUE
Where may there be gradients of contaminants present?
near cities, or other developed areas, or may develop near mining or other human activities
What is the problem associated with pollutants present at higher than normal concentrations which are causing deleterious effects & why ?
Proving it. - because its difficult even in situations with a single major contaminant and generally most problems are mixtures of contaminants
give an example for when complex interactions in an environment may further complicate things
Aluminum is toxic to aquatic plants, and acid rain will decrease pH, at low pH, the dominant form of aluminum changes from bound to rocks to soluble in water, BUT low pH on its own is not toxic
Transport processes are influenced by how the contaminant partitions between phases. what are the three portioning phases?
- Gas/ aqueous phase
- Aqueous/ sediment phase
- Dissolved liquid/ solid phase
Thermodynamic equilibrium cannot be assumed on a broad scale, but what can be assumed?
You can assume that local distribution of a compound is such that a steady state can be approximated.
Why does the thermodynamic equilibrium assumption work ?
because portioning is assumed to be rapid
What are the two assumptions of thermodynamic equilibrium
- Xphase A is in equilibrium with Xphase B
2. Partition coefficient (Kp) or the distribution coefficient (Kd) can be determined
Define the Sorption coefficient & 3 facts
Kp for aqueous phase and particulate phase
- Adsorption implies association with surface only as its difficult to distinguish surface & subsurface
- usually equilibrium with two phases ( reversible, irreversible )
- estimated based on lab experiments
- don’t always account for environmental effects
Henry’s Law
Can be used to predict portioning aq and gas phases and predict the partitioning of compounds of a mixture.
What does a Low Henrys coefficient mean
means the compound tends to stay in the aq phase ( can mean high water solubility or low vapour pressure or both )
What does a High Henrys coefficient mean
means more likely to travel atmospherically if discharged aqueously
Define Degradation
Usually oxidative (with oxygen) or with water (hydrolysis)
- can be biological (enzymes) or abiotic (UV, heat)
- Biological degradation can proceed to mineralization (rarely occurs abiotically)
- Photolysis: chemical bonds broken when they destabilize due to absorbed light (usually UV-vis)
Photolysis:
- Rings & double bonds are more vulnerable (i.e. more substituted carbons)
- can be direct: the compound absorbs light & breaks on its own
- can be indirect: other compounds absorb light and become reactive with the compound of interest
When does indirect photolysis occur
indirect when:
- via formation of radicals
- humid substances
What is hydrolysis
water is added, usually across a double bond
- results in hydroxy addition and molecular splitting
- doesn’t occur abiotically at a significant rate
Organic Compounds
include those used as poisons and those wastes, by-products and products of industrial processes
- CFC’s (refridgerants)
- Organochlorine alkenes (solvents, degreasers)
- Chlorinated phenols (wood preservatives)
- Organochlorine pesticides (DDT)
- PAH
- PCB
- Dioxins
- Herbicides
Inorganic gases
- CO2
- Nix
- SO2
Metals & Metalloids
- Al - acid ppt or mine drainage
- As - product of gold, lead mining
- Cd - alloys, electroplating, batteries
- Cr - alloys, pigments, catalysts, preservatives
- Cu - wiring, plumbing, biocontrol agent
Nutrients
- Nitrogen species
- Phosphate species
Organometals
- Tin - antifouling paints (TBT, TMT, TET)
- Lead - tetra alkyl lead (anti knock additive in gasoline)
- Mercury - methyl mercury, aslo as biocides for seed coatings
- radionuclides - weapons production/medical uses
What was Parcelsus responsible for ?
responsible for the recognition that all substances are poisonous given a sufficient concentration
What are the 3 ideas that summarize toxicology on a biochemical scale
- toxic molecules react with biomolecules & disturb their normal processes
- as toxin concentration increases so does the severity of the symptoms at the site of action
- concentration of the toxin at the action site increases with increasing dose
What are the limited number of ways which toxins can cause death
- a given toxin may have more than one mode of action
- toxins that use the same category of toxicity mechanism don not need to be chemically related - everything that inhibits an enzyme doesn’t necessarily have the same structure
How may a toxic substance interact with an enzyme or transport protein to inhibit its normal function ?
May interact at the active site or an allosteric site.
What is an allosteric site ? and will adding more substrate over come the inhibition ?
is a site that will change the activity of an enzyme without changing the shape of the active site - adding more substrate WONT over come the inhibition.
what makes it possible for heavy metals to inactivate enzymes. whats an example
the sulfhydryl group (SH) in the active site
ex - mercury will bind to the active site of enzymes and block it
How potent an enzyme inhibitor is depends on
depends on the enzyme and its relative importance in the cells
Give an example of an enzyme inhibitor in insects
acetyl cholinesterase - Insects use this enzyme as a critical regulatory point in controlling their muscles, Plants do not have a nervous system & don’t use acetyl cholinesterase therefore organophosphate insecticides don’t effect them as much. VERY effective to insects
