Ch 2b & 2c

Question 1

Describe metals

Answer 1

Shiny, malleable, ductile & conductive

Question 2

Describe metalloids

Answer 2

semiconductors, some metallic properties ex - arsenic, silicon

Question 3

Describe Heavy metals

Answer 3

Originally metals with densities greater than iron, however NOW defined as metallic elements of concern regardless of density

Question 4

Describe Trace elements

Answer 4

those present in low concentrations (less than ppm)

Question 5

TRUE or FALSE

Many important contaminants have both natural & anthropogenic sources

Answer 5

TRUE

Question 6

Where may there be gradients of contaminants present?

Answer 6

near cities, or other developed areas, or may develop near mining or other human activities

Question 7

What is the problem associated with pollutants present at higher than normal concentrations which are causing deleterious effects & why ?

Answer 7

Proving it. - because its difficult even in situations with a single major contaminant and generally most problems are mixtures of contaminants

Question 8

give an example for when complex interactions in an environment may further complicate things

Answer 8

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

Question 9

Transport processes are influenced by how the contaminant partitions between phases. what are the three portioning phases?

Answer 9

1. Gas/ aqueous phase
2. Aqueous/ sediment phase
3. Dissolved liquid/ solid phase

Question 10

Thermodynamic equilibrium cannot be assumed on a broad scale, but what can be assumed?

Answer 10

You can assume that local distribution of a compound is such that a steady state can be approximated.

Question 11

Why does the thermodynamic equilibrium assumption work ?

Answer 11

because portioning is assumed to be rapid

Question 12

What are the two assumptions of thermodynamic equilibrium

Answer 12

1. Xphase A is in equilibrium with Xphase B

2. Partition coefficient (Kp) or the distribution coefficient (Kd) can be determined

Question 13

Define the Sorption coefficient & 3 facts

Answer 13

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

Question 14

Henry’s Law

Answer 14

Can be used to predict portioning aq and gas phases and predict the partitioning of compounds of a mixture.

Question 15

What does a Low Henrys coefficient mean

Answer 15

means the compound tends to stay in the aq phase ( can mean high water solubility or low vapour pressure or both )

Question 16

What does a High Henrys coefficient mean

Answer 16

means more likely to travel atmospherically if discharged aqueously

Question 17

Define Degradation

Answer 17

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)

Question 18

Photolysis:

Answer 18

• 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

Question 19

When does indirect photolysis occur

Answer 19

indirect when:

• via formation of radicals
• humid substances

Question 20

What is hydrolysis

Answer 20

water is added, usually across a double bond

• results in hydroxy addition and molecular splitting
• doesn’t occur abiotically at a significant rate

Question 21

Organic Compounds

Answer 21

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

Question 22

Inorganic gases

Answer 22

• CO2
• Nix
• SO2

Question 23

Metals & Metalloids

Answer 23

• 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

Question 24

Nutrients

Answer 24

• Nitrogen species

- Phosphate species

Question 25

Organometals

Answer 25

• 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

Question 26

What was Parcelsus responsible for ?

Answer 26

responsible for the recognition that all substances are poisonous given a sufficient concentration

Question 27

What are the 3 ideas that summarize toxicology on a biochemical scale

Answer 27

1. toxic molecules react with biomolecules & disturb their normal processes
2. as toxin concentration increases so does the severity of the symptoms at the site of action
3. concentration of the toxin at the action site increases with increasing dose

Question 28

What are the limited number of ways which toxins can cause death

Answer 28

1. a given toxin may have more than one mode of action
2. 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

Question 29

How may a toxic substance interact with an enzyme or transport protein to inhibit its normal function ?

Answer 29

May interact at the active site or an allosteric site.

Question 30

What is an allosteric site ? and will adding more substrate over come the inhibition ?

Answer 30

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.

Question 31

what makes it possible for heavy metals to inactivate enzymes. whats an example

Answer 31

the sulfhydryl group (SH) in the active site

ex - mercury will bind to the active site of enzymes and block it

Question 32

How potent an enzyme inhibitor is depends on

Answer 32

depends on the enzyme and its relative importance in the cells

Question 33

Give an example of an enzyme inhibitor in insects

Answer 33

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