7. Source & Fate

Question 1

How do pollutants enter the ecosystem? (4)

Answer 1

1. Unintended release from human activities (e.g. nuclear accidents, mining operations, shipwrecks, fires)
2. Disposal of wastes (e.g. sewage, industrial effluents)
3. Deliberate application of biocides (e.g. pest and vector controls, pharmaceuticals)
4. Natural processes (e.g. weathering of rocks, volcanoes, forest fires)

Question 2

Natural sources of PAHs (Polycyclic Aromatic Hydrocarbons) (4)

Answer 2

• Oil seeps
• Forest/grass fires
• Volcanoes
• Wood and animal decay

Question 3

Anthropogenic sources of PAHs (3)

Answer 3

• Oil spills, leaks
• Burning of fossil fuels (car exhaust)
• Cigarettes

Question 4

Overall source of PAHs (1)

Answer 4

Incomplete combustion of organic matter

Question 5

Pyrogenic source of PAHs

Answer 5

• Originate from high temperature combustion
• Mostly unsubstituted → do not have any groups attached to the benzene rings
• High molecular weight

Question 6

Petrogenic source of PAHs

Answer 6

• Originate from petroleum: crude oil, fuels, lubricants, and their derivatives
• Higher percentage of alkylated PAHs
• Tend to be alkylated (here has a methyl group)
• Alkyl = carbon group e.g. methyl

Question 7

Are the sources of PCBs (a HAH) natural or anthropogenic

Answer 7

Anthropogenic → they are manufactured compounds

Question 8

Source of PCBs (what specifically)

Answer 8

Dielectric fluids in transformers and capacitors, coolant, lubricant, etc.

Question 9

Are PCBs PBTs?

Answer 9

Yes

Question 10

What does PBT stand for

Answer 10

Persistent
Bioaccumulative
and Toxic substance

Question 11

PCBs were banned. These legacy contaminants’ concentration decrease as years go by. But why are there still background levels today (if they are manufactured only and banned)?

Answer 11

• Because there are still hotspots, or places where there were leaks, so its like a secondary source
• We cannot get completely rid of them, bc there are small point sources here and there that leak into the environment, even though they are not perpetually persistent

Question 12

What is the OG source of mercury?

Answer 12

Mercury is a naturally occuring element

Question 13

Why has the concentration of mercury increase in the environment?

Answer 13

Human activities

Question 14

What is chemical fate?

Answer 14

It is what happens to a chemical once it enters the environment

Question 15

What are the 4 major compartments that contaminants are distributed to?

Answer 15

1. Air (atmosphere)
2. Surface waters (hydrosphere)
3. Land surface (soil/sediment)
4. Living organisms (biosphere)

Question 16

What determines the fraction of each chemical that will be found in each compartment?

Answer 16

Physical-chemical properties are a major determinant of the fraction of each chemical that will be found in each compartment

Question 17

What properties of chemicals can influence their fate? (4)

Answer 17

• polarity and water solubility
• partition coefficients
• vapour pressure
• molecular stability (has to do with persistence)

Question 18

What environmental conditions can influence the fate of a chemical? (2)

Answer 18

• temperature
• flows of water, air, solid matter

Question 19

What patterns of use of the chemicals can influence their chemical fate? (3)

Answer 19

• which compartment the chemical is introduced into
• if the introduction of the chemical is episodic or continuous
• if the introduction is in conjuction with other chemicals (e.g. pesticides + additives, oil + dispersants)

Question 20

What is an example of an episodic introduction of a contaminant?

Answer 20

A pesticide you only put out a few times per season

Question 21

What is an example of an continuous introduction of a contaminant?

Answer 21

Coal burning

Question 22

Key physical-chemical properties (3)

Answer 22

• Solubility in water
• Partition between environmental compartments, and Octanol-water partition coefficient
• Susceptibility to degradation/transformation

* solibility: more polar molecules are more water soluble

Question 23

hydrophobic

Answer 23

chemicals that are relatively insoluble and tend to move out of the aqueous phase

Question 24

hydrophillic

Answer 24

chemicals that are quite soluble in water

Question 25

lipophobic

Answer 25

chemicals that are relatively insoluble in lipids

Question 26

lipophilic

Answer 26

chemicals that are soluble in oil and accumulate in fatty tissues

Question 27

If a chemical is lipophilic does it have to be hydrophobic?

Answer 27

No

Question 28

What is the log kow of a lipophilic chemical?

Answer 28

Greater than 0

Question 29

Non polar molecules are usually lipophilic or hydrophilic?

Answer 29

Lipophilic

Question 30

What is the octanol water partition coefficient (KOW)?

Answer 30

it describes the partitioning behaviour of chemicals in the environment

Question 31

What is the “formula” for the octanol water partition coefficient (KOW)?

Answer 31

KOW = concentration in octanol / concentration in water

Question 32

What is the Kow and Log Kow of a chemical that equally partitions between water and octanol

Answer 32

• Kow = 1
• Log kow = 0 (Log(1)=0)

Question 33

Influence of chlorine atoms on log Kow

Answer 33

More chlorine atoms = higher log kow

Question 34

Influence on the number of rings (number of carbons) on log kow

Answer 34

More rings = higher log kow

Question 35

What is global distillation?

Answer 35

Global distillation is the concept that contaminants are transported from water to colder regions.
So contaminants arrive in high concentrations in the poles

Question 36

Is global distillation done in 1 hop or multiple hops?

Answer 36

haha trick question its both
the contaminants can either move up directly or move up seasonally.

Question 37

Why does the arctic have an alarming amount of organic contaminants (discovered in breast milk of women living there)

Answer 37

• global distillation
• traditional diet