L3: Sources & Fate

Question 1

2 sources of contaminants to ecosystems

Answer 1

Normal activities:
disposal/release of wastes –industrial, sewage effluents, landfills
deliberate application of biocides for pest control
product use

Disasters: mining, shipwrecks, fires, nuclear accidents, etc.

Question 2

Polybrominated biphenyls (PBBs)

Answer 2

Widely used as flame retardant, added to plastics in laptops, foams, textiles, appliances, etc.
Causes immunotoxicity, common nervous system disorders, cancers in mice
Prenatal exposure related to early menarche (earlier periods) in girls
Possible human carcinogen

Question 3

PBB contamination in Michigan

Answer 3

Michigan Chemical Corporation produced FireMaster (mix of different PBB congeners), white powder
Plant also produced feed ingredient for livestock, magnesium oxide (white powder)

FireMaster accidentally used in feed fed to more than 1.5 million chickens, 30,000 cattle, 5900 pigs
People exposed from: meat from cattle/pigs, eggs from chickens, farm workers handling the feed, industrial exposure
Animals suffered, and euthanized
Large increase in PBB in human blood

Question 4

Octanal-water partition coefficient (Kow)

• measured in lab
• trends/relationships (WS, Cl, aromatic rings)

Answer 4

Measured in lab: ratio of compound that partitions in n-octanal (lipid surrogate) to water

Higher Kow compounds have lower water solubility (WS)
Contaminants with more Cl atoms have higher log Kow
Contaminants with more aromatic rings have higher log Kow

Question 5

Chemicals with lower Kow, more water soluble…

Answer 5

Transported more in water
Degraded more rapidly in bacteria, sunlight
Bind less to sediments
Less lipophilic –lipid soluble

Question 6

Chemicals with higher Kow, less water soluble

Answer 6

Accumulate more and organisms
Bind more to sediments, slower to degrade
More lipophilic –lipid soluble

Question 7

Water solubility (WS)

• measured in lab
• trends/relationships (temp, Kow)

Answer 7

Measured in lab: Max amount of chemical dissolved in pure water at specific temp and pressure

WS increases with higher water temperatures
WS decreases with higher Kow
Higher WS =Hydrophilic, hydrophilicity –water soluble

Question 8

Vapor pressure (VP)

• measured in lab
• trends/relationships (temp)

Answer 8

Measured in lab: equilibrium pressure between a pure liquid chemical and the air space above it in closed container

VP increases with increasing temperature
Important in controlling chemical behaviors such as volatilization from: water, plant surfaces, soil

Question 9

Transformation

Biotic degradation of contaminants

Answer 9

bacteria and other organisms (fish, humans, wildlife) may convert parent molecule into another more or less toxic form (often less toxic)

Question 10

Mineralization

Biotic degradation of contaminants

Answer 10

contaminants used by bacteria such as carbon sources can be degraded to carbon dioxide, water and inorganic salts

Question 11

Photolysis

Abiotic degradation of contaminants

Answer 11

light (UV to visible range) –breaks chemical bonds and chemicals

Question 12

Hydrolysis

Abiotic degradation of contaminants

Answer 12

reaction of water with the contaminant, usually results in the addition of hydroxyl (-OH) group to the compound

Question 13

Oxidation

Abiotic degradation of contaminants

Answer 13

addition of oxygen, removal of hydrogen, or the removal of electrons from an element or compound

Question 14

As number of rings on PAHs increase…

WS, VP, Kow trends

Answer 14

water solubility and vapor pressure decreases and log Kow increases

Question 15

As Chlorination decreases, 
Bioaccumulation
Adsorption to particles
Solubility
Volatilization 
Excretion in animals

Answer 15

decreases 
decreases 
increases
increases
increases

Question 16

As Chlorination increases,
Bioaccumulation
Adsorption to particles
Solubility
Volatilization 
Excretion in animals

Answer 16

increases
increases
decreases 
decreases 
decreases

Question 17

Labile vs Non-labile

inorganic and organic

Answer 17

Inorganic complexes (carbonate, sulfate) tend to be labile (reversible)
Organic complexes (humic and fluvic acids) tend to be non-labile (stable)

Question 18

Dissolved metals & Availability

Answer 18

more biologically available

1) free cations and anions
2) hydroxy ions
3) complexed with organic ligands (humic acids)

Question 19

Non dissolved metals & Availability

Answer 19

less biologically available

1) complexed with inorganic ligands –likely precipitate
2) may aggregate (form a flocculant)
3) adsorbed to particles

Question 20

Metals tend to be more toxic to aquatic organisms in waters that are…

Answer 20

low pH, low alkalinity, low organic acids (less binding)

Question 21

Metals tend to be less toxic to aquatic organisms in waters that are…

Answer 21

high pH, high alkalinity, high organic acids