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
