Earth and Environmental Systems

What is the definition of a pollutant and how is “water pollution” defined.
Pollutant: Any substance that does not belong in the natural system and disrupts the natural balance
Water pollution: Degradation of water quality in a manner that disrupts/prevents its intended or
original use.
Know what an MCL, and know what a secondary MCL is.
MCL=Maximum Contaminant Level
– The highest concentration of a pollutant
allowed in drinking water by law
– Concentration above which adverse
health affects are believed to occur
Secondary MCL
– Concentration of a pollutant above which
the water is unpleasant in odor or taste
– May not be hazardous to your health at
that level
What is the term for the idea that small doses of toxins can be beneficial for an organism?
Know the difference between point source and non-point source pollution and give examples of each.
• Point-source: any source of a pollutant that you can point to
– Smokestack /industrial effluent
– Oil Tanker spill
• Non point source: area-wide discharge
– Atmospheric deposition
– Farm field runoff
Besides water itself, what are the three essential ingredients for an aquatic ecosystem?
Light, oxygen, and nutrients
What are the main differences between the limnetic, metalimnion, and hypolimnion zones of a lake in terms of its abiotic factors?
Limnetic – top, high light more photosynthesis, warmer, less dense, thinner, more DO
Metalimnion – middle
Hypolimnion – bottom, darker, colder, denser, less DO
Know how the photic/euphotic zone is defined and what controls its depth.
• Photic or Euphotic Zone
–Depth to which adequate light for
photosynthesis can penetrate.
–Controlled by amount of particulate
matter (sediment, plankton, and
organic debris) in the water column.
Know the definition of and the influences of DO and BOD and what level they tend to take on in polluted waters.
Dissolved Oxygen – DO
– Amount of oxygen available in the water.
– Oxygen in water maintained by
• exchange with the atmosphere
• Production of oxygen by photosynthetic organisms
• Circulation of water (essential to maintain oxygen
levels in deeper portions)
– Oxygen consumed by decaying organic
matter and oxygen breathing organism.
• Biochemical Oxygen Demand
–Measure of the amount of oxygen
required for the aerobic degradation
of organic and non-organic
compounds in the water.
–Highly polluted waters have very
high BOD implying that oxygen is
consumed rapidly.
Know how the relative levels of DO and BOD respond downstream from an organic pollution point source. How could you measure to determine the level of pollution for an organic pollutant?
Polluted: high BOD low DO
Measure DO and put in an opaque jar, in a room at 70 degrees then check DO
Be able to describe an oligotrophic and eutrophic body of water and how an oligotrophic becomes eutrophic.
Oligotrophic Condition
• Under normal conditions (preanthropogenic
most surface water are:
1. low in nutrients (particularly
phosphorous and nitrogen)
2. well oxygenated
3. have few particulates in the
water column

Eutrophic Condition
• Caused by the excess nutrient and
sediments (sequence of event outlined
in prior slides).
• Major cause is the use of fertilizers,
excess erosion from farmland or
nutrient rich soils (deforestation), and
disposal of phosphate bearing
compounds (many detergents) through
sewer systems.

What can be done to reduce eutrophic conditions?
• Reduce nutrients and sediments
• Chemical Treatment
• Aeration
• Harvesting plants
• Dredging
What type of water pollution causes the most stream pollution in the U.S. and what is the major source of this pollution type?
Sediment pollution from agriculture
What is the most serious form of pollution for most Rocky Mountain streams like Clear Creek, and what is a good remediation technique for this problem?
Mining Pollution
Artificial Wetland Construction
What is the term for the increased concentration of a toxin as it is passed along a biological food chain?
Where is the “Dead Zone” and what type of pollution is it?
Coast of Louisiana and Mexico
Farmers, sediment, pesticides
What is the largest source of groundwater contamination in the U.S.?
Leaky underground gas storage tanks
Know the difference between a DNAPL and an LNAPL, which one is more mobile, and which one is harder to clean up.
•DNAPL: harder to clean up
–Dense Non-Aqueous Phase Liquid
•LNAPL: mobile
–Light Non-Aqueous Phase Liquid