soils water quality

Question 1

effects of extreme values of turbidity on env

Answer 1

Effects:
o Light penetration, and therefore plants can’t photosynthesize and die. OM accumulates on bottom
o Temperature: as heat rises amount of O2 in water decreases, this affects anything living in the water
o Effects on fish: reduced growth, feeding, hatching effected. Fish may die
o Clogging of habitats, and fish gills
o Vehicle for contaminants, bacteria

Question 2

effects of extreme values of nutrientson env

Answer 2

o Eutroprophication
 Excessive richness (could be small amount) of nutrients (normally N or P) in a lake or body of water
• Cause: Usually human activity that cause imbalance between production and consumption of living material
Effects:
• Anoxic water, algal bloom, decrease in diversity and food supply, habitat destruction
• Oxygen levels effected, become anaerobic
• Sunlight decreases
• Aquatic organisms die
o In sea: hypoxic zone in gulf. Same as eutrophication but in ocean. Excess N from missisipi

Question 3

Describe how the inorganic N content changes during the year.

Answer 3

• Influenced by 2 main things:
  o Mineralisation by microbes
   Microbes don’t like hot, dry conditions. So inorganic N low in January. When rain starts, there is an increase in ammonification, nitrification
  o Processes which reduce N (plant uptake, denitrification)
• Graph:
  o So inorganic N low in January. When rain starts, there is an increase in ammonification, nitrification (so inorganic N increases)
  o However, in (May?) plants grow, and increase uptake. Also there is more leaching and denitrification (so inorganic N decreases) (but in May/ July still higher lvls than in summer)
  o Then in September, it starts to get hot, warm again. There is also another surge in plant uptake (so inorganic N continues to decrease)

Question 4

Describe the purpose (be specific), the operating principles (also be specific), plus three advantages and three disadvantages of the neutron probe. (SAME Q 2015 AND 2014)

Answer 4

Purpose: Widely used in agriculture, forestry, hydrology and engineering to follow changes in water content. Recommended where single ______(whats this word, obscured by hole punch) to be monitored over a long period (e.g. rotation trials).

Advantages: 
-	Rapid, non destructive
-	Repeatable on fixed sites
-	Large sample volume (a few m3, whereas OD soil is small soil sample)
Disadvantages:
-	Calibration required for site
-	Low resolution, can’t detect steep gradients in ϴv
-	High initial cost (>$10,000 2nd hand)
-	License required
-	Potential hazard