CWD Water Quality & Management 3 — Questions and Answers
Question 1: Which process converts ammonium (NH4+) to nitrate (NO3-) in wetland soils?
- Denitrification
- Nitrification (Correct answer)
- Nitrogen fixation
- Ammonification
Correct answer: Nitrification
Nitrification is the aerobic microbial oxidation of ammonium to nitrate, occurring in the thin oxidized surface layer of wetland soils.
Question 2: A wetland delineator observes iron-rich orange precipitates coating stream cobbles downstream of a wetland. This indicates:
- High phosphorus concentrations binding to iron oxides in aerobic conditions
- Reducing conditions within the wetland releasing ferrous iron that oxidizes upon exposure to air (Correct answer)
- Algal biofilm dominated by cyanobacteria with iron pigments
- Acid mine drainage with elevated aluminum concentrations
Correct answer: Reducing conditions within the wetland releasing ferrous iron that oxidizes upon exposure to air
Ferrous iron (Fe2+) released under anaerobic wetland conditions oxidizes to ferric iron (Fe3+) when exposed to oxygen, precipitating as iron oxyhydroxide coatings on stream substrates.
Question 3: Total Maximum Daily Loads (TMDLs) are established under which section of the Clean Water Act?
- Section 402
- Section 303(d) (Correct answer)
- Section 404
- Section 401
Correct answer: Section 303(d)
Section 303(d) of the Clean Water Act requires states to identify impaired water bodies and establish TMDLs to restore water quality standards.
Question 4: Which macrophyte growth form is most efficient at intercepting non-point source sediment runoff entering a wetland?
- Floating-leaved aquatics such as water lilies
- Dense emergent vegetation such as cattails and bulrushes along the wetland edge (Correct answer)
- Submersed aquatics such as pondweed
- Free-floating mats of duckweed
Correct answer: Dense emergent vegetation such as cattails and bulrushes along the wetland edge
Dense emergent vegetation along wetland margins physically intercepts and slows overland flow, allowing sediment particles to settle before entering open water.
Question 5: Sulfate reduction in anaerobic wetland soils produces which compound that can be toxic to plants?
- Methane (CH4)
- Hydrogen sulfide (H2S) (Correct answer)
- Nitrous oxide (N2O)
- Carbon dioxide (CO2)
Correct answer: Hydrogen sulfide (H2S)
Sulfate-reducing bacteria in anaerobic sediments produce hydrogen sulfide, which is toxic to plant roots at elevated concentrations and contributes to the characteristic rotten-egg odor.
Question 6: The 'first flush' phenomenon in wetland hydrology refers to:
- Initial spring snowmelt recharging wetland water levels after winter drawdown
- Disproportionately high pollutant loads transported during the early portion of a storm runoff event (Correct answer)
- Tidal flushing of salt marsh channels during spring high tides
- Groundwater discharge that clears turbid wetland water after summer drought
Correct answer: Disproportionately high pollutant loads transported during the early portion of a storm runoff event
The first flush describes the elevated concentration of pollutants in stormwater runoff at the beginning of a rain event, when accumulated surface contaminants are mobilized by initial flow.
Question 7: Which wetland function describes the capacity of a wetland to store carbon in organic-rich soils and reduce atmospheric CO2?
- Nutrient cycling
- Carbon sequestration (Correct answer)
- Flood attenuation
- Biogeochemical transformation
Correct answer: Carbon sequestration
Carbon sequestration refers to the long-term storage of atmospheric carbon in wetland peat and organic soils, making wetlands globally significant carbon sinks.
CWD Water Quality & Management 3
Which process converts ammonium (NH4+) to nitrate (NO3-) in wetland soils?