Environmental Engineering Reference
In-Depth Information
precipitating with OH
). Chelators are organic molecules that
complex with iron.
9. Gradients of redox that occur in natural waters allow for complex
populations of microbes that are capable of a wide variety of
nutrient transformations to form in localized hot spots. There is a
predictable order in which each process will occur across the redox
gradient, given the relative potential energy of each chemical reaction
at each redox point.
10.
Nutrient cycles do not occur in isolation. Complex interactions
occur among all of them, in part because organisms have similar
nutrient requirements. Interactions also occur because different
chemicals interact with each other in the absence of organisms.
QUESTIONS FOR THOUGHT
1. How might acid precipitation dominated by sulfuric acid increase the
availability of phosphate, aside from pH effects?
2. Why are isolated chemosynthetic communities, such as those found
where sulfide enters oxic cave waters or methane enters sediments,
still ultimately dependent on photosynthetic organisms?
3. When people control eutrophication, if only nitrogen is removed,
cyanobacteria can dominate. Why?
4. What was the earth like before oxygenic photosynthesis and how did
the sulfur cycle likely drive the redox processes of ecosystems in
aquatic habitats at that time?
5. Why are areas downstream from hyporheic zones where water
reenters streams often sites of very high algal production?
6. Why do sewage treatment plant operators generally want to avoid
denitrification in ponds designed to settle solids?
7. How might phosphate-rich water be treated with iron to remove
phosphate (including O
2
concentrations and forms of iron used)?
8. Why does silicon often disappear from the epilimnion of lakes more
rapidly than phosphorus or nitrogen?
9. Why is it difficult to reduce the effects of excessive phosphorus
pollution in lakes when O
2
disappears from the hypolimnion?
Search WWH ::
Custom Search