Limnology Chapter 13 Summary
Holaway
This chapter leads out by discussing what the inorganic forms of
carbon are, this is integral to understanding how they move and change
through the cycle. It is also important to understand how much energy each
type can hold and how well it can buffer pH change. CO2 is the most
abundant form in the air, its dissolved amount controls the pH of water. It
can take multiple forms in water like carbon dioxide, carbonic acid,
bicarbonate, and carbonate (in ascending order). These are listed in that
order in the equilibrium reaction. The equilibrium reactions show how pH is
more easily buffered the farther toward carbonate you are. Atmospheric
pressure can increase the amount of CO2, causing the pH to drop. Carbonate
may offer the highest buffering capacity but CO2 is the most easily used
form of inorganic carbon for photosynthesis. As photosynthesis removes
CO2, it can cause calcite to precipitate as a reaction to the bicarbonate in the
equilibrium equation. On the flip side is organic carbon. It is bonded with
hydrogen, oxygen, and other elements. It is divided into dissolved organic
carbon and particulate organic carbon. You can estimate the amount of
organic carbon by understanding biochemical demand for oxygen. This helps
us also understand the influence of sewage on water systems. Organic
carbon can also be divided into two classes: humic and nonhumic. Humic
substances are large molecules that give the water a brown color. Nonhumic
substances include sugars and amino acids. Organic carbon is important
because it can form bonds with organic pollutants, form complexes with
metal ions, and absorb light that would otherwise be used for
photosynthesis. There are two key processes that allow organic carbon to be
used without oxygen, although they are much less efficient: fermentation
and methanogenesis. These are critical to life in anoxic environments.
Holaway
This chapter leads out by discussing what the inorganic forms of
carbon are, this is integral to understanding how they move and change
through the cycle. It is also important to understand how much energy each
type can hold and how well it can buffer pH change. CO2 is the most
abundant form in the air, its dissolved amount controls the pH of water. It
can take multiple forms in water like carbon dioxide, carbonic acid,
bicarbonate, and carbonate (in ascending order). These are listed in that
order in the equilibrium reaction. The equilibrium reactions show how pH is
more easily buffered the farther toward carbonate you are. Atmospheric
pressure can increase the amount of CO2, causing the pH to drop. Carbonate
may offer the highest buffering capacity but CO2 is the most easily used
form of inorganic carbon for photosynthesis. As photosynthesis removes
CO2, it can cause calcite to precipitate as a reaction to the bicarbonate in the
equilibrium equation. On the flip side is organic carbon. It is bonded with
hydrogen, oxygen, and other elements. It is divided into dissolved organic
carbon and particulate organic carbon. You can estimate the amount of
organic carbon by understanding biochemical demand for oxygen. This helps
us also understand the influence of sewage on water systems. Organic
carbon can also be divided into two classes: humic and nonhumic. Humic
substances are large molecules that give the water a brown color. Nonhumic
substances include sugars and amino acids. Organic carbon is important
because it can form bonds with organic pollutants, form complexes with
metal ions, and absorb light that would otherwise be used for
photosynthesis. There are two key processes that allow organic carbon to be
used without oxygen, although they are much less efficient: fermentation
and methanogenesis. These are critical to life in anoxic environments.
