Water and antifreeze circulate in automobile cooling systems to cool the engine. If the water level gets low, more water or antifreeze is added to allow the cooling cycle to operate. Unlike this example, however, the relative number of atoms of the chemical elements upon which our lives depend cannot be increased. The total quantity of the elements available to living organisms on earth is constant: the same atoms must be used repeatedly. This circulation of a fixed amount of the chemical elements between living organisms and the physical environment is a biogeochemical cycle. There are several important features of biogeochemical cycles. First, every element has its own cycle, and the cycles are interrelated. This means, of course, that anything that interferes with the biogeochemical cycle of one element will alter the cycle of other elements. In this module, we will deal with three gaseous biogeochemical cycles: carbon, oxygen, and nitrogen. Second, there is usually more than one pathway available to an element or its compounds from one point to another in its cycle. If something should block one path, another path is usually available to take over. This is comparable to the collateral circulatory system of the heart after an infarction or a river channelling around an obstruction. Third, external factors can alter the natural cycles, producing adverse effects on the biota. Pollution of the environment is a primary factor that alters biogeochemical cycles today. Since it is impractical to take an in-depth look at entire biogeochemical cycles, we will look at important selective parts of the cycles of carbon, oxygen, and nitrogen. As part of this investigation, we will conduct activities, perform demonstrations, and suggest additional assignments to look at the chemistry of specific steps in these cycles.
1. Nature of carbon and its reactions, producing inorganic carbon compounds.
2. Nature of oxygen and its reactions, producing compounds containing oxygen.
3. Nature of nitrogen and its reactions, producing nitrogenous compounds.
4. Stratospheric ozone and its absorption of specific solar electromagnetic radiation (wavelength and frequency).
5. Structure and function of carbohydrates, proteins, and lipids.
6. Oxidation/reduction
7. Acid/base properties and reactions
8. Equilibrium
9. Stoichiometry
1. Be able to set up, generate, and collect gases in the laboratory.
2. Be able to use common acid/base indicators.
3. Be able to balance molecular and ionic equations.
After completing a study of biogeochemical cycles, students should be able to:
1. Define biogeochemical cycle.
2. Identify three major gaseous biogeochemical cycles.
3. Distinguish between two major carbon “sinks”&emdash;carbon held in reserve in ocean sediments and in fossil fuels.
4. Describe generally the movement of carbon, oxygen, and nitrogen in their respective biogeochemical cycles, between nonliving and living environments of earth.
5. Relate how human intervention such as deforestation, the burning of fossil fuels, and industrial processes interrupt normal biogeochemical cycles.
Biogeochemical Cycles: Carbon, Oxygen, Nitrogen (BICY) 3