Although many of the requirements of Statements 67 and 68 are the same regardless of what type of defined benefit plan a government participates in, there are some key differences depending on whether an employer participates in a single-employer, agent multiple-employer, or cost-sharing multiple-employer pension plan.
Oxygen cycle. From Wikipedia, the free encyclopedia. Jump to: navigation, search. The oxygen cycle is the biogeochemical cycle that describes the movement of oxygen within and between its. three main reservoirs: the atmosphere (air), the biosphere (living things), and the lithosphere (Earth's crust). The main driving factor of the oxygen cycle is photosynthesis, which is responsible for the modern Earth's. atmosphere and life. [edit] Reservoirs and Fluxes.
Answer 1: The oxygen that we currently find in the air has two main sources. The first, and major, source is that oxygen is liberated as a by-product of photosynthetic chemical reactions. The second source occurs in the atmosphere itself when water molecules are split apart after being struck with ultraviolet radiation. This process is called photolysis. The molecule is broken down into one diatomic hydrogen molecule and one free oxygen. The hydrogen molecule is light, and has a quick thermal velocity,so it can escape Earth's atmosphere leaving behind the free oxygen to form a diatomic oxygen molecule. The main source of this atmospheric water was volcanic eruptions and outgassing. Basically before photosynthesis began on large scales, free oxygen molecules in the atmosphere were drawn down in oxidation reactions with free metal ions on the Earth's surface, mainly iron.