Global environment, biosphere cycle

In this book air chemistry is defined as a branch of atmospheric science dealing with the atmospheric part of the biogeochemical cycle of different constituents. In other words this means that we will deal mainly with the atmospheric pathways of those components that are involved in the mass flow between the atmosphere and biosphere, as well as in chemical interactions between the air and the other media of our environment (soils, oceans etc.). It follows from this definition that, on the one hand, our discussion will be restricted to the troposphere and the stratosphere4 and, on the other hand, the photochemistry of the upper layers, the subject matter of the aeronomy (e.g. Nicolet, 1964), will be omitted. This separation of the (photo) chemistry of the lower (troposphere and stratosphere) and upper atmosphere makes it possible to give a more compact treatment of our problem, including the global anthropogenic effects due to the increase of air pollution. 

Plants are diverse, especially the angiosperms (anthophyta), and inhabit all but the most extreme environments on the Earth s surface. They are vital components of the global carbon cycle (see Section 2.3 and Figure 2.17) as they flux vast quantities of carbon dioxide from the atmosphere to the biosphere, and they constitute a large carbon store. In addition, oxygen is released by photosynthesis (see Section 3.6.1). This maintains oxygen concentrations in the atmosphere which favours aerobic life forms and processes. 

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