Lightning and atmospheric chemistry: The rate of atmospheric NO production
Although 80% of the atmosphere is composed of molecular nitrogen (N2), this element is often the limiting nutrient in both terrestrial and marine photosynthesis. The reason for this apparent paradox arises from the high chemical stability of nitrogen when it is in its molecular form. Before molecular nitrogen can be used by green plants to make proteins, it must first be converted into a less stable chemical form, often referred to in the aggregate as fixed nitrogen. Fixed nitrogen includes all nitrogen-containing compounds in which the nitrogen atom or atoms are bonded to an element other than nitrogen itself. Ammonium ions and nitrate ions found in soils and aquatic systems are fixed nitrogen compounds, as are reactive nitrogen compounds found in the atmosphere, such as the nitrogen oxides (NOx = NO + NO2). Because the natural abundance of fixed nitrogen - many orders of magnitude less than molecular nitrogen - is often at a level sufficientiy low to be the limiting factor in plant growth, its rate of production often plays a key role in controlling the rate of growth of ecological systems.
