Atmospheric cycle of trace constituents

The concentration of trace substances in the atmosphere is very variable in space and time and their residence time (see Table 1) is only some years, weeks or even less. The only exceptions are the noble or rare gases which, with the exception of helium and radon, have no sources and sinks so that we cannot speak of atmospheric cycles in this case. For this reason they are considered permanent constituents and will be omitted from further consideration. 

The problems related to the water cycle will also not be considered in spite of the fact that, taking into account its quantity and atmospheric effects, water is one of the most important trace materials. This omission is explained by a historical precedent. The study of the atmospheric cycle of the water as well as the measurement of its concentration were included in the past in the program of other branches of atmospheric science. Thus, the formation of clouds and precipitation, the subject of the cloud physics (e.g. Mason, 1957, Fletcher, 1962), will only be discussed in relation with the wet removal of aerosol particles and water-soluble gases. 

Furthermore it seems appropriate not to discuss radioactive materials here, but to leave them to a separate volume. The atmospheric fate of radioactive aerosols and gases is similar in some respects to that of other trace substances (e.g. dry and wet removal). However, the presentation of their formation and decay would render the present volume too diffuse. Thus, results gained by radioactive tracers will only be mentioned in Chapter 5 dealing with the removal processes. Concerning atmospheric radioactivity, the reader is referred to other textbooks (Junge, 1963 Cadle, 1966 Israel and Israel, 1973). 

It should be mentioned in this introduction that atmospheric concentrations of trace constituents are sometimes given by the authors in different units. For this reason we have to discuss this problem in some detail. In Table 1 the concentration of trace gases is expressed either in ppm or in /ig/m3 STP. The ppm is a so-called volume mixing ratio1 which is equal to unity if the concentration of a certain gas in the air is 1 cm3 m-3. 

1 The more exact abbreviation is ppmv (v volume). In this book for the sake of simplicity we always use ppm for ppmv. 

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The aim of this book is, first of all, to present the atmospheric cycle of the trace constituents. We will discuss in more detail the trace substances (Chapter 3) with relatively short residence time (<10 yr). The study of these compounds is particularly interesting since their sources and sinks as well as their concentrations are very variable in space and time. They undergo several physical and chemical transformations in the atmosphere. Among these transformations the processes leading to the formation of aerosol particles have unique importance. The aerosol particles control the optical properties of the air, the formation of clouds and precipitation and, together with some gases, the radiation and heat balance of the Earth-atmosphere system. Because of their importance the physical and chemical characteristics of aerosol particles will be summarized in a separate chapter (see Chapter 4). 

Arimoto R, Duce RA, Savoie DL et al (1996) Relationships among aerosol constituents Irom Asia and the North Pacific during PEM-West A. J Geophys Res 10 2011-2023 Bacardit M, Camarero L (2009) Fluxes of Al, Fe, Ti, Mn, Pb, Cd, Zn, Ni, Cu, and As in monthly bulk deposition over the Pyrenees (SW Europe) the influence of meteorology on the atmospheric component of trace element cycles and its implications for high mountain lakes. J Geophys Res. doi 10.1029/2008jg000732... 

Slinn W. G. N., Some influences of the atmospheric water cycle on the removal of atmospheric trace constituents, pp. 57-92 in Atmospheric Chemistry (E. D. Goldberg, Editor), Dahlem Konferenzen, Springer, Berlin, 384 pp. (1982). 

One can clearly see from the data tabulated that the preponderance of trace gases is of biological origin. They are mostly produced by microbiological processes (for further details see Schlegel, 1974). This means that the biosphere plays an important role not only in cycling the main atmospheric constituents, but also in the... 

Friedrich, R. (2009) Natural and biogenic emissions of environmentally relevant atmospheric trace constituents in Europe. Atmospheric Environment 43 1377-1379 Friend, J. R (1973) The global sulfur cycle. In Chemistry of the lower atmosphere (Ed. I. E. 

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