In recent years, trace concentrations of H2S have been measured employing a fluorescence analytical method. Automatization of the method caused enhancement of its analytical capacity. Thus it became possible to observe variations of the H2S concentration during days, months, and years at different sampling sites. The obtained data showed that swamps and tidal flats are natural sources of H2S. Their contributions to the atmospheric sulfur cycle are compared with those of volcanic activity measured at Etna (Italy) and with those of anthropogenic activity measured in the environment of Frankfurt (Germany). The observed daily and seasonal variations of the H2S concentrations showed that photochemical reactions are probably the main sink of atmospheric H2S. The measured data of a vertical H2S concentration profile were used to calculate a mean removal coefficient for H2S of 2.27¿10-5 s-1, corresponding to a mean lifetime of 12.2 hours. The removal coefficient is compared with the reaction constants of some photochemical processes which may determine the atmospheric removal of H2S. This comparison leads to the conclusion that the reaction of H2S with OH radicals is the main sink of atmospheric H2S.