Abstract
Sulfur is an element commonly occurring in the environment. It is present in the atmosphere, in the hydrosphere, and in live organisms; it is one of the most important physicochemical and geological indicators. Depending on the natural conditions, sulfur compounds in the environment may play the role of electron acceptor or donor in the redox processes. These compounds influence the ion concentration and ion balance in benthic sediments. They also determine the speciation, bioavailability and toxicity of heavy metals. Comprehensive knowledge of the processes mediated by sulfur can be a valuable source of information about the past and present state of the ecosystem.