Formation of Polysulfides in an Oxygen Rich Freshwater Lake and Their Role in the Production of Volatile Sulfur Compounds in Aquatic Systems

We present the first observations on the occurrence of inorganic polysulfides in an oxygen rich aquatic system. Inorganic polysulfides were found both in the hypolimnion and the epilimnion of a freshwater lake Lake Kinneret. The presence of these compounds in oxic systems resolves the enigma concerning the mechanism of formation of dimethyl disulfide, dimethyltrisulfide, and dimethyltetrasulfide in oxygen rich aquatic systems and marine water. The abundance of low molecular weight organic and inorganic polysulfides relative to the a priori postulated dominance of the pentasulfide family is explained by the low level of polysulfides in oxygen-rich aquatic systems. Thermodynamic calculations show that for trace levels of reduced sulfur compounds, dimethyl disulfide becomes the dominant polysulfide form.