Methane and sulfide sulfur in water and bottom sediments of streams of the steppe zone of the European part of Russia

The results of long-term studies of the conjugate distribution of concentrations of methane (CH ₄ ) and sulfide sulfur (S _sulfide ) in bottom sediments of streams of the steppe zone of the European part of Russia are analyzed. In addition to CH ₄ and S _sulfide , Eh and pH values, humidity and density were determined in various sediment horizons; CH ₄ , dry residue and pH values were determined in water. Concentrations of CH ₄ in the water of watercourses vary from <0.1 to 2007.0 µl/l (median 24.3 µl/l), with the largest number of values (72 %) in the range 10.1–100.0 µl/l. The concentrations of CH ₄ and Ssulfide in the bottom sediments of watercourses are quite high and vary, respectively, from <0.01 to 51.0 µg/g of wet sediment (median 1.35 µg/g) and from <0.001 to 4.50 mg/g of wet sediment (median 0.813 mg/g). Usually, there is an increase in CH ₄ and S _sulfide from the surface layer to the subsurface horizons, after which their concentrations decrease. The difference between the distribution of sulfides and the distribution of CH ₄ is the more frequent occurrence of maximum concentrations of sulfides in less deep sediment horizons. Seasonal changes in the distribution of CH ₄ and S _sulfide along the vertical of sediments were recorded not only in terms of their concentrations, but also in the location of maximum and minimum values. There is a weak direct relationship between the concentrations of CH ₄ and S _sulfide , which indicates synchronous processes of formation of these gases in separate layers of sediments of the studied watercourses. The direct relationship established between the concentrations of CH ₄ in water and the 0–2 cm layer of bottom sediments indicates sediments as an important source of CH ₄ entering water and its emission into the atmosphere.