Anna Georgievna Zavarzina

Structural peculiarities of the organic component of dissolved organic matter (DOM) of typical chernozems (Protocalcic Chernozem), differing in the principal direction of soil organic matter transformation (accumulation or mineralization), has been analyzed in relation to the mineral composition of DOM. To characterize the structural features of the organic component, spectrometry in the ultraviolet and visible range and fluorescence spectroscopy were applied as approaches most often used for these purposes due to the expressiveness and accessibility of the instrumental design. The content of mineral elements (Al, B, Ba, Ca, Fe, K, Li, Mg, Mn, Na, P, S, Si, Zn) was carried out by optical emission spectrometry with inductively coupled plasma. DOM of arable chernozems, where the mineralization of organic matter is the prevalent process of organic matter transformation, was found to possess higher values of the indexes E2/E3, BIX and SUVA254. The latter indicates a smaller MM, a greater contribution of organic matter of microbial origin and aromatic structures to the composition of DOM as compared to soils not involved in agricultural use. The analysis of the mineral component showed Si and Ca were the most abundant elements in the DOM. The involvement of chernozems in agricultural use resulted in a decrease in Ca content and an increase in Si, Fe and Al, what reflected an increase in the degree of weathering of the mineral matrix of chernozems. The conducted rank correlation analysis showed the presence of significant relationships between the structural characteristics of the DOM (E2/E3, SUVA254, MM, BIX, T) and the content of mineral elements (Ca, Al, Fe, Si) indicating the influence of weathering processes on the formation of the soil DOM.