Seasonal Changes in Qualitative and Quantitative Characteristics of Humic Substances in Waters of Different Genesis:...

Membrane filtration methods were applied in this study to research natural waters specification (and speciation). Lysimetric waters (soil waters) of background territories in different seasons are considered. Features of the change in molecular weights, elemental composition, and zeta potential of organic matter during fractionation from 8 μm to 100 kDa were found. The number of labile and non-labile speciation of some elements obtained by membrane filtration and ion-exchange separation methods were found and compared. The highest molecular weights of organic substances were found in summer samples of lysimetric waters (more than 100 kDa) with a predominance of the aromatic component in the IR spectra of the samples. Several maxima were also found in the molecular weight distribution, including the increase in autochthonous organic substances. The most stable negative zeta potential, as a stabilized colloid matter, are represented in summer (near -26 mV) and in autumn (near -22 mV) lysimetric water. A slight increase in metal ions bound into organic complexes is typical for summer and autumn samples.