Transformation of the group composition of organic matter from the channel deposits of a small river affected by anthropogenic activity

The group composition of organic matter (OM) was studied in the channel sediments of the Pakhra River under natural condition and in the zone affected by the town of Podol’sk, Moscow oblast. It was found that the natural alluvium is poor in OM (C org = 0.65%), the composition of which is dominated by humus acids (81.8% of C org ) at minor fractions of residual OM (16.7%) and lipids (1.5%). Anthropogenic muds formed in the river channel in the zone affected by urban pollution are conspicuous in high OM content (C org = 1.26–2.60%), the composition of which is enriched in lipids (up to 10–20%) and residual OM (up to 27.3–48.6%), whereas the fraction of humus acids decreases to 29.6–57.1%. The muds are most significantly enriched in lipids (their specific concentration increases by factors of 6–59 compared with the natural alluvium) and residual OM (by factors of 3–11). The amount and character of the group composition of OM from anthropogenic muds are controlled by the specific features of the sources of sedimentary material in the river and the character of the environment of alluvium sedimentation in the zone affected by an industrial town.