Nonspecific Organic Compounds and Their Role in the Formation of Organic Matter in Bottom Sediments and Soils from the Catchment Areas of Streams in Voronezh Heights (Khabarovsk)

This paper presents data on the pigment composition, organic carbon (Corg) content, and molecular composition of n-alkanes in the bottom sediments and adjacent soils of streams in Voronezh Heights (Khabarovsk). The Corg (1.85–25.34%) and total phytopigment (10.55–212.93 μg/g) of the bottom sediments varied significantly and decreased from silt to sand. The influence of primary production on the formation of organic matter in the stream sediments is confirmed by positive correlations between the contents of Corg and individual phytopigments (chl a, chl c, and carotenoids) and their total amount (τ = 0.51–0.69). The pigment inventory of the bottom sediments contains 35.1–60.1% chlorophylls. In most watercourses, blue-green algae dominate in the composition of algal communities. The Corg content in the soil of the stream catchment areas ranged from 1.75 to 5.32%, whereas the total phytopigment content varied from 11.61 to 27.97 μg/g and depended primarily on soil moisture rather than on Corg content. The fraction of carotenoids in the pigment inventory of the soil ranged from 41.48 to 70.97%. The dominance of chl c in the composition of chlorophylls (up to 100%) is consistent with the predominant development of diatoms in the soil algal community. The quantitative contributions of newly formed, biochemically altered, and total plant-derived Corg were calculated using an algorithm involving pigment indices. The agreement between pigment‑based and molecular marker‑based estimates of the fraction of primary production and the contribution of hydrobiont‑derived organic matter, respectively, allows a more reliable assessment of the input of plant‑derived organic matter into bottom sediments and soils during early diagenesis.