Impact of organic matter and inorganic contaminants on physicochemical characteristics in riverine sediments

Abstract

Purpose The dynamics of contaminant-sediment interactions in degraded natural environments can be studied using synthetic or natural model systems of contaminated fluvial sediments with high concentrations of heavy metals and organic matter. This study aims to characterize naturally contaminated sediments and their physicochemical properties, with a preliminary exploration of the associated microbial communities and their potential correlations with heavy metals and organic matter. These findings are essential for understanding the complex interplay of organic, inorganic, and biological factors that influence the characteristics of contaminated fluvial sediments. Methods Physicochemical determinations were conducted on water and sediments from a highly contaminated site and compared with determinations from sediments of an anthropogenically less affected site (control site). Key characterizations included X-ray diffraction, Mössbauer spectroscopy, and assessments of heavy metal distribution, organic matter, inorganic components, specific surface area, porosity, particle size and microbial community analysis. Results Analysis of contaminated sediments revealed a substantial increase in organic matter, heavy metal concentrations, and inorganic constituent levels relative to control sediments. Notably, changes in physicochemical properties, including particle size distribution, specific surface area, and porosity, were observed, despite the preservation of the original mineral composition. The preliminary sequencing analysis revealed variations in microbial diversity between the contaminated site and other sites within the Reconquista River, particularly the control site. Conclusion The observed elevated levels of organic matter and inorganic constituents in contaminated sediments appear to influence both the accumulation of heavy metals and the alteration of physicochemical properties, and could affect the diversity of microbial community, compared to the control sediments. The use of model systems based on contaminated fluvial sediments facilitated the study of environmental dynamics, revealing interactions among contaminants, microorganisms, organic matter, and clay minerals. The advanced analytical techniques employed provided data to assess the environmental quality of sediments and the fate of contaminants.