Surface sediments play a crucial role in freshwater ecosystems as sinks for harmful pollutants and indicators of aquatic health. While localized studies have provided insights into pollution levels, a global assessment of freshwater sediments has been lacking. This study addresses this gap by analyzing data from 149 freshwater sites across 32 nations using multivariate statistical methods (PCA and NMDS were used; receptor models such as PMF, APC-MLR, and UNMIX were not applicable due to lack of primary raw data) and established environmental indicators. Results revealed that average metal concentrations, except for cobalt and zinc, exceeded safety standards, with arsenic, cadmium, and mercury being the most prominent contaminants. Severe contamination was observed in 29-69 % of locations, with arsenic, cadmium, chromium, and nickel posing significant risks to aquatic life in 4-31 % of sites. The ecological risk index (CSI > 5, RI ∼ 600) indicated that 65 % of sites face severe environmental threats. Advanced statistical analyses, including principal component analysis and non-metric multidimensional scaling, identified pollution patterns and sources. Four principal components explained 89 % of the variance, with strong linear correlations (R2 = 0.93) and minimal ordination stress (Stress = 0.023), ensuring the reliability of findings. Source enrichment analysis linked contamination to both natural and human activities, including agriculture, mining, industry, municipal wastewater, and fossil fuel emissions. These findings highlight the urgent need for effective sediment contamination management in freshwater ecosystems.
Keywords: Contamination assessment; Environmental indices; Freshwater sediments; Multivariate statistical approaches; Toxic metal pollution.
Copyright © 2025. Published by Elsevier Ltd.