Heavy metal contamination and ecological risk assessment in drainage channel sediments from urban and agricultural areas.

Heavy metal contamination in sediments poses a significant environmental challenge, as sediments are fundamental components of aquatic ecosystems, impacting overall ecosystem health. While numerous studies have assessed heavy metal concentrations in various aquatic systems, there remains a lack of comprehensive analysis comparing the quality of drainage sediments from diverse (urban, agricultural) areas within large-scale hydrosystems. This study addresses this gap by examining metal contamination in drainage channel sediments across the Danube-Tisza-Danube (DTD) Hydrosystem in Northern Serbia, which spans 1.42 Mha. Sediments from urban areas (Urb, n = 45) exhibited significantly higher concentrations of all analysed metals (Pb, Cd, Cr, Ni, Cu, and Zn) compared to those from agricultural areas (Agr, n = 41), except for Cr. While all metal concentrations in Agr sediments remained within the safe limits, a minority of Urb sediments exceeded the maximum allowable concentration. The calculated Geoaccumulation Index (I_geo), Potential Ecological Risk Factor (E_r), and Potential Ecological Risk Index (RI) differed significantly between Agr and Urb sediments. The majority of Agr sediments (95-100 %) were classified as unpolluted to moderately polluted (0 < I_geo <1). In contrast, while most Urb sediments fell within acceptable quality classes (I_geo < 2), some samples exhibited poorer sediment quality (2 < I_geo < 5), indicating moderate to strong pollution levels. Additionally, Agr (vs Urb) sediments exhibited lower E_r values with a narrower range. All Agr sediments scorred the low-risk class (RI < 150), while 89 % of Urb sediments were also classified as low risk, with 6.7 % and 4.4 % categorized as moderate and very high risk, respectively. Principal Component Analysis identified two significant factors in Agr sediments, explaining 78.5 % of the total variance, whereas in Urb sediments, a more complex three-factor structure accounted for 88 % of the total variance. These findings highlight the substantial impact of urban pollution on sediment quality, emphasizing the need for targeted monitoring and remediation strategies to mitigate metal contamination and protect aquatic ecosystems within the DTD hydrosystem.