River transport of Hg as a potential contamination pathway for sediments, soils and vegetation: management practices

River systems, besides shaping their landscapes through the formation of Fluvisols, can also act as pathways for transporting significant pollutants, affecting both the river and its surrounding areas. One such pollutant is mercury (Hg). To assess the impact on sediments and adjacent riverbanks, including Fluvisols and their vegetation, the alluvial plains near Poland's most important river have been studied to understand this process and propose effective management measures. Additionally, basic soil properties, iron forms, and the mineralogical composition of the clay fraction were analysed. The risk of mercury contamination was assessed using the contamination factor, enrichment factor, geoaccumulation index, and ecological risk factor. The bioaccumulation and translocation factors were used to gauge mercury accumulation in herbs. Mercury contamination in the Vistula River and its floodplain soils is generally moderate, with localised hotspots near the confluence with the Bug River, primarily caused by industrial, agricultural, and cross-border activities. The retention and movement of mercury are heavily influenced by soil composition, especially smectite, iron oxides, the clay fraction, and organic matter, as well as land use and flooding patterns. Effective soil management in these floodplains should focus on reducing disturbance in smectite-rich areas, increasing organic content and the stability of iron oxides, and applying erosion and flood control methods. Prioritising soil conservation and nature-based solutions can significantly lower mercury risks in floodplain regions. Ongoing monitoring and research are essential for the sustainable management of floodplain ecosystems.