The extensive mercury contamination in soil and legacy sediments of the Paglia River basin (Tuscany, Italy): interplay between Hg-mining waste discharge along rivers, 1960s economic boom, and ongoing climate change

Abstract Purpose The extensive Hg contamination in soil and sediments occurring along the Paglia River (Central Italy) is result of interplay between geomorphological changes river anthropic activities, primarily associated to exploitation Hg-deposits "The Monte Amiata mining district" (MAMD). present study determines implications morphological that occurred last 200 years on distribution floodplain riverbed, which today represent one main Hg-reservoirs MAMD. Materials methods temporal riverbed extent its alluvial deposits were reconstructed by a GIS-based analysis available maps aerial photos. Hg-concentration sediment samples, collected five transects transverse channel, was determined ICP-MS. Results discussion Samples investigated segment typically show Hg-contents exceeding Italian threshold for residential public green use (1 mg kg −1 ). results from combination exceedance yield during fed with large amounts Hg-contaminated braided stage about 100 ago, river, led evolution present-day single channel river. magnitude extension Hg-contamination, geomorphologic changes, processes transport, deposition, re-suspension did not allow natural “clean up” system, shows low resilience. Under high flow conditions, especially coincidence intense rain events, stored overbank are mobilized redistributed, contributing make secondary Hg-source. Extreme weather expected intensify as consequence climate change, will contribute recurrent legacy course. Conclusion From water/land management perspective, variability flow, an increase extreme flood events driven affect particles River, input into Mediterranean Sea future. Graphical abstract