Rivers under stress: Geochemical changes along a rural–urban gradient during extreme hydrological events (Greve River, Italy)

Rivers under stress: Geochemical changes along a rural–urban gradient during extreme hydrological events (Greve River, Italy) | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Rivers under stress: Geochemical changes along a rural–urban gradient during extreme hydrological events (Greve River, Italy) Martina Ferrari, Rebecca Biagi, Stefania Venturi, Federica Frezzi, and 1 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-9497175/v1 This work is licensed under a CC BY 4.0 License Status: Under Revision Version 1 posted 9 You are reading this latest preprint version Abstract Rivers play a crucial role in supporting human settlements by providing water for domestic, agricultural, and industrial uses, while facing increasing anthropogenic pressures. Many rivers exhibit a longitudinal gradient, from relatively pristine rural headwaters to densely populated and industrial lowlands, reflecting progressive changes in land use, population density, and potential contaminant sources that strongly affect water quality. Climate change is intensifying extreme hydrological events, including prolonged droughts and intense rainfall, which can significantly alter river hydrology and biogeochemical processes. Droughts increase water residence time, promoting the accumulation of chemical constituents, while subsequent high-flow events, particularly first-flush events, can remobilize these materials from soils and urban surfaces, posing severe risks to water security and ecosystem resilience. This study investigates the spatial and seasonal evolution of river geochemistry along a rural-to-urban gradient, using the Greve River (Tuscany, Italy), a tributary of the Arno River, as a representative case study during the exceptional drought and subsequent heavy rainfall of summer 2022. By analyzing this extreme event to assess climate-related risk, we analyzed chemical tracers (TDS, nutrients, sulfate, trace elements) and stable isotopes. The results reflect the increasing influence of anthropogenic pressures and identify critical transitions in contaminant dynamics that define the system's vulnerability. These findings demonstrate that the interaction between land-use and climatic extremes creates transient but hazardous chemical flushes. Combining isotopic analysis with spatial geochemical monitoring provides a transferable framework to assess environmental health risk and supports climate-resilient river basin water management under increasing hydroclimatic variability. Hydroclimatic variability Rural-urban gradient Drought-flood events River geochemistry Water security Climate change Full Text Additional Declarations No competing interests reported. Supplementary Files TableS1.xlsx Cite Share Download PDF Status: Under Revision Version 1 posted Editorial decision: Revision requested 17 May, 2026 Reviews received at journal 16 May, 2026 Reviewers agreed at journal 14 May, 2026 Reviews received at journal 12 May, 2026 Reviewers agreed at journal 11 May, 2026 Reviewers invited by journal 26 Apr, 2026 Editor assigned by journal 24 Apr, 2026 Submission checks completed at journal 24 Apr, 2026 First submitted to journal 22 Apr, 2026 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-9497175","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":630194686,"identity":"2730b92e-3bf4-40f8-9e9d-cb14d90447c7","order_by":0,"name":"Martina 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