Search

Gypsum (CaSO 4 ·2H 2 O) is increasingly used to bind P to soil on agricultural fields, which mitigates eutrophication caused by runoff of excess PO 4 3- fertilizers into adjacent aquatic environments. Gypsum also binds dissolved organic matter (DOM) to soil particles. Gypsum that gets into fresh water after field applications may result in enhanced particle formation by DOM flocculation and alter C transfer in rivers draining agricultural catchments. We tested the potential effects of gypsum additions on DOM cycling by adding concentrated gypsum solution into river water before subjecting it to controlled mixing to increase particle collisions and flocculation. Gypsum addition increased the amount of suspended particulate matter in river water three to four times higher than in controls without gypsum. The flocs contained a relatively high amount of minerogenic particles. Gypsum-induced flocculation removed colored dissolved organic matter which, together with removal of minerogenic particles, may result in increased water clarity. Gypsum addition and the associated changes in the DOM pool did not affect microbial growth or DOM processing, suggesting that flocculation did not target the labile fraction of the DOM pool. While acknowledging that the responses detected in our study might depend on the region, we propose that the changes in riverine DOM cycling caused by gypsum application results in either no changes or slightly positive changes to the water quality of the rivers and should not be considered an obstacle for eutrophication prevention using gypsum applications., (© 2025 The Author(s). Journal of Environmental Quality © 2025 American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America.)

We discuss the outcomes of our 16th horizon scan of issues that are novel or represent a considerable step-change and have the potential to substantially affect conservation of biological diversity in the coming decade. From an initial 96 topics, our international panel of 32 scientists and practitioners prioritised 15 issues. Technological advances are prominent, including metal and non-metal organic frameworks, deriving rare earth elements from macroalgae, synthetic gene drives in plants, and low-emission cement. We include new insights into accelerated impacts of changes to Antarctic ice masses and air and water quality. We hope that anticipating and mitigating negative impacts, and making best use of new opportunities related to these issues, will contribute to better outcomes for biological diversity., Competing Interests: Declaration of interests No interests are declared., (Copyright © 2024 The Authors. Published by Elsevier Ltd.. All rights reserved.)