Differential Adsorption of Dissolved Organic Matter and Phosphorus on Clay Mineral in Water-Sediment System

Abstract

Lake sediments connection to the biogeochemical cycling of phosphorus (P) and carbon (C) influences streamwater quality. However, it is unclear whether and how the type of sediment controls P and C cycling in water. Here, the adsorption behavior of montmorillonite (Mt) with different interlayer cations (Na+, Ca2+, or Fe3+) on dissolved organic matter (DOM) and P was investigated to understand the role of Mt in regulating the organic carbon-to-phosphate (OC/P) ratio within freshwater systems. The adsorption capacity of Fe–Mt for P was 3.2-fold higher than that of Ca–Mt, while it was 1/3 lower for DOM. This dissimilarity in adsorption led to an increased OC/P in Fe–Mt-dominated water and a decreased OC/P in Ca–Mt-dominated water. Moreover, an in situ atomic force microscope and high-resolution mass spectrometry revealed molecular fractionation mechanisms and adsorptive processes. It was observed that DOM inhibited the nucleation and crystallization processes of P on the Mt surface, and P affected the binding energy of DOM on Mt through competitive adsorption, thereby governing the interfacial P/DOM dynamics on Mt substrates at a molecular level. These findings have important implications for water quality management, by highlighting the role of clay minerals as nutrient sinks and providing new strategies for controlling P and C dynamics in freshwater systems.

In Situ Evolution of Ionic Sites at Clay Mineral Interfaces Facilitates Fluoride and Phosphorus Mineralization

“…Soil remediation strategies to fix F include ion exchange, surface complexation, coprecipitation, and mineralization mechanisms, such as adding hydroxyapatite, gypsum, lime, and calcite passivators. − P is a macronutrient that is essential for crop growth. Maintaining appropriate P levels in the soil is crucial to prevent eutrophication and ensure efficient P utilization . The latest strategies for sustainable P use involve P mineralization, which helps balance effective P activity through the in situ formation of slow-release P pools, e.g., hydroxyapatite, struvite, and Fe- and Al-phosphorus oxide. − Currently, there is limited research on the intricate interplay mechanisms and synergism of F and P in the environment.…”