Effect of Ionic Strength and Electrolyte Type on Phosphorus Deposition and Release from the Sediments

Purpose of Review

Assessing the risk of sediment phosphorus (P) release is essential for managing eutrophication in watershed. However, the crucial effects of electrolytes type and ionic strength on the potential for P release from sediments remain underexplored. This study investigates the influence of common types of electrolyte (CaCl₂, NaCl, KCl) and ionic strength (0 M, 0.001 M, 0.01 M CaCl₂) on indexes of P release from sediments.

Recent Findings

Here, our results show that (1) increasing the ionic strength in the water corresponded to an increase in the maximum adsorption capacity of sediment for P (SP_max), while the maximum desorption amount (R_max) and the equilibrium concentration of adsorbed P (EPC₀) decreased, which can be attributed to the electrostatic repulsion between the negatively charged sediment surface particles and P; (2) the presence of CaCl₂ resulted in lower EPC₀ and R_max values of the sediments, while the adsorption constant (k) and SP_max were higher. There was no difference in the NaCl and KCl systems. This discrepancy is believed to be due to calcium ions being more effective in inhibiting P release from sediments as they can form Ca-P precipitates with P and precipitates with anions, promoting P deposition in sediments. Furthermore, potassium ions, due to their smaller hydration radius and lower hydration energy compared to sodium ions, facilitate a closer approach to sediment colloid adsorption layers, favoring sediment P deposition stably.

Summary

This study aims to promote the proper use of buffer solutions in standardized experiments, particularly in the sediment of heavily P-polluted watersheds, minimizing biases due to incorrect procedures, and to provide accurate data and theoretical support for the broader scientific community.

Graphical Abstract