River Bank Materals As Potential Sources and Sinks of of P in Lake Pepin.

Although the majority of sediments in Lake Pepin are coming from river banks, there is a perception that phosphorus is coming from agricultural lands. This research evaluated whether the bank materials can adsorb soluble P from river waters and release it when deposited in Lake Pepin. In this study, we analyzed 16 river bank materials for equilibrium phosphorus concentration (EPC₀), their potential to adsorb and desorb soluble P, and its P fractions.  Results show that bank materials have a low EPC₀ (<0.1 mg/L), a high P adsorption potential, minimal desorption capacity, and mostly Ca-bound phosphorus.  Prior to 1830, phosphorus concentrations in Lake Pepin sediments can be explained simply by sediment enrichment during transport. After 1830, we outline scenarios using enrichment ratios and historical river pollution as potential reasons for higher total P concentrations. Low EPC₀ suggests continued P adsorption by bank materials from river waters even under current conditions.