Phosphorous partitioning in sediments by particle size distribution in shallow lakes: From its mechanisms and patterns to its ecological implications.

This study revealed a general pattern of P partitioning onto sediment particles that has ecological implications for shallow lakes. Six individual sediment samples from two large shallow lakes in eastern China were sieved into five sediment particle size classes ranging from 0.5 μm to 50 μm. These particle size groupings were subjected to P fractionation and P adsorption isotherm analyses as well as bioavailable P bioassays. A P-adding experiment was used to validate the initial P partitioning onto the sediment particles. Multiple lines of evidence revealed that P partitioning onto the particles was dependent on the amounts of P adsorbents or P-containing compounds in the sediments, such as iron and aluminum oxides, organic matter, and calcium compounds. An exponential equation, c(x) = cmaxexp(-kdx), was proposed to describe the relationship between the partitioning of bioavailable P and particle size. In the equation, cmax represents the maximum P concentration adsorbed by the finest particles, and kd is a constant reflecting the decrease in the P concentration with particle size (x).