Phosphorus Retention and sorption by constructed wetland soils.

Abstract

Phosphorus plays a major role in the eutrophication of freshwater systems. Wetland systems either natural or constructed have an inherent ability to cycle and retain P. Physical, chemical and biological processes regulate P retention in wetland soils and sediments. Of those processes, sorption and precipitation are important in retaining P. Sorption is typically greater under aerobic soil/sediment conditions than anaerobic conditions. Under anaerobic conditions, Fe plays a major role in P dynamics, whereas Al is not affected by changes in redox. Precipitation of P as insoluble Ca bound P is a dominant transformation at high pH. Long-term P retention by wetland systems includes accretion and decomposition of organic and detrital material, and its associated P content. Case studies reviewed illustrated that P retention in natural and constructed wetland systems can vary by several orders of 30 magnitude depending on site-specific factors. The literature reviewed also indicates that using wetlands to retain P from agricultural practices is significant and variable.