Phosphorus adsorption and removal by sediments of a constructed marsh in Korea

The Shihwa marsh is the largest Korean marsh recently constructed to treat contaminated stream water. To characterize P sorption and removal in the marsh, we examined soil physicochemical variables affecting P dynamics, soluble reactive P (SRP) sorption parameters such as P sorption maximum (PSmax), equilibrium P concentration at zero sorption (EPC0), and P retention capacity of sediments through a batch experiment. We also simulated SRP removal pattern in flooded sediments through a 22-day column experiment. Significant correlations of PSmax with pH, organic matter (OM), exchangeable Ca, and oxalate-extractable Al and Fe concentrations of sediments showed that P sorption by sediments was closely related to amorphous and some poorly crystalline forms of Fe and Al, organic matter, and Ca. Estimated P retention capacity of the sediments suggests that the sediments can function as a P sink for 6-13 years under current P loading conditions. However, the turnover from a net P sink to a source could not be predicted from EPC0, since algal P uptake contributes much to net P removal in sediments rich in organic matter and available P. Therefore, this study suggests that P removal characteristic of sediments should be predetermined for site-specific design criteria of constructed marshes.