Spatial variation of phosphorus distribution in the sediment of a constructed wetland

MAINE, M.A.; SUÑÉ, N.L.; HADAD, H.R.; SÁNCHEZ, G.C.

Carmona, España

Simposio; 4th International Symposium on Phosphate in Sediments; 2003

This study is aimed at determining the spatial variation of phosphorus distribution in sediments of an artificial wetland for sewage treatment and which fraction is potentially involved in the exchange processes. Water, sediment and macrophytes were sampled at different distances from the discharge point. The concentration of nutrients in water was periodically determined throughout the experiment (150 days). Sequential extractions of P-fractions in sediment were performed applying the EDTA method (Golterman, 1996) at the beginning and end of the experiment. According to the concentration values of o-P at the inlet and outlet of the wetland, it was found that the wetland carried out an efficient removal of nutrients until anoxia occurred in the outlet zone. Fe (OOH)-P and Tot-P (r= 0.9158, p < 0.005), org- P alk and Tot-P (r= 0.9093, p < 0.005), pH and org-P acid fraction (r= 0.7742, p < 0.005), pH and CaCO3-P fraction (r= 0.6321, p < 0.005) presented significant linear correlations. Tot-P in sediment increased in the inlet zone, with an increase in the fractions Fe (OOH)-P and org-P alk. At the outlet zone instead, probably due to the anoxic conditions, there was a release of P from the fraction org-P alk. This fact was reflected not only in the increase of o-P concentration but also in the external morphological characteristics and P concentration of Eichhornia crassipes tissues. Sediment was the main P compartment, however macrophytes carried out the highest P removal during the experiment period, probably due to their high productivity.