Spatial variation of phosphate distribution in the sediment of an artificial wetland.

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

Phosphates in Sediments

Backhuys Publishers

Lugar: Leiden; Año: 2005; p. 33 - 42

This study aims to determining the spatial variation of the P- distribution in sediments of an artificial wetland for sewage treatment, and the fractions that are 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 measured throughout the experiment (150 days). Sequential extractions of P-fractions in sediment were performed applying the EDTA method at the beginning and end of the experiment. According to the concentration values of i-Pdiss 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. Significant correlations were found between Tot-P and Fe(OOH)»P (r= 0.8932, p < 0.005) and Tot-P and org- P→alk (r= 0.8822, p < 0.005), Fe and Tot-P (r= 0.7494, p < 0.05), Ca and Tot-P (r= 0.8083, p < 0.05), pH and org- P acid fraction (r=  0.8664, p < 0.005), pH and CaCO3»P fraction (r=  0.6428, p < 0.01). 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, there was a release of P from the fraction org-P→alk probably due to the anoxic conditions. This fact was reflected not only by the increase of i-Pdiss concentration but also by 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 from water during the experiment period (approximately 80%), probably due to their high productivity.