Authors: Oksana Coban Peter Kuschk Naomi S Wells Gerhard Strauch Kay Knoeller
Publish Date: 2014/09/20
Volume: 22, Issue: 17, Pages: 12829-12839
Abstract
Pathways of ammonium NH4 + removal were investigated using the stable isotope approach in constructed wetlands CWs We investigated and compared several types of CWs planted horizontal subsurface flow HSSF unplanted HSSF and floating plant root mat FPRM including spatial and seasonal variations Plant presence was the key factor influencing efficiency of NH4 + removal in all CWs what was illustrated by lower NH4 +N removal by the unplanted HSSF CW in comparison with planted CWs No statistically significant differences in NH4 + removal efficiencies between seasons were detected Even though plant uptake accounted for 32–100 of NH4 + removal during spring and summer in planted CWs throughout the year most of NH4 + was removed via simultaneous nitrificationdenitrification what was clearly shown by linear increase of δ15NNH4 + with decrease of loads along the flow path and absence of nitrate NO3 − accumulation Average yearly enrichment factor for nitrification was −79 ‰ for planted HSSF CW and −58 ‰ for FPRM Lack of enrichment for δ15NNO3 − implied that other processes such as nitrification and mineralization were superimposed on denitrification and makes the stable isotope approach unsuitable for the estimation of denitrification in the systems obtaining NH4 + rich inflow waterThis research was completed within the framework of the Marie Curie Initial Training Network ADVOCATE—Advancing sustainable in situ remediation for contaminated land and groundwater funded by the European Commission Marie Curie Actions Project No 265063 SAFIRA project and the Helmholtz Interdisciplinary Graduate School for Environmental Research HIGRADE We are also grateful to Martina Neuber of the stable isotope laboratory Halle/Salle for conducting isotope analyses of the samples Thank is also addressed to Dang Thi Kim Anh for her valuable assistance in the laboratory and field
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