The effect of water velocity on nitrate removal in vegetated waterways

JOURNAL OF ENVIRONMENTAL MANAGEMENT

卷:215

Article

Castaldelli, Giuseppe¹  Aschonitis, Vassilis^1,2  Vincenzi, Fabio¹  Fano, Elisa Anna¹  Soana, Elisa¹ 

[1] Univ Ferrara, Dept Life Sci & Biotechnol, Via L Borsari 46, I-44121 Ferrara, Italy

[2] Hellen Agr Org Demeter, Inst Soil & Water Resources, Thermi 57001, Greece

关键词: NO3- removal;    Denitrification;    Aquatic vegetation;    Flow velocity;    Slow-flow waterways;    Wetlands;   

DOI  :  10.1016/j.jenvman.2018.03.071

来源: Elsevier

【 摘 要 】

The extended networks of canals and ditches in agricultural landscapes provide high buffer capacity towards nitrogen (N) excess. Their N mitigation potential depends on several biotic and abiotic factors, among which water velocity is poorly explored and generally omitted from the parameterization of this remarkable ecosystem service. The present work reports new insights on the role of flow velocity in regulating N removal via denitrification in sediments colonized by Phragmites australis. Denitrification was investigated in outdoor mesocosms in the presence and absence of P. australis and over a small range of flow velocity (0-6 cm s(-1)) typical of low-gradient water bodies. Simultaneous measurements of NO3- consumption and N-2 production based on analyses of N-2:Ar by Membrane Inlet Mass Spectrometry were undertaken. Vegetated sediments were found more efficient in converting NO3- to N-2 via microbial mediated denitrification (27-233 mmol N m(-2) d(-1)) than bare sediments (18-33 mmol N m(-2) d(-1)) Vegetation provides multiple interfaces, i.e. in the rhizosphere and on epiphytic biofilms, that support the development and activity of bacterial communities responsible for NO3- dissipation. NO3- removal and denitrification rates exhibited one order of magnitude raise when water velocity passed from 0 to 6 cm s(-1) in vegetated sediments. Indeed, in slow-flow vegetated waterways denitrification may be physically limited and the increase of water velocity enhances the rate of NO3- supply through the diffusive boundary layer, thereby promoting its consumption and loss from the system. Water velocity should be taken into account as a key factor for management and restoration actions aimed at maximizing the NO3- buffer capacity of low-flow drainage networks. (C) 2018 Elsevier Ltd. All rights reserved.

【 授权许可】

Free