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The inside story of gas processes within stormwater biofilters - does greenhouse gas production tarnish the benefits of nitrogen removal? Emily G.I. Payne, Tracey Pham, Perran Louis Miall Cook, Ana Deletic, Belinda E. Hatt, and Tim D. Fletcher Environ. Sci. Technol., Just Accepted Manuscript • DOI: 10.1021/acs.est.6b05653 • Publication Date (Web): 08 Mar 2017 Downloaded from http://pubs.acs.org on March 8, 2017
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Environmental Science & Technology
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The inside story of gas processes within
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stormwater biofilters - does greenhouse gas
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production tarnish the benefits of nitrogen
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removal?
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Emily G.I. Payne1,*, Tracey Pham1, Perran L.M. Cook2, Ana Deletic1, Belinda E. Hatt1, Tim
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D. Fletcher1,3
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Department of Civil Engineering, Monash University, Clayton, Victoria, Australia, 3800 Water Studies Centre, School of Chemistry, Monash University, Clayton, Victoria, Australia, 3800
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School of Ecosystem & Forest Sciences, The University of Melbourne, Burnley, Victoria,
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Australia, 3121
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ABSTRACT Stormwater biofilters are dynamic environments, supporting diverse processes
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that act to capture and transform incoming pollutants. However, beneficial water treatment
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processes can be accompanied by undesirable greenhouse gas production. This study
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investigated the potential for nitrous oxide (N2O) and methane (CH4) generation in dissolved
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form at the base of laboratory-scale stormwater biofilter columns. The influence of plant
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presence, species, inflow frequency and inclusion of a saturated zone and carbon source were
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studied. Free-draining biofilters remained aerobic with negligible greenhouse gas production 1 ACS Paragon Plus Environment
Environmental Science & Technology
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during storm events.
Designs with a saturated zone were oxygenated at their base by
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incoming stormwater before anaerobic conditions rapidly re-established, although extended
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dry periods allowed the re-introduction of oxygen by evapotranspiration. Production of CH4
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and N2O in the saturated zone varied significantly in response to plant presence, species and
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wetting and drying. Concentrations of N2O typically peaked rapidly following stormwater
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inundation, associated with limited plant root systems and poorer nitrogen removal from
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biofilter effluent. Production of CH4 also commenced quickly, but continued throughout the
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anaerobic inter-event period and lacked clear relationships with plant characteristics or
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nitrogen removal performance. Dissolved greenhouse gas concentrations were highly variable
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but peak concentrations of N2O accounted for
