title: Salt tolerant plants increase nitrogen removal from biofiltration systems affected by saline stormwater.
abstract: Biofiltration systems are used in urban areas to reduce the concentration and load of nutrient pollutants and heavy metals entering waterways through stormwater runoff. Biofilters can, however be exposed to salt water, through intrusion of seawater in coastal areas which could decrease their ability to intercept and retain pollutants. We measured the effect of adding saline stormwater on pollutant removal by six monocotyledonous species with different levels of salt-tolerance. Carex appressa, Carex bichenoviana, Ficinia nodosa, Gahnia filum, Juncus kraussii and Juncus usitatus were exposed to six concentrations of saline stormwater, equivalent to electrical conductivity readings of: 0.09, 2.3, 5.5, 10.4, 20.0 and 37.6 mS cm(-1). Salt-sensitive species: C. appressa, C. bichenoviana and J. usitatus did not survive ≥10.4 mS cm(-1), removing their ability to take up nitrogen (N). Salt-tolerant species, such as F. nodosa and J. kraussii, maintained N-removal even at the highest salt concentration. However, their levels of water stress and stomatal conductance suggest that N-removal would not be sustained at concentrations ≥10.4 mS cm(-1). Increasing salt concentration indirectly increased phosphorus (P) removal, by converting dissolved forms of P to particulate forms which were retained by filter media. Salt concentrations ≥10 mS cm(-1) also reduced removal efficiency of zinc, manganese and cadmium, but increased removal of iron and lead, regardless of plant species. Our results suggest that biofiltration systems exposed to saline stormwater ≤10 mS cm(-1) can only maintain N-removal when planted with salt-tolerant species, while P removal and immobilisation of heavy metals is less affected by species selection.
authors.affiliation: Waterway Ecosystem Research Group, School of Ecosystem and Forest Sciences, The University of Melbourne, 500 Yarra Boulevard, Richmond, Victoria 3121, Australia. Electronic address: cszota@unimelb.edu.au.
authors.forename: Christopher
authors.initials: C
authors.lastname: Szota
authors.affiliation: Green Infrastructure Research Group, School of Ecosystem and Forest Sciences, The University of Melbourne, 500 Yarra Boulevard, Richmond, Victoria 3121, Australia.
authors.forename: Claire
authors.initials: C
authors.lastname: Farrell
authors.affiliation: Green Infrastructure Research Group, School of Ecosystem and Forest Sciences, The University of Melbourne, 500 Yarra Boulevard, Richmond, Victoria 3121, Australia.
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Livesley
authors.affiliation: Waterway Ecosystem Research Group, School of Ecosystem and Forest Sciences, The University of Melbourne, 500 Yarra Boulevard, Richmond, Victoria 3121, Australia.
authors.forename: Tim D
authors.initials: TD
authors.lastname: Fletcher
mesh_terms: D029785:Cyperaceae / Q000378:metabolism; D005374:Filtration; D019216:Metals, Heavy / Q000378:metabolism*; D009584:Nitrogen / Q000378:metabolism*; D010758:Phosphorus / Q000378:metabolism*; D011891:Rain; D054712:Salinity; D055051:Salt-Tolerant Plants / Q000378:metabolism*; D012965:Sodium Chloride / Q000009:adverse effects; D014874:Water Pollutants, Chemical / Q000378:metabolism*; D018508:Water Purification / Q000379:methods*
chemical_list: D019216:Metals, Heavy; D014874:Water Pollutants, Chemical; D010758:Phosphorus; D012965:Sodium Chloride; D009584:Nitrogen
keywords: Biofiltration; Nitrogen; Phosphorus; Salt-tolerant species; Stormwater treatment; Water sensitive urban design