TY - JOUR
T1 - Seawater inundation of coastal floodplain sediments
T2 - Short-term changes in surface water and sediment geochemistry
AU - Wong, Vanessa N.L.
AU - Johnston, Scott G.
AU - Burton, Edward D.
AU - Hirst, Phillip
AU - Sullivan, Leigh A.
AU - Bush, Richard T.
AU - Blackford, Mark
N1 - Funding Information:
We thank the Environmental Analysis Laboratory at Southern Cross University for the sample analysis, Lachlan Macquarie for the assistance with the statistical analysis and the reviewers for their comments on improving this manuscript. This research was funded by the Australian Research Council ( LP0882141 ), Richmond River County Council , New South Wales Department of Primary Industries and the Northern Rivers Catchment Management Authority . Research expenses and salary support for Scott Johnston was provided by the Australian Research Council Future Fellowship (grant no. FT110100130 ). The TEM analysis was funded by the Australian Institute of Nuclear Science and Engineering ( ALNGRA 10095 ).
Publisher Copyright:
© 2015 .
PY - 2015
Y1 - 2015
N2 - Coastal floodplains are highly vulnerable to seawater inundation as a result of storm surge and sea-level rise due to their low elevation and proximity to the coastline. Intact soil cores from a levee, acid-sulfate soil scald and four backswamp sites on a coastal floodplain in eastern Australia were inundated with artificial seawater treatments (0%, 50% and 100%) for 14days to examine the short term consequences for surface water and floodplain sediment geochemistry. All sites displayed an initial decrease in surface water pH following inundation with 50% and 100% seawater. In addition, higher concentrations of trace metals (Al, Fe, Mn, Ni and Zn) were observed in most sites inundated with 50% or 100% seawater. This was generally attributed to competitive exchange and desorption of trace metals from sediments due to the higher ionic strength of the seawater solutions and upward diffusive flux of metals from the sediments to surface waters. At one backswamp site, reductive processes had established by day 7, which also resulted in elevated Fe2+ concentrations in the overlying surface waters. Transmission electron microscopy (TEM) identified the presence of poorly crystalline ferrihydrite and schwertmannite, and goethite and jarosite. These meta-stable Fe(III) minerals can act as a source of metals for desorption and can also be readily reduced and act as a source of Fe2+ to surface waters. Importantly, inundation with either 50% or 100% seawater resulted in a similar magnitude of acidity and trace metal mobilisation. The data suggest that an inundation event of ~0.2m depth with either 50% or 100% seawater could cause a pulse mobilisation of up to 64.8 and 9.1kgha-1 of Fe and Al, respectively - quantities of similar magnitude to previous estimates of annual drainage fluxes from similar backswamps. This study suggests that the short term inundation of coastal floodplain sediments by either brackish water or seawater will result in rapid declines in surface water quality as a result of increased liberation of acidity and trace metals.
AB - Coastal floodplains are highly vulnerable to seawater inundation as a result of storm surge and sea-level rise due to their low elevation and proximity to the coastline. Intact soil cores from a levee, acid-sulfate soil scald and four backswamp sites on a coastal floodplain in eastern Australia were inundated with artificial seawater treatments (0%, 50% and 100%) for 14days to examine the short term consequences for surface water and floodplain sediment geochemistry. All sites displayed an initial decrease in surface water pH following inundation with 50% and 100% seawater. In addition, higher concentrations of trace metals (Al, Fe, Mn, Ni and Zn) were observed in most sites inundated with 50% or 100% seawater. This was generally attributed to competitive exchange and desorption of trace metals from sediments due to the higher ionic strength of the seawater solutions and upward diffusive flux of metals from the sediments to surface waters. At one backswamp site, reductive processes had established by day 7, which also resulted in elevated Fe2+ concentrations in the overlying surface waters. Transmission electron microscopy (TEM) identified the presence of poorly crystalline ferrihydrite and schwertmannite, and goethite and jarosite. These meta-stable Fe(III) minerals can act as a source of metals for desorption and can also be readily reduced and act as a source of Fe2+ to surface waters. Importantly, inundation with either 50% or 100% seawater resulted in a similar magnitude of acidity and trace metal mobilisation. The data suggest that an inundation event of ~0.2m depth with either 50% or 100% seawater could cause a pulse mobilisation of up to 64.8 and 9.1kgha-1 of Fe and Al, respectively - quantities of similar magnitude to previous estimates of annual drainage fluxes from similar backswamps. This study suggests that the short term inundation of coastal floodplain sediments by either brackish water or seawater will result in rapid declines in surface water quality as a result of increased liberation of acidity and trace metals.
KW - Acidity
KW - Diffusive flux
KW - Floodplain sediments
KW - Metal mobilisation
KW - Sea-level rise
KW - Seawater inundation
UR - http://www.scopus.com/inward/record.url?scp=84923064513&partnerID=8YFLogxK
UR - http://www.mendeley.com/research/seawater-inundation-coastal-floodplain-sediments-shortterm-changes-surface-water-sediment-geochemist
U2 - 10.1016/j.chemgeo.2015.01.016
DO - 10.1016/j.chemgeo.2015.01.016
M3 - Article
AN - SCOPUS:84923064513
VL - 398
SP - 32
EP - 45
JO - Chemical Geology (Isotopic Geoscience) Section
JF - Chemical Geology (Isotopic Geoscience) Section
SN - 0009-2541
ER -