TY - JOUR
T1 - Seawater causes rapid trace metal mobilisation in coastal lowland acid sulfate soils
T2 - Implications of sea level rise for water quality
AU - Wong, Vanessa N L
AU - Johnston, Scott G.
AU - Burton, Edward D.
AU - Bush, Richard T.
AU - Sullivan, Leigh A.
AU - Slavich, Peter G.
PY - 2010
Y1 - 2010
N2 - Coastal floodplains are highly vulnerable to inundation with saline water and the likelihood of inundation will increase with sea level rise. Sediment samples from floodplains containing coastal lowland acid sulfate soils (CLASS) in eastern Australia were subjected to increasing seawater concentration to examine the probable effects of sea level rise on acidity and metal desorption. Ten soils were mixed with synthetic seawater concentrations varying from 0% to 100% at a solid:solution ratio of 1:10 for 4h. There was a slight decrease in pH (≈0.5 units) with increasing seawater concentration following treatment, yet, calculated acidity increased significantly. In most soil treatments, Al was the dominant component of the calculated acidity pool. Al dominated the exchange complex in the CLASS and, correspondingly, was the major metal ion desorbed. In general, concentrations of soluble and exchangeable Al, Fe2+, Ni, Mn and Zn in all soil extracts increased with increasing salinity. Increasing trace metal concentrations with increasing seawater concentration is attributed to the combined effects of exchange processes and acidity. The increasing ionic strength of the seawater treatments displaces trace metals and protons adsorbed on sediments, causing an initial decrease in pH. Hydrolysis of desorbed acidic metal cations can further contribute to acidity and increase mobilisation of trace metals. These findings imply that saline inundation of CLASS environments, even by relatively brackish water may cause rapid, shorter-term water quality changes and a pulse release of acidity due to desorption of acidic metal cations.
AB - Coastal floodplains are highly vulnerable to inundation with saline water and the likelihood of inundation will increase with sea level rise. Sediment samples from floodplains containing coastal lowland acid sulfate soils (CLASS) in eastern Australia were subjected to increasing seawater concentration to examine the probable effects of sea level rise on acidity and metal desorption. Ten soils were mixed with synthetic seawater concentrations varying from 0% to 100% at a solid:solution ratio of 1:10 for 4h. There was a slight decrease in pH (≈0.5 units) with increasing seawater concentration following treatment, yet, calculated acidity increased significantly. In most soil treatments, Al was the dominant component of the calculated acidity pool. Al dominated the exchange complex in the CLASS and, correspondingly, was the major metal ion desorbed. In general, concentrations of soluble and exchangeable Al, Fe2+, Ni, Mn and Zn in all soil extracts increased with increasing salinity. Increasing trace metal concentrations with increasing seawater concentration is attributed to the combined effects of exchange processes and acidity. The increasing ionic strength of the seawater treatments displaces trace metals and protons adsorbed on sediments, causing an initial decrease in pH. Hydrolysis of desorbed acidic metal cations can further contribute to acidity and increase mobilisation of trace metals. These findings imply that saline inundation of CLASS environments, even by relatively brackish water may cause rapid, shorter-term water quality changes and a pulse release of acidity due to desorption of acidic metal cations.
KW - Desorption
KW - Metal mobilisation
KW - Sea level rise
KW - Seawater inundation
UR - http://www.scopus.com/inward/record.url?scp=78649449145&partnerID=8YFLogxK
U2 - 10.1016/j.geoderma.2010.10.002
DO - 10.1016/j.geoderma.2010.10.002
M3 - Article
AN - SCOPUS:78649449145
SN - 0016-7061
VL - 160
SP - 252
EP - 263
JO - Geoderma
JF - Geoderma
IS - 2
ER -