title: Isotopically exchangeable Al in coastal lowland acid sulfate soils.
abstract: Periodic discharges of high concentrations of aluminium (Al) causing fish kills and other adverse effects occur worldwide in waterways affected by coastal lowland acid sulfate soils (CLASS). The exchangeability - a metal's ability to readily transfer between the soil solid- and solution-phases - of Al in these soils is therefore of particular importance as it has implications for metal transport, plant availability and toxicity to living organisms. In the present study, the concentrations of isotopically exchangeable Al (E values) were measured in 27 CLASS and compared with common salt extractions (i.e. KCl and CuCl2) used to estimate exchangeable soil pools of Al. E values of Al were high in the soils, ranging from 357 to 3040 mg·kg(-1). Exchangeable concentrations estimated using 1 M KCl were consistently lower than measured E values, although a reasonable correlation was obtained between the two values (E=1.68×AlKCl, r(2)=0.66, n=25). The addition of a 0.2 M CuCl2 extraction step improved the 1:1 agreement between extractable and isotopically exchangeable Al concentrations, but lead to significant mobilisation of non-isotopically exchangeable Al in surficial 'organic-rich' CLASS having E values<1000 mg·kg(-1). It was concluded that currently used (i.e. 1 M KCl) methodology severely underestimates exchangeable Al and total actual acidity values in CLASS and should be corrected by a factor similar to the one determined here.
authors.affiliation: UNSW Water Research Centre, School of Civil and Environmental Engineering, UNSW Australia, Sydney, NSW 2052, Australia; Centre Européen de Recherche et d'Enseignement des Géosciences de l'Environnement, Aix-Marseille Université, Aix en Provence, France.
authors.forename: Yliane A M
authors.initials: YA
authors.lastname: Yvanes-Giuliani
authors.affiliation: Centre Européen de Recherche et d'Enseignement des Géosciences de l'Environnement, Aix-Marseille Université, Aix en Provence, France.
authors.forename: D
authors.initials: D
authors.lastname: Fink
authors.affiliation: Institute for Environmental Research, Australian Nuclear Science and Technology Organisation, Locked Bag 2001, Kirrawee DC, NSW 2232, Australia.
authors.forename: J
authors.initials: J
authors.lastname: Rose
authors.affiliation: UNSW Water Research Centre, School of Civil and Environmental Engineering, UNSW Australia, Sydney, NSW 2052, Australia.
authors.forename: T David
authors.initials: TD
authors.lastname: Waite
authors.affiliation: UNSW Water Research Centre, School of Civil and Environmental Engineering, UNSW Australia, Sydney, NSW 2052, Australia. Electronic address: richard.collins@unsw.edu.au.
authors.forename: Richard N
authors.initials: RN
authors.lastname: Collins
mesh_terms: D000535:Aluminum / Q000032:analysis*; D004784:Environmental Monitoring; D007554:Isotopes; D012987:Soil / Q000737:chemistry*; D012989:Soil Pollutants / Q000032:analysis*; D013431:Sulfates
chemical_list: D007554:Isotopes; D012987:Soil; D012989:Soil Pollutants; D013431:Sulfates; D000535:Aluminum
keywords: Exchangeable aluminium; Extractable aluminium; Isotope exchange