Quantifying retained acidity in acid sulfate soil materials: an evaluation of routine methods

Retained Acidity is an important aspect of acid sulfate soil (ASS) but techniques for the quantification of this property have not yet been systematically assessed. In this study, the utility of routine techniques for quantifying the Retained Acidity fraction will be examined. The relatively insoluble minerals such as jarosite and schwertmannite are major contributors to Retained Acidity in ASS. Known quantities of synthetic and natural jarosites and schwertmannite will be added to two non-acid sulfate soil samples plus to one quartz sand sample. By using SNAS in the chromium suite and SRAS in the SPOCAS suite (Ahern et al. 2004), the Retained Acidity fraction of the spiked samples will be assessed. The method introduced by Li et al. (2007) and the acidified ammonium oxalate method (Regenspurg et al. 2004) will be undertaken to recover the added jarosite and schwertmannite, respectively. The mineralogy of the samples will be characterized by X-ray diffraction (XRD). In the second part of this study, the potential interference from