Improved laboratory test for the acid neutralising capacity of acid sulfate soils

Funding / collaborators:

CRC-CARE Project - Developing a Hydrogeochemical Model for Predicting Contaminant Production, Consumption and Export from Acid Sulfate Soil (ASS) 2-4-01-05/06

Oyster Shells

Project description:

Current methods for determining the acid neutralising capacity (ANC) of acid sulfate soils lead to an overestimation of the lime requirement for neutralisation. One contributing factor is the fine grinding process used to prepare samples for analysis, in which the surface area and reactivity of carbonate sources such as shells are increased. Another factor is the current ANC back titration method, which involves acidifying the sample as low as pH 2. This can cause dissolution of clay, as well as neutralisation of acceptable forms of ANC such as carbonate, exchangeable alkalinity and organic bases. The aim of this project is to develop a more accurate laboratory test for ANC in order to remove the uncertainties associated with current methods.

Team members:

  • Kym Watling
  • Angus McElnea
  • Ed Burton
  • Andrew Rose
  • Annabelle Keene
  • Scott Johnston
  • Col Ahern
  • Leigh Sullivan
  • Richard Bush

Outcomes / key findings:

  • Incubation to determine relationship between ANC and particle size for carbonate sources of geological and biological origin
  • Analysis of buffer curves to determine and differentiate neutralisation processes
  • Measurement of CO2 evolution during bicarbonate neutralisation
  • Surface studies of passivation of carbonate during leaching processes
  • Kinetic studies of dissolution processes of various carbonate sources and particle sizes
  • Formulation of standard particle sizes for lime application
  • Development of an improved method for ANC determination