Total sulphide acidity for the definition and quantitative assessment of the acid sulphate hazard: Simple solution or a new suite of problems

Recent investigations show that the TSA (Total Sulphide Acidity) method for the definition and quantitative assessment of acid sulphate soils is unreliable. Although potential acid sulphate soils do produce high TSA values, high TSAs may also be recorded from non-acid sulphate soils; this problem may arise when organic matter oxidises during the hydrogen peroxide treatment to form short-chained organic acids, or when reduced iron in the soil undergoes ferrolysis. Because significant overestimations of acid production from non-acid sulphate soils are common, we recommend that the TSA procedure be abandoned as a method for assessing acid sulphate soils. We propose that assessment of both actual and potential acid sulphate soils must be based on a sulphur species specific method [1].