Prediction of Plant Metal Bioaccessibility in Mineralized and Sulfidic Rocks

Successful rehabilitation of mine sites requires a solid knowledge of waste and mine soil properties. In particular, there is a need for a predictive test that allows forecasting of risks to plant growth on contaminated mine soils and waste repositories. In this contribution, a new plant bioaccessibility test is described that meets this need. The methodology for the new test oxidizes the sample with hydrogen peroxide and then extracts the solubilized metals and metalloids from the sample using 1 M ammonium acetate solution. The test is based on aspects of two established tests: (1) the sequential NAG test, which is suitable for sulfidic samples but does not determine metals and metalloids; and (2) the BCR^® extraction, which gives information on the geochemical fractionation of these elements but is not suitable for highly sulfidic samples. Learnings from the method development, a stepwise test protocol and a simplified flow diagram for the test are presented. The proposed new plant bioaccessibility test represents a predictive tool that allows forecasting of metal fractions that may become available to plants upon colonization of sulfidic soils and wastes at mine sites.