*This is an abstract only. No full paper is available for this abstract.* The current use of bioaccessibility tests in contaminated site assessments is dominated by techniques designed to assess the oral bioaccessibility of potentially harmful elements to humans. Determining the plant bioaccessibility of toxic trace elements is also important because: uptake by plants can represent an important transfer route for these elements from the geosphere to the biosphere delayed re-vegetation can impact negatively on-site rehabilitation._x000D_
In mining landscapes, sulfides are an important source of potentially toxic elements. Simple tests to evaluate readily leachable metals and metalloids exist but do not extract contaminant elements temporarily constrained within the sulfide fraction. Some sequential extractions describe the association of trace elements with different geochemical fractions, including sulfides, but are time-consuming, costly and provide excessive detail unnecessary for a mine site waste classification scheme._x000D_
A new test for plant bioaccessibility in sulfidic wastes and soils was proposed by van Veen et al (in press). The test was developed to establish the operationally defined bioaccessibility of trace metals and metalloids in sulfidic mine wastes (eg waste rock, tailings). Acid stabilised hydrogen peroxide is used to simulate accelerated environmental oxidation of the sample. Extraction with ammonium acetate solution then mobilises and extracts the released metals and metalloids, these are subsequently determined in the extractant solution. The test design is inspired by aspects of the net acid generating (NAG) test (Smart et al, 2002) and the BCR sequential extraction scheme (Rauret et al, 1999). The methodology uses reagents and equipment commonly available at mine site laboratories._x000D_
To validate the test, a case study at a historic mine waste repository site in Cornwall, UK was conducted. Four material types were sampled (n = 41); mine waste (MW), granular capping (GC), grey tailings (GT) and marbled tailings (MT). At this site, As concentrations exceeded average crustal abundance by four times, whilst other elements exceeded average crustal abundance by one (Pb), two (Cu and Cd) and three (Zn and Sb) orders of magnitude. The results reported in van Veen et al (in press) show that the pyritic GT samples presented an elevated risk for the plant bioaccessibility of Cd, Cu, Pb, Zn and As. The bioaccessibility of As was found to be partly due to release from pyrite on oxidation. For Cd, Cu, Pb and Zn there was some release on oxidation from sulfide minerals, principally chalcopyrite and sphalerite. In the GT samples rozenite, a secondary sulfate mineral, was considered to be an additional source of the bioaccessible forms of Cd and Zn. The organic matter associated with site re vegetation was suspected as an additional source of bioaccessible Cu in the GC samples. High concentrations of As in the oxidised marbled tailing samples were not found to be plant bioaccessible due to their immobilisation with iron oxyhydroxides and ferro-saponite phases._x000D_
Results from the case study indicate that this test provides useful information on the future bioaccessibility of contaminants, allowing for classification of mineralised sulfidic waste materials that otherwise cannot be obtained using established geochemical and mineralogical techniques. Furthermore, the test is rapid, repeatable and cost-effective and can be effectively used as part of early environmental characterisation work undertaken for mine sites._x000D_
CITATION: van Veen, E, Parbhakar-Fox, A, Fox, N, Hunt, J and Lottermoser, B G, 2016. Fingerprinting Environmental Impacts of Mining - a Test for Plant Bioaccessibility, in Proceedings The Third AusIMM International Geometallurgy Conference (GeoMet) 2016, pp 205-206 (The Australasian Institute of Mining and Metallurgy: Melbourne).