V. P. Matanitobua

In Vitro Physiologically Based Extraction Test (PBET) and Bioaccessibility of Arsenic and Lead from Various Mine Waste Materials

In vivo models show that the bioavailability of soil contaminants varies between site and type of matrix. Studies demonstrated that assuming 100% bioavailability of arsenic (As) and lead (Pb) from soils and mine waste materials overestimates the risk associated with human exposure. In in vitro systems, the simulated bioavailability of a contaminant is referred to as the “bioaccessibility” and is used as an alternative quantitative indicator for in vivo derived bioavailability estimates. The general concept of the in vitro extraction test is to predict the bioavailability of inorganic substances from solid matrices by simulating the gastrointestinal tract (GIT) environment. The aims of this study were to: (1) investigate the bioaccessibility of As and Pb from various mine wastes, including tailings, heap leach, and waste rock, using a physiologically based extraction test (PBET); (2) validate the bioaccessibility values from PBET with in vivo bioavailability values measured using animal models; and (3) correlate PBET results with the bioavailability values measured from alternative in vivo models (rats and cattle, from Bruce, 2004). Significant correlation was observed between bioaccessibility values from PBET, and bioavailability values generated for both rats and cattle, demonstrating the potential to utilize PBET as a relatively inexpensive alternative to in vivo models for bioavailability assessment.

Using Synchrotron‐based X‐ray Absorption Spectrometry to Identify the Arsenic Chemical Forms in Mine Waste Materials

X-ray Absorption Near Edge Spectroscopy (XANES) gives arsenic form directly in the solid phase and has lower detection limits than extraction techniques. An important and common application of XANES is to use the shift of the edge position to determine the valence state. XANES speciation analysis is based on fitting linear combinations of known spectra from model compounds to determine the ratios of valence states and/or phases present. As(V)/As(III) ratios were determined for various Australian mine waste samples and dispersed mine waste samples from river/creek sediments in Vatukoula, Fiji.