『Abstract
　Arsenopyrite (FeAsS) is the most common As-bearing sulfide mineral. Under oxidising conditions, such as those in mine waste systems, it beaks down to release acids of As and S into the environment, resulting in acid mine drainage with high concentrations of dissolved As. In this communication, current knowledge of arsenopyrite oxidation is reviewed based on a survey of the existing literature, which has focused on processes and reactions at the mineral surface. X-ray photoelectron spectroscopy (XPS) has shown that the oxidation of arsenopyrite in acid is more rapid than in air, water, or in alkaline solutions. Oxidation products reported by XPS include Fe(III) oxide, As (III), As(V), SO3^2- and SO4^2-. The elemental constituents of arsenopyrite oxidise at different rates, although there is no consensus as to which is the fastest or slowest to oxidise. Electrochemical studies have highlighted the formation of elemental S on the arsenopyrite surface, while XPS studies suggest that only oxy-anions of S form. Kinetic studies of arsenopyrite oxidation suggest that O2 and Fe³⁺ are the dominant inorganic agents causing arsenopyrite dissolution. The bacterially-mediated oxidation of arsenopyrite by acidophilic Fe- and S-oxidising bacteria such as Acidithiobacillus ferrooxidans and Acidithiobacillus caldus, is more extensive than abiotic oxidation. The literature pertaining to arsenopyrite oxidation is divided regarding the reaction stoichiometry, and the composition and layering of surface overlayers.』

Contents
1. Introduction
2. Surface investigations of arsenopyrite oxidation
　2.1. Introduction
　2.2. Clean/vacuum-fractured surfaces
　2.3. Inorganic surface oxidation
　　2.3.1. Air
　　2.3.2. Aqueous solutions (pure water, acid and alkali solutions)
　　　2.3.2.1. Pure water
　　　2.3.2.2. Acid solutions
　　　2.3.2.3. Alkaline solutions
　2.4. Biogenic surface oxidation
3. Electro-oxidation studies
　3.1. Electro-oxidation in acidic solutions
　3.2. Electro-oxidation in alkaline solutions
　3.3. Electro-oxidation in the presence of micro-organisms
4. The kinetics of arsenopyrite dissolution
　4.1. Oxidation by Fe(III)
　4.2. Oxidation by dissolved oxygen (DO)
5. Geomicrobiological studies of arsenopyrite oxidation
　5.1. Introduction
　5.2. Acidophilic bacteria and arsenopyrite
　　5.2.1. Bacterial adhesion and attachment to arsenopyrite
　　5.2.2. Surface precipitates
　　5.2.3. Arsenic toxicity and detoxification
6. Discussion and conclusions
　6.1. Fate of sulfur species
　6.2. Elemental oxidation rates
　6.3. Surface overlayer composition
　6.4. Stoichiometry
　6.5 Implications for the mechanism of arsenopyrite oxidation
Acknowledgements
References