『Abstract
　Lead- and Pb-As-jarosites are minerals common to acidic, sulphate-rich environments, including weathering zones of sulphide ore deposits and acid rock or acid mine drainage (ARD/AMD) sites, and often form on or near galena. The structures of these jarosites are based on linear tetrahedral-octahedral-tetrahedral (T-O-T) sheets, comprised of slightly distorted FeO6 octahedra and SO4^2- (-AsO4^3- in Pb-As-jarosites) tetrahedra. To better understand the dissolution mechanisms and products of the break down of Pb- and Pb-As-jarosite, preliminary batch dissolution experiments were conducted on synthetic Pb- and Pb-As-jarosite at pH 2 and 20℃, to mimic environments affected by ARD/AMD, and at pH 8 and 20℃, to simulate ARD/AMD environments recently remediated with slaked lime (Ca(OH)2). All four dissolutions are incongruent. Dissolution of Pb-jarosite at pH 2 yields aqueous Pb, Fe and SO4^2-. The pH 8 Pb-jarosite dissolution yields aqueous Pb, SO4^2- and poorly crystalline Fe(OH)3, which does not appear to resorb Pb or SO4^2-, possibly due to the low solution pH (3.44-3.54) at the end of the experiment. The pH 2 and 8 dissolutions of Pb-As-jarosite result in the formation of secondary compounds (poorly crystalline PbSO4 for pH 2 dissolution; poorly crystalline PbSO4 and Fe(OH)3 for pH 8 dissolution), which may act as dissolution inhibitors after 250 to 300 h of dissolution. In the pH 2 dissolution, aqueous Fe, SO4^2- and AsO4^3- also form, and in the pH 8 dissolution, Fe(OH)3 precipitates then subsequently resorbs aqueous AsO4^3-. The dissolutions probably proceed by preferred dissolution of the A- and T-sites, which contain Pb, and SO4^2- and AsO4^3-, respectively, rather than Fe, which is sterically remote, within the T-O-T Pb- and Pb-As-jarosite structures. These data provide the foundation necessary for further, more detailed investigations into the dissolution of Pb- and Pb-As-jarosites.

Keywords: Pb-jarosite; Pb-As-jarosite; Fe hydroxide; Pb sulphate; acid mine drainage; dissolution』

1. Introduction
2. Methods and materials
　2.1. Synthesis of Pb- and Pb-As-jarosites
　2.2. Characterization of synthetic Pb- and Pb-As-jarosites
　2.3. Dissolution experiments
3. Results
　3.1. Characterization of synthetic Pb- and Pb-As-jarosites
　3.2. Dissolution at pH 2
　　3.2.1. Solution chemistry
　　3.2.2. Residual solids
　3.3. Dissolution at pH 8
　　3.3.1. Solution composition
　　3.3.2. Residual solids
4. Discussion
　4.1. Pb-jarosite
　　4.1.1. Dissolution at pH 2
　　4.1.2. Dissolution at pH 8
　4.2. Pb-As-jarosite
　　4.2.1. Dissolution at pH 2
　　4.2.2. Dissolution at pH 8
　4.3. Comparison of Pb-jarosite and Pb-As-jarosite dissolutions, and environmental implications
5. Conclusions
Acknowledgements
References