Copper sulfates, phosphates, and arsenates as pollution containers and vectors

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The principal source of copper are primary sulfide minerals. Their oxidation leads to the formation of secondary and tertiary copper minerals at sites where copper ores were mined in the past or are being mined currently. These minerals are sulfates, phosphates, arsenates, or carbonates of copper. They can be also found in soils polluted by copper where this element was introduced as a component of cheap fungicides and they form by degradation of man-made copper structures, for example, statues. In all these environments, formation processes of the secondary and tertiary Cu minerals are controlled by their thermodynamic properties. Here I propose to study the thermodynamic properties of a number of copper sulfates, phosphates, and arsenates. Within the study, we will determine the formation enthalpies (AH°f) and standard entropies (S°) of these phases by acid-solution and low-temperature quasi-adiabatic calorimetry, respectively. Material for this study will be exclusively synthetic, prepared and thoroughly characterized in our laboratory. An integral part of this study will be the research of secondary and tertiary copper minerals at the locality Lubietova (Libethen in German) where copper sulfates, phosphates, and arsenates are found in abundance. We will investigate especially the pooriy crystalline tertiary minerals by the means of transmission electron microscopy, with two questions in mind: (1) What are the initial phases that control precipitation of Cu under the conditions present here, and (2) Do microorganisms aid or assist the precipitation processes? Using the measured AH°f and S° values, we will calculate Gibbs free energy for each studied phase and construct phase diagrams relevant to environmental conditions. The phase diagrams will be applied to the assemblages determined at lubietova, at sites polluted by Cu in general, including the polluted soils and degrading copper structures. The ultimate goal of the proposed work is to present a reliable and consistent thermodynamic database for the copper minerals applicable to any polluted site where such data may be needed.