Ferrihydrite as a powerful scavenger of As: A thermochemical and a field study

砷是毒性最大的元素之一，一般被列为优先污染物。在此，我建议通过实验和实地考察来研究砷和铁氧化物矿物的结合。本文提出的工作目标是确定1)As-铁水化物(~Fe(OH)3（nAs2O5(mH2O)）和scorodite （FeAsO4(2H2O)）的热化学性质，以及2)As在选定的斯洛伐克Nizny Hrusov严重污染地点的化学缔合和氧化状态。用酸溶液量热法测定砷铁水合体和铁云母的热化学性质。了解所选矿物的这些特性对于评估和预测砷铁酸盐的命运非常重要，砷铁酸盐是一种用于固定和长期储存砷的常见废物形式。选择下赫鲁索夫的实地地点是因为我们的初步工作点是大规模的砷污染，水中有机碳含量升高，以及砷的生物利用度。As（与水合铁和有机物）的化学结合及其氧化态将分别通过顺序萃取和x射线吸收光谱进行探测。了解As的种类将指导未来在这个地点和其他类似污染地点的清理工作。

Arsenic is one of the most toxic elements, generally classified as a priority pollutant. Here I propose to investigate the association of As and Fe oxide minerals by experimental and field work. The goal of the work proposed here is to determine 1) the thermochemical properties of As-ferrihydrite (~Fe(OH)3(nAs2O5(mH2O) and scorodite (FeAsO4(2H2O), and 2) the chemical association and oxidation state of As at a selected heavily polluted site Nizny Hrusov, Slovakia. The thermochemical properties of As-ferrihydrite and scorodite will be measured by acid-solution calorimetry. The knowledge of these properties for the selected minerals is important for assessing and predicting the fate of As-ferrihydrite, a common waste-form for immobilization and long-term storage of As. The field site in Nizny Hrusov was selected because our preliminary work points at a massive As contamination, elevated organic carbon content in the water, and bioavailability of As. The chemical association of As (with ferrihydrite versus organic matter) and its oxidation state will be probed by sequential extractions and X-ray absorption spectroscopy, respectively. Understanding the speciation of As will direct the future cleanup effort at this site and other similarly polluted sites.