Arsenic mineralogy and mobility in the arsenic-rich historical mine waste dump

0446768 - GLÚ 2016 RIV NL eng J - Journal Article
Filippi, Michal - Drahota, P. - Machovič, V. - Böhmová, Vlasta - Mihaljevič, M.
Arsenic mineralogy and mobility in the arsenic-rich historical mine waste dump.
Science of the Total Environment. Roč. 536, 1 December (2015), s. 713-728. ISSN 0048-9697. E-ISSN 1879-1026
R&D Projects: GA AV ČR KJB300130702
Institutional support: RVO:67985831
Keywords : arsenopyrite * pitticite * scorodite * sulfur * kaňkite * amorphous ferric arsenate (AFA)
Subject RIV: DD - Geochemistry
Impact factor: 3.976, year: 2015

A more than 250 year-old mine dumpwas studied to document the products of long-termarsenopyrite oxidation under natural conditions in a coarse-grained minewaste dump and to evaluate the environmental hazards associated with this material. Using complementary mineralogical and chemical approaches (SEM/EDS/WDS, XRD, micro-Raman spectroscopy, pore water analysis, chemical extraction techniques and thermodynamic PHREEQC-2 modeling), we documented the mineralogical/geochemical characteristics of the dumped arsenopyrite-rich material and environmental stability of the newly formed secondary minerals. A distinct mineralogical zonationwas found (listed based on the distance fromthe decomposed arsenopyrite): scorodite (locally associated with native sulfur pseudomorphs) plus amorphous ferric arsenate (AFA/pitticite), kaňkite, Asbearing ferric (hydr)oxides and jarosite. Ferric arsenates and ferric (hydr)oxides were found to dissolve and again precipitate from downward migrating As-rich solutions cementing rock fragments. Acidic pore water (pH 3.8) has elevated concentrations of As with an average value of about 2.9 mg L⁻¹. Aqueous As is highly correlated with pH (R² = 0.97, p < 0.001) indicating that incongruent dissolution of ferric arsenates controls dissolved As well as the pH of the percolating waste solution. Arsenic released from the dissolution of ferric arsenates into the porewater is, however, trapped by latter and lower-down precipitating jarosite and especially ferric (hydr)oxides. The efficiency of As sequestration by ferric (hydr)oxides in the waste dump and underlying soil has been found to be very effective, suggesting limited environmental impact of the mine waste dump on the surrounding soil ecosystems.
Permanent Link: http://hdl.handle.net/11104/0248737