Microbial Fe(II) oxidation and heavy metal co-precipitation in the Rio Tinto region, Spain

• Applicant: Professor Dr. Andreas Kappler
• Subject Area: Hydrogeology, Hydrology, Limnology, Urban Water Management, Water Chemistry, Integrated Water Resources Management ; Mineralogy, Petrology and Geochemistry
• Term: from 2016 to 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 329562988

Pollution of aquatic environments by heavy metals (HMs) has long been considered a major threat to living organisms that are in contact with contaminated water. Acid mine drainage (AMD) forming in mining regions often discharges substantial loads of HMs into local rivers, which then become contaminated with toxic metals. The Rio Tinto river region in the province of Huelva, Spain, is of great interest as it is considered to be one of the most polluted fluvial-estuarine systems in the world. The Rio Tinto basin is divided into two three zones based on topological, geological and geochemical characteristics: the northern region characterized by stable hydrogeochemical parameters with a mean pH of 2.3 and high concentrations of Fe in solution, the estuary with a daily pH gradient in the range of 2.5-6.8 and the transitional zone. Despite acidic pH and high HM content, the Rio Tinto is characterized by a high level of microbial Fe(II)-oxidizing activity that can stimulate Fe(III) precipitation and thus accelerate the process of HM retardation by co-precipitation with or by sorption onto Fe(III) minerals. The first goal of the present proposal is to determine the influence of the spatial and temporal pH fluctuations on the abundance and the activity of Fe(II)-oxidizing microorganisms and to evaluate if and how pH fluctuations stimulate or supress the activity of acidophilic Fe(II)-oxidizing microorganisms in the transitional zone. The second goal is to determine whether the pH dynamics in the transitional zone influence or even control the identity and composition of the primary minerals that are produced by abiotic and biotic Fe(II) oxidation. The third goal is to determine how the key biogeochemical processes (microbial and abiotic Fe(II) oxidation) and the composition of precipitated minerals control the fate and transport of HMs in the northern region and transitional zones. The results from this project will help us to understand changing patterns in HM mobility not only in the transitional zone of the Rio Tinto but also in other former mining areas contaminated with HMs.

• DFG Programme: Research Grants
• Co-Investigator: Professorin Sara Kleindienst, Ph.D.