Microbial sulfate reduction (MSR) as nature-based solution (NBS) to mine
drainage: Contrasting spatio-temporal conditions in northern Europe
Abstract
An emerging solution in mine waste remediation is the use of biological
processes, such as microbial sulfate reduction (MSR), to immobilize
metals, reducing their bioavailability and buffering the pH of acid mine
drainage. Apart from laboratory tests and local observations of natural
MSR in e.g. single wetlands, little is known about spatio-temporal
characteristics of freshwater MSR from multiple locations within entire
hydrological catchments. We here applied an isotopic fractionation
(δ34S-values in SO42-) and Monte-Carlo based mixing analysis scheme to
detect MSR and its variation across two major mining regions (Imetjoki,
Sweden and Khibiny, Russia) in the Arctic part of Europe under different
seasonal conditions. Results indicate a range of catchment-scale
MSR-values in the Arctic of ~ 5-20% where the low end
of the range was associated with the non-vegetated, mountainous terrain
of the Khibiny catchment, having low levels of dissolved organic carbon
(DOC). The high-end of the range was related to vegetated conditions
provided by the Imetjoki catchment that also contains wetlands, lakes
and local aquifers. These prolong hydrological residence times and
support MSR hot-spots reaching values of ~40%. Present
results additionally show evidence of MSR-persistence over different
seasons, indicating large potential, even under relatively cold
conditions, of using MSR as part of nature-based solutions to mitigate
adverse impacts of (acid) mine drainage. The results call for more
detailed investigations regarding potential field-scale correlations
between MSR and individual landscape and hydro-climatic characteristics,
which e.g. can be supported by the here utilized isotopic fractionation
and mixing scheme.