BCR fractionation of mine-affected sediments as a basis for NbS design and implementation

Acid mine drainage (AMD) poses a persistent threat to freshwater ecosystems by causing acidification and mobilizing heavy metals that have adverse effects on aquatic biota. Especially in Arctic regions, these impacts are amplified by the changing redox conditions due to the low temperatures and seasonal ice cover. Nature-based solutions (NBS), including constructed wetlands, offer an ecologically friendly option to remediate the water quality under various environmental conditions, including AMD. Before developing an NbS to mitigate AMD, we analyze sediment composition in the target area to understand heavy metal behavior, including water–sediment transfer and their potential (bio) availability. Langvatnet Lake, located in northern Norway, functions as the main receiving water body and the lowest point within the historic Sulitjelma mining district, where extensive metal mining activities (primarily copper and zinc extraction) occurred for more than a century (Davids, 2018). These long-standing operations have resulted in highly acidic inflows originating from abandoned mine workings that, despite being closed, continue to leak acidic water and generate small drainage streams that flow into the lake. This ongoing discharge transports elevated concentrations of dissolved metals, contaminating both the water column and lake sediments. While the overarching aim of this research is to develop and evaluate NbS strategies to improve the water quality of the inlet streams, our first step is to quantify how mine-derived contaminants accumulate, persist, and potentially remobilize within lake sediments. Therefore, we use the Community Bureau of Reference (BCR) sequential extraction procedure to quantify the heavy metal concentration in different geochemical fractions of the sediments (Rauret et al., 1999). The inlet samples are compared with a range of sediment samples from the lake’s surrounding areas. This approach enables us to assess their potential release under varying environmental conditions. By identifying the dominant binding fractions, this contributes to designing the best suitable NbS for the investigated area. Our findings provide a basis for understanding the local sediment geochemistry in relation to the targeted remediation strategy. In this context, improved understanding of sediment-water interactions supports the development of resilient, passive NBS to enhance water quality, promote ecosystem recovery, and ensure long-term sustainability in AMD-impacted Arctic Lake systems.

 

References:

Davids, C. (2018). Mapping of abandoned mine tailings and acid mine drainage using in situ hyperspectral measurements and WorldView-3 satellite imagery (Case Study Report No. 20/2018). Northern Research Institute.

Rauret, G., López-Sánchez, J. F., Sahuquillo, A., Rubio, R., Davidson, C., Ure, A., & Quevauviller, Ph. (1999). Improvement of the BCR three step sequential extraction procedure prior to the certification of new sediment and soil reference materials. Journal of Environmental Monitoring, 1(1), 57–61. https://doi.org/10.1039/a807854h