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Research article2024Peer reviewedOpen access

Ce anomaly in hemiboreal headwater streams: An indicator of dominant groundwater flow paths through the catchment

Conrad, Sarah; Lofgren, Stefan; Ingri, Johan

Abstract

The water quality in headwater streams depends on the groundwater origin and its transport pathways before it eventually discharges as surface water. In this case study, we present the Ce anomaly of over 100 hemiboreal headwater streams in Sweden and discuss the potential of the Ce anomaly to define two stream end members as proxies for the stream origin. The data show a relation between topography and the Ce anomaly, with more negative values (-0.8 to -0.4) in hilly catchments with distinct slopes, defined as an oxidized groundwater end member. The second end member is dominated by groundwater discharge from reduced, organic-rich riparian and wetland soils (reduced groundwater) having small Ce anomalies (-0.3 to zero). Element concentrations show a wide range, depending on the end member of the stream. For example, redox elements (Fe, Mn, S and N) show concentrations up to five times in streams with small negative Ce anomalies (reduced groundwater) compared to the concentrations in streams with large negative Ce anomalies. While element concentrations (of the classic redox elements Fe, Mn, S, N) show seasonal variations due to a summer drought period and the resulting reduced conditions, the Ce anomaly is constant, offering an excellent indicator of the dominant groundwater flow paths regardless of seasonal variations.

Keywords

Rare earth elements; End member classification; Summer drought; pH sensitivity; Organic carbon; Redox chemistry

Published in

Ecological Indicators
2024, Volume: 166, article number: 112491Publisher: ELSEVIER

    UKÄ Subject classification

    Environmental Sciences
    Oceanography, Hydrology, Water Resources

    Publication identifier

    DOI: https://doi.org/10.1016/j.ecolind.2024.112491

    Permanent link to this page (URI)

    https://res.slu.se/id/publ/132552