Natural nanoparticles and colloids in European forested headwater catchments: new insights on spatiotemporal dynamics and potential origin

• Applicant: Dr. Melanie Braun, since 6/2020
• Subject Area: Hydrogeology, Hydrology, Limnology, Urban Water Management, Water Chemistry, Integrated Water Resources Management ; Soil Sciences
• Term: from 2017 to 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 354742818

• Final Report Year: 2025

Final Report Abstract

The element loss from forested ecosystems is largely reflected by the so-called dissolved phase (< 450 nm) in stream waters. However, natural colloids (1 nm – 1 µm), including natural nanoparticles (NNP, 1-100 nm), constitute a major but so far, largely unexplored part of this dissolved phase. We hypothesised that i) there is a systematic seasonal variation in elemental concentrations in NNP and colloid fractions across different European catchments and ii) that a peak flow export of NNP and colloid fractions exists, without a memory effect on the elemental baseline concentrations in the fractions before the event. Further we assume that iii) the NNP and colloid fractions in stream waters mainly originate from soils through riverbank erosion and that iv) seasonal variations of NNP and fine colloids in stream water exist, which differ in origin depending on catchment inflow parameters. To test these hypotheses, we sampled different stream waters across Europe and analyzed the elemental composition and as well as lignin (as biomarker) and δ13C and δ56Fe isotopes. We could confirm i) that there is a seasonal variation in the NNP and colloidal load of European stream waters. This seasonal pattern, however, differed between the catchments with distinct soil groups, hence the categorized soil group was identified here as the main controlling factor for the elemental composition in stream water. We further ii) found that after high discharge events (a combined snowmelt and rainfall event in winter and a rainfall event in spring) for most elements the colloidal export returned back to the baseline within hours or days. The peak export during the high discharge events was both, element and event-specific, with a higher export during the winter event. iii) We were not able to align the colloidal source to specific soil horizons by using lignin or δ13C and δ56Fe isotopes, but iv) could show that seasonal variations of NNP and fine colloids in stream water exist, with highest export in winter, and that groundwater mainly fed the streams throughout the whole year. Overall, our work confirms the important role of NNPs and colloids for elemental export in European streams, with surrounding soils as key controlling factor for NNP and colloid load in stream waters.

Publications

• Groundwater controls on colloidal transport in forest stream waters. Science of The Total Environment, 717, 134638.
  Gottselig, N.; Sohrt, J.; Uhlig, D.; Nischwitz, V.; Weiler, M. & Amelung, W.
  
• Colloidal catchment response to snowmelt and precipitation events differs in a forested headwater catchment. Vadose Zone Journal, 20(3).
  Burger, Dymphie J.; Vogel, Johnny; Kooijman, Annemieke M.; Bol, Roland; de Rijke, Eva; Schoorl, Jorien; Lücke, Andreas & Gottselig, Nina
  
• Spatiotemporal dynamics of natural nanoparticles and colloids in European forested headwater catchments, oral presentation at the OZCAR-TERENO Conference in Strasbourg
  Schimmel, H., Gottselig, N., Amelung, W. & Braun, M.
  
• Spatiotemporal dynamics of natural nanoparticles and colloids in European forested headwater catchments, poster on the Annual Meeting of the German Soil Science Society in Trier
  Schimmel, H., Gottselig, N., Amelung, W. & Braun, M.