Fine colloidal and nanoparticulate P, Fe, Al and C distribution in stream water of a German mountainous forest catchment

Nina Gottselig1, Roland Bol1, Volker Nischwitz2, Harry Vereecken1, Wulf Amelung1, Erwin Klumpp1
1 Agrosphere, IBG-3, Research Center Jülich
2 Analytics, ZEA-3, Research Center Jülich

O 9.1 in Critical unknowns in the cycling of P in forest, grassland and wetland ecosystems

15.07.2014, 15:30-15:50, H20

Natural fine colloids and nanoparticles have the potential to encapsulate and bind nutrients. Their size and composition is therefore relevant to understand the transport of essential nutrients like phosphorus in an aquatic ecosystem. The aim of the study was to characterize fine colloidal and nanoparticulate bound phosphorus of distinct hydromorphological areas in stream water from a forested test site in a small headwater catchment. Asymmetric Flow Field Flow Fractionation (AF4) coupled online to inductively coupled plasma mass-spectrometry (ICP-MS) was applied for size resolved detection of phosphorus (P), iron (Fe), and aluminum (Al) in the fractions. A challenge was online P detection due to the low concentrations (in this study down to 0.1 µg/L) in many natural waters. Additionally, the “dissolved” organic matter (DOM) content was derived from the online UV signal. The colloidal P occurred in two size fractions (ranges: 2 – 20 nm and 21 – 300 nm), which constituted up to 100% of total river P discharge depending on hydromorphology. For the small size fraction, variations in P concentrations correlated to the course of Al variations; in addition, high Fe presence in both fractions was accompanied by high P concentrations. Moreover, DOM was detected with P in presence of Fe and Al, suggesting that Fe and Al are carriers of P and associated with organic matter. The developed methodology enables for the first time to trace and conceptually define the inputs and source regions of fine colloidal and nanoparticulate fractions within a small river of a headwater catchment.

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last modified 2014-04-03