Elemental composition of natural nanoparticles and fine colloids in European forest stream waters and their role as phosphorus carriers

Abstract

Biogeochemical cycling of elements largely occurs in dissolved state, but many elements may also be bound to natural nanoparticles (NNP, 1-100 nm) and fine colloids (100-450 nm). We examined the hypothesis that the size and composition of stream water NNP and colloids vary systematically across Europe. To test this hypothesis, 96 stream water samples were simultaneously collected in 26 forested headwater catchments along two transects across Europe. Three size fractions (1-20 nm, >20-60 nm, >60 nm) of NNP and fine colloids were identified with Field Flow Fractionation coupled to inductively coupled plasma mass-spectrometry and an organic carbon detector. The results showed that NNP and fine colloids constituted between 2±5% (Si) and 53±21% (Fe; mean ± SD) of total element concentrations, indicating a substantial contribution of particles to element transport in these European streams, especially for P and Fe. The particulate contents of Fe, Al and organic C were correlated to their total element concentrations, but those of particulate Si, Mn, P and Ca were not. The fine colloidal fractions >60 nm were dominated by clay minerals across all sites. The resulting element patterns of NNP <60 nm changed from North to South Europe from Fe- to 108 Ca-dominated particles, along with associated changes in acidity, forest type and dominant lithology.

The authors gratefully acknowledge the assistance of the following people in locating suitable sampling sites, con- tacting site operators, performing the sampling, and providing data: A. Avila Castells (Autono mous University of Barcelona), R. Batalla (University of Lleida), P. Blomkvist (Swedish University of Agricultural Scien ces), H. Bogena (Jülich Research Center), A.K. Boulet (University of Aveiro), D. Estany (University of Lleida ), F. Garnier (French National Institute of Agricultural Research), H.J. Hendricks-Franssen (Research Center Jü lich), L. Jackson- Blake (James Hutton Institute, NIVA), T. Laurila (Finnish Meteorological Institute), A. Lindroth (Lund University), M.M. Monerris (Universitat Politècnica de València), M. Ottosson Löfvenius (Swedish University of Agricultural Sciences), I. Taberman (Swedish University of Agricultural Sciences), F. Wendland (Research Center Jülich), T. Zetterberg (Swedish University of Agricultural Sciences and The Swedish Environmental Research Institute, IVL) and further unnamed contributors. The Swedish Infrastructure for Ecosystem Science (SITES) and the Swedish Integrated Monitoring, the latter financed by the Swedish Environmental Protection Agency, and ICOS Sweden have supported sampling and provided data for the Swedish sites. J. J. K. grate- fully acknowledges the support from CESAM (UID/AMB/50017/ 2013), funded by the FCT/MCTES (PIDDAC) with cofunding by FEDER through COMPETE. N. G. gratefully acknowledges all those who contributed to organizing and implementing the continental sam- pling. The raw data can be found at http://hdl.handle.net/2128/14937. This project was partly funded by the German Research Foundation (DFG KL 2495/1-1).