Groundwater controls on colloidal transport in forest stream waters

[Display omitted] •The origin of colloids in streams indicates elemental transport pathways.•Monthly analysis of stream & groundwater, rainwater, throughfall, soil leachate.•Field flow fractionation revealed three fractions in all sample types.•Groundwater derived colloids dominated the stream signal.•Water flux and particle reformation affect the seasonal dynamics of particles. Biogeochemical changes of whole catchments may, at least in part, be deduced from changes in stream water composition. We hypothesized that there are seasonal variations of natural nanoparticles (NNP; 1–100 nm) and fine colloids (