文摘
Diffuse reflectance infrared Fourier transform (DRIFT)spectrometry was applied to a set of sediment samplescollected by traps over one and a half years in a mid-mountainous river. Dynamic changes in hydrological and life-cycle conditions generated sediment particles of differentCorg content and organic composition. Periods in themidst of or shortly after flood events left particles poor inCorg content with spectral features that were enrichedin carboxylic and aromatic signals. These are characteristicof terrestrial oxidized vascular plant debris. Low-flowconditions saw the consequent build-up of amide, aliphatic,and polysaccharide moieties as expected for autochthonousbiofilm derived material. A peak ratio of two bandsrepresenting the alternation of these two types of organicmatter showed that flood particle Corg had a higheraffinity for metals than the high Corg of mature biofilms,probably owing to higher COO- contents in the first. Therelative dietary bioavailability of the metals from sedimentCorg, which is related to the nutritional value of thesubstrate, is therefore probably lower in the aftermath ofa flood than in prolonged low-flow situations. This needs tobe accounted for in future metal speciation and bioavailabilitymodeling approaches.