An FTIR-DRIFT Study on River Sediment Particle Structure:  Implications for Biofilm Dynamics and Pollutant Binding

Abstract

Diffuse reflectance infrared Fourier transform (DRIFT) spectrometry was applied to a set of sediment samples collected 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 different C(org) content and organic composition. Periods in the midst of or shortly after flood events left particles poor in C(org) content with spectral features that were enriched in carboxylic and aromatic signals. These are characteristic of terrestrial oxidized vascular plant debris. Low-flow conditions saw the consequent build-up of amide, aliphatic, and polysaccharide moieties as expected for autochthonous biofilm derived material. A peak ratio of two bands representing the alternation of these two types of organic matter showed that flood particle C(org) had a higher affinity for metals than the high C(org) of mature biofilms, probably owing to higher COO- contents in the first. The relative dietary bioavailability of the metals from sediment C(org), which is related to the nutritional value of the substrate, is therefore probably lower in the aftermath of a flood than in prolonged low-flow situations. This needs to be accounted for in future metal speciation and bioavailability modeling approaches.

DOM characteristics along the continuum from river to receiving basin: a comparison of freshwater and saline transects

“…Peaks at 1,660-1,650 cm -1 and 1,560-1,540 cm -1 can stem from primary and secondary amide functional groups, which may imply proteins (Arouri et al 1999;Dignac et al 2000;Jouraiphy et al 2005). Gallé et al (2004) analyzed laboratory-grown green algae by diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy and found prominent peaks at 1,658 and 1,535 cm -1 due to proteins and a peak at 1,062 cm -1 due to polysaccharides. The presence of strong amide peaks in the CBB and OSC spectra imply extensive primary production, particularly as compared to the more oligotrophic Lake Superior offshore sites (Figs.…”

“…Spectra also showed evidence of nitrogen compounds, likely from proteins with peaks around 1,660-1,650 cm -1 and 1,560-1,540 cm -1 (Gallé et al 2004). Peaks around 1,636-1,596 cm -1 likely relate to C=C, C=O bonds of carboxylic acids or aromatics possibly from humic substances or recalcitrant organic material (Arouri et al 1999).…”

FTIR Spectroscopic Study of Biogenic Mn-Oxide Formation byPseudomonas putidaGB-1

“…A decrease in peak intensity at 1390 cm −1 (ν sym , COO − ) is observed with Mn-oxidation, as is the formation of a doublet (at 1658 and 1648 cm −1 ) from the amide I peak (at 1652 cm −1 in the absence of MnO x ). IR spectral effects of MnO x were quantified using peak intensity ratios determined by comparison of maximum IR absorbance values at selected wavenumbers (Niemeyer et al 1992;Ishida and Griffiths 1993;Wander and Traina 1996;Gallé et al 2004). Values appear to be independent of the type of transmission window and the amide II (1540 cm −1 ) / amide I (1650 cm −1 ) ratio is not affected by Mn oxidation ( Table 2).…”

Sediment Characterization

“…Usually, a drawback is the presence of inorganic carbonate in the sediment samples submitted to FTIRS analysis, because it gives rise to a broad signal around 1650 cm − 1 that can mask the asymmetric COO − /C -C stretches bands. However, the sediment samples studied by Gall é et al (2004) were practically free from inorganic carbonate. Therefore, the refractory organic matter contribution to the overall C org was easily detectable in the DRIFTS spectra, without the removal of inorganic carbonates by chemical methods.…”

“…DRIFT is a surface characterization method, involving a refl ection experiment where the typical depths of penetration of the infrared beam into the surface are 1 -10 μ m, suffi cient depth to characterize the organic layer on mineral surfaces. However, obtaining reproducible quantitative DRIFT measurements requires strict attention to experimental details, especially to particle size distribution and packing density of the sample (Belton & Wilson 1990 ;Gall é et al 2004 ).…”