Particle size characteristics of suspended and bed sediments in the rhône river

Abstract

Ten large volume water samples were taken from the RhBne River (Switzerland-France) in November 1989 for recovery of total suspended sediment by continuous flow centrifugation. The samples were freeze-dried and analysed for particle size, organic carbon, total nitrogen, and carbonate. For comparative purposes, four bed sediments collected in July 1989 are also described. The RhBne can be subdivided into three sections on the basis of the origins of the water. The first section is the Upper RhBne River draining into Lake Geneva. Waters are derived from glaciers, with low temperature and conductivity and high turbidity. Suspended sediment is coarse, has a bimodal distribution, and is low in both organic matter and carbonate. The second reach is from Lake Geneva to the confluence with the Sabne at Lyon and has warmer water with higher conductivity and very low turbidity. Suspended sediment is higher in organic matter, with high carbonate originating from the lake. The final section is from Lyon to Arles, with warmer water and higher conductivity and turbidity due to modification by the SaBne. Sediment is rich in organic matter, which may account for an observed decline in oxygen in the river waters downstream from Lyon. Carbonate in these sediments also decreases due to increased turbidity from the SaBne. Suspended sediments other than from the Upper RhBne show a remarkable consistency in grain size, predominantly in the fine silts (mode 9-11 pm). This consistency indicates a high degree of suitability for geochemical analysis. Bed sediments were bimodal throughout, with a dominant coarse population in two out of the four samples. Grain size statistical parameters could be easily explained by application of the theory of mixing of two major populations in the sand size (bed traction load) and the fine silt/clay size (suspended sediment load).KEY WORDS Sediments Rhbne River Particle size 088 5 -608 7/92/02022 7 -1

Calibration of a Par-Tec 200 laser back-scatter probe FORin situ sizing of fluvial suspended sediment

“…This technology has been widely used in studies of suspended sediment (e.g. Bale and Morris, 1991;Walling and Woodward, 1993), and a Coulter laser diraction device was employed by Santiago et al (1992) in a study of the particle size characteristics of Rhone River sediments.…”

Comparative ecotoxicity of suspended sediment in the lower Rhone River using algal fractionation, Microtox® and Daphnia magna bioassays

“…Suspended sediments have been studied to determine the real time transport of nutrients, metals and organic pollutants and for the calculation of loadings of sediment bound pollutants (Shear & Watson, 1977;Frank et al, 1981;Thomas & Frank, 1982;Burrus et al, 1990b;Santiago et al, 1992). Except for run-off periods, grain size analyses have pointed out the homogeneous texture of suspended solids and this consistency, eliminating the need for sieving or artificially normalizing the particles, supports the high suitability of suspended sediments for comparative geochemical analyses (Santiago et al, 1991).…”

Temperature signal in suspended sediment export from an Alpine catchment

“…Previous analysis on the grain size distribution of suspended sediment at the outlet of the upper Rhône River reports a bimodal distribution, with mode diameters equal to 13.7 µm (silt) for the finer fraction and 39.6 µm (silt) for the coarser grains (Santiago et al, 1992). The composition of grains cover a wide range of values, including clay (16.9 %), silt (64.7 %), and sand (18.4 %).…”

“…The composition of grains cover a wide range of values, including clay (16.9 %), silt (64.7 %), and sand (18.4 %). The mean suspended sediment size is reported to be equal to 17.7 µm (silt), and the largest grains transported in suspension during summer high-flow conditions are in the range of coarse sand (> 500 µm) (Santiago et al, 1992).…”