Trace metal distribution in the bed, bank and suspended sediment of the Ravensbourne River and its implication for sediment monitoring in an urban river

Purpose This study aims to identify a suitable sediment compartment for sediment quality monitoring by: (a) studying the concentration of trace metals (Cd, Cu, Ni, Pb and Zn) in the bed, bank and suspended sediment compartments of the Ravensbourne River to establish any differences in trace metal concentrations with compartment; (b) determining the influence of sediment particle size fractions ( 0.05) in the concentrations of metals between the suspended sediment and the < 63 μm bed sediment fraction, but there was a significant difference (p < 0.05) between the suspended sediment and the < 63 μm bank sediment fraction. There were also significant differences between the concentrations of metals in the < 63 μm and the 63 μm–2 mm fractions. Generally, the Ravensbourne River did not comply with the draft UK sediment quality guidelines for the metals analysed. Conclusions This study shows the importance of identifying a suitable sediment compartment to sample for compliance with sediment quality standards. The bed and suspended sediments are the most widely used sediment compartments for sediment monitoring, but collecting sufficient mass of the < 63 μm sediment fraction for monitoring presents a challenge for urban gravel bed rivers like the Ravensbourne River. It seems appropriate to establish individual monitoring regimes for different rivers

Cadmium uptake by durum wheat in presence of citrate

The aim of this study was to determine the mechanisms underlying the uptake of Cd by durum wheat (Triticum turgidum L. ssp. durum cv. “acalou”) in the presence of citrate under hydroponic conditions. Wheat seedlings were exposed for 3 h to simplified nutrient solutions initially containing 35 nM of free Cd with or without citrate. Uptake experiments with citrate alone were also performed. Solutions were radio labelled with 109Cd or citrate-14C. The depletion of Cd and citrate in the exposure solution was followed, and at the end of the exposure Cd and citrate were quantified in all compartments of the experimental system (root surface, inner roots and aerial parts). The apparent rates of internalization of Cd (r Cd) and citrate (r cit) were estimated from the ratio of the uptake flux to the contents adsorbed at the root surface. About two times more Cd was taken up in the presence of citrate. Assuming that citrate and Cd-citrate complexes were taken up at the same rate, a direct uptake of intact complexes could not account for the higher uptake of Cd in presence of citrate. In addition, Cd was internalized at the same rate in the absence or presence of citrate (r Cd = 3.62 h−1), whereas the internalization rate constants of Cd and citrate were different (r Cd ≈ 8 r cit). This strengthens the idea that a direct uptake of non-dissociated Cd-citrate complexes probably did not account for the higher Cd uptake in presence of citrate. A dissociation of Cd-citrate complexes within the diffusion layer or at the root surface and the subsequent additional supply of free Cd were more likely to explain the higher Cd uptake in presence of citrate