Assessment of enrichment factors and grain size influence on the metal distribution in riverbed sediments (Anllóns River, NW Spain)

Abstract

The metals distribution in the bed sediments of the Anllóns River was studied, with special emphasis on the evaluation of the metal distribution as a function of the granulometric fraction chosen for the analysis. Statistical significant differences between the distribution of K, Ca, Cr, Mn, As, Rb, Sr and Nb in the bulk (<2 mm) and fine fraction (<63 μm) were not found. Fe, Ni, Cu, Ga, Zr, Zn and Pb commonly appear in higher concentrations in the fine fraction, whereas Ti appears in higher concentrations in the bulk fraction. In general, it was observed that contamination phenomena tend to equalise the concentrations of both fractions, and this was mainly explained as the result of two processes. First, the formation of coatings over sands and, second, the formation of large aggregates (pseudo-sands) at sites located over basic rocks, whose chemical behaviour is closer to that of clays and could be responsible for significant adsorption processes. Normalisation techniques to evaluate contamination were applied by testing Nb, Sr, Rb or Ga as normaliser elements and by using crustal or shale average values for background concentrations. The most satisfactory result was obtained when using shale average values and Ga as the normaliser element. Arsenic was identified as the main contaminant of the basin, exceeding in all cases the low-effect reference values proposed by sediment quality guidelines and in two cases the medium-effect reference values. These sites were identified by multivariate techniques, which allow differentiating site 10 as affected by anthropogenic inputs related to past mining activities.

Metal contamination of bed sediments in the Irwell and Upper Mersey catchments, northwest England: exploring the legacy of industry and urban growth

“…None of the particle size fractions or the specific surface area (SSA) of the sediments demonstrate a significant relationship with any of the selected metal(loid)s. This is counter to many of the trends reported in the literature where a decrease in particle size is shown to increase contaminant loadings Horowitz and Elrick 1987;Walling and Woodward 1992;Borovec et al 1993;Rhoads and Cahill 1999;Devesa-Rey et al 2011). Our findings are consistent with those reported by Moore et al (1989) and Bertin and Bourg (1995).…”

Phosphorus transfer across boundaries: from basin soils to river bed sediments

“…The significant adsorption of the sandy fraction was explained in a previous study (Devesa-Rey et al 2011b) due to the formation of coatings over sands, whose maximum degree of oxyhydroxides coating was 10%. Also the formation of large aggregates (pseudo-sands), whose chemical behaviour is closer to that of clays and could be responsible for significant adsorption processes.…”

Arsenic Mobility in As-Containing Soils from Geogenic Origin: Fractionation and Leachability

“…High As concentrations have been found in the bed sediments of the Anllóns River, downstream of the mineralized area, with a maximum of 264 mg kg −1 , which have been attributed to natural geogenic arsenic enrichment, exacerbated by gold mining activities carried out since Roman times [31][32][33]. At some points along the river course, these high As concentrations have been identified as being responsible for ecotoxicity [34,35]. Arsenic concentrations exceeding ten to sixty times the legal limit for As in drinking water, set at 10 g L −1 by WHO [36], have been detected in groundwater near the mineralized area.…”