Trace metal behaviour in riverine sediments: Role of organic matter and sulfides

Abstract

Three sediment cores were collected in the Scheldt, Lys and Spiere canals, which drain a highly populated and industrialized area in Western Europe. The speciation and the distribution of trace metals in pore waters and sediment particles were assessed through a combination of computational and experimental techniques. The concentrations of dissolved major and trace elements (anions, cations, sulphides, dissolved organic carbon, Cd, Co, Fe, Mn, Ni, Pb and Zn) were used to calculate the thermodynamic equilibrium speciation in pore waters and to evaluate the saturation of minerals (Visual Minteq software). A sequential extraction procedure was applied on anoxic sediment particles in order to assess the main hosting phases of trace elements. Manganese was the most labile metal in pore waters and was mainly associated to carbonates in particles. On the contrary, a weak affinity of Cd, Co, Ni, Pb and Zn with carbonates was established because (1) a systematic under-saturation was noticed in pore waters and (2) less than 10% of these elements were extracted in the exchangeable and carbonate sedimentary fraction. In the studied anoxic sediments, the mobility and the lability of trace metals, apart from manganese, seemed to be rather controlled through the competition between sulphidic and organic ligands. In particular, the necessity of taking into account organic matter in the modelling of thermodynamic equilibrium was demonstrated for Cd, Ni, Zn and Pb, the latter element exhibiting the stronger affinity with humic substances. Consequently, dissolved organic matter could favour the stabilization of trace metals in the liquid phase. Conversely, sulphide minerals played a key role in the scavenging of trace metals in sediment particles. Finally, similar trace metal lability rankings were obtained for the liquid and solid phases.

Sulfur isotope fractionation and sequential extraction to assess metal contamination on lake and river sediments

“…3, minor amounts of Fe were associated with the labile and oxidizable fractions. However, it was mainly extracted in the reducible and residual steps which are similar to the results reported in the literature (Morillo et al 2008;Charriau et al 2011). The reducible fraction (E2) comprises 12 to 30 % and consists of oxyhydroxides present in highly weathered environments (amorphous Fe).…”

“…In addition, the metastable iron monosulfides (FeS) can be a precursor of pyrite (FeS 2 ) that is a fairly stable sulfide which is capable of adsorbing contaminants. Therefore, the assessment of sulfur isotopic fractionation, the quantification of the sulfides, and the determination of the solid phases along with their association with the contaminants are essential for the following reasons: firstly they provide information about distribution, mobility, and bioavailability of the contaminants, and secondly, they indicate the occurrence of natural attenuation processes (Morillo et al 2008;Sarmiento et al 2009;Byrne et al 2010;Charriau et al 2011).…”

Metal bioleaching from anaerobic sediments from Reconquista River basin (Argentina) as a potential remediation strategy

“…This fact leads to a high benthic oxygen demand generation and sets an anoxic environmental condition suitable for the biocatalyzed formation of sulphides (Di Nanno et al 2007;Porzionato et al 2013Porzionato et al , 2014. Under these low redox potential conditions, most of heavy metals might precipitate as poorly soluble sulphides and hydroxides or are adsorbed to the different mineral components of the sediment matrix (Eggleton and Thomas 2004;Atkinson et al 2007;Charriau et al 2011). These processes maintain metals in a low bioavailable state as long as low redox potential conditions are not altered.…”

Bioaccumulation of Lead and Arsenic in Gastropods Inhabiting Salt Marsh Ponds in Coastal Bay of Fundy, Canada

“…Water chemistry strongly influences the mobility of trace elements in aquatic systems and is likely differentiating the species and availabilities of Pb and As in the CMR wetlands despite their close proximity (Scheuhammer et al 1997). Parameters including pH and alkalinity, dissolved oxygen, temperature, salinity, and water hardness influence all bioavailability of non-essential trace elements when they are within the optimal range to trigger metal releases from the bottom sediment into the sediment-water interface (Gupta 1997;Hung and Chmura 2007;Zhou et al 2007) but also may directly affect metal accumulation rates and absorption in gastropod tissues (Albers and Camardese 1993;Weis and Weis 2004;Penha-Lopes et al 2010;Charriau et al 2011). Thus, adverse effects are possible if there are significant levels of Pb and As in these wetlands, and demonstrated environmental conditions and biomagnification vectors exist that are conducive to uptake and accumulation in waterfowl.…”