Suspended particulate matter determines physical speciation of Fe, Mn, and trace metals in surface waters of Loire watershed

Mohamed Baalousha (1) , Serge Stoll (2) , Mikael Motelica-Heino (3, 4) , Nathalie Guigues (5) , Gilles Braibant (6) , Frederic Huneau (7, 8) , Philippe Le Coustumer (9)

1 Center for Environmental Nanoscience and Risk
2 Forel Institute
3 ISTO - Institut des Sciences de la Terre d'Orléans - UMR7327
4 Biogéosystèmes Continentaux - UMR7327
5 LNE - Laboratoire National de Métrologie et d'Essais [Trappes]
6 BRGM - Bureau de Recherches Géologiques et Minières (BRGM)
7 SPE - Sciences pour l'environnement
8 UPP - Université Pascal Paoli
9 IPREM - Institut des sciences analytiques et de physico-chimie pour l'environnement et les materiaux

This study investigates the spatiotemporal variability of major and trace elements, dissolved organic carbon (DOC), total dissolved solids (TDS), and suspended particulate matter (SPM) in surface waters of several hydrosystems of the Loire River watershed in France. In particular, this study aims to delineate the impact of the abovementioned water physicochemical parameters on natural iron and manganese physical speciation (homoaggregation/heteroaggregation) among fine colloidal and dissolved (< 10 nm), colloidal (10–450 nm) and particulate (> 450 nm) phases in Loire River watershed. Results show that the chemistry of the Loire River watershed is controlled by two end members: magmatic and metamorphic petrographic context on the upper part of the watershed; and sedimentary rocks for the middle and low part of the Loire. The percentage of particulate Fe and Mn increased downstream concurrent with the increase in SPM and major cations concentration, whereas the percentage of colloidal Fe and Mn decreased downstream. Transmission electron microscopy analyses of the colloidal and particulate fractions (from the non-filtered water sample) revealed that heteroaggregation of Fe and Mn rich natural nanoparticles and natural organic matter to the particulate phase is the dominant mechanism. The heteroaggregation controls the partitioning of Fe and Mn in the different fractions, potentially due to the increase in the ionic strength, and divalent cations concentration downstream, and SPM concentration. These findings imply that SPM concentration plays an important role in controlling the fate and behavior of Fe and Mn in various sized fractions.

Keywords: Natural iron and manganese; Hetero-aggregation; Suspended particle matter; Colloids; Physical speciation; Surface waters; Loire River watershed; Natural nanoparticles

Domains: Environmental Sciences; Sciences of the Universe [physics]; Earth Sciences; Geochemistry

Mohamed Baalousha, Serge Stoll, Mikael Motelica-Heino, Nathalie Guigues, Gilles Braibant, et al.. Suspended particulate matter determines physical speciation of Fe, Mn, and trace metals in surface waters of Loire watershed. Environmental Science and Pollution Research, 2019, 26 (6), pp.5251-5266. ⟨10.1007/s11356-018-1416-5⟩. ⟨insu-01706563⟩