Persisting impact of historical mining activity to metal (Pb, Zn, Cd, Tl, Hg) and metalloid (As, Sb) enrichment in sediments of the Gardon River, Southern France

Abstract

In this study, we assessed past and present influence of ancient mining activity on metal(loid) enrichment in sediments of a former mining watershed (Gardon River, SE France), that is now industrialized and urbanized. A sedimentary archive and current sediments were characterized combining geochemical analyses, zinc isotopic analyses and sequential extractions. The archive was used to establish local geochemical background and recorded (i) increasing enrichment factors (EFs) for Pb, Zn, Cd, Tl, Hg, As and Sb throughout the industrial era, (ii) a contamination peak in 1976 attributed to a tailings dam failure, and (iii) current levels in 2002 and 2011 similar to those of 1969, except for Sb and Hg, reflecting a persisting contamination pattern. Inter-element relationships and spatial distribution of EF values of current sediments throughout the watershed suggested that both ancient and current contamination had a common origin for Pb, Zn, Cd, Tl and As related to the exploitation of Pb/Zn mineralization while old Sb mines and coal extraction area were the main sources for Sb and Hg respectively. This prevailing mining origin was reflected for Zn by a relatively uniform isotopic composition at δ(66)Zn=0.23 ± 0.03‰, although slight decrease from 0.23‰ to 0.18‰ was recorded from upstream to downstream sites along the river course in relation with the contribution of the lighter δ(66)Zn signature (~0.08‰) of acid mine drainage impacted tributaries. Results from sequential extractions revealed that the potential mobility of the studied metal(loid)s varied in the order Sb<Tl≈As<Zn<Pb<Cd, with an increase of the mobile pool for Cd, Pb, Zn and to a lesser extent for As and Tl associated to increased enrichment. Altogether, these results tend to demonstrate that ancient mining activity still contributes to metal enrichment in the sediments of the Gardon River and that some of these metals may be mobilized toward the water compartment.

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

“…These environments form a longer-term storage and have the potential to contribute historically contaminated sediment during modern-day flood events, as has been reported for floodplains downstream of former metal mining areas (e.g. Wolfenden and Lewin 1977;Hudson-Edwards et al 1999;Resongles et al 2014). The widespread practice of riparian dumping of physical waste across Manchester during the industrial period is likely to have established a complex network of contaminated sediment stores, which reflect the changing industrial and urban environments both locally and upstream.…”

Variation of dissolved and particulate metal(loid) (As, Cd, Pb, Sb, Tl, Zn) concentrations under varying discharge during a Mediterranean flood in a former mining watershed, the Gardon River (France)

“…8c, d); these two latest rivers are located downstream from the ancient mining district of Pallières which is close to Carnoulès mining district. Correlation line from Event 2" also fitted with data from sulfide-rich tailings of the Carnoulès mine and with data from a sediment layer in a flooding terrace recovered at 45 km downstream from Lezan; this contaminated layer was attributed to the failure of a tailing dam at the Carnoulès mine Resongles et al, 2014).…”

“…The middle and lower parts are underlain by Jurassic (west) to Cretaceous (east) carbonated formations (BRGM, Infoterre website; Resongles et al, 2014).…”

Trace metal storage in recent floodplain sediments along the Dill River, central Germany

“…19 is the case, near-channel sediments along the Dill River may serve as potential sources of downstream trace metal pollution in the foreseeable future, something noted by others working in western European watersheds (e.g., Förstner, 2003;Krüger et al, 2005;Macklin et al, 2006;Foulds et al, 2014;Resongles et al, 2014).…”

“…Vertical trends in trace metals, which have been used to document movement of metal-contaminated sediments through drainage basins, permit assessment of the potential for near-channel floodplain sediments to serve as future sources of downstream contamination (Gocht et al, 2001;Middelkoop, 2002;Vallius, 2014;Lecce and Pavlowsky, 2014). When age control on vertical metal trends is available, either through knowledge of the upstream industrial or mining history or through radiometric ages, calculation of recent overbank sedimentation rates is possible (Krüger et al, 2006;Lecce et al, 2008;Matys Grygar et al, 2011;Lecce and Pavlowsky, 2014;Resongles et al, 2014).…”