Chronology and sources of trace elements accumulation in the Rhône pro-delta sediments (Northwestern Mediterranean) during the last 400 years

Abstract

The Rhône pro-delta sediments receive the particulate inputs from the Rhône River, the largest freshwater discharge of the Western Mediterranean Sea. Trace element (TEs: Ag, Cd, Co, Cr, Cu, Ni, Pb, and Zn) concentrations and stable Pb isotope ratios were determined along a 7.7-meter-long sediment core collected from the Rhône prodeltaic lobe, archiving the deposits of the last 400 years. Trace element mean concentrations during the pre-industrialized era (before 1850 AD) were no different from the average composition of Earth's upper crust, except for Cr. Principal component analysis, performed on TEs and tracers, suggests three origins for TEs that we identified as (i) marine biogenic material (Ag, Cd), (ii) ultramafic rocks (Li, Cr, Ni), and (iii) other clay minerals (Co, Cu, Pb and Zn). During the pre-industrial period, several changes in the TE/Al ratios coincided with flood events or/and modifications in the channelization of the Rhône River mouth. Some frequencies in the TEs temporal variations allow us to hypothesize some influence of climate variation. Sediments deposited after 1850 AD exhibited concentrations of certain TEs exceeding 1.3 to 3.5 times the concentrations of the preindustrial era (Ag> Cd-Pb>Cu-Zn). Principal component analysis, performed on post-1850 AD data, allows to distinguish pristine and "anthropogenically impacted" TEs. Pristine TEs, such as Co, Cr, and Ni, are linked with clay markers (Al, Li and Fe), Co and Ni are associated with Mn-enrichment, whereas Cr is correlated with Fe. "Anthropogenically impacted" elements consist of Ag, Cd, Cu, Pb, and Zn. Vertical profiles show that TE contamination has increased dramatically after the IInd World War and reached a maximum between 1970 and 1980, consistently with anthropogenic atmospheric emissions changes. Sediment deposited on the Rhône prodelta at the beginning of XVIIth Century have 206/207Pb ratios close to values of natural Pb (1.200), whereas sediments deposited after 1850 AD are clearly contaminated by European gasoline and industrial Pb pools (<1.180). In addition, peak-events can be related to flooding periods, natural and man-induced channelization of the Rhône River mouth, or diagenetic processes. Highlights ► Trace elements are accumulated in the Rhône prodelta sediments. ► Preindustrial sediments recorded floods and channelization of the Rhône River. ► Contamination reached a maximum between 1970 and 1980 AD.

Application of Zn Isotope Compositions in Oysters to Monitor and Quantify Anthropogenic Zn Bioaccumulation in Marine Environments over Four Decades: A “Mussel Watch Program” Upgrade

“…On a regional scale, this punctual source closure may also have impacted Zn contamination in the Loire estuary, because Zn often tracks with Pb in metallurgical emissions. , From a broader national perspective, some of the reductions in Zn, Pb, Cu, Hg, and Cd emissions have been explained by the ban on leaded gasoline (year 2000), fume trapping systems in industry plants, and a gradual shift from coal burning to nuclear power in the energy sector in the 1970s . Similar decreasing tendencies for these trace metals were observed in sedimentary archives from the four major French watersheds (Loire, Seine, , Garonne, and Rhône , ) and attributed to the same economic and regulatory reasons . All of these results point to an overall diminution of anthropogenic Zn circulation in the French watersheds in the past two decades and, consequently, of its inputs into marine and coastal systems.…”

Hydro-climatic drivers of land-based organic and inorganic particulate micropollutant fluxes: The regime of the largest river water inflow of the Mediterranean Sea

“…To that purpose, it would be useful to resort to sediment cores to evaluate micropollutant volumes stored, as well as their chemical composition. Still based on sediment cores, they could be used as archives of past SPM and particulate micropollutant fluxes (Ferrand et al, 2012;Cossa et al, 2018) able to fill the gap between recent measurements from the monitoring station network and past fluxes. Such a perspective would provide a pluri-secular historical depth to the spatial and temporal trajectories of the development of the urban societies.…”

Records of Holocene climatic fluctuations and anthropogenic lead input in elemental distribution and radiogenic isotopes (Nd and Pb) in sediments of the Gulf of Lions (Southern France)

“…(a) Binary diagram showing sediment samples from Core KSGC-31 and ore deposits (coloured ellipses) from the Cévennes (Mont Lozère: Baron et al, 2006), ore deposits from Spain (Cabo de Garta and Sierra Mazzaron: Stos-Gale et al, 1995; Cartagena: Graeser and Friedrich, 1970; Rio Tinto: Marcoux, 1998; Pomiès et al, 1998; Stos-Gale et al, 1995) and ore deposits from Germany (Harz; Brockner, 1989; Lévêque and Haack, 1993; Tischendorf et al, 1992; Wedepohl et al, 1978; Zwicker et al, 1991). (b) Binary diagram showing lead isotopic data from the Rhône pro-delta sediments over the last 400 years (Cossa et al, 2018) compared to pre- and post-Roman Core KSGC-31 samples.…”

“…Marine sediments give access to continuous anthropogenic archives. In that regard, lead isotopic data from the Rhône pro-delta sediments over the last 400 years (Cossa et al, 2018) has been compared to pre- and post-Roman core KSGC-31 data (Figure 5(b)). Core KSGC-31 post-Roman lead isotopic ratios lie in-between two end-members that are (1) sediments deposited before 2000 cal.…”