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Volcanismis one of the major natural processes emitting mercury (Hg) to the atmosphere, representing a significant component of the global Hg budget. The importance of volcanic eruptions for local-scale Hg deposition was investigated using analyses of Hg, inorganic elemental tracers, and organic biomarkers in a sediment sequence from Lake Chungara (4520 m a.s.l.). Environmental change and Hg deposition in the immediate vicinity of the Parinacota volcano were reconstructed over the last 2700 years, encompassing the pre-anthropogenic and anthropogenic periods. Twenty eruptions delivering large amounts of Hg (1 to 457 mu g Hg m(-2) yr(-1) deposited at the timescale of the event) were locally recorded. Peaks of Hg concentration recorded after most of the eruptions were attributed to a decrease in sedimentation rate together with the rapid re-oxidation of gaseous elemental Hg and deposition with fine particles and incorporation into lake primary producers. Over the study period, the contribution of volcanic emissions has been estimated as 32% of the total Hg input to the lake. Sharp depletions in primary production occurred at each eruption, likely resulting from massive volcaniclastic inputs and changes in the lake-water physico-chemistry. Excluding the volcanic deposition periods, Hg accumulation rates rose from natural background values (1.9 +/- 0.5 mu g m(-2) yr(-1)) by a factor of 2.3 during the pre-colonial mining period (1400-900 yr cal. BP), and by a factor of 6 and 7.6, respectively, during the Hispanic colonial epoch (400-150 yr cal. BP) and the industrial era (similar to 140 yr cal. BP to present). Altogether, the dataset indicates that lake primary production has been the main, but not limiting, carrier for Hg to the sediment. Volcanic activity and climate change are only secondary drivers of local Hg deposition relative to the magnitude of regional and global anthropogenic emissions.

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 pre-industrial 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 cle

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 pre-industrial 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 cle

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 pre-industrial 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 cle