Major and trace element partition and fluxes in the Rhône River

Dissolved and particulate major and trace element concentrations and suspended particulate contents were determined during three years on the lower Rhône River (France) from subsurface water samples collected about twice a month and more regularly during flood events.Dissolved elements can be grouped into two sets showing similar relationship between concentration and water discharge related to dilution process and to local and diffuse inputs of dissolved elements in the Rhône basin.The variation of NO3/Na and Cl/Na ratios and the absence of correlation between NO3 and the enrichment in Cl show that Rhône River is not highly affected by fertilizer applications compared to other large French rivers (Seine and Loire rivers).In particulate phase, Ca, Sr, U, Pb, Bi, Cd, Sb and Zn displayed high enrichment factors over shale composition. Lead, Bi, Cd and Zn enrichment could be related to the anthropogenic inputs, while Ca, Sr and U enrichment was explained by lithological composition of the Rhône basin dominated by carbonate rocks.Distribution coefficients of elements (Kd) are relatively stable with however some variations with increasing SPM concentrations. These variations were attributed to local and diffuse inputs and to a higher contribution of carbonate bedrock in the Rhône basin during flood events.Dissolved and particulate major and trace elements, and suspended particulate matter (SPM) fluxes of the Rhône River to the Mediterranean Sea were estimated for the period 2001–2003. SPM and particulate element fluxes were highly dependent on flood events: 69 to 91% of the annual fluxes were exported in less than 12% of the time.Rhône River inputs were the principal source of particulate elements (except for Cd and Zn) in the north-western Mediterranean Sea, while the major part of dissolved elements were carried out by atmospheric inputs except dissolved As, for which Rhône River contributed to more than 50% of the input to the marine system.

Research highlights
► Dissolved elements can be grouped into two sets showing similar relationship between concentration and water discharge related to dissolved element inputs in the Rhône basin during high flow. Rhône River is not highly affected by fertilizer applications.
► Distribution coefficient of elements is relatively stable with however some variations with increasing SPM concentrations related to local and diffuse inputs and to a higher contribution of carbonate bedrock in the Rhône basin during flood events.
► Dissolved and particulate major and trace elements, and suspended particulate matter (SPM) fluxes of the Rhône River to the Mediterranean Sea were estimated for the period 2001–2003. SPM and particulate element fluxes were highly dependent on flood events: 69 to 91% of the annual fluxes were exported in less than 12% of the time.
► Rhône River inputs were the principal source of particulate elements (except for Cd and Zn) in the north-western Mediterranean Sea, while the major part of dissolved elements was carried out by atmospheric inputs except As, for which Rhône River contributed to more than 50% of the input to the marine system.