Flood inputs in a Mediterranean coastal zone impacted by a large urban area: Dynamic and fate of trace metals

Type Article
Date 2014-12
Language English
Author(s) Oursel B.1, Garnier C.1, Zebracki Mathilde2, 3, Durrieu G.1, Pairaud IvaneORCID2, Omanović D.4, Cossa Daniel2, 5, Lucas Yves1
Affiliation(s) 1 : Université de Toulon, PROTEE, EA 3819, 83957 La Garde, France
2 : IFREMER, Centre de Méditerranée, Laboratoire Environnement Ressources Provence-Azur-Corse, BP 330, Zone Portuaire de Brégaillon, 83507 La Seyne-sur-Mer, France
3 : IRSN, Laboratoire d'études radioécologiques en milieu continental et marin, CEN Cadarache, 13115 Saint Paul lez Durance, France
4 : Ruđer Bošković Institute, Center for Marine and Environmental Research, PO Box 180, 10002 Zagreb, Croatia
5 : ISTerre, Université J. Fourier, BP 53, 38041 Grenoble, France
Source Marine Chemistry (03044203) (Elsevier BV), 2014-12 , Vol. 167 , P. 44-56
DOI 10.1016/j.marchem.2014.08.005
WOS© Times Cited 18
Note In : Estuarine Biogeochemistry
Keyword(s) WWTP, metals contamination, coastal zone, flood events, Mediterranean Sea, small rivers
Abstract Trace elements and organic carbon inputs to the Mediterranean sea from an urbanized area (Marseille city) were studied and characterized during flood events. Inputs were brought to the sea by two small coastal rivers whose waters were mixed together and also with treated wastewaters (TWW) just before discharge. The monitoring of the rivers during flood events showed the high temporal dynamics of water flow, suspended particulate matter (SPM), organic carbon and trace metals concentrations, typical of small coastal Mediterranean rivers and requiring an appropriate sampling strategy. Dissolved/particulate partition coefficient (log Kd) in rivers during floods remained quasi-constant for a given trace element, but differed from one element to another according to their affinity toward particles. Because of high SPM concentrations, trace elements were mainly brought to the sea during floods as particles, despite a weaker affinity for particles when compared to baseflow conditions for all studied elements but Pb. If the contribution of TWW dominated the elements baseflow discharge to the coastal zone, rivers outweighed during floods. When discharged to the sea, most trace elements underwent partial desorption in the salinity gradient, especially at highest salinity. Laboratory desorption experiments results were consistent with field data and showed slower desorption kinetics than in baseflow conditions, suggesting that trace elements desorption rates from particles are slower than sedimentation rates. With regard to heavy particles, it results in a potential impact of the sediment on benthic organisms and a possible further desorption after sediment resuspension events. With regard to light particles, it results possible additional desorption during offshore transport.
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