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

Abstract

Trace elements and organic carbon inputs to the Mediterranean Sea from an urbanised area (Marseille City) were studied and characterised 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 experiment 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 to a possible additional desorption during offshore transport.

Evidencing the natural and anthropogenic processes controlling trace metals dynamic in a highly stratified estuary: The Krka River estuary (Adriatic, Croatia)

“…release of Cd from the SPM into solution as a result of the formation of stable chloro-complexes (ElbazPoulichet et al, 1996;Elbaz-Poulichet et al, 1991;Kraepiel et al, 1997;Oursel et al, 2013;Waeles et al, 2005). Although such behaviour is consistent with other studies, in most of these studies which reported non-conservative Cd behaviour in an estuarine mixing, the concentration of SPM was much higher than in our case, and the distribution is characterised by the "concentration peak" appearing mainly at salinities between 10 and 20 (Dabrin et al, 2013;Elbaz-Poulichet et al, 1996;Elbaz-Poulichet et al, 1987;Fu et al, 2013;Hatje et al, 2003a;Kraepiel et al, 1997;Oursel et al, 2013;Oursel et al, 2014;Paucot and Wollast, 1997;Waeles et al, 2005;Waeles et al, 2004). As the particulate concentration of Cd measured in the freshwater end-member is very low (<10%), the release of Cd from SPM is excluded as a main contributor to the observed trends in the Krka River estuary (although it can contribute partly to the overall increase).…”

“…The variability of elements partitioning related to the fluctuating KD could be perceived by plotting the relationship of particulate metal fraction (in %) on SPM concentration (Fig. SI-10) along the lines representing theoretically expected values for a defined logKD (Deycard et al, 2014;Oursel et al, 2014). Relatively high dispersion of values shows complexity, but also "sensitivity" of the studied estuary, in which even small change in either SPM concentration or their nature can be strongly reflected on KD value.…”

“…salinity) is driven largely by the particles content and their nature Deycard et al, 2014;Duarte et al, 2014;Elbaz-Poulichet et al, 1996;Hatje et al, 2003a;Koshikawa et al, 2007;Martino et al, 2002;Ollivier et al, 2011;Oursel et al, 2014;Petit et al, 2013;Robert et al, 2004;Waeles et al, 2007). Dissolved-particulate fractionation in natural waters is usually described and explained by the particle-water distribution coefficients (KD):…”

Nickel retention by an ion-imprinted polymer: Wide-range selectivity study and modelling of the binding structures

“…4). Such pronounced competition could be explained by the close chemical properties and behavior between nickel and cobalt as already stated within environmental studies [42,43].…”

Evaluation of Discrete and Passive Sampling (Diffusive Gradients in Thin-films – DGT) Approach for the Assessment of Trace Metal Dynamics in Marine Waters – a Case Study in a Small Harbor

“…For example, while very high variability was measured for cadmium (Cd) for the first four deployment periods at sites SP1 and SP3, relatively low variability was found for the same period at site SP2. Such specific variability patterns clearly show the overall dynamics of trace metal concentrations at the study area, but also demonstrates that the discrete sampling methodology, most widely used in environmental monitoring programs and research studies, [2,3,37,38] is not ideal for (highly) dynamic aquatic systems. [39][40][41] Examining the entire 5-month period, specific trends of trace metal concentrations varied by metals and sites.…”