Rivers Gironde

The results of two surveys are reported on Fig. 6, S.S.A. appears to be lower in the river part, especially for the Gironde estuary. It usually increases as soon as the tidal influence is observed with a clear maximum located around the salt intrusion. Many processes can affect particulate matter in this part of estuaries. The increase could be due to the destruction of some floes formed upstream as observed by Eisma (personal communication) or to a chemical evolution of the superficial composition of particles as discussed below. 

The mean pre-industrial concentration of dissolved Cd in rivers has been estimated to be 45 pM [13]. As a result of anthropogenic contamination, the mean for dissolved Cd measured in all rivers worldwide in the early 1980s was four times higher (200 pM) [14]. Many river systems have much higher Cd concentrations as a result of pollution from industry and historic mining. For example, the mean dissolved Cd concentrations in the Lot and Garonne rivers (which feed the Gironde estuary in France see below) were 1.3 and 0.8 nM, respectively (measured from 1992-1998 [15]). 

Figure 8 Dissolved cadmium in the Gironde Estuary System. D = Dordogne River, G1 = Garonne River, G2 = Garonne River at high flow. Open square is the water-discharge weighted mean of the Dordogne and Garonne Rivers. Circles represent estuarine samples. Line shows the fit of a mass balance and chemical equilibrium model to measurement data. Redrawn from Ref. [29].

The Shell refinery in Pauillac formerly used to need 90 m h"" of water from the Gironde river to provide make up for the open recirculating coaling system. Recycling process WW enabled them to reduce the final discharge of effluents from 200 m h to 50 with... 

The first report on the estuarine distribution and chemistry of lanthanides was published for the Gironde estuary by Martin et al. (1976). This work pointed to the reactive nature of these elements during estuarine mixing, specifically the removal of dissolved lanthanides from river water. Papers on the estuarine chemistry of the lanthanides are few in number and include Martin et al. (1976), Hoyle et al. (1984), Goldstein and Jacobsen (1988c), Sholkovitz and Elderfield (1988), Elderfield et al. (1990), Sholkovitz et al. (1992) and Sholkovitz (1992b, 1993, 1995). The subject of these works, reactivity of dissolved and colloidal phases, is the focus of this section. While there are no review articles on the estuarine chemistry of lanthanides, Elderfield et al. (1990) and Sholkovitz (1995) provide the most comprehensive overviews. Papers on lanthanides in suspended particles and sediments (Gordeev et al. 1985, Sholkovitz 1990, Somayajulu et al. 1993) will not be discussed here. 

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