Noèle Maillet

Bio: Noèle Maillet is an academic researcher from University of Bordeaux. The author has contributed to research in topics: Tributary & Eutrophication. The author has an hindex of 2, co-authored 4 publications receiving 86 citations.

A cadmium budget for the Lot-Garonne fluvial system (France)

Abstract: Routine measurements of river discharge and total suspended sediment concentration (TSS) are combined with regular analyses for particulate and dissolved cadmium to produce a box model that allows us to propose a cadmium mass balance for the Lot-Garonne man-influenced river system (8400 km2). Nearly half the cadmium in the Garonne river is supplied by the tributary Lot river. Cadmium input onto the Lot river comprises wet deposition from the atmosphere, molecular diffusion at the sediment-water interface, surface-water runoff and discharge from the leaching of waste at a zinc refining plant. Approximately 85% of the cadmium in the Lot river is derived from anthropogenic origin. Cadmium in the industrial discharge is 80% dissolved and 20% in the particulate phase (4.2 and 1.1 t yr−1, respectively). Total inputs are estimated at 4.81 t yr−1 and 1.54 t yr−1 for the dissolved cadmium and for the particulate phase, respectively. Budgeting estimates an output onto the Garonne river of 0.54 t yr−1 for the dissolved cadmium (about 8%) and 6.13 t yr−1 for the particulate cadmium (about 92%) indicating that downstream sediment-associated cadmium fluxes are enhanced by the 4.27 t yr−1 removed from solution and the 0.32 t yr−1 remobilized by the erosion of sediment blanketing the Lot river bed. These figures are found to be comparable with those generated by a dilution model which suggests that 97% of dissolved cadmium is taken up by the particulate phase over 0.5 km downstream from the primary anthropogenic source.

Role of the dams on the River Lot on two types of pollution:point-sources (cadmium) and non-point sources (phosphorus)

Abstract: The concentrations of cadmium and bioavailable phosphorus were determined in sediments samples of a large section of the River Lot (a 248-km section of 57 artificial stretches and dams). Phosphorus inputs include an important agricultural watershed (diffuse sources) and main point-sources such as towns. Cadmium pollution is mainly due to an industrial activity in the upper reach: high concentrations existed some years ago, the pollution is now lower. The concentration data related to a lithological cartography of the river bottom (sand/gravels/mud) and of the thickness of soft deposits, provide a longitudinal assessment of Cd and P storage in the whole river. The results show the location in the river where the two elements are associated to the sediment muds which are mainly stored in the largest dams situated in the lower section of the river. The sedimentary amounts represent potential sources (i) of metallic pollution in case of river flood or dam emptying (e.g. 69 tons of Cd in the last lower dam), (ii) for eutrophication processes in the lower course (near 10 000 tons of bioavailable-P in the last five dams). The cadmium flux leaving the watershed of river Lot is still important and remains greater than the industrial source (strongly reduced since 1986) of the pollutant located in the upper part of the river.