Satellite assessment of the coupling between in water suspended particulate matter and mud banks dynamics over the French Guiana coastal domain

2013 ◽  
Vol 44 ◽  
pp. 25-34 ◽  
Author(s):  
V. Vantrepotte ◽  
E. Gensac ◽  
H. Loisel ◽  
A. Gardel ◽  
D. Dessailly ◽  
...  
2018 ◽  
Vol 10 (11) ◽  
pp. 1733 ◽  
Author(s):  
Noelia Abascal Zorrilla ◽  
Vincent Vantrepotte ◽  
Erwan Gensac ◽  
Nicolas Huybrechts ◽  
Antoine Gardel

The coast of French Guiana is characterised by the northwestward migration of large mud banks alongshore and by high concentrations of suspended particulate matter (SPM) resulting from the strong influence of the Amazon River outflow. Surface OLI SPM concentration, linked to the footprint of the subtidal part of mud banks due to resuspension and migration processes, was used to develop a method to estimate the location of this footprint. A comparison of the results from this method with those obtained by locating the limit of the wave damping, which characterises muddy coasts, revealed good performance of the method based on recurring SPM values. The migration rates of the mud banks in French Guiana were calculated according to the delimitation of their subtidal parts, and showed slightly higher values (2.31 km/year) than suggested by earlier studies. In comparison with other methods, the migration rate estimated using the method proposed within the framework of this study takes into account the variability of the shape of the subtidal part for the first time. It was also shown that the mud banks existing on the coastal area of French Guiana present two different shapes. Our results clearly demonstrate the advantage of ocean colour data to describe mud banks according to their subtidal part, delimited using the assessment of SPM temporal variability.


2020 ◽  
Vol 10 (21) ◽  
pp. 7829
Author(s):  
Jennifer Hellal ◽  
Jörg Schäfer ◽  
Régis Vigouroux ◽  
Laurent Lanceleur ◽  
Valérie Laperche

In 2006 the use of mercury (Hg) was banned for gold mining in French Guiana. However, mining of old placers could mobilize Hg accumulated in soils and sediment. This study aimed to measure the current impact of a mining concession (Boulanger site) on the Hg load in the watershed. Turbidity, Total Mercury (THg), and Monomethylmercury (MMHg) were measured in water, suspended particulate matter (SPM), river sediment and sediments from old tailing ponds along a river section of 30 km up and downstream from a mining concession in French Guiana during a dry and a rainy season. Total dissolved Hg (THgD) concentrations varied little from up- to down-stream but were all higher (fourfold on average) during the rainy season (3.2 to 4.4 ng L−1), than during the dry season and consistent with previous data known for the Amazonian area. Dissolved MMHg (MMHgD) represented up to 30% of THgD during the dry season, which is higher than previous results (typically around 2%). Mercury concentrations in sediments were highest in the vicinity of areas affected by old (before 2006) rather than new gold mining practices. Even though Hg was banned in 2006, present gold mining practices still release natural Hg and Hg inherited from older mining practices into the watershed.


1998 ◽  
Vol 38 (6) ◽  
pp. 327-335
Author(s):  
Yasunori Kozuki ◽  
Yoshihiko Hosoi ◽  
Hitoshi Murakami ◽  
Katuhiro Kawamoto

In order to clarify the origin and behavior of suspended particulate matter (SPM) in a tidal river, variation of SPM in a tidal river was investigated with regard to its size and constituents. SPM was separated into three groups according to size. Change of contents of titanium and organic substances of each group of SPM was examined. SPM which was discharged by run-off was transported with decomposition and sedimentation in a tidal river. Concentration of SPM with a particle size greater than 0.45 μm increased due to resuspension in a tidal river. Origin of SPM with a size of less than 0.45 μm at upstream areas was from natural soil and most of such SPM which had been transported settled near a river mouth. It was determined from examination of the CN ratio and the ratio of the number of attached bacteria to free bacteria that SPM with a size greater than 1.0 μm at upstream areas was decomposing intensively. At the downstream areas, SPM with a size of less than 0.45 μm came from the sea. SPM with particle size greater than 1.0 μm consisted of plankton and substances which were decomposed sufficiently while flowing.


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