Signature isotopique et chimique des précipitations (pluies et pluviolessivats) en Guyane française

Millet, Antoine; Bariac, Thierry; Grimaldi, C.; Boulègue, Jacques

doi:10.7202/705375ar

Cited by 3 publications

(4 citation statements)

References 23 publications

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“…Thus, it appears that no Cl is released from litter during the storm event studied. Chloride is first of all supplied by the rain, so its concentration classically increases between rainwater and throughfall (Brouwer, 1996;Grimaldi and Pedro, 1996;Cornu et al, 1998), a feature also observed in the stormflow event studied by Millet et al (1999). This increase is due to the washing out of dry deposits and salts left on the leaves by the evaporation of rain between downpours.…”

Section: Chloridementioning

confidence: 87%

“…For the storm-flow event studied, Millet et al (1999) showed that H 4 SiO 4 and Al are released during the passage of rain through the canopy. Nevertheless, the concentrations remain low in the throughfall, being lower than 5 µM for H 4 SiO 4 and up to 30 µM for Al (Figure 4).…”

Section: Silica and Aluminiummentioning

confidence: 99%

“…Throughfall samples were collected over the whole catchment in 31 rain gauges on a within-event basis in order to cover six fractions (Molicova et al, 1997;Millet et al, 1999). Throughfall was analysed after pooling together all 31 samples.…”

Section: Sampling and Analysesmentioning

confidence: 99%

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Behaviour of chemical solutes during a storm in a rainforested headwater catchment

Grimaldi

Millet

et al. 2003

Hydrological Processes

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International audienceThe aim of this study is to identify, in a small catchment area located within a tropical forest, the pedological compartments in which the export of nutrients and chemical erosion of solutes occur during a stormflow event. The catchment area displays two types of lateral flow: (i) overland flow at the surface of the soil in the litter and root mat and (ii) groundwater flow in a macroporous subsurface horizon. We interpret the variations of stream-water chemistry during a storm-flow event using the separation of storm-flow hydrograph data between overland and groundwater flow, and (Cl as a chemical parameter characterizing the residence time of water in the soil. It appears that K+ especially was released into the throughfall, whereas Ca++, Mg++ and Na+ were clearly released from the litter. K+ disappeared rapidly from soil solution, whereas Ca++ and Mg++ were more progressively absorbed by the vegetation. The Ca++ and Mg++ contents in groundwater increased with increasing residence time owing to the transpiration of trees. The export of H4SiO4 in the overland flow was moderate, i.e. 24% of total H4SiO4 export in the stream flow, as overland flow represented 39% of total runoff. The subsurface horizon—where active groundwater flow occurs—was successively affected by chemical erosion during the storm-flow peak, and then by neoformation of kaolinite favoured by increasing water residence time

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Section: Chloridementioning

confidence: 87%

Section: Silica and Aluminiummentioning

confidence: 99%

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Behaviour of chemical solutes during a storm in a rainforested headwater catchment

Grimaldi

Millet

et al. 2003

Hydrological Processes

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“…The initial excess deuterium in rainfall deviates from 10 in relation to the evaporation conditions at the origin of the vapor and the influence of continental vapor [17][18][19]. This probably reflects the recycling of air masses by water vapor from water body evaporation and soil evapotranspiration [2,20,21].…”

Section: Discussionmentioning

confidence: 99%

Isotopic study of rainfall and definition of local meteoric water lines: Case of the rainfall stations of the city of Bangui in Central African Republic

Foto,

Allahdin,

Biteman

et al. 2023

Eur J Chem

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The study of the isotopic composition of rainwater discussed in this article allows isotopic characterization of rainfall recorded in the Bangui region over 11 years at two stations. It will highlight the relationships between isotopes, climatic parameters, and temporal variation before defining the local meteoric line, which constitutes the reference point for the region. The results obtained after a follow-up of eleven years without interruption showed two major physical effects, the effect of the rainfall influences more strongly the composition in isotopes, the contents in isotopes vary inversely with the precipitation. For example, heavy rainfall in August and September saw a strong depletion of δ¹⁸O and δ²H contents. These values reach up to -4.96‰ for δ¹⁸O and -28.3‰ for δ²H. Similar, although weaker, effects are observed for July and October precipitation. We also note that the isotope contents at the Bangui University station are lower than those measured at the Bangui Sodeca station located at 386 m altitude on the Lower Ubangi Hill, which is similar to a pseudo-altitude effect. The evolution of stable isotope content in water as a function of meteorological parameters (temperature, rainfall, altitude) has allowed us to determine a local meteorological line for the city of Bangui from two measuring stations defined as follows: δ2H = 7.6 × δ18O + 10.4 (R2 = 0.9909) Université de Bangui, δ2H = 8.4 × δ18O + 12.5 (R2 = 0.9909) Bangui-Sodeca and δ2H = 7.9 × δ18O + 11.3 (R2 = 0.9939) Bangui local meteoric water lines.

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Suspended sediment and dissolved load budgets of two Amazonian rivers from the Guiana Shield: Maroni River at Langa Tabiki and Oyapock River at Saut Maripa (French Guiana)

Sondag

Guyot²,

Moquet³

et al. 2010

Hydrological Processes

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Abstract:This study presents the data collected within the framework of an Observatory of Research in Environment on the Amazonian Basin-the ORE HYBAM. It relates to the dissolved and solid loads of the two main rivers of French Guiana, the Maroni and Oyapock rivers, running on the Guiana Shield and draining respectively 64 230 and 24 630 km 2 . The low coefficient of variation of the average annual flows of the two rivers indicates an inter-annual hydrological stability probably related to the immediate vicinity of the Atlantic Ocean. The sedimentary load is mainly composed of quartz and kaolinite. The total suspended solid (TSS) concentrations are among the world's lowest values; they range from 1 to 130 mg l 1 during the hydrological cycle, with averages of 22 and 12 mg l 1 , for the Maroni and Oyapock rivers, respectively. The seasonal variability of these values is significantly higher than that of hydrologic flows, but without simple relationship with the discharge. Water chemical composition of the two rivers indicates a very weak mineralization, very similar to that found in the Amazonian rivers running on the Brazilian and Guianese shields, and in the Congo River and its tributaries in the Central African Shield. Seasonal variations are observed in both basins; they correspond to higher concentrations during low water stage (from October to February) and to more diluted water during the flood, from April to July. A signature enriched in Cl is present at the Saut Maripa station on the Oyapock River indicating a more marked influence of the trade winds in this basin. The computation of atmospheric contributions to ions budget indicated a weak contribution for Ca 2C and Mg 2C , which originates mainly from water-rock interactions in both stations, while more than half of Na C is derived from atmospheric inputs.

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Signature isotopique et chimique des précipitations (pluies et pluviolessivats) en Guyane française

Cited by 3 publications

References 23 publications

Behaviour of chemical solutes during a storm in a rainforested headwater catchment

Behaviour of chemical solutes during a storm in a rainforested headwater catchment

Isotopic study of rainfall and definition of local meteoric water lines: Case of the rainfall stations of the city of Bangui in Central African Republic

Suspended sediment and dissolved load budgets of two Amazonian rivers from the Guiana Shield: Maroni River at Langa Tabiki and Oyapock River at Saut Maripa (French Guiana)

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