| 3 | Role of the floodplain lakes in the methylmercury distribution and exchanges with the Amazon River,Brazil显示文摘Seasonal variability of dissolved and particulate methylmercury(F-MeHg, P-MeHg) concentrations was studied in the waters of the Amazon River and its associated Curuai floodplain during hydrological year 2005–2006, to understand the MeHg exchanges between these aquatic systems. In the oxic white water lakes, with neutral pH, high F-MeHg and P-MeHg concentrations were measured during the rising water stage(0.70 ± 0.37 pmol/L, n = 26) and flood peak(14.19 ± 9.32 pmol/g, n = 7) respectively, when the Amazon River water discharge into the lakes was at its maximum. The lowest mean values were reported during the dry season(0.18 ± 0.07 pmol/L F-MeHg, n = 10 and 1.35 ± 1.24 pmol/g P-MeHg, n = 8), when water and suspended sediments were outflowing from the lakes into the River. In these lakes,the MeHg concentrations were associated to the aluminium and organic carbon/nitrogen changes. In the black water lakes, with acidic pH and reducing conditions, elevated MeHg concentrations were recorded(0.58 ± 0.32 pmol/L F-MeHg, n = 16 and 19.82 ± 15.13 pmol/g PMeHg, n = 6), and correlated with the organic carbon and manganese concentrations. Elevated values of MeHg partition coefficient(4.87 < Kd< 5.08 log(L/kg) indicate that MeHg is mainly transported associated with the particulate phase. The P-MeHg enrichment detected in all lakes suggests autochthonous MeHg inputs from the sediments into the water column. The MeHg mass balance showed that the Curuai floodplain is not the source of P-MeHg for the Amazon River. | Poliana Dutra Maia Laurence Maurice Emmanuel Tessier David Amouroux Daniel Cossa Patricia Moreira-Turcq Henri Etcheber | 2018 | Journal of Environmental Sciences2018，30，6： | 1 |
| 5 | Magnetic Characterization of Amphibolites from the Fomopéa Pluton(West Cameroon):Their Implication in the Pan-African Deformation of the Central African Fold Belt显示文摘The Fomopea granitic pluton is emplaced in gnessic and amphibolitic basement.These gneissic and amphibolitic basement rocks are represented in the pluton's body as sub-rounded,elongated or stretched xenoliths.Amphibolitic xenoliths display testimonies of two main tectonic events namely:(i) E1 flattening deformation event characterized by a NW-SE to E-W foliation with a best pole at 246/57 and a mineral stretched lineation with a best line at 293/47;and(ii) E2 compressive event typified by(1) N-S to NNE-SSW steeply dipping foliation;(2) S-type flexion-fold indicating a sinistral shear movement.These amphibolite rocks indicate a magnetic susceptibility magnitude(Km) range from 418 μSI to 90092 μSI for 87% of the stations showing a ferromagnetic behavior.K-T curves reveal the presence of Ti-poor magnetite as susceptibility mineral carrier.Magnetic foliation and lineation suggest that the N-S strike direction observed in the Bamendou amphibolite is,as pointed out elsewhere in the Central African Fold Belt,of paramount importance in the tectonic evaluation of the Fomopea area,since it has most likely acted as major deformation phase in the second tectonic event in the belt. | NJANKO Théophile FOZING Eric Martial KWéKAM Maurice YAKEU SANDJO Angéline Flore NJONFANG Emmanuel | 2012 | Acta Geologica Sinica(English Edition)2012，86，1： | 0 |
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