Combined uses of water-table fluctuation (WTF), chloride mass balance (CMB) and environmental isotopes methods to investigate groundwater recharge in the Thiaroye sandy aquifer (Dakar, Senegal)

The quaternary sandy sediments which cover most part of the Cap Vert peninsula bear considerable groundwater resources. The aquifer lying beneath a densely populated suburb zone is encountered with major issues such as induced recharge from anthropogenic surface derived pollution and rising water table to ground surface. The present study was aimed at investigating the recharge in the unconfined aquifer of Thiaroye zone using both water table fluctuation (WTF), chloride mass balance(CMB) methods and environmental isotopes. Seasonal fluctuations of groundwater in response to precipitation are monitored during time period (2010 to 2011) using “Thalimede Orpheus mini” recorders in two piezometers (P3-1 and PSQ1) as well as long term record. Chemical and isotopic characterization of groundwater, rainfall and the unsaturated zone were also carried out using a network of 48 points consisting of 8 rainfall stations, 10 unsaturated zone profiles and 30 dug wells, boreholes and piezometers. The concentrations of chloride in rainwater are between 3.2 and 53.4 mg/L. These unsaturated zone profiles range from 65 and 572 mg/L. The recharge obtained by WTF method ranged between 18 and 144 mm during the rainy season (June to October), whereas the recharge givenby CMB method ranged between 8.7 and 73 mm/year. The Thiaroye aquifer recharge obtained from these different methods also showed relatively similar range values. In this study, the WTF method applied computes both infiltration from rainwater and domestic waste water, while the CMB method estimates potential recharge from rainwater. Therefore, in the urban area, the CMB method cannot be applied due to the chloride input from waste water infiltration.Key words: Thiaroye basin, recharge, isotopes, chloride mass balance (CMB), quaternary sandy aquifer (Dakar)

Workshop on mobile laboratories deployed in the Ebola outbreak in West-Africa 2014-2015

First paragraph: Ebola virus disease (EVD) is a haemorrhagic fever caused by Ebola virus (EBOV) with high infectivity and mortality. EBOV is an enveloped, single-stranded, and negative-sense RNA virus belonging to the Filoviridae family. In contrast to the genus Marburgvirus which contains one single species, the genus Ebolavirus contains 5 species: Zaire ebolavirus (ZEBOV), Sudan ebolavirus (SUDV), Taï Forest ebolavirus (TAFV), Bundibugyo ebolavirus (BDBV) which are pathogenic for humans, and Reston Ebolavirus (RESTV) which infects non human primates. EBOV was first discovered in 1976 in the Democratic Republic of Congo (DRC) and simultaneously in Sudan. Since 1976, EVD has appeared sporadically in DRC, Sudan, Gabon, Uganda, and Congo, with small to large outbreaks and lethality ranging from 50 to 100% with about 2500 cumulative cases until 2013