Identification of hydrogeological and geoelectrical parameters influencing the productivity of boreholes in the commune of Daloa (Central-Western of Côte d'Ivoire).

This study was to determine the hydrogeological and geoelectrical parameters affecting the productivity of water boreholes in the Daloa commune. Using the Schlumberger configuration, we carried out 15 parallel and perpendicular electrical profiling and 40 Vertical Electrical Soundings (VES). We also performed Electrical Resistivity Tomography (ERT) with a pole-dipole configuration at one site. The data processing allowed the identification of the different layers of the subsurface and their geoelectric properties that influence the productivity of the boreholes in the study area. These geoelectric data have shown that the productivity of the boreholes is more related to the conductive anomalies (W and U) than to the vertical electrical sounding. The processing of the hydrogeological data has shown that borehole productivity in the study area using Self-Organising Map (SOM) is a function of the hydraulic conductivity but also the thickness and density of the fracturing. Sixteen new boreholes on the main campus of Jean Lorougnon Guede University, Daloa, validate these results. The yield of these productive boreholes varies between 7.5 and 22 m3/h, with an average of 15.2 m3/h, four times higher than the values usually obtained in the study area. The success rate of these boreholes is about 70 %. This study has shown how effectively integrating hydrogeological and geoelectrical parameters provides information on the lithology and structural conditions in the subsurface necessary for productive drilling.

Assessment of the health risks associated with the consumption of bivalve mollusks potentially contaminated with phycotoxins from the coastal ecosystem of the Ebrié lagoon, Côte d'Ivoire.

This work focused on assessing of the risk associated with the consumption of bivalve mollusks, potentially contaminated with phycotoxins. The studied phycotoxins are saxitoxin (STX), okadaic acid (OA), dinophysistoxins (DTXs), yessotoxins (YTXs), pectenotoxins (PTX), azaspiracids (AZAs), and domoic acid (DA). These toxins were investigated in three species of bivalve mollusks (Anadara senilis, Crassostrea gasar, and Perna perna), originating from the Ebrié lagoon. Chemical analyses were carried out by LC-MS/MS, HPLC-FLD, and HPLC-UV. The level of OA and DTXs, STX, and DA was 10.92 µg OA eq./kg, 9.6 µg STX eq./kg, and 0.17 mg DA eq./kg, respectively. The level of PTXs and AZAs was 3.3 µg PTX-2 eq./kg and 13.86 µg AZA-1 eq./kg; that of YTXs was 0.01 mg YTX eq./kg. The daily exposure dose (DED) was 0.019 µg OA eq./kg bw for OA and DTXs; 0.285 µg DA eq./kg bw for DA; 0.006 µg PTX-2 eq./kg bw for PTXs; 0.016 µg STX eq./kg bw for STX; 0.01 µg YTX eq./kg bw for YTXs; and 0.024 µg AZA-1 eq./kg bw for AZAs for the oyster Crassostrea gasar. These estimated values are lower than the acute reference dose (ARfD) of each phycotoxin recommended by the European Food Safety Agency (EFSA). The risk of harmful effects is acceptable. The absence of risk is valid only for the study period (11 months) and concerns coastal populations living near the sampling points.

Effect of resistant starch on the cooking quality of yam (Dioscorea spp.) and cassava (Manihot esculenta) based paste products.

Total starch (TS) and resistant starch (RS) contents in pasty edible product of mealy and hard cooking tubers of three yam varieties and four cassava varieties were determined to evaluate their contribution in their cooking quality. TS and RS contents appeared as the main components in determining yam cooking quality. Mealy cooking yam varieties were characterized by a significant higher TS content (75.2 ± 7.7 g/100 g d.m.) and lower RS content (13.8 ± 3.4 g/100 g d.m.) than hard cooking yam varieties, which, in contrast, contained less TS (61.7 ± 12.1 g/100 g d.m.) and particularly high RS (21.8 ± 9.9 g/100 g d.m.), possibly as a consequence of the prevalence of large granules (35-40 µm) observed by light microscope. Conversely, TS and RS contents appeared not determinant on the cooking quality of cassava. Moreover, higher amylose contents were associated with substantially elevated percentages of RS in yam and cassava, and high RS content in samples modulates their pasting properties by reducing the peak viscosity and the breakdown and requiring higher temperature and longer time to the peak.