Cheikh Diop

Effects of environmental cadmium and lead exposure on adults neighboring a discharge: Evidences of adverse health effects

The purpose of the study was to determine Pb and Cd concentrations in humans and to assess the effect of co-exposure to these metals on biomarkers of oxidative stress and nephrotoxicity. Blood and urine levels of Pb and Cd, oxidative stress and urinary renal biomarkers were measured in 77 subjects neighboring a discharge and 52 in the control site. Exposed subjects showed significantly higher levels of lead and cadmium in blood and urine than the controls. Excessive production of reactive oxygen species induced by these metals in exposed subjects conducted to a decrease in antioxidant defense system (GPx, Selenium, GSH) and an increase in lipid peroxidation (MDA). Moreover, changes in markers of nephrotoxicity (high urinary concentrations of total protein, RBP and CC16, as well as GSTα and LDH increased activities) suggested the occurrence of discrete and early signs of impaired renal function for the discharge neighboring population.

Assessment of contamination, distribution and chemical speciation of trace metals in water column in the Dakar coast and the Saint Louis estuary from Senegal, West Africa

The water column from Dakar coast and Saint Louis estuary in Senegal, West Africa, was sampled in order to measure the contamination level by trace metals. The speciation of metals in water allowed performing a distribution between dissolved and particulate trace metals. For the dissolved metals, the metallic concentration and repartition between the organic fraction and the inorganic fraction were performed. The results show that the pollution of the estuary was more serious than in Dakar coast for Co, Cr, Ni, Pb and Zn; while, Cd and Cu were higher in Dakar coast. A strong affinity between metals and suspended particles has been revealed. Dissolved metals that have a tendency to form organic metal complexes are in decreasing order: Cd, Zn, Pb, Co=Cr=Mn, Cu and Ni. The results showed that the mobility of trace metals in estuary is controlled by dissolved organic carbon, while in coast it depends on chlorides.

Assessment of trace element contamination and bioaccumulation in algae (Ulva lactuca), mussels (Perna perna), shrimp (Penaeus kerathurus), and fish (Mugil cephalus, Saratherondon melanotheron) along the Senegalese coast.

Concentrations of 11 elements were quantified in five marine species from different trophic levels of a food web (algae, mussel, shrimp and fish), representative for shallow Senegalese coastal waters, and including species of commercial importance. Significant differences in element concentrations and bioaccumulation were demonstrated, revealing the utility of employing a suite of organisms as bioindicators to monitor metal contamination in coastal areas. There was no clear seasonal pattern in concentration of elements, however inter-site differences were observed. Calculations of transfer factors for all the studied elements showed that transfer factors from water were greater than those from sediments. For shrimp and mussel, the concentrations of Pb and Cd were below the EUs maximum level for human consumption, however high concentrations of arsenic in shrimp were recorded at all sites.

Spatial and seasonal variations of trace elements concentrations in liver and muscle of round Sardinelle (Sardinella aurita) and Senegalese sole (Solea senegalensis) along the Senegalese coast.

Concentrations of 11 elements (As, Cd, Cr, Cu, Fe, Mn, Ni, Pb, Se,V and Zn) were quantified in liver and muscle from two commercially important fish species from the Senegalese coast. The fish, a small pelagic species (the round sardinella) and a benthic species (the Senegalese sole) were collected from five sites during the dry and wet seasons in 2013. For both species, elements were more concentrated in liver than in muscle. There was no clear seasonal pattern in concentration of elements, however inter-site differences were observed. We found significant differences in element concentrations between the two studied species, likely associated with their behavior, feeding and habitat use. The concentrations of Cd, Fe, and Pb were significantly higher in sardinella whereas concentration of As, Cu, Cr, Mn and Se were highest in sole. The concentration of cadmium was particularly high in the liver of sardinella (from 0.9 to 56 mg kg(-1), with a mean ± sd of 17.2 ± 11.5 mg kg(-1)) and may be related to anthropogenic pressure such as the phosphate industry but also to the upwelling current which brings dissolved elements to the surface that are taken up by plankton. The results showed that concentrations of Cd and Pb were below the limit values established by the European Community and pose no threat to public health.

SYNTHESIS, CHARACTERIZATION AND X-RAY STRUCTURE OF POLYMERIC [TRIPHENYLTIN(IV)][AQUATRIPHENYLTIN(IV)] SULPHATE, [(Ph3Sn)(H2OSnPh3)SO4]n

1 L a b o r a t o i r e de C h i m i e M i n e r a l e et A n a l y t i q u e ( L A C H I M I A ) , D e p a r t e m e n t de C h i m i e , Facul te^des S c i e n c e s et T e c h n i q u e s , U n i v e r s i t e Che ikh An ta D iop , D a k a r S e n e g a l 2 Ins t i tu to de Q u i m i c a , U n i v e r s i d a d N a c i o n a l A u t o n o m a de M e x i c o , C i r c u i t o Ex te r io r , C i u d a d Un ive r s i t a r i a , M e x i c o 0 4 5 1 0 , D. F., M e x i c o cakdiop@ucad.sn

Characterization of natural and chemically modified kaolinite from Mako (Senegal) to remove lead from aqueous solutions

Abstract The chemical and sorption properties of clay minerals from the Mako area, Senegal, were investigated using FTIR spectroscopy, X-ray diffraction, scanning electron microscopy equipped with an X-ray energy dispersion spectrometer, thermal analysis and chemical analysis. The clay sample is essentially dominated by kaolinite and quartz as also shown by treatment with ethylene glycol and dimethylsulfoxide (DMSO). The clay fraction of this natural clay was organically modified by grafting with 3-aminopropyltriethoxysilane (APTES) in order to improve significantly its retention ability of heavy metals. The silane groups of the APTES reagent were partly grafted on the surface of platy kaolinite particles and the remaining ethoxy groups could be hydrolysed by aqueous treatment. The natural clay, its clay fraction and the organo-functionalized clay (with APTES) were investigated as adsorbents for the removal of Pb(II) from aqueous solutions. Evidence for an organic grafting has been demonstrated by comparing the spectroscopic characteristics of the natural clay and those of its chemically modified derivatives. The effects of different parameters (i.e. initial Pb(II) concentration and contact time) on the adsorption efficiency were studied. For an initial concentration of 10 mg L-1 Pb(II), the adsorption was maximized after 30 min contact time both for the raw material and its clay fraction and after 90 min for the APTES grafted clay. Although the maximum of sorption for the APTES grafted clay is reached with slower kinetics, this maximum amount of Pb(II) uptake at room temperature (Xmax) is significantly higher since it is 0.99 mg g-1 for the raw clay, 1.46 mg g-1 for its clay fraction and 3.02 mg g-1 for the organically modified clay, i.e. three times greater than the raw clay.

New selenito SnPh3 residue containing complexes and adducts: Synthesis and spectroscopic studies

Ten organotin selenito compounds obtained on allowing Se03(SnPh3)2 to react with triphenylphosphine oxyde, urea and tetraphenylphosphoniumtetramethylammoniumacetonyltriphenylphosphoniumand tetraethylammonium halides or pseudo halides have been studied by infrared and Mössbauer spectroscopies, then discrete and infinite chains structures suggested on the basis of spectroscopic data.

R4NXO4SnPh3 (R = cy, H, Bu, Me; X = S, Se). Synthesis, IR, NMR and Mossbauer studies

Derivatives of general formulae R4NXO4SnPh3 (R = cy, H, Bu, Me; X= S, Se) have been synthesized and their elemental analyses performed. From the spectroscopic data (i.r, NMR,and Mossbauer) an infinite chain structure with a trigonal bipyramidal environment around the tin center has been suggested in the solid state.

Mineralogical and physico-chemical characterizations of clay from Keur Saër (Senegal)

Abstract There is interest in exploiting and developing natural resources, particularly deposits of natural clays. Senegal has several clay mineral deposits for which chemical and mineralogical compositions have been little studied. Some of these natural materials are nowadays used in pottery and ceramics. To extend applications, a better basic knowledge is required and, for this objective, the raw clay and separated <2 μm clay fraction from Keur Saër (Senegal) were subjected to chemical and mineralogical studies. Several techniques including X-ray diffraction (XRD), thermal analysis (TG-DTA), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), N2 adsorption-desorption isotherms, cation exchange capacity (CEC) measurements and solid state nuclear magnetic resonance (NMR) have been used to characterize the material. It was found that the raw clay and the separated clay fraction consist of a mineral mixture in which kaolinite is the main component. 29Si and 27Al MAS-NMR spectra show the presence of silicon atoms linked to three other silicon atoms via an oxygen atom and six coordinated Al atoms. Significant increases in the specific surface area and cation exchange capacity were observed on purification, reaching a maximum of about 73.2 m2g−1 and 9.5 meq/100 g for the separated fine clay fraction while the values for the raw material were around 28.9 m2g−1 and 7.3 meq/100 g.

(2-benzoylbenzoato)triphenyltin(IV)

The structure of the title compound, [Sn(C6H5)(3)(C14H9O3)], consists of monomeric species featuring a distorted tetrahedral environment around the Sn centre. The tetrahedral angles are non-equivalent, owing to the relatively close approach of a carboxylate O atom.