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The depositional histories of trace metals (Pb, Cu, and Zn) in sediment cores from three Ghanaian estuaries were reconstructed using radioisotope-derived ( 210 Pb and 137 Cs) geochronologies. A core collected from each of the Amisa, Sakumo II and Volta estuaries was analyzed for trace metals and radionuclides. Lead-210 and 137 Cs dating via gamma spectroscopy, and trace metal analysis via inductively coupled plasma mass spectrometry (ICP-MS) were used in deriving sedimentation rates, geochronologies and accumulation trends of trace metals. The sedimentation rates in all three estuaries (in the range of 0.54–0.83 cm yr −1 ) were greater than the predicted sea level rise (∼0.33 cm yr −1 ) for the Accra Coast of Ghana. The 210 Pb depositional rates of 6.83 dpm cm −2 y −1 , 2.74 dpm cm −2 y −1 and 1.75 dpm cm −2 y −1 estimated for the Amisa, Sakumo II and Volta estuaries, respectively, are higher than those recorded in other latitudes. Trace metal analysis revealed differences in the concentrations of Cu, Pb and Zn between deeper and surficial layers of each core to be in the range of 10–20%, which is well within the natural variations attributed to geochemical factors. Relative to the Amisa and Volta estuaries, the temporal profiles of Al-normalized metal concentrations and estimated fluxes suggest anthropogenic processes augmented the natural fluxes of trace metals, particularly Zn into the Sakumo II estuary during the last 7 years. [ABSTRACT FROM AUTHOR]

The trypanocidal effects of aqueous gold(III) and palladium(II) and their metalloporhyrin derivatives on Trypanosoma brucei brucei growth in culture have been studied using an Alamar Blue indicator assay. All the experiments were conducted in the dark. As previously described for mercury(II), cadmium(II) and lead(II) porphyrins [Chem.-Biol. Interact. 139 (2002) 177], the toxicity of the metalloporphyrin complex of palladium(II) to T. b. brucei parasites was much higher compared to the aqueous free palladium(II) and free base porphyrin. Palladium(II) porphyrin, free palladium(II), and the free base porphyrin were trypanocidal to T. b. brucei at concentrations >1.5×10-6, >6.1×10-6 and >1.9×10-5 M, respectively. While gold(III) porphyrin was effective against the parasites at concentrations >4.8×10-6 M, its aqueous gold(III) was toxic at concentrations as low as 2.0×10-7 M due to the generation of free radicals in the presence of this metal ion which enhanced its toxicity to the T. b. brucei parasites. Although some cell division was observed in some of the cells treated with palladium(II) porphyrin, some dividing cells had no nucleus due to unequal division and delivery of the nuclei into the daughter cells. As a result, the rate of cell division decreased with time and cell death occurred within 24 h. Interestingly, trypanosomes treated with metalloporphyrin complexes displayed different morphological features from those cells treated with free base porphyrin or metal ions. Of all the porphyrins and free metal ions tested, only mercury(II) porphyrin and aqueous gold(III) ion were toxic to the trypanosomes in the 10-7 M range. The chemotherapeutic potential of these observations is discussed. [Copyright &y& Elsevier]

The fluorescence and phosphorescence studies on the interactions of Au(III), Pt(II) and Pd(II) derivatives of tetrakis(1-methylpyridinium-4yl)porphyrin (H2(TMPyP)4+) with pBluescript II plasmid DNA have been conducted at 0.1 M NaCl, pH 7.5 and 25 °C. The free base porphyrin (H2(TMPyP)4+), Au(III)(TMPyP)5+ and Pt(II)(TMPyP)4+ emitted fluorescence. On the other hand, the Pd(II)(TMPyP)4+ emitted both fluorescence and phosphorescence at room temperature. Upon the addition of excess amounts of DNA the broad fluorescence spectra of H2(TMPyP)4+ and Au(III)(TMPyP)5+ changed to two clear peaks centred at 650 and 710 nm for H2(TMPyP)4+, and 659.2 and 719.6 nm for Au(III)(TMPyP)5+, respectively. However, the fluorescence intensity of the Pt(II)(TMPyP)4+ increased with addition of high amounts of DNA, giving a peak at 660 nm with a shoulder. Interestingly for Pd(II)(TMPyP)4+, it was observed that in the presence of increasing amounts of DNA, the phosphorescence intensity observed at 700 nm increased. In order to confirm the chemical species of the porphyrins (that is monomer or dimer) the fluorescence and phosphorescence spectra of these porphyrins were also measured at different concentrations of NaCl (0.001–0.1 M) and ethanol (0–40% v/v). Comparison of these current data to previous studies suggests that H2(TMPyP)4+ and Au(III)(TMPyP)5+ show aggregates in aqueous solution, Pt(II)(TMPyP)4+ partially aggregates, and they become converted to the monomer form by intercalation or outside binding to DNA. The weak phosphorescence intensity observed for Pd(II)(TMPyP)4+ that was increased by the addition of large amounts of DNA is due to shielding of the intercalated porphyrin by the DNA which prevents it from reacting with molecular oxygen dissolved in water. The UV–Vis and CD results indicate that, like H2(TMPyP)4+, Pt(II)(TMPyP)4+ and Pd(II)(TMPyP)4+ intercalate into the DNA bases while Au(III)(TMPyP)5+ interacts with DNA via the out-side binding mode but with partial intercalation at high concentrations. [Copyright &y& Elsevier]

The effects of free mercury(II), cadmium(II) and lead(II) ions and their metalloporphyrin-derivatives on Trypanosoma brucei brucei growth in culture were studied. All experiments were conducted in the dark. IC50 values on growth obtained in 24-h time-course experiments were 1.5×10−7, 2.4×10−6, 4.4×10−6 and 2.6×10−5 M for mercury(II) porphyrin, cadmium(II) porphyrin, lead(II) porphyrin and free base porphyrin, respectively. While the IC50 values for Hg2+, Cd2+ and Pb2+ were 3.6×10−6, 1.5×10−5 and 1.6×10−5 M, respectively. These results clearly indicate that the toxicity of the metalloporphyrin complexes of mercury(II), cadmium(II) and lead(II) to T. b. brucei parasites was much higher compared to their free metal ions and free base porphyrin at low concentrations. It was also observed after 8 h incubation that the metalloporphyrins were effective in inhibiting the division of the parasites at concentrations >1.25×10−7 M for mercury(II) porphyrin, concentrations >1.2×10−6 M for cadmium(II) and lead(II) porphyrins and at concentrations >3.6×10−6 M for Hg2+ ion. These observations were not detected in samples treated with the free metal ions and the free base porphyrin at the same concentrations. Interestingly, trypanosomes treated with metalloporphyrin complexes displayed different morphological features from those cells treated with free base porphyrin or metal ions. The chemotherapeutic potential of the metalloporphyrins of H2TMPyP for treatment of African trypanosomiasis is discussed. [Copyright &y& Elsevier]

Abstract This paper discriminates the source of sediment supply (provenance), degree of chemical weathering, and redox conditions of Holocene sediments cored from the Ankobra and Pra estuaries of Ghana in the Gulf of Guinea using their geochemical characteristics. Considerable stratigraphical variations were observed in major element compositions in the sediments from both the Ankobra (Al 2 O 3 : 5.3–14.2%, SiO 2 : 75.9–88.2%, CaO: 0.3–1.2%, K 2 O: 0.5–1.2%) and the Pra (Al 2 O 3 : 7.8–16.9%, SiO 2 : 72.8–86.5%, CaO: 0.3–0.4%, K 2 O: 0.7–1.2%) estuaries. Elemental compositions were similar in both estuaries depicting similarities in their source rock characteristics. Some of the major and trace elements correlated significantly (r2 > 0.8) with Al 2 O 3 in the Pra estuary confirming their possible hydraulic fractionation. Geochemical classification showed the sediments from both estuaries were predominantly composed of sub-arkoses with only a few litharenites. The chemical index of alteration (CIA*), Chemical index of weathering (CIW*), plagioclase index of alteration (PIA*), the Index of compositional variability (ICV), the SiO 2 /Al 2 O 3 ratios and SiO 2 vs. (Al 2 O 3 +K 2 O + NaO), suggest high degrees of chemical weathering coinciding with warm climatic conditions in the source regions as well as sub-matured to mature estuarine sediments deposited under semi-arid to semi-humid conditions. The sediment geochemistry and discrimination diagrams denote similar continental signature derivatives of the sediments from both estuaries. Both sediments are likely derived from intermediate to felsic granitoid source rocks as well as from a quartzose sedimentary provenance formed in a passive continental margin. The Ni/Co and V/Cr ratios depict sediment deposition under oxic conditions through time in both estuaries. [ABSTRACT FROM AUTHOR]

This study aimed at assessing trace element concentrations in two representative estuaries of Ghana (Pra and Ankobra) affected by gold-mining, relative to the levels of the unaffected Volta estuary. Surficial sediments ( n  = 16–17) were sampled at each estuary and analysed by ICP-MS for 25 elements after pseudo-total digestion. The enrichment and geoaccumulation indexes revealed a moderate to significant contamination of As, Ag and Cu in the Pra and Ankobra estuaries. Spatial maps of concentrations revealed non-localized sources. High As concentrations were attributable to runoff transport and sedimentation of gold mining-tailing particles, as suggested by results from granulometric distributions, correlation and PCA analysis. The probabilities of surpassing the probable effects level (PEL) were 77% for As, 50% for Cr and 27% for Ni in Ankobra; these values were of 13%, 23% and 10% for the Pra. Results reveal potential future implications on ecosystems and human health in these both estuaries as result of the gold-mining activity. [ABSTRACT FROM AUTHOR]

The interactions of the metalloporphyrins of tetrakis (1-methylpyridinium-4yl)porphyrin ([M(TMPyP)]4+) where M=Hg(II), Cd(II) and Pb(II)) with pBluescript II plasmid DNA have been studied by the measurement of circular dichroism (CD), UV–visible and fluorescence spectra at 0.1 M NaNO3, pH 7.5 and 25 °C. The CD spectra of the DNA changed quite significantly, with the conformational changes in the presence of the metalloporphyrins being much more enhanced compared to that of their free metal ion counterparts. The conformational changes in DNA upon binding to the Hg(II) porphyrin and Hg(II) were, however, different from those of the Cd(II) porphyrin, Pb(II) porphyrin, Pb(II), Cd(II) and H2(TMPyP)4+. In the concentration range of 0−2.30×10−5 M of DNA, the absorption spectra of H2(TMPyP)4+ showed substantial hypochromicity at 423 nm and a red shift of Δλ=16 nm in the presence of DNA whereas the Hg(II)-, Pb(II)- and Cd(II) porphyrins showed blue shifts of absorption maximum wavelengths of Δλ=−17 nm, Δλ=−35 nm and Δλ=−4.5 nm, respectively. Furthermore, the shifted absorption maximum wavelengths/nm of the porphyrins in excess amount of DNA were comparable; 438, 439, 440 and 440 for H2(TMPyP)4+, Hg(II)-, Pb(II)- and Cd(II) porphyrins, respectively. The changes in absorption spectra for Hg(II)-, Pb(II)- and Cd(II) porphyrins revealed that these metalloporphyrins dissociated upon binding to DNA which was confirmed by CD as well as fluorescence spectra. The CD results, UV–Vis and fluorescence data indicate that the metalloporphyrins interact differently with DNA based on their binding modes. And the enhanced changes in conformation of DNA in the presence of the metalloporphyrins are due to the synergistic effects of the simultaneous binding of the metal ions and the free base porphyrin to DNA compared to their free metal ion counterparts: [M(TMPyP)]4++DNA+2H+⇌[M(II)(DNA)H2(TMPyP)4+]. The detailed equilibrium reactions have been described along with suggestions of possible applications in the medical and biological fields. [Copyright &y& Elsevier]

Settling fluxes and sediment accumulation rates in coastal Tema Harbour (Ghana) were investigated by the combined analyses of results in sediment traps and sediment cores. Sediment traps were deployed at 5 stations within the Tema Harbour at two sampling depths and were retrieved every two weeks till the end of 12 weeks to estimate the Settling Fluxes (SFs). Four sediment cores from the harbour were analysed for their radioactivity ( 7 Be, 234 Th, 210 Pb, 212 Pb, 226 Ra, 40 K and 137 Cs) profiles to quantify Sediment Accumulation Rates (SARs). The sediment cores exhibited variable bulk density profiles, indicating highly dynamic and non-steady sedimentation conditions. 7 Be-derived gross-estimates of very recent SARs using the constant flux-constant sedimentation (CF-CS) model were in the range of 2.5–9.0 g·cm − 2 ·y − 1 . These values were much lower than the estimated average SFs (15.2–53.8 g·cm − 2 ·y − 1 ), indicating sediment resuspension plays an important role. On a decadal time scale, conventional 210 Pb sediment dating models did not allow any estimation of SARs in the Tema Harbour. Thus, the 210 Pb-based TERESA model was applied to depict a reliable scenario for sedimentation with time-averaged SARs in the range of 1.4–3.0 g·cm − 2 ·y − 1 and fluxes of matter contributed by the marine inflow and local sources. Sediment accretion rates of 1.7–3 cm·y − 1 were also inferred, which may pose a moderate problem of sustainability for the Tema Harbour. This study reveals how the geochemical behaviour of different radionuclides with Gamma spectrometry in the marine environment can be used to obtain reliable information on the complex dynamics of Suspended Particulate Matter (SPM), even in a very disturbed and anthropic environment as a coastal harbour area where (1) conventional 210 Pb-based dating methods fail and (2) the use of sediment traps and 234 Th and 7 Be profiles in sediment cores show serious constraints. [ABSTRACT FROM AUTHOR]

The potential ecological hazard, risk and impact of tropical marine sediments from the Tema Harbour (Greater Accra, Ghana) was investigated by integrating Corophium volutator and Hediste diversicolor whole-sediment toxicity bioassays with data on the metals (Cd, Pb, Cr, Ni, Cu, Zn and As) concentrations of the sediments. The whole-sediment toxicity bioassay results showed that sediments of the Tema Harbour are potentially hazardous to marine benthic invertebrates. C . volutator exhibited a higher vulnerability to the sediment toxicity than H . diversicolor , although the latter showed higher biota-sediment accumulation factors for the investigated metals. Statistically significant correlations were observed between C . volutator mortality and sediment Cd concentration ( r = 0.84, p < 0.05; n = 6) and between H . diversicolor mortality and sediment Cu concentration ( r = 0.94, p < 0.05; n = 5). Comparison of metal concentrations with international action levels for contaminated sediment disposal indicates that the Tema Harbour sediments contain potentially hazardous concentrations of Cu and Zn. This study shows that sediments from the Tema Harbour are not suitable for disposal at sea without remediation. There is, therefore, a need to improve environmental management and regulate the disposal of dredged material originating from the Tema Harbour. [ABSTRACT FROM AUTHOR]

Abstract: We report the concentrations of 28 PAHs, 15 oxygenated PAHs (OPAHs) and 11 trace metals/metalloids (As, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, Se, and Zn) in muscle and gut+gill tissues of demersal fishes (Drapane africana, Cynoglossus senegalensis and Pomadasys peroteti) from three locations along the coast of the Gulf of Guinea (Ghana). The concentrations of ∑28PAHs in muscle tissues averaged 192ngg−1 dw (range: 71–481ngg−1 dw) and were not statistically different between locations. The concentrations of ∑28 PAHs were higher in guts+gills than in muscles. The PAH composition pattern was dominated by low molecular weight compounds (naphthalene, alkyl-naphthalenes and phenanthrene). All fish tissues had benzo[a]pyrene concentrations lower than the EU limit for food safety. Excess cancer risk from consumption of some fish was higher than the guideline value of 1×10−6. The concentrations of ∑15 OPAHs in fish muscles averaged 422ngg−1 dw (range: 28–1715ngg−1dw). The ∑15 OPAHs/∑16 US-EPA PAHs concentration ratio was >1 in 68% of the fish muscles and 100% of guts+gills. The log-transformed concentrations of PAHs and OPAHs in muscles, guts+gills were significantly (p <0.05) correlated with their octanol–water partitioning coefficients, strongly suggesting that equilibrium partitioning from water/sediment into fish tissue was the main mechanism of bioaccumulation. The trace metal concentrations in the fish tissues were in the medium range when compared to fish from other parts of the world. The concentrations of some trace metals (Cd, Cu, Fe, Mn, Zn) were higher in guts+gills than in muscle tissues. The target hazard quotients for metals were<1 and did not indicate a danger to the local population. We conclude that the health risk arising from the consumption of the studied fish (due to their PAHs and trace metals content) is minimal. [Copyright &y& Elsevier]

In the present study, the concentrations of persistent organochlorine (OC) pesticides such as dichlorodiphenyltrichloroethane and its metabolites (DDTs), hexachlorocyclohexane isomers (HCHs), hexachlorobenzene (HCB) and dieldrin in pooled samples of human breast milk (n=109), and serum (n=115) from vegetable farmers in Ghana, during 2005, were determined. Gas chromatography with mass spectrometry was used to quantify residue levels on a lipid basis of the OCs. The pattern of OCs in human fluid showed that DDTs was consistently the prevalent OC in milk and blood. The levels of DDTs, HCHs, and dieldrin in the breast milk samples were found to correlate positively with age of the milk sample donors (r s=0.606, 0.770, and 0.540, respectively). When blood serum levels of the OCs were compared between male and female farmers, no pronounced relationship for HCHs and HCB (p>0.05) was observed. However, DDTs and dieldrin residues were significantly higher (p<0.05) in males than in females. There was association between breast milk and serum residues. When daily intakes of DDTs and HCHs to infants through human breast milk were estimated, some individual farmers (in the case of DDTs) and all farmers (in the case of HCHs) accumulated OCs in breast milk above the threshold (tolerable daily intake, TDI, guidelines proposed by Health Canada) for adverse effects, which may raise concern on children health. [Copyright &y& Elsevier]

This paper reports concentrations of γ-emitter radionuclides (40K, 137Cs, 210Pb, 226Ra, 228Ra, 228Th and 234Th) and some metals (Al, Cr, Fe, Co, Ni, Cu, Zn, As, Sr, Cd, Sb, Cs, Pb, Th and U) in surficial sediments from the Ankobra, Pra and Volta estuaries, in Ghana. Artisanal gold-mining in the Ankobra and Pra basins promoted moderate enrichments of As, Sb, Cu, Cs and Cr in their estuarine sediments, with respect to the reference background of the Volta Estuary. Radionuclide concentrations were in the range found in the Earth's crust. Present data do not support any conclusion on their potential enrichments due to gold-mining activities. Radionuclide isotopic ratios revealed a transfer of 228Ra from sediments to the water column. Pearson correlation coefficient matrices showed different patterns, which were reasonably understood after novel approaches: i) inter-estuaries comparison of slopes in the linear regressions of element-concentrations vs Al, Fe and Cs; ii) study of Al-normalized concentrations of elements; iii) excess 210Pb informing on local sedimentary conditions. The metal enrichments observed in the Ankobra and Pra estuaries are associated with the Fe-rich compounds in sulphide ores (such as FeAsS) transported along the river course and deposited in the estuary. • Sediments sampled from the Ankobra, Pra and Volta estuaries in Equatorial Africa. • 238U and 232Th series and 40K in the range of concentrations in the Earth's crust. • Enrichments of As, Sb, Cu, Cs and Cr by gold-mining in the Ankobra and Pra basins. • They can be associated to Fe-rich compounds in sulphide ores (such as FeAsS). • 210Pb informing on local sedimentary conditions and pollution pathways. [ABSTRACT FROM AUTHOR]

Theoretical and experimental studies have shown that activity concentrations of fallout radionuclides (such as 137Cs and excess 210Pb) decrease with particles size in aqueous suspensions. This paper is aimed at reviewing the theoretical fundamentals for granulometric speciation of radionuclides, and at exploring its practical use in the analytical context of gamma spectrometry for the radiometric dating of recent sediments, with view to: i) improving the detection of 137Cs (since its use as independent chronostratigraphic mark is challenging in the southern hemisphere because its low fallout rate), ii) supporting refined CIC models and normalization techniques in 210Pb-based radiogeochronologies. The work uses surface sediments sampled from the Tinto Estuary (SW Spain), affected by mining and phosphate-fertilizer industries, and from the Ankobra Estuary (Ghana), affected by intensive artisanal gold-mining. Granulometric classes have been separated by a sieving column with decreasing mesh sizes and the obtained cumulative percentage of mass mathematically described by a Rosin-Rammler particle-size distribution. The target radionuclides for gamma spectrometry were 210Pb, 226Ra and137Cs, complemented with 40K, 234Th and 228Ra. Results revealed that, far from ideal experiments, under actual environmental conditions the increase in activity concentrations with decreasing particle sizes is too moderate, and in general they are affected by larger counting uncertainties due to the small available amount of mass. Indeed, there was no correlation between grain-size and 137Cs concentrations (p = 0.25), and similarly for excess 210Pb (p = 0.53). No effect of the organic matter content was observed in 137Cs (p = 0.58) and excess 210Pb (p = 0.85) concentrations. Present results pose some concerns to the general use of granulometric speciation in the context of gamma spectrometry for supporting the radiometric dating of recent sediments. A detailed discussion on the use of normalization methods is also presented. • Radionuclide uptake in aqueous suspensions is proportional to particles surface. • Measuring 137Cs and 210Pb in physically separated grain-size class in sediment core. • Target: improving detection of 137Cs in southern hemisphere and 210Pb normalization. • Results reveal weak particle-size effects under actual environmental conditions. [ABSTRACT FROM AUTHOR]