Dissolution Kinetics of Stilbite at Various Temperatures under Alkaline Conditions

Experiments measuring the dissolution rates of stilbite (NaCa [Al Si O ].14H O) in pH-buffered solutions were 2 5 13 36 2 performed in batch reactors at 4, 25, 40 and 60 oC. The pH conditions of the buffer solutions ranged from 8.5 to 12.5. The dissolution rates calculated from silicon concentration of the reacting fluid increased with increasing temperature (4–60 oC) and pH. The dissolution rates ranged from 3.45 x 10-15 (mol cm-2 s-1) at pH 10.7 and 4oC to 1.93 x 10-9 (mol cm-2 s-1) at pH 12 and 60oC and were pH dependent. The rate law was established as R = k (a -)n , where k is OH the rate constant, a is the activity of the OH- species and n the reaction order. The n values obtained were, 0.32 at 4 oC, 0.35 at 25 oC, 0.38 at 40 oC and 0.38 at 60 oC. Activation energy determined using Arrhenius plot was 48.45 kJ/mol at pH 9 and 30.88 kJ/mol at pH 12

Pesticide residues in fish from the Densu River Basin in Ghana

The Densu River is a typical river flowing through agricultural areas in Southern Ghana. Six fish species from different locations in the river were sampled and analyzed for residues of pesticides and metabolites using GC with ECD/FID. The results of the study indicate that all the detected residues and metabolites in fish samples from the Densu River Basin were organochlorines (OCs). Among the pesticides residues analyzed, DDE, α-endosulfan, γ- HCH, δ- HCH, heptachlor and endosulfan sulphate, were predominant in all the samples. About 50% of the samples recorded positive detection of DDE while α-endosulfan was detected in 60% of the samples. γ- HCH, δ- HCH were detected in 75% and 65% of the samples respectively with heptachlor occurring in 80% of the samples. In almost all the fish species analyzed, DDE was the predominant compound having a mean value of 7.99 μgKg-1. Higher concentrations of pesticide residues were detected in fish samples from the Densu River at Nsawam than the other locations. The total concentration of residues in the fish samples ranged between 0.49 μgKg-1 and 8.90 μgKg-1 with the highest level detected in Hepsetue odoe (HO-N). The sequence of pesticide residues detected in fish samples were HO-N > HN-N > CO-N > CG-N > TZ-N > CN-W > TZ-W > CG-W. The high ratio of DDE/DDT in fish samples (0.1 – 6.9 with a mean of 2.51) indicated probably old input of DDT and significant degradation. The γ -HCH isomer (lindane) was the dominant HCH in fish samples suggesting a preferential usage of lindane (purified γ-HCH) in these areas. The δ-HCH/γ-HCH ratios in most fish samples were low indicating the present input of the pesticide lindane from non-point sources.Keywords: Pesticide residues, Fish, Densu River Basin, Ghana, exposur

Water quality assessment of streams draining the Akwapim Ridge of Ghana

Surface water samples from seven streams on the Akwapim Ridge were analysed over a period of 1 year for various water quality parameters following standard methods prescribed in APHA, AWWA, WEF and AOAC. The study was carried out in order to assess the suitability of the streams for drinking and other domestic purposes. Additionally, the effect of land use activities was assessed. The study revealed that, generally, most of the physico-chemical parameters of the streams were below the World Health Organization (WHO) limits recommended for drinking water, with the exception of the levels of sulphate and conductivity in three of the streams (Opiafo: 224 mg/1, 908.5 ìS/cm; Kwati: 221.3 mg/1, 920 ìS/cm; and Ademi: 246 mg/1, 1292 ìS/cm), respectively, which were above the WHO requirements. Nevertheless, taking these factors into consideration (except the sulphate and conductivity), the waters may be regarded as excellent and good for drinking and other domestic uses

Trace and heavy metals analysis of Phyllanthus amarus and Phyllanthus fraternus in Ghana

Ethno-pharmacological uses and information about Phyllanthus species have prompted this work. The aim was to investigate the presence and levels of aluminum (Al), magnesium (Mg), iron (Fe), manganese (Mn) lead (Pb), cadmium (Cd), copper (Cu), zinc (Zn), chromium (Cr) and nickel (Ni) in Phyllanthus amarus (PA) and Phyllanthus fraternus (PF) in Ghana. Three different extracts (hot aqueous, hot ethanol and cold ethanol) were prepared from dried powdered samples of these plants. These extracts, including the dried samples of the plants were analyzed for the presence and levels of Al, Mg, Fe, Mn, Pb, Cd, Cu, Zn, Cr, and Ni using Atomic Absorption Spectrophotometry (AAS). The levels of Ni (0.43±0.24 ppm), Cr (0.35±0.04 ppm) and Cd (0.18±0.10 ppm) in both plant species were found to be very low in the dried samples plants and below the FAO/WHO maximum limits for vegetables, but were below the detectable limits of our AAS in the extract. Pb was not detected in the dried plant samples and in the extracts of the PA and PF; hence the plants may not pose serious health threat to consumers. PA and PF contain appreciable amounts of trace metals though they were all below the FAO/WHO maximum permissible limits in vegetables. The level of Fe in PA and PF (145.11±11.69 ppm and 179.94±14.60 ppm respectively) was found be to relatively high compared to the other elements analyzed. This finding makes the two plants suitable candidates for use in formulating effective remedies against iron deficiency diseases besides conferring some nutritive value to the patients.Keywords: Ethno-pharmacological, phytoextration, concentration, medicinal valu

Artificial and Natural Radioactivity Measurements and Radiation Dose Assessment in the Vicinity of Ghana Nuclear Research Reactor-1 (GHARR-1)

Radioactivity concentrations of <sup>226</sup>Ra, <sup>232</sup>Th, <sup>40</sup>K and <sup>137</sup>Cs in soil samples and water sources around the Ghana Research Reactor-1 (GHARR-1) and the immediate surroundings have been measured using gamma spectrometry. The primary aim of the study was to establish baseline radioactivity levels in the environs of GHARR-1. The average activity concentration of <sup>226</sup>Ra, <sup>232</sup>Th, <sup>40</sup>K and <sup>137</sup>Cs were 22.3 ± 1.12 Bq kg<sup>-1</sup>, 49.8 ± 1.60Bq kg-1, 99.60 ± 5.81 Bq kg<sup>-1</sup> and 1.48 ± 0.25 Bq kg<sup>-1</sup> for soil and 0.60 ± 0.11 Bq l<sup>-1</sup>, 2.13 ± 0.21 Bq l<sup>-1</sup>, 10.75 ± 0.84 Bq l<sup>-1</sup> and 0.47 ± 0.05 Bq l<sup>-1</sup>for the water, respectively. The <sup>226</sup>Ra and <sup>232</sup>Th concentrations compare quite well with world averages, whilst the <sup>40</sup>K concentration was lower than the world average. The levels of <sup>137</sup>Cs observed in the samples are within the range of ‘background’  concentrations. The estimated average annual effective doses from external exposure to soil and ingestion of water samples were calculated to be 0.06 mSv and 0.53 mSv, respectively. The estimated outdoor  external gamma dose rate measured in air ranged from 20-430 nGy h<sup>-1</sup> with an average value of 100 nGy h<sup>-1</sup>, which is higher than the world average value of 59 nGy h<sup>-1</sup>. In the case of water samples, the average value was higher than the guidance level of 0.1 mSv y<sup>-1</sup>, as recommended by the European Union and the World Health Organization