Dissolved trace metals, i.e Fe, Mn, Al, Cu, Zn, Pb and Cd were determined in the Umtata River. High levels of Al, Cd, Pb, Zn and Cu were observed, which may affect the "health" of the aquatic ecosystem. The high levels of Al, Cd and Pb may also affect the health of the rural community that uses the river water directly for domestic use without treatment. Generally the sources of the metals in the river appear to be diffuse, which include rural, urban and agricultural runoff sources in the catchment, although there may be contributions from natural and point sources.

The Keiskamma River and the impoundment, downstream were characterised over a one-year period by using standard physicochemical methods to assess their present qualities. The pH levels are normal in the river and in the impoundment but turbidity values and the levels of electrical conductivity are high in both water systems. Also, the nutrient levels in both systems are eutrophic. The DO and BOD levels exceeded EU guideline values for the protection of the aquatic ecosystem. The Keiskammahoek Sewage Treatment Plant (KSTP) was identified as a pollution point source into the receiving river and the impoundment. Its treatment performance was investigated. Significant pollution of the river and the impoundment from the KSTP was indicated for electrical conductivity, nutrients and oxygen-demanding substances.

In this study, three streams-Amuta, Agbogbo and Abagbooro were examined for salinity and sodium hazards and suitability of the water for irrigational purpose. The three streams are located within areas of three different agricultural practices and land uses. Water samples from the streams were collected twice a month for 1 year. Irrigation water quality parameters assessed included pH, electrical conductivity (EC), sodium adsorption ratio (SAR), percentage sodium, permeability index and potential salinity. Water samples were analyzed using standard chemical procedures. Results of the irrigation water quality parameters studied showed that water samples from the three streams do not exhibit toxicity problem in relation to salinity and sodium hazard. Although the data obtained for the three catchment areas for pH, EC and SAR were closely related, least concentrations of these irrigation water indices were obtained for Abagbooro stream where there is secondary forest; highest concentrations were found in Agbogbo stream and moderate values were obtained for water from Amuta stream where subsistent and mechanized farming are practiced, respectively.

This study investigated levels of organochlorine pesticide (OCP) residues in water and sediment samples from eleven rivers serving as drinking water sources and receiving runoff from nearby cocoa plantations in Ondo State, Nigeria. Twenty-two composite samples of surface water and sediments (0–3 cm) were collected randomly using grab technique and replicated thrice per season. The efficiency of the two techniques [supercritical fluid extraction (SFE) and liquid/liquid extraction (LLE)] was evaluated with percentage analyte recoveries to for SFE and to 1 for LLE. Determination of OCPs by gas chromatography with electron capture detection gave higher concentrations for sediments compared to the equivalent water samples. The commonly occurring pesticide residues in the sediments were (range, μg g−1) cis-chlordane 0.03–6.99; α-endosulfan 0.03–6.99; p,p′-DDE 0.08–19.04; and dieldrin 0.01–7.62; in the sediments and dieldrin (not detected-1.51 μg L−1) in water samples, during the dry season. OCP levels were significantly higher in dry season than wet season among the rivers. The study concluded that most of the rivers in cocoa growing areas were contaminated with OCPs associated with agricultural activities.

No abstract

This study was conducted to evaluate the levels and seasonal variations of some organochlorine pesticides (OCPs) in the cultivated land of Oke-Osun farm settlement, Osogbo, Nigeria. A field sampling programme was conducted in the rainy and dry seasons for 4 months each resulting in the analysis of a total of 40 samples. Soil samples collected at 20-m intervals were air-dried to a constant weight, sieved through a mesh of 2.0-mm pore size and selected by coning and quartering method. Solid-liquid extraction was used to extract OCPs from the soil. Qualitative identifications and quantitative evaluation of the OCPs were carried out with the aid of a Perkin Elmer gas chromatograph coupled with electron capture detector. Seasonal mean ranges of OCPs in soil (μg/kg) were 13.09 ± 21.66 β-BHC-42.01 ± 17.50 p, p(')-DDT in rainy season and 30.74 ± 17.38 α-BHC-82.88 ± 32.24 p, p(')-DDT in the dry season. The results obtained from this study revealed that agricultural soil samples of Oke-Osun farm settlement were contaminated with persistent organochlorine pesticides mainly as a result of their applications by farmers. Higher levels of OCPs were obtained for dry season than the rainy season. There were indications from this study that pesticides that have deleterious health effects on humans previously placed under legal restrictions by regulatory agencies were still being used by the farmers of Oke-Osun farm settlement and this gives cause for environmental concern.

No abstract

Biosorption of heavy metal ions can be an effective process for the removal of Cd(II) from wastewater. In this study, the batch removal of Cd(II) from dilute aqueous solution using Stereophyllum radiculosum as the biosorbent has been investigated. The Cd(II) uptake was dependent on the initial pH, contact time, initial metal ion concentration, and temperature. The residual Cd(II) in the solution was determined using Atomic Absorption Spectrophotometer. The optimum pH for the biosorption was pH 6. Maximum biosorption was obtained after 60 min of the process. Kinetic study showed that the pseudo-second-order rate equation best described the biosorption process. The adsorption isotherms obtained fitted well into the Freundlich and Langmuir isotherm. The Freundlich equation obtained was log À ¼ 2.6924 logC e þ 0.1131, while the Langmuir equation obtained was 1/À ¼ 0.0008/C e þ 17.41. The correlation factors obtained were 0.0995 and 0.9904, respectively. The free energy change obtained for the biosorption of Cd(II) at 300 K, initial Cd(II) concentration of 100 mg L À1 and pH 6 was À20.894 kJ mol À1 . The thermodynamic study showed that the increase in temperature led to increase in the amount of the metal ion biosorbed. These results indicate that S. radiculosum has potential for the uptake of Cd(II) from industrial effluents.