Fractionation and ecotoxicological implication of potentially toxic metals in sediments of three urban rivers and the Lagos Lagoon, Nigeria, West Africa

The potential environmental impact of sediment-bound Cd, Cr, Cu, Pb and Zn in three trans-urban rivers in Lagos state and in the Lagos Lagoon was assessed by use of the modified Community Bureau of Reference (BCR) sequential extraction. The quality of the data was checked using BCR CRM 143R and BCR CRM 701. Good agreement was obtained between found and certified/indicative values. Of the rivers, the Odo-Iyaalaro, was generally the most contaminated and the Ibeshe the least. Higher concentrations of metals were generally found in the dry season compared to the wet season. Cadmium and Zn were released mostly in the acid exchangeable step of the sequential extraction, indicating that they have the greatest potential mobility and bioavailability of the analytes studied. Chromium and Cu were associated mainly with the reducible and oxidisable fractions, and Pb predominantly with the reducible and residual fractions. Sediments with the highest pseudototal analyte concentrations also released higher proportions of analytes earlier in the sequential extraction procedure. The study suggests that, during the dry season, potentially toxic metals (PTM) may accumulate in sediments in relatively labile forms that are released and can potentially be transported or bioaccumulate in the rainy season. Application of risk assessment codes and Hankanson potential risk indices indicated that Cd was the element of greatest concern in the Lagos Lagoon system. The study indicated that there is a need to strengthen environmental management and pollution control measures to reduce risk from PTM, but that even relatively simple strategies, such as seasonal restrictions on dredging and fishing, could be beneficial

Summary of assessment of GESAMP Working Group 37

This presentation is based on the summary of the GESAMP report to UNEP on mercury in the aquatic environment. The summary is divided into three main sections: Sources and releases, aquatic and oceanic transport and assessment of monitoring and evaluation. Sources can be natural or anthropogenic in origin with both diffuse and point sources being considered. While point sources are the most direct entry into an aquatic system, atmospheric deposition is the dominant input component to the world oceans. Consequently, reduction of mercury emissions must be the dominant mechanism of control. Wet deposition is a primary mechanism for transporting mercury from the atmosphere to surface water and land. Once in aquatic systems, it can exist in dissolved or particulate forms and can undergo a number of chemical transformations. Contaminated sediments at the bottom of surface waters serves as a mercury reservoir with sediment-bound mercury, recycling back into the aquatic ecosystem for decades or longer. Mercury has a long retention time in soils, so mercury that has accumulated in soils may continue to be released to surface waters and other media for long periods. Methylmercury (CH3Hg+)is the most common form of organic mercury in the environment and is more toxic than elemental or inorganic mercury with the potential for bioconcentration and bioaccumulation via the aquatic food web. This places people, all over the world, who consume predatory fish (or where fish is a dietary staple) at risk. The methylation of mercury occurs by biotic and abiotic processes, and transformation processes are influenced by several environmental factors such as pH, temperature, sulphate deposition, and availability of biodegradable organic carbon. Currently there are 2 main ways to evaluate concentrations of mercury in the environment based on principles of modelling or measuring techniques. Modelling programs have been studied to better understand the behaviour of substances in environmental media and used to estimate for mercury and its compounds in various environmental compartments. The advantages and disadvantages of modelling versus measuring techniques will be presented in full

Determinants and impact of production planning and control accounting techniques on competitiveness of manufacturing companies: a structural equation modelling approach

Purpose: this study aims to investigate four internal (organisational structure, quality of information technology, business strategy and market orientation) and two external (competition intensity and perceived environmental uncertainty) contextual factors affecting the use of production planning and control accounting techniques (PPC), as well as the impact of PPC usage on organisational competitiveness.Design/methodology/approach: seven major PPC techniques were investigated, namely: attribute costing, lifecycle costing, quality costing, target costing, value-chain costing, activity-based costing and activity-based management. By deploying a multi-informant strategy, a structured questionnaire was used to gather survey data from 129 senior accounting, finance and production personnel of publicly quoted manufacturing companies in Nigeria. Findings: the results, using structural equation modelling, show that market orientation is the strongest determinant of PPC usage. The inability of competition intensity and perceived environmental uncertainty to notably affect PPC usage suggests that external environmental pressure to use PPC is weak. Although PPC can engender organisational competitiveness, their interactive usage yields optimal results. Originality/value: the study contributes to knowledge by: (i) presenting evidence that although PPC techniques can engender organisational competitiveness, it is their interactive usage that yields optimal results; (ii) empirically demonstrating that contextual factors influence PPC usage in line with the contingency theory; and (iii) validating the diffusion of innovation theory that organisations will typically deploy PPC techniques because of their relative advantage of improving organisational competitiveness.</p

Assessment of occupational exposure to Polycyclic Aromatic Hydrocarbons via involuntary ingestion of soil from contaminated soils in Lagos, Nigeria

Abstract Soils from twelve sites in Lagos area, Nigeria impacted by anthropogenic activities were extracted by ultrasonication and analysed for the concentration of 16 priority polycyclic aromatic hydrocarbons (PAHs) by gas chromatograph-mass spectrometer (GC-MS). Th

Introduction and Overview of GESAMP assessment on mercury in the marine environment

GESAMP (Joint Group of Experts on the Scientific Aspects of Marine Environmental Protection) continues to play a leading role in the assessment of global marine pollution. The regular sessions of GESAMP over more than 30 years have produced a large number of reports and studies relating to marine pollution problems, covering a wide range of topics of the greatest relevance to marine environmental policy. The work of the GESAMP is accomplished through working groups with participation of a large number of experts selected by the organizations sponsoring GESAMP. The co-ordination of GESAMP is provided by a joint secretariat of the sponsoring organizations. WG 37 was formed at the request of UNEP with a particular remit for mercury in the aquatic environment. The remit was to target an assessment of the main contributions to the global mercury budget with particular reference to the aquatic environment, possible control options, transformations, pathways and toxicity and how these parameters can be measured or evaluated. A compilation of fate and transport models and current measuring techniques was also assessed. Monitoring efforts were evaluated and showed disparity between the northern and southern hemisphere and it was concluded that developing countries are severley hindered by lack of environmental protection regulations and a need for capacity building. A list of all participants and the main areas covered by the assessment will be presented in full