Victor Wepener

Bio: Victor Wepener is an academic researcher from North-West University. The author has contributed to research in topics: Water quality & Bioaccumulation. The author has an hindex of 29, co-authored 165 publications receiving 2884 citations. Previous affiliations of Victor Wepener include University of Johannesburg & Council of Scientific and Industrial Research.

Uptake and distribution of a copper, iron and zinc mixture in gill, liver and plasma of a freshwater teleost, Tilapia sparrmanii

Abstract: Since polluted environments contain mixtures of different contaminants, the aim of this study was to investigate the time-integrated uptake of individual metals by a freshwater teleost, Tilapia sparrmanii following exposure to a metal mixture containing Cu, Fe and Zn. The metal concentrations used during the bioassays were chosen to represent ecologically relevant concentrations as found in the Olifants River, Kruger National Park, South Africa. The concentrations used in the bioassay were 0.16 mg·l-1, 4.3 mg·l-1 and 1.003 mg·l-1 for Cu, Fe and Zn respectively. Gill, plasma and liver were sampled at 0, 2, 4, 6, 12, 24, 24, 48, 72, 96 h and four weeks. Gill tissue is the initial site of accumulation of water-borne metals. Although the fish were exposed to a metal mixture, the interactions between metals and the external gill surface, as well as the subsequent uptake rate, were associated with the particular chemical properties of individual metals. The tendency of the individual metals in the metal mixture to bind to the external gill surface via ionic bonds, and to gill cytosolic compounds via covalent bonds, was Cu > Fe > Zn. The ensuing uptake rates into the extracellular compartment (blood) and intracellular compartment (liver tissue) were Zn > Fe > Cu. The toxic effects of Cu and Fe were, therefore, primarily exerted on the gill surface and in the gill cytosol, whereas the toxic action of Zn was primarily limited to the internal organs. WaterSA Vol.27(1) 2001: 99-108

A Conceptual Framework for Using Mussels as Biomonitors in Whole Effluent Toxicity

Abstract: As a main source of direct and continuous input of pollutants in the aquatic ecosystem, studying the effects of effluents on receiving ecosystems has a high ecological relevance. While ecological risk assessment procedures are usually based on a chemical-based single component approach, their application for complex mixtures and effluents is less straightforward. A chemical-based approach has to rely on the knowledge of what chemicals are present in effluents, their potential toxicity, how all of these individual chemicals interact and what their individual and combined contribution to the mixture is. Whole effluent toxicity (WET) testing, however, is an integrative tool that measures the toxic effect of an effluent as a whole and accounts for uncharacterized sources of toxicity and for interactions. This paper addresses the use of transplanted bivalves, i.e., caged mussels, as a biomonitoring tool in WET testing with special reference to field situations in both freshwater and marine environments. We ind...

An assessment of the influence of multiple stressors on the Vaal River, South Africa

Abstract: The Vaal River is situated in the mining and industrial heartland of South Africa. It is regarded as a “work horse” river in South Africa and as a consequence it receives treated waste water from the largest metropolitain area in South Africa. It is only with the more frequent occurance of fish kills in the Vaal Barrage area during the past few years that public attention has been drawn towards the decreasing water quality and subsequent deterioration in the aquatic health of the Vaal River system. The aim of this study was to apply a multi-metric approach to assessing the risk of the multiple stressors to fish populations of the Vaal River system. A relative risk assessment approach was applied to divide the Vaal River Barrage into four risk regions. Field sampling was undertaken to validate the predicted risks in each region. The sampling included abiotic (i.e. water and sediment quality) and biotic (fish components) assessment. General water quality parameters (pH, conductivity, dissolved oxygen) together with nutrient, bacteriological and metal concentrations were measured in the four regions. Sediment quality was determined through physical (particle size distribution) and chemical (metal and organic pollutant) analyses. The fish assessment was undertaken at different levels of biological organisation ranging from biomarkers at subcellular levels (cytochrome P450-EROD, metallothionein, acetycholine esterase, antioxidant enzymes, cellular energy), tissue (histopathology), whole organism (fish health index), population and community level. These biological responses were related to environmental exposure through bioaccumulation analyses of metals and organic pollutants in fish tissues. Multivariate statistical analyses were applied to integrate the environmental exposure and effects. The results indicated that those regions that were predicted to be at greatest risk to exposure of multiple stressors did indeed display the greatest disturbance in fish community structures. This was related to decreased fish health as demonstrated by increased oxidative stress due to exposure to metals such as copper and nickel as well as organic pollutants such as PCBs, HCHs and bromated flame retardants. This study clearly demonstrates the importance of the inclusion of higher tier assessment endpoints to elucidate the effects of multiple stressors in aquatic ecosystems. The study further allowed for the identification of specific effect endpoints that need to be included in future monitoring programmes such as viral immunoassays.

An international database for pesticide risk assessments and management

Abstract: Despite a changing world in terms of data sharing, availability, and transparency, there are still major resource issues associated with collating datasets that will satisfy the requirements of comprehensive pesticide risk assessments, especially those undertaken at a regional or national scale. In 1996, a long-term project was initiated to begin collating and formatting pesticide data to eventually create a free-to-all repository of data that would provide a comprehensive transparent, harmonized, and managed extensive dataset for all types of pesticide risk assessments. Over the last 20 years, this database has been keeping pace with improving risk assessments, their associated data requirements, and the needs and expectations of database end users. In 2007, the Pesticide Properties DataBase (PPDB) was launched as a free-to-access website. Currently, the PPDB holds data for almost 2300 pesticide active substances and over 700 metabolites. For each substance around 300 parameters are stored, cover...