Effect of laundry activities on in-stream concentrations of linear alkylbenzene sulfonate in a small rural South African river
- Gordon, Andrew K, Muller, Wilhelmine J, Gysman, N, Marshall, S J, Sparham, C J, O'Connor, S M, Whelan, M J
- Authors: Gordon, Andrew K , Muller, Wilhelmine J , Gysman, N , Marshall, S J , Sparham, C J , O'Connor, S M , Whelan, M J
- Date: 2009
- Language: English
- Type: text , Article
- Identifier: vital:7094 , http://hdl.handle.net/10962/d1012427
- Description: In many parts of the world clothes are washed near to or in rivers and streams. Little information is available on resulting concentrations of detergent ingredients or on any potential effects caused. In this study, the fate of a commonly used anionic surfactant, linear alkylbenzene sulphonate (LAS) was investigated in a reach of the Balfour River (Eastern Cape Province, South Africa) which was regularly used as a site for laundry activity. Samples of river water were collected upstream of the main washing site and at a number of locations downstream on several occasions in winter and summer. Sediment samples were also collected and analysed. In addition, a household survey was conducted to ascertain the amount of detergent used and the distribution of washing practices. The results of the survey suggested that the use of riverside locations for laundry activities was seasonal. Most washing tended to be done at home during the winter with riverside sites used more frequently during the summer months. The monitoring data showed that LAS concentrations in water were very variable. They were occasionally high in the immediate vicinity of the laundry site (up to 342 µg L− 1) but were generally very low (< 11 µg L− 1) at downstream monitoring stations, suggesting that LAS was rapidly dissipated by a combination of degradation, hydrodynamic dispersion and dilution. Concentrations in the immediate vicinity of the washing site were lower than expected on the basis of the household survey because most waste water was disposed of on the river bank rather than directly in the river. No ecological effects are expected from LAS emissions at this site.
- Full Text:
- Date Issued: 2009
- Authors: Gordon, Andrew K , Muller, Wilhelmine J , Gysman, N , Marshall, S J , Sparham, C J , O'Connor, S M , Whelan, M J
- Date: 2009
- Language: English
- Type: text , Article
- Identifier: vital:7094 , http://hdl.handle.net/10962/d1012427
- Description: In many parts of the world clothes are washed near to or in rivers and streams. Little information is available on resulting concentrations of detergent ingredients or on any potential effects caused. In this study, the fate of a commonly used anionic surfactant, linear alkylbenzene sulphonate (LAS) was investigated in a reach of the Balfour River (Eastern Cape Province, South Africa) which was regularly used as a site for laundry activity. Samples of river water were collected upstream of the main washing site and at a number of locations downstream on several occasions in winter and summer. Sediment samples were also collected and analysed. In addition, a household survey was conducted to ascertain the amount of detergent used and the distribution of washing practices. The results of the survey suggested that the use of riverside locations for laundry activities was seasonal. Most washing tended to be done at home during the winter with riverside sites used more frequently during the summer months. The monitoring data showed that LAS concentrations in water were very variable. They were occasionally high in the immediate vicinity of the laundry site (up to 342 µg L− 1) but were generally very low (< 11 µg L− 1) at downstream monitoring stations, suggesting that LAS was rapidly dissipated by a combination of degradation, hydrodynamic dispersion and dilution. Concentrations in the immediate vicinity of the washing site were lower than expected on the basis of the household survey because most waste water was disposed of on the river bank rather than directly in the river. No ecological effects are expected from LAS emissions at this site.
- Full Text:
- Date Issued: 2009
Finding the optimum: fluoridation of potable water in South Africa
- Muller, Wilhelmine J, Heath, R G M, Villet, Martin H
- Authors: Muller, Wilhelmine J , Heath, R G M , Villet, Martin H
- Date: 1998
- Subjects: Water SA
- Language: English
- Type: Article
- Identifier: vital:6921 , http://hdl.handle.net/10962/d1011904
- Description: Since the South African Department of Health has tabled legislation to make fluoridation of public water supplies mandatory, the issue of whether fluoride is beneficial or harmful has, once again, become controversial in South Africa. We reviewed the literature, the experiences of fluoridation in overseas countries and the latest WHO recommendations, and have found that fluoride is desirable at certain levels, and undesirable above these. The following recommendations are made for optimum fluoride levels in South Africa's potable water: The decision to fluoridate a public water supply must be a community decision taken after public consultation. However, it can only be reached when the public is properly informed about the issue. Optimum levels of fluoride for human health range from 0.4 to 0.7 mg F/l, depending on the maximum mean annual temperature. The maximum level of 0.7 mg F/l should not be exceeded. Accordingly, it is recommended that in areas where natural fluoride concentrations in the drinking water exceed 0.7 mg F/l steps be taken to defluoridate the water. As an interim measure, a scale of temperature-adjusted optimum fluoride levels should be adopted in South Africa, rather than a single level covering the wide-ranging ambient temperatures (and corresponding consumption rates of drinking water) in the country. A sliding scale would mean that the community within a water supply region can determine its own fluoride consumption within the optimum range. Fluoridation should be considered only a short-term measure, until economic conditions are such that all South Africans have access to proper dental health care. The duration of fluoridation of a community water supply, and the level of fluoridation (within the optimum range of fluoride levels) should both be considered community decision. However, defluoridation should be a permanent necessity in those areas where the drinking water exceeds levels of 0.7 mg F/l.
- Full Text:
- Date Issued: 1998
- Authors: Muller, Wilhelmine J , Heath, R G M , Villet, Martin H
- Date: 1998
- Subjects: Water SA
- Language: English
- Type: Article
- Identifier: vital:6921 , http://hdl.handle.net/10962/d1011904
- Description: Since the South African Department of Health has tabled legislation to make fluoridation of public water supplies mandatory, the issue of whether fluoride is beneficial or harmful has, once again, become controversial in South Africa. We reviewed the literature, the experiences of fluoridation in overseas countries and the latest WHO recommendations, and have found that fluoride is desirable at certain levels, and undesirable above these. The following recommendations are made for optimum fluoride levels in South Africa's potable water: The decision to fluoridate a public water supply must be a community decision taken after public consultation. However, it can only be reached when the public is properly informed about the issue. Optimum levels of fluoride for human health range from 0.4 to 0.7 mg F/l, depending on the maximum mean annual temperature. The maximum level of 0.7 mg F/l should not be exceeded. Accordingly, it is recommended that in areas where natural fluoride concentrations in the drinking water exceed 0.7 mg F/l steps be taken to defluoridate the water. As an interim measure, a scale of temperature-adjusted optimum fluoride levels should be adopted in South Africa, rather than a single level covering the wide-ranging ambient temperatures (and corresponding consumption rates of drinking water) in the country. A sliding scale would mean that the community within a water supply region can determine its own fluoride consumption within the optimum range. Fluoridation should be considered only a short-term measure, until economic conditions are such that all South Africans have access to proper dental health care. The duration of fluoridation of a community water supply, and the level of fluoridation (within the optimum range of fluoride levels) should both be considered community decision. However, defluoridation should be a permanent necessity in those areas where the drinking water exceeds levels of 0.7 mg F/l.
- Full Text:
- Date Issued: 1998
Larval development of the carrion-breeding flesh fly, Sarcophaga (Liosarcophaga) tibialis Macquart (Diptera: Sarcophagidae), at constant temperatures
- Villet, Martin H, MacKenzie, B, Muller, Wilhelmine J
- Authors: Villet, Martin H , MacKenzie, B , Muller, Wilhelmine J
- Date: 2006
- Language: English
- Type: text , Article
- Identifier: vital:7091 , http://hdl.handle.net/10962/d1012422
- Description: Larvae of Sarcophaga (Liosarcophaga) tibialis Macquart were raised on chicken liver under six different constant temperatures. Maximum survival indicated an optimal developmental temperature of near 20°C, while trends in mortality, larval length and larval mass implied that the thermal window for successful development lay between 15°C and 30°C. Using a recently described method to estimate a simple thermal summation model, it was found that the timing of the end of the feeding phase could be estimated by a developmental zero (D0) of 5.2°C (S.E. = 1.21) and a thermal summation constant (K) of 106.4 d°C (S.E. = 8.31) and of the end of the wandering phase by D0 = 4.1°C (S.E. = 0.39) and K = 126.7 d°C (S.E. = 3.28). Published development times at constant temperatures were compiled for 19 other species of flesh flies, and the developmental constants were calculated for six species for which sufficient data were accumulated.
- Full Text:
- Date Issued: 2006
- Authors: Villet, Martin H , MacKenzie, B , Muller, Wilhelmine J
- Date: 2006
- Language: English
- Type: text , Article
- Identifier: vital:7091 , http://hdl.handle.net/10962/d1012422
- Description: Larvae of Sarcophaga (Liosarcophaga) tibialis Macquart were raised on chicken liver under six different constant temperatures. Maximum survival indicated an optimal developmental temperature of near 20°C, while trends in mortality, larval length and larval mass implied that the thermal window for successful development lay between 15°C and 30°C. Using a recently described method to estimate a simple thermal summation model, it was found that the timing of the end of the feeding phase could be estimated by a developmental zero (D0) of 5.2°C (S.E. = 1.21) and a thermal summation constant (K) of 106.4 d°C (S.E. = 8.31) and of the end of the wandering phase by D0 = 4.1°C (S.E. = 0.39) and K = 126.7 d°C (S.E. = 3.28). Published development times at constant temperatures were compiled for 19 other species of flesh flies, and the developmental constants were calculated for six species for which sufficient data were accumulated.
- Full Text:
- Date Issued: 2006
Microbial monitoring of surface water in South Africa: an overview
- Luyt, Catherine D, Tandlich, Roman, Muller, Wilhelmine J, Wilhelmi, Brendan S
- Authors: Luyt, Catherine D , Tandlich, Roman , Muller, Wilhelmine J , Wilhelmi, Brendan S
- Date: 2012
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/71636 , vital:29927 , https://doi.org/10.3390/ijerph9082669
- Description: Infrastructural problems force South African households to supplement their drinking water consumption from water resources of inadequate microbial quality. Microbial water quality monitoring is currently based on the Colilert®18 system which leads to rapidly available results. Using Escherichia coli as the indicator microorganism limits the influence of environmental sources on the reported results. The current system allows for understanding of long-term trends of microbial surface water quality and the related public health risks. However, rates of false positive for the Colilert®18-derived concentrations have been reported to range from 7.4% to 36.4%. At the same time, rates of false negative results vary from 3.5% to 12.5%; and the Colilert medium has been reported to provide for cultivation of only 56.8% of relevant strains. Identification of unknown sources of faecal contamination is not currently feasible. Based on literature review, calibration of the antibiotic-resistance spectra of Escherichia coli or the bifidobacterial tracking ratio should be investigated locally for potential implementation into the existing monitoring system. The current system could be too costly to implement in certain areas of South Africa where the modified H2S strip test might be used as a surrogate for the Colilert®18.
- Full Text:
- Date Issued: 2012
- Authors: Luyt, Catherine D , Tandlich, Roman , Muller, Wilhelmine J , Wilhelmi, Brendan S
- Date: 2012
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/71636 , vital:29927 , https://doi.org/10.3390/ijerph9082669
- Description: Infrastructural problems force South African households to supplement their drinking water consumption from water resources of inadequate microbial quality. Microbial water quality monitoring is currently based on the Colilert®18 system which leads to rapidly available results. Using Escherichia coli as the indicator microorganism limits the influence of environmental sources on the reported results. The current system allows for understanding of long-term trends of microbial surface water quality and the related public health risks. However, rates of false positive for the Colilert®18-derived concentrations have been reported to range from 7.4% to 36.4%. At the same time, rates of false negative results vary from 3.5% to 12.5%; and the Colilert medium has been reported to provide for cultivation of only 56.8% of relevant strains. Identification of unknown sources of faecal contamination is not currently feasible. Based on literature review, calibration of the antibiotic-resistance spectra of Escherichia coli or the bifidobacterial tracking ratio should be investigated locally for potential implementation into the existing monitoring system. The current system could be too costly to implement in certain areas of South Africa where the modified H2S strip test might be used as a surrogate for the Colilert®18.
- Full Text:
- Date Issued: 2012
Similarities and differences between rivers of the Kruger National Park
- Muller, Wilhelmine J, Villet, Martin H
- Authors: Muller, Wilhelmine J , Villet, Martin H
- Date: 2004
- Language: English
- Type: text
- Identifier: vital:537 , http://hdl.handle.net/10962/d1009527
- Description: [From Introduction] Aquatic ecosystems play an important role in the maintenance of ecological diversity and ecosystem functioning at both local and regional scales (Roux et al, 1999). Effective management of riverine ecosystems requires an understanding of their ecosystem processes, hi order to understand ecosystem processes, and interactions between the landscape and riverine ecosystems, it is necessary to have both spatial and temporal data at both landscape and site-specific scales (Allan and Johnson, 1997). There are many tools available for the analysis of these data to provide insight and understanding of the data in order to understand influences on aquatic ecosystems. Increasingly complex computational tools allow analysis and modeling of data in order to explain river, and subsequent biological, processes from landscape (catchment) processes (Johnson and Gage, 1997), although the scale at which analysis and interpretation occurs is important. Science and management need to interact in order to truly succeed in effectively applying adaptive management and incorporate monitoring and assessment programmes in management processes (Rogers and Biggs, 1999). However, water resource management is often undertaken in the context of incomplete information and knowledge of functioning ecosystem processess and responses: this inevitably leads to uncertainty and unpredictability (Roux et al. 1999). One of the major challenges for managing rivers is to be able to monitor rivers effectively in order to detect changes as they occur, to identify the causes of the changes and to distinguish between natural and anthropogenic causes of change. Adaptive management is required to effectively manage rivers, but this does require that there is an understanding of, and information for, the rivers being managed. Rogers and Biggs (1999) highlighted the need to integrate monitoring programmes with indicators in order to undertake assessments of ecosystem health as part of the management plan of the rivers of the Kruger National Park in order to maintain, and restore, natural river ecosystem health and biodiversity (Rogers and Bestbier, 1997). One of the main aims of the Kruger National Park Rivers Research Programme (KNPRRP) was to contribute to the conservation of the natural environment by developing skills and methods to understand the ecological functioning of the natural environment and to predict responses of the river systems to natural and anthropogenic changes in order to effectively manage them (Breen, 1994, in van Rensburg and Dent, 1997). Classification systems are able to provide useful management information, but many have focussed on abiotic rather than biotic factors because resultant biotic patterns are likely to be correlated with abiotic components (Solomon et al., 1999). Much of the classification of the Kruger National Park has focussed on classification of land with little regard for rivers (these were incorporated into the two classification systems proposed by Venter and Gertenbach (in Solomon et al., 1999)). The objective of this project is to identify similarities and differences between the five major rivers of the Kruger National Park, towards the design and testing of a classification framework in order to aid management of the KNP rivers by contributing to effective monitoring. This will be achieved through the following: 1. collate available (current and historical) information concerning physical and biological variables for the Luvuvhu, Letaba, Olifants, Sabie and Crocodile Rivers, using a common dataset to establish the degree of similarities and differences between these five major rivers of the KNP; and 2. determine how different the rivers are, in order to optimize monitoring and management programmes for these differences. The aim of this project was not to classify the rivers of the KNP. The project rather aims to identify gaps in data availability which may result in inadequate and inappropriate management of the rivers. Results (in the form of a data matrix) emanating from this study could assist in establishing expected natural conditions and biota in the five major rivers of the KNP, and knowledge from data-rich rivers (e.g. Sabie River) could potentially be extrapolated to data-poor rivers, or sections of rivers. Invertebrates and fish are the main tools of aquatic species biodiversity monitoring, and require an understanding of the natural presence, absence and abundance patterns in aquatic ecosystems. This study contributes to this understanding by organising available information of biotic and abiotic information.
- Full Text:
- Date Issued: 2004
- Authors: Muller, Wilhelmine J , Villet, Martin H
- Date: 2004
- Language: English
- Type: text
- Identifier: vital:537 , http://hdl.handle.net/10962/d1009527
- Description: [From Introduction] Aquatic ecosystems play an important role in the maintenance of ecological diversity and ecosystem functioning at both local and regional scales (Roux et al, 1999). Effective management of riverine ecosystems requires an understanding of their ecosystem processes, hi order to understand ecosystem processes, and interactions between the landscape and riverine ecosystems, it is necessary to have both spatial and temporal data at both landscape and site-specific scales (Allan and Johnson, 1997). There are many tools available for the analysis of these data to provide insight and understanding of the data in order to understand influences on aquatic ecosystems. Increasingly complex computational tools allow analysis and modeling of data in order to explain river, and subsequent biological, processes from landscape (catchment) processes (Johnson and Gage, 1997), although the scale at which analysis and interpretation occurs is important. Science and management need to interact in order to truly succeed in effectively applying adaptive management and incorporate monitoring and assessment programmes in management processes (Rogers and Biggs, 1999). However, water resource management is often undertaken in the context of incomplete information and knowledge of functioning ecosystem processess and responses: this inevitably leads to uncertainty and unpredictability (Roux et al. 1999). One of the major challenges for managing rivers is to be able to monitor rivers effectively in order to detect changes as they occur, to identify the causes of the changes and to distinguish between natural and anthropogenic causes of change. Adaptive management is required to effectively manage rivers, but this does require that there is an understanding of, and information for, the rivers being managed. Rogers and Biggs (1999) highlighted the need to integrate monitoring programmes with indicators in order to undertake assessments of ecosystem health as part of the management plan of the rivers of the Kruger National Park in order to maintain, and restore, natural river ecosystem health and biodiversity (Rogers and Bestbier, 1997). One of the main aims of the Kruger National Park Rivers Research Programme (KNPRRP) was to contribute to the conservation of the natural environment by developing skills and methods to understand the ecological functioning of the natural environment and to predict responses of the river systems to natural and anthropogenic changes in order to effectively manage them (Breen, 1994, in van Rensburg and Dent, 1997). Classification systems are able to provide useful management information, but many have focussed on abiotic rather than biotic factors because resultant biotic patterns are likely to be correlated with abiotic components (Solomon et al., 1999). Much of the classification of the Kruger National Park has focussed on classification of land with little regard for rivers (these were incorporated into the two classification systems proposed by Venter and Gertenbach (in Solomon et al., 1999)). The objective of this project is to identify similarities and differences between the five major rivers of the Kruger National Park, towards the design and testing of a classification framework in order to aid management of the KNP rivers by contributing to effective monitoring. This will be achieved through the following: 1. collate available (current and historical) information concerning physical and biological variables for the Luvuvhu, Letaba, Olifants, Sabie and Crocodile Rivers, using a common dataset to establish the degree of similarities and differences between these five major rivers of the KNP; and 2. determine how different the rivers are, in order to optimize monitoring and management programmes for these differences. The aim of this project was not to classify the rivers of the KNP. The project rather aims to identify gaps in data availability which may result in inadequate and inappropriate management of the rivers. Results (in the form of a data matrix) emanating from this study could assist in establishing expected natural conditions and biota in the five major rivers of the KNP, and knowledge from data-rich rivers (e.g. Sabie River) could potentially be extrapolated to data-poor rivers, or sections of rivers. Invertebrates and fish are the main tools of aquatic species biodiversity monitoring, and require an understanding of the natural presence, absence and abundance patterns in aquatic ecosystems. This study contributes to this understanding by organising available information of biotic and abiotic information.
- Full Text:
- Date Issued: 2004
Survival of bifidobacteria and their usefulness in faecal source tracking
- Luyt, Catherine D, Khamanga, Sandile M, Muller, Wilhelmine J, Tandlich, Roman
- Authors: Luyt, Catherine D , Khamanga, Sandile M , Muller, Wilhelmine J , Tandlich, Roman
- Date: 2015
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/76117 , vital:30508 , https://doi.org/10.1515/lwr-2015-0001
- Description: Bifidobacteria have long since been recommended as indicators of human and animal pollution. Concentration ratio (tracking ratio) of the sorbitol-utilising bifidobacteria (SUB) and the total bifidobacteria (TB) can be used to distinguish between animal and human sources of faecal water contamination. The cut-off value needs to be calibrated in a given geographical area. Seven sites with permanent faecal contamination were selected in South Africa. Concentrations of SUB ranged from 10-50000 cells/100 mL, while TB ranged from 0-8000 cells/100 mL. The tracking ratio ranged from 0.10 to 6.25, but no clear cut-off value could be established. The YN-17 agar was replaced for TB with the modified Beerens medium with pH = 5.70, to suppress the growth of faecal streptococci. Tracking ratios observed are most likely the results of different survival rates of SUB and TB. Bifidobacteria die-off due to nutrients was not found to be significant using design of experiment. Thus a lack of continuous input or oxygen levels in water may be major factors. This would limit the ratios used as a faecal source tracking method.
- Full Text:
- Date Issued: 2015
- Authors: Luyt, Catherine D , Khamanga, Sandile M , Muller, Wilhelmine J , Tandlich, Roman
- Date: 2015
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/76117 , vital:30508 , https://doi.org/10.1515/lwr-2015-0001
- Description: Bifidobacteria have long since been recommended as indicators of human and animal pollution. Concentration ratio (tracking ratio) of the sorbitol-utilising bifidobacteria (SUB) and the total bifidobacteria (TB) can be used to distinguish between animal and human sources of faecal water contamination. The cut-off value needs to be calibrated in a given geographical area. Seven sites with permanent faecal contamination were selected in South Africa. Concentrations of SUB ranged from 10-50000 cells/100 mL, while TB ranged from 0-8000 cells/100 mL. The tracking ratio ranged from 0.10 to 6.25, but no clear cut-off value could be established. The YN-17 agar was replaced for TB with the modified Beerens medium with pH = 5.70, to suppress the growth of faecal streptococci. Tracking ratios observed are most likely the results of different survival rates of SUB and TB. Bifidobacteria die-off due to nutrients was not found to be significant using design of experiment. Thus a lack of continuous input or oxygen levels in water may be major factors. This would limit the ratios used as a faecal source tracking method.
- Full Text:
- Date Issued: 2015
The development of a toxicity database using freshwater macroinvertebrates, and its application to the protection of South African water resources
- Palmer, Carolyn G, Muller, Wilhelmine J, Gordon, Andrew K, Scherman, Patricia A, Davies-Coleman, Heather D, Pakhomova, L, de Kock, E
- Authors: Palmer, Carolyn G , Muller, Wilhelmine J , Gordon, Andrew K , Scherman, Patricia A , Davies-Coleman, Heather D , Pakhomova, L , de Kock, E
- Date: 2004
- Language: English
- Type: text , Article
- Identifier: vital:7073 , http://hdl.handle.net/10962/d1009528
- Description: There is a growing international trend towards the protection of freshwater resources from pollution by imposing instream guidelines and specified waste-discharge conditions. Current methods for devising freshwater quality guidelines are based on species sensitivity distributions (SSDs) that are used to identify pollutant concentrations, ensuring the protection of a modelled percentage of species (95% protection is a common goal). SSDs are derived from the toxicity test results of as many taxa as possible for each polluting substance. Waste-discharge licences can be for single substances, specified in terms of chemical concentrations, and derived in conjunction with instream guidelines; or for complex mixtures, specified in terms of toxic units. In both cases toxicity test results are the core data used. The emphasis on SSDs calls into question the species constituting the test populations. It is likely that SSDs based in part on the responses of local organisms will achieve superior site-specific ecological protection. Until the early 1990s, there were very few data on the tolerances of South African freshwater organisms. In the intervening decade, the Unilever Centre for Environmental Water Quality at Rhodes University has developed a toxicity database that, to date, records the responses of 21 South African freshwater taxa to 26 single-substance pollutants or mixtures. This is the most comprehensive database of South African toxicity responses available and has been used in the drawing up of methods and guidelines to protect water resources. This paper aims to make these data available and to describe applications of the data using selected case studies.
- Full Text:
- Date Issued: 2004
- Authors: Palmer, Carolyn G , Muller, Wilhelmine J , Gordon, Andrew K , Scherman, Patricia A , Davies-Coleman, Heather D , Pakhomova, L , de Kock, E
- Date: 2004
- Language: English
- Type: text , Article
- Identifier: vital:7073 , http://hdl.handle.net/10962/d1009528
- Description: There is a growing international trend towards the protection of freshwater resources from pollution by imposing instream guidelines and specified waste-discharge conditions. Current methods for devising freshwater quality guidelines are based on species sensitivity distributions (SSDs) that are used to identify pollutant concentrations, ensuring the protection of a modelled percentage of species (95% protection is a common goal). SSDs are derived from the toxicity test results of as many taxa as possible for each polluting substance. Waste-discharge licences can be for single substances, specified in terms of chemical concentrations, and derived in conjunction with instream guidelines; or for complex mixtures, specified in terms of toxic units. In both cases toxicity test results are the core data used. The emphasis on SSDs calls into question the species constituting the test populations. It is likely that SSDs based in part on the responses of local organisms will achieve superior site-specific ecological protection. Until the early 1990s, there were very few data on the tolerances of South African freshwater organisms. In the intervening decade, the Unilever Centre for Environmental Water Quality at Rhodes University has developed a toxicity database that, to date, records the responses of 21 South African freshwater taxa to 26 single-substance pollutants or mixtures. This is the most comprehensive database of South African toxicity responses available and has been used in the drawing up of methods and guidelines to protect water resources. This paper aims to make these data available and to describe applications of the data using selected case studies.
- Full Text:
- Date Issued: 2004
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