Adegbenro Daso | Tshwane University of Technology (original) (raw)

Papers by Adegbenro Daso

African Journal of Biotechnology, Jan 24, 2011

Samples of water from two rivers (River Ona and River Alaro) in Oluyole Industrial Estate, Ibadan... more Samples of water from two rivers (River Ona and River Alaro) in Oluyole Industrial Estate, Ibadan, Nigeria were analysed to evaluate the impact of industrial discharges on the surface water quality. The results obtained indicated that most of the parameters analysed (pH, total hardness, sulphate, chloride, nitrate and dissolved solids) were lower than the World Health Organisation (WHO) maximum permissible limit for drinking water. However, the levels of nitrate, chloride, total phosphorus, total solids and oil and grease were higher in the industrial zones than those found in the upstream of both rivers. These ranged between 3.00-8.55, 7.48-11.78, 2.14-3.57, 260-520 mg/l and 381.20-430.80 mg/l, respectively. Nitrate and total phosphorus which are essential nutrients for plants were the most accumulated in both rivers. The gross organic pollution indicators monitored (chemical oxygen demand and oil and grease) revealed that River Alaro was more polluted than River Ona. It was established from the results of this study that industrial discharges had negative impact on the surface water qualities of both rivers. Hence, extraction of water from both rivers for domestic and agricultural purposes requires some forms of physical and chemical treatment.

Chemosphere, 2015

This study was undertaken to assess the levels of eight PBDE congeners, namely: PBDE-17, 47, 100,... more This study was undertaken to assess the levels of eight PBDE congeners, namely: PBDE-17, 47, 100, 99, 154, 153, 183 and 209 in eggshells of Southern Ground-Hornbill (SGH) Bucorvus leadbeateri and Wattled Crane (WC) Bugeranus carunculatus obtained from different nesting sites within the eastern savanna of Limpopo Province and the midlands of KwaZulu-Natal, respectively. Analyses were performed using gas chromatography-mass spectrometry employing the electron impact ionization technique. The results obtained indicated that the lower brominated congeners were predominant in both species. The total PBDEs ranged between not detected (ND) to 264 µg g-1 lipid weight and 5.98 to 7146 µg g-1 lipid weight in the SGH and WC samples, respectively. More so, the mean recoveries of the 13 C-labelled surrogate standards ranged between 40% (PBDE-100) to 136% (PBDE-99). The potential hazards to these birds via PBDEs exposure were evaluated by determining the hazard quotients (HQs) by employing the established Lowest Observed Effect Level (LOEL) values associated with impaired pipping and hatching success as well as that associated with impaired reproduction. HQs values varying from 0.58 to 0.94 and 27.71 to 45.27, respectively were obtained for SGH and WC species. This implies that the SGH populations are exposed to low to moderate hazards, while the WC populations are susceptible to high hazards. Considering the potential threats posed by PBDEs, particularly to the WC species, it is likely that exposure to the current environmental levels of PBDEs by these birds may contribute to their reduced breeding success and declining population trends.

Environmental Technology and Innovation, Feb 1, 2018

A review of the application of agricultural wastes as precursor materials for the adsorption of p... more A review of the application of agricultural wastes as precursor materials for the adsorption of per-and polyfluoroalkyl substances: A focus on current approaches and methodologies. Environmental Technology & Innovation (2017),

Ecotoxicology and Environmental Safety, Mar 1, 2017

Unregulated electronic waste (e-waste) recycling operations have become a significant environment... more Unregulated electronic waste (e-waste) recycling operations have become a significant environmental issue as well as human health risk in developing countries across the world. The present study evaluated the extent of pollution in Agbogbloshie e-waste recycling site in Accra, Ghana. The concentrations of polybrominated diphenyl ethers (PBDEs) and some selected trace metals were determined using gas chromatography electron impact ionization mass spectrometry and flame atomic absorption spectrophotometry, respectively. The concentrations of ∑ PBDEs ranged from 15.6 to 96.8 ng g −1 dry weight, with an overall mean of 54.8 ng g −1 dw. BDE-28 was the dominant congener followed by BDE-209 and BDE-47. The order of mean concentrations of the abundant trace metals was Fe>Cu>Pb≫Mn, with a mean range of .531-289 mg kg −1. Geoaccumulation index suggested that the surface soils deteriorated from moderate to high metal pollution, particularly for Cu, Pb and Fe. Of the trace metals analysed, Fe exhibited the highest concentration ranging from 3.97 to 918 mg kg −1. Correlation and principal component analyses suggested possible interactions between PBDEs and the trace metals analysed, while source assessment suggested that PBDEs and trace metals were mostly derived from inputs from the e-waste recycling activities. Average daily dose (ADD) was estimated using concentrations corresponding to 5th percentile, median and 95th percentile. Hazard quotients of 380 and 862 were obtained for adults and children respectively, for Cu and Pb which is a cause for concern especially for local children.

International Journal of Environmental Analytical Chemistry, Oct 6, 2022

Environmental Monitoring and Assessment, Jul 27, 2017

The occurrence of selected brominated flame retardants, including nine PBDE congeners, HBCDD and ... more The occurrence of selected brominated flame retardants, including nine PBDE congeners, HBCDD and TBBPA in leachate samples from 8 landfill sites in South Africa were investigated. In addition, the possible influences of dissolved organic carbon on their levels were also evaluated. Filtered leachate samples were subjected to solid-phase extraction to isolate the various target compounds. PBDEs with six bromine substituents and above, as well as α-HBCDD, β-HBCDD and TBBPA were generally found below the detection limit. However, the mean value of the total lower PBDE congeners ranged between 0.04 and 0.48 µg L-1 and the concentrations of γ-HBCDD ranged from not detectable (ND) to 0.05 µg L-1. No significant correlation was observed between the target compounds and DOC, although weak to moderate correlations were mostly observed for the lower PBDEs.

Emerging Contaminants, Dec 1, 2017

Triclosan and triclocarban are industrial chemicals that are frequently added into consumer and p... more Triclosan and triclocarban are industrial chemicals that are frequently added into consumer and personal care products. Information on the levels on these compounds in water systems in the African continent is still very scarce. In the present study, the occurrence, seasonal variation, and estimated removal of TCS and TCC in six different wastewater treatment plants in Gauteng Province, South Africa, were investigated over a period of two years, together with effluent receiving river water. The instrumental analysis was carried out using Shimadzu LCMS/MS 8030, employing negative electrospray ionization. Both target compounds were ubiquitously detected with influent and raw sludge having elevated concentrations. Generally, TCS concentrations were higher than those of TCC. The concentrations obtained for TCS were (influent, 2.01–17.6 μg/L; effluent, 0.990–13.0 μg/L; river, 0.880–8.72 μg/L; raw sludge, 3.65–15.0 μg/kg; treated sludge, 2.08–7.81 μg/kg and biosolids, 2.16–13.5 μg/kg); while TCC levels were obtained to be (influent, 0.0860–2.84 μg/L; effluent, <LOD - 1.89 μg/L; river, nd - 0.360 μg/L; raw sludge, 3.65–11.8 μg/kg; treated sludge, 1.21–9.19 μg/kg; biosolids, 2.59–8.23 μg/kg). Occurrence of TCS in wastewater was found to be influenced by temporal changes. This was not the case for occurrence of TCS and TCC in sludge samples. Similar to their environmental occurrence, the estimated treatment efficiencies also varied across the wastewater treatments plants, with the highest elimination rates of 63% and 97% for TCS and TCC, respectively.

Waste and Biomass Valorization, Nov 29, 2018

Modification of sodium alginate (NaAlg) was carried out using N,N-dimethylacrylamide (DMAAm) as a... more Modification of sodium alginate (NaAlg) was carried out using N,N-dimethylacrylamide (DMAAm) as a monomer and azobisizobutyronitrile (AIBN) as an initiator under microwave irradiation. The effect of reaction conditions such as concentrations of DMAAm, AIBN, NaAlg as well as microwave power and temperature on grafting and grafting efficiency has been explored. Maximum grafting and grafting efficiency has been observed at 1 h of grafting time, 0.291 M of DMAAm concentration, 500 W microwave irradiation power, 0.134 M of AIBN concentration, 75 • C of reaction temperature and 0.5 g/dL of NaAlg concentration. The grafted copolymer has been characterized by FTIR, DSC, TGA, 13 C NMR, XRD, SEM, and GPC analysis. Cytotoxicity as standard MTT assay, apoptotic and necrotic effects of graft copolymer were investigated on L929 fibroblast cell. It has been found that the grafted copolymer is biocompatible and thermally more stable than the ungrafted alginate.

Water SA, Aug 1, 2011

A simple analytical procedure was developed for simultaneous determination of trace levels of tri... more A simple analytical procedure was developed for simultaneous determination of trace levels of tri-to hepta-BDEs as well as 2,2′,4,4′,5,5′-hexabromobiphenyl (BB 153). The mechanical shaking extraction technique for the isolation of target analytes was optimised. Different extraction solvent combinations were tested under different extraction time periods of 3, 6, 12 and 16 h. The n-hexane:acetone (2:1, v/v) combination gave the best recovery at the optimum extraction of 12 h. Target analytes were quantified using a high capillary gas chromatograph (GC) equipped with an electron capture detector. Under the optimum GC conditions, the resolution of the co-eluting BDE 154 and BB 153 was achieved. The overall recoveries of target analytes in the matrix spike experiment conducted ranged between 84.4 and 110% for BDE 183 and BDE 28, respectively. The method was applied to 19 field sediment samples collected from a control site and from 3 sampling locations (upstream, point of discharge and downstream) of the Black River, which receives effluent from a wastewater treatment plant (WWTP). The sum of the mean concentrations of all of the 7 PBDE congeners was 4.63, 0.35, 'not detectable' and 4.43 ng/g, for the control site, upstream, point of discharge and downstream samples, respectively. The concentrations of BB 153 were generally low in these samples and ranged between ND and 0.89 ng/g. The developed method allows for the simultaneous determination of PBDE congeners and BB 153. It is efficient, moderately rapid and cost-effective.

Water SA, Apr 30, 2019

Mercury has been used for many centuries in the production of consumer products such as thermomet... more Mercury has been used for many centuries in the production of consumer products such as thermometers, electrical switches, fluorescent light bulbs, batteries, biocides and pesticides, cosmetics and dental amalgam filling, among others. After use, these mercury-containing consumer products form part of the municipal solid waste (MSW). As a result of an unseparated solid waste collection system, mercury-containing wastes tend to end up in landfills where mercury and other pollutants can leach out of products into landfill leachates. The present study, therefore, was conducted with the aim of determining the total mercury (THg) concentrations in leachate and sediment samples collected from 4 selected landfill sites (3 sites in Gauteng Province-Soshanguve, Hatherly, Onderstepoort and 1 site in Limpopo Province-Thohoyandou). Groundwater samples were collected from the monitoring boreholes at the four selected landfill sites in the summer and winter periods. An acid digestion method was employed for sample preparation and this was followed by analysis using cold vapour atomic absorption spectrophotometry (CVAAS). The concentration range of total mercury in the Thohoyandou leachate, sediment and groundwater samples was 0.12-2.07 µg/L, 0.03-0.48 µg/g and 0.09-2.12 µg/L, respectively. In Soshanguve, the concentration range of total mercury in leachate, sediment and groundwater samples was 0.10-1.20 µg/L, 0.04-0.62 µg/g and nd-1.66 µg/L respectively, Hatherly concentration range was 0.42-1.31 µg/L and 0.06-0.78 µg/g in leachate and sediment, respectively and in Onderstepoort the concentration range was 0.12-2.41 µg/L, 0.03-0.50 µg/g and 0.05-2.44 µg/L, in leachate, sediment and groundwater, respectively. The findings from this study suggest that there is a likelihood of groundwater pollution by mercury from landfill leachate seepage, particularly for landfills that are not lined with a geomembrane.

$Research paper thumbnail of Determination of mercury and its fractionation products in samples from legacy use of mercury amalgam in gold processing in Randfontein, South Africa$

Emerging Contaminants, Sep 1, 2016

This study aimed at determining the levels of total mercury (THg) in tailings dams, soil, sedimen... more This study aimed at determining the levels of total mercury (THg) in tailings dams, soil, sediments and water samples collected in the vicinity of legacy mercury amalgam gold mines. Acid digestion was employed in sample digestion followed by analysis using CVAAS. Tailings dams, community and garden soil, and stream sediments were further investigated for mercury fractions using a five step sequential extraction procedure. The concentrations of THg in tailings dams, community and gardens soil were 0.890e6.755 mg/g, 0.431e0.968 mg/g and 0.471e1.019 mg/g, respectively and the concentrations of THg in the sediments obtained from tailings dams, streams and wetlands were 0.649e1.998 mg/g, 0.604 e1.356 mg/g and 0.681e1.356 mg/g, respectively. The concentrations of THg, in aqueous samples obtained from tailings, streams and wetlands were 0.032e0.070 mg/l, 0.004e0.068 mg/l and 0.007e0.012 mg/l, respectively. The sequential extraction procedure showed that most Hg in the tailings dams was largely elemental Hg and Hg bound to sulphur. Soil and sediments were largely dominated by organic bound Hg. Moderate seasonal correlation was observed in tailings dams soil, but weak seasonal correlation in soils collected in the vicinity of tailings. However, a strong seasonal correlation was observed in sediments and water samples. The concentrations of Hg obtained largely existed in organic and sulphate bound Hg and there is elevated potential to methylate Hg.

Environmental Pollution, Nov 1, 2018

Polyurethane foam passive samplers were deployed between May 2016 and January 2017 to evaluate co... more Polyurethane foam passive samplers were deployed between May 2016 and January 2017 to evaluate concentrations of polybrominated diphenyl ethers (PBDEs), selected alternative flame retardants (AFRs) and total hexabromocyclododecane (HBCDD) (sum of a-, band nd g-HBCDD). The PUF air samplers were deployed in semieurban, urban, industrial and landfill sites in Gauteng Province, South Africa. The acquired results presented a clear semi urbaneindustrialeurbanelandfill concentration gradient for all BFRs measured. Taking into account 2 sampling periods (cold and warm periods) (n ¼ 16), the atmospheric concentrations of P 9 PBDEs, HBCDDs and P AFRs were 100e2820 pg m À3 , 12e117 pg m À3 and 41 e4660 pg m À3 , respectively, for the sparsely populated residential area, densely populated residential area, industrial area and the landfill area. In all cases, BDE 47, 99, and 209 were the most dominant congeners with high detection frequencies. The highest calculated daily exposure dose in Gauteng Province atmosphere was 0.61 and 1.54 ng kg À1 e bw d À1 for adults and children respectively. The estimated total intake of PBDEs was 0.47e33.4 ng kg À1 e bw d À1 , which was generally below the lowest adverse effect limit (LOAEL), suggesting that the residents of Gauteng Province may not be significantly affected as a result of their exposure to these pollutants through inhalation. However, this does not necessarily suggest that the pollutants are harmless to human health, since they have the tendency to bioaccumulate in biological systems. Incidentally, this is the first study from Africa to report on the atmospheric concentrations of PBDEs, HBCDDs and AFRs in urban, landfill and industrial areas. The findings from this study further highlight the contributory role of landfills as potential sources of BFRs into the atmosphere.

Environmental Science and Pollution Research, Jan 30, 2013

Until recently, studies reporting the concentrations of polybrominated diphenyl ethers (PBDEs) as... more Until recently, studies reporting the concentrations of polybrominated diphenyl ethers (PBDEs) as well as polybrominated biphenyls (PBBs) are generally scarce in the literature. Consequently, this study was aimed to investigate the occurrence and concentrations of certain PBDE congeners (BDE 28, 47, 100, 99, 154, 153, 183 and 209) and BB 153 in river water samples collected bi-monthly from the Diep River. The routine analyses of the target compounds were performed using a high-capillary GC-microelectron capture detection, while their structural elucidation was assessed using GC-TOF-MS technique. The overall mean concentrations of the sum of the eight PBDE congeners were 2.60, 4.83 and 4.29 ng/L for the upstream, point of discharge and downstream sampling points, respectively. Similarly, the overall mean concentrations of BB 153 were 0.25, 4.85 and 1.56 ng/L for the upstream, point of discharge and downstream sampling points, respectively. BDE 47 was the dominant congener found in these samples contributing between 19 and 26 % to the total PBDEs across the sampling points. The statistical analyses performed on the results obtained showed that all the congeners, except BDE 209 in certain instances, had strong positive correlations with one another, thus suggesting that these contaminants could be emanating from the same source. In this study, potential sources of these pollutants other than WWTP discharges into the investigated river were also identified. However, the relatively high concentrations of the target compounds found at the point of discharge sampling point coupled with the large volume of treated effluent being discharged suggested that the contributions from this source could be very significant over time.

Environmental Reviews, Dec 1, 2010

The presence of brominated flame retardants (BFRs) in various environmental matrices, including h... more The presence of brominated flame retardants (BFRs) in various environmental matrices, including humans, has been well documented. Increasing levels of these emerging contaminants in various environmental compartments suggest the wide application of these chemicals in products of everyday use. The release of BFRs from treated products is generally believed to be the major source of these contaminants into the environment, particularly in indoor environments. The sources and pathways through which BFRs enter the human system are evaluated in this paper. Human exposure via consumption of contaminated food and water, inhalation and ingestion of dust, as well as dermal absorption, are important pathways for these contaminants. Consumption of fatty foods especially fish, meat, dairy products as well as human milk constitute important routes for human exposure to these contaminants. Although brominated diphenyl ether (BDE) 209 has been found to be less bioaccumulative due to its high molecular weight, its dominance in indoor dust samples could be responsible for its detection in most human tissues investigated. BDE 47 is the most dominant polybrominated diphenyl ether (PBDE) congener found in human tissues. Regional differences in BFR levels in various environmental and biological matrices reflect their consumption patterns with higher levels mostly reported in the North American environments than in other regions of the world.

This chapter presents a general overview of the traditional extraction techniques commonly applie... more This chapter presents a general overview of the traditional extraction techniques commonly applied to both solid and liquid matrices are evaluated with a view to emphasize their sustained significance in a rapidly changing analytical chemistry discipline as evidenced with the introduction of newer and more sophisticated extraction techniques. For this purpose, the conventional Soxhlet extraction technique for solid matrices and the traditional liquid-liquid extraction techniques for liquid matrices are critically evaluated. The use of evaporation as a traditional method for extraction and/or separation of target analytes are also considered to further bolster the relevance of this technique in modern analytical chemistry studies. Besides the conventional sample extraction techniques such as Soxhlet extraction (SE), liquid-liquid extraction (LLE), and mechanical shaking, newer and more sophisticated techniques such as microwave-assisted extraction (MAE), accelerated solvent extraction (ASE), also known as pressurized liquid extraction (PLE), and supercritical fluid extraction (SFE), have been developed. Keywords: evaporation; liquid-liquid extraction; microwave-assisted extraction; pressurized liquid extraction; Soxhlet extraction technique; supercritical fluid extraction

Ecotoxicology and Environmental Safety, Apr 1, 2015

In this study, wild hatched eggshells were collected from the nests of the threatened Wattled Cra... more In this study, wild hatched eggshells were collected from the nests of the threatened Wattled Crane and South Ground-Hornbill in an attempt to determine total Hg concentrations. A total of fourteen eggshell samples from both bird species were collected from different study areas in the Mpumlanga and KwaZulu-Natal Provinces, South Africa. The eggshells were acid digested under reflux and their total Hg contents were determined using cold-vapour atomic absorption spectrophotometry (CV-AAS). The observed total Hg levels for the South Ground-Hornbill samples ranged from 1.31 to 8.88 µg/g dry weight (dw), except for one outlier which had an elevated 75.0 µg/g dw. The levels obtained for the Wattled Crane samples were relatively higher and these ranged from 14.84 to 36.37 µg/g dw. Generally, all the measured total Hg concentrations for the Wattled Crane samples exceeded the estimated total Hg levels derived for eggshell which were known to cause adverse reproductive effects in avian species from previous studies. Based on these findings, it is, therefore, possible that the exposure of these birds to elevated Hg may have contributed to their present population decline.

Environmental Reviews, Jun 1, 2017

The Minamata Convention on mercury has received a number of criticisms and challenges that potent... more The Minamata Convention on mercury has received a number of criticisms and challenges that potentially hinder its progress on reducing and controlling mercury use and release by Artisanal Small Scale Gold Mining (ASSGM). The resulting weak environmental control has repercussions for the social and environmental wellbeing of countries that subsist on ASSGM in their territory. Lack of distinguishing and categorizing ASSGM, the absence of a contextual implementation plan, and no defined means of communication are some of the aspects that lead to unsuccessful initiatives, particularly on effectively introducing mercury-free technologies. Moreover, an underestimation of the active mining population implies that the problem is greater than what is perceived. ASSGM is a viable source of poverty alleviation which cannot be ignored and therefore the resulting socioeconomic and environmental challenges need to be addressed while optimizing economic benefits. In this paper a compendium of issues and challenges that need to be addressed to reduce and control mercury use and release by ASSGM are discussed. By reviewing the challenges of successful case studies, a comprehensive approach is proposed to enhance the implementation of the Minamata Convention on mercury.

Science of The Total Environment, May 1, 2018

• XRF was used to measure the levels of bromine in electronic equipment and furniture. • GC-MS wa... more • XRF was used to measure the levels of bromine in electronic equipment and furniture. • GC-MS was employed in order to verify the presence of BFRs. • Legacy and novel BFRs were detected in the dust samples analysed. • The study provides first time concentrations of NBFRs and T-HBCDD in dust samples in South Africa.