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Batch equilibrium studies on the adsorptive capacity of powdered and pelleted maize tassel to remove PFoA and PFoS from aqueous medium

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Emerging Contaminants 2022年第1期8卷 75-82页

作者： Pinky Mokwena o.j.okonkwo Department of Environmental Water and Earth SciencesFaculty of ScienceTshwane University of TechnologyPretoriaSouth Africa

This study was aimed at evaluating the potential of raw maize tassel powder and pellets to remove PFoA and PFoS from *** experiments were first conducted using ultrapure water to investigate the effects of pH,adsorbent dosage,initial PFASs concentration,contact time and temperature in adsorption efficiency of powdered and pelleted maize *** optimum conditions for the removal of PFoA/PFoS observed for both maize tassel powder and pellets were as follows:pH 2.0,adsorbate initial concentrations of 20 mg g1,adsorbent dosage of 0.5 g(20 pellets),1 h contact time,all at 25℃.These optimum conditions were,thereafter,applied to surface water samples from Apies River in Pretoria,spiked with 20 mg L^(-1)PFoS/*** LC-MS/MS was employed in analysis and the Langmuir and Freundlich isotherm models were used to determine the types of adsorption *** percentage removal 91.3%and 89.7%for PFoA and PFoS respectively using both MT powder and pellets were *** maximum adsorption capacities identified for the monolayer of the Langmuir isotherm model was found to be between 41.6 mg g^(-1)and 58.82 mg g^(-1)for PFoA using powder and pellets respectively;and between 42.37 mg g^(-1)and 176.5 mg g^(-1)for PFoS for the same adsorbents *** results showed very insignificant conformity to the Langmuir model;therefore it can be assumed that the Langmuir model was not ***,the experiments proved to be primarily consistent with the Freundlich model,with high correlation coefficient(R2)values ranging from 0.900 to 0.998 for both PFoA and *** adsorption capacities of 142.8 mg g^(-1)and 78.57 mg g^(-1)for PFoA and 107.4 mg g^(-1)and 85.7 mg g^(-1)for PFoS at 25℃using both powder and pellets respectively were obtained suggesting that adsorption took place on heterogeneous layers for both targeted PFASs.

关键词： Batch equilibrium Maize tassel PFASs Removal Aqueous medium

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The impact of a Wastewater Treatment Works in Southern Gauteng, South Africa on efavirenz and nevirapine discharges into the aquatic environment

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Emerging Contaminants 2017年第2期3卷 95-106页

作者： C.Schoeman M.Dlamini o.j.okonkwo Rand Water 2 Barrage RoadVereenigingSouth Africa Tshwane University of Technology 175 Mandela DrivePretoriaSouth Africa

There has been growing concern regarding the pollution of the aquatic environment with synthetic organic *** drugs,such as efavirenz and nevirapine,are pharmaceutical drugs and are referred to as emerging *** drugs can be environmentally persistent and may be expected to pose potential risks to drinking water *** of pharmaceutical drugs include effluents from Wastewater Treatment Works(WWTPs),hospital and pharmaceutical production facilities and the incorrect disposal of unused and expired *** there are no monitoring programs and legislative guidelines for their regulations in South *** aims of this study were firstly to develop a semi-quantitative method to extract and analyse efavirenz and nevirapine in the primary settling tank *** to use that method,and an existing method for liquid wastewater samples,to monitor the concentrations of efavirenz and nevirapine as the wastewater passes through the different stages of purification(anoxic;aerobic;pre and post chlorination)in the *** was repeated weekly over a period of 4 ***,to determine if binding of efavirenz and nevirapine to the solids in the WWTP played a role in the removal of these compounds from the WWTP liquid *** references to the analysis of ARVDs in WWTP sludge were found in the *** samples of wastewater and sludge samples were collected from a WWTP(activated sludge treatment process)weekly for 4 *** samples were extracted solid phase extraction,solid samples were extracted using sonication followed by a QuEChERs *** extracts were then subjected to gas chromatography-time of flight mass spectrometry for analyte *** concentrations entering the WWTP ranged between 5500 to almost 14000 ng/*** removal of efavirenz by the WWTP ranged between 27 and 71%.The largest removal occurred in the anoxic zone,smaller amounts were removed in the *** inc

关键词： Antiretroviral drug removal Wastewater Treatment Works Purification Aqueous Sludge Solid phase extraction Semi-quantitative Gas chromatography-time of flight mass spectrometry

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Seasonal variations and the influence of geomembrane liners on the levels of PBDEs in landfill leachates,sediment and groundwater in Gauteng Province,South Africa

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Emerging Contaminants 2017年第2期3卷 76-84页

作者： I.V.Sibiya o.I.olukunle o.j.okonkwo Tshwane University of Technology Department of EnvironmentalWater and Earth SciencesPrivate Bag X680PretoriaSouth Africa

In the present study,the seasonal concentrations of polybrominated diphenyl ethers(PBDEs)in leachate and sediment samples,and the influence of geomembrane liners on PBDE levels and the extent of their infiltration into groundwater on selected landfill sites in Gauteng Province,South Africa were *** and sediment samples were collected from seven operational landfill sites namely:Goudkoppies,Robinson Deep,Marie Louis,Soshanguve,onderstepoort,Hatherly and Garankuwa from johannesburg and Pretoria,in winter and *** samples were collected from monitoring boreholes from two landfill ***-liquid and Soxhlet extraction techniques were employed for the extraction of leachate and groundwater,and sediment respectively using *** extracted samples were subjected to column clean up and,thereafter,analysed using gas chromatographyemass spectroscopy(GC-MS).PBDEs selected for the study were:BDE-17,-28,-47,-100,-99,-153,-154,-183 *** P9PBDE concentrations in leachate samples for winter and summer ranged from 0.316e1.36 ng L-1 and 0.560e1.08 ng L-1 *** P9 PBDE concentrations obtained for sediment in winter and summer were 3.00e4.91 ng g-1 and 2.50e3.71 ng g-1 *** samples exhibited higher(poncentrations for both leachate and sediment samples compared to summer *** trend was attributed to high precipitation rate in summer which may have infiltrated into the landfills,subsequently diluting the leachate and sediment *** contrast,the winter period is generally dry and PBDEs are,therefore,more likely to be *** concentrations of PBDEs in leachate and sediment samples were higher in landfill sites with geomembrane liners compared to those without *** samples taken from the vicinity of selected landfill sites without geomembrane liners exhibited high concentrations of P9PBDEs,indicating possible migration of PBDEs from landfill site into ***

关键词： Seasonal trend PBDEs concentrations Landfill leachates Sediment Groundwater Geomembrane liners

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Apples to oranges:environmentally derived,dynamic regulation of serotonin neuron subpopulations in adulthood?

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Neural Regeneration Research 2025年第9期20卷 2596-2597页

作者： Christopher j.o’Connell Matthew j.Robson Department of Genetics College of MedicineHarvard UniversityBostonMAUSA james L.Winkle College of Pharmacy Division of Pharmaceutical SciencesUniversity of CincinnatiCincinnatiOHUSA Neuroscience Graduate Program College of MedicineUniversity of CincinnatiCincinnatiOHUSA

Traumatic brain injury(TBI)is a public health problem with an undue economic burden that impacts nearly every age,ethnic,and gender group across the globe(Capizzi et al.,2020).TBIs are often sustained during a dynamic range of exposures to energetic environmental forces and as such outcomes are typically heterogeneous regarding severity and pathology(Capizzi et al.,2020).

关键词： sustained orange dynamic

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Effects of cutting parameter on microstructure and corrosion behavior of 304 stainless steel in simulated primary water

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journal of Materials Science & Technology 2022年第27期122卷 219-230页

作者： Honglin Yan jianqiu Wang Zhiming Zhang Bright o.okonkwo Key Laboratory of Nuclear Materials and Safety Assessment Institute of Metal ResearchChinese Academy of Sciences School of Materials Science and Engineering University of Science and Technology of China

The influence of surface conditions on the corrosion behavior of engineering structures has been paid more ***,there is still a lack of systematic research on the effect of cutting parameters on material’s microstructure and performance in *** this paper,the effect of cutting parameters on microstructure and corrosion behaviors of 304 stainless steel in simulated primary water is well *** results show that different cutting parameters can cause the superficial layer a gradient microstructure with nanocrystalized layer on top and deformation band structures *** the similar surface roughness,the deformation microstructure can be very different due to the different cutting *** effect degree on the depth of deformation zone is feed rate>cutting depth>cutting *** larger feed rate,lower cutting depth,lower cutting rate may induce a deeper deformation *** the increasing depth away from the machined surface,the localized corrosion rate is decreased,and at the same depth the localized corrosion rate along the deformation bands is higher than that along the grain boundaries(GBs).The nanocrystalized surface has a smallest general corrosion rate due to the quick formation of Cr rich oxide ***,once the corrosion penetrates through this nanocrystalized layer,subsequent preferential corrosion at deformation bands and GBs will dominate and may lead to the significant increase of corrosion rate of the component in high temperature pressurized water.

关键词： Stainless steel Transmission electron microscopy(TEM) High temperature corrosion Cutting parameter

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A new method to determine the synergistic effects of area ratio and microstructure on the galvanic corrosion of LAS A508/309 L/308 L SS dissimilar metals weld

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journal of Materials Science & Technology 2021年第19期78卷 38-50页

作者： Bright o.okonkwo Hongliang Ming jianqiu Wang En-Hou Han Ehsan Rahimi Ali Davoodi Saman Hosseinpour CAS Key Laboratory of Nuclear Materials and Safety Assessment Institute of Metal ResearchChinese Academy of SciencesShenyang 110016China School of Materials Science and Engineering University of Science and Technology of ChinaShenyang 110016China Materials and Metallurgical Engineering Department Faculty of EngineeringFerdowsi University of MashhadMashhad ***Iran Polytechnic Department of Engineering and Architecture University of Udine33100 UdineItaly john A.Paulson School of Engineering and Applied Sciences Harvard UniversityCambridgeMA 02138USA Institute of Particle Technology(LFC) Friedrich-Alexander-Universitdt-Erlangen-Numberg(FAU)91058 ErlangenGermany

The synergistic effects of area ratio and microstructure on the galvanic corrosion of A508/309 L/308 L dissimilar metals weld(DMW)are studied by a multi-analytical *** was demonstrated that decreasing the anode/cathode surface area ratio obviously enhances the corrosion rate of A508,both locally and *** analyses of the AFM results enabled quantitative comparison of the corrosion behaviour of the different surface *** was revealed that in the galvanic interaction of the DMW,the grain refined region corrodes most,followed by the partial grain refined region and base metal matrix of the A508,*** electrochemical localization index(LI)estimation method and AFM analysis both confirmed the presence of a mixed(localized and uniform)corrosion phenomenon occurring on the surface of the A508 anode metal in the galvanic interaction of the dissimilar ***,the degree of synergism equation was utilized to describe the synergistic effects of anode/cathode area ratio and the microstructure of the samples on the galvanic corrosion of LAS A508/309 L/308 L SS DMW.

关键词： Low alloy steel Stainless steel SEM AFM Galvanic corrosion Inclusion

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occurrence,distribution and ecological risk assessment of organophosphorus flame retardants and plasticizers in sediment samples along the Vaal River catchment,South Africa

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Emerging Contaminants 2019年第1期5卷 173-178页

作者： Tlou B.Chokwe jonathan o.okonkwo Scientific Services Rand WaterP.O.Box 3526Vereeniging1930South Africa Department of Water Environmental and Earth SciencesTshwane University of Technology175 Mandela RoadPretoria0001South Africa

The occurrence,distribution and ecological risk assessment of twelve(12)organophosphorus flame retardants(oPFRs)were investigated in sediments from the Vaal River,South *** halogenated oPFRs[tris-(2-chloroethyl)phosphate(TCEP),three isomers of tris-(chloropropyl)phosphate(TCiPPs),tris-(1,3-dichloro-2-propyl)phosphate(TDCiPP)and tris-(2,3 dibromopropyl)phosphate(TDBPP)]and six non-halogenated oPFRs[tris-(n-butyl)phosphate(TBP),tris-(phenyl)phosphate(TPhP),tris-(butyl ethoxy)phosphate(TBoEP),tris-(2-ethylhexyl)phosphate(TEHP),diphenyl-2-ethylhexyl phosphate(DPEHP)and tris-(m-cresyl)phosphate(m-TCP)]were detected in this *** concentrations of twelve oPFRs in total(S12oPFRs)ranged from 68 to 278 ng g^-1 dry weight(dw)with the mean and median of 138 and 120 ng g^-1;*** non-halogenated oPFRs showed more abundances than the halogenated oPFRs with TDBPP,TBP,and TBoEP the most abundant ***,concentrations of oPFRs in more urbanized region were higher than those in less urbanized *** the concentrations of oPFRs and total organic carbon(ToC)were correlated,a moderate and significant correlation(pour results showed that m-TCP poses high risk(HQ>1)while TBoEP,TPhP,and TBP posed medium risk(0.1osing negligible risk(HQobtained in this study provides valuable information on the occurrence and risks of the investigated oPFRs within Vaal River.

关键词： oPFRs Concentrations Risk assessment Sediments Vaal river

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

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Emerging Contaminants 2016年第3期2卷 157-165页

作者： Tshia Malehase Adegbenro P.Daso jonathan o.okonkwo Department of Environmental Water and Earth SciencesTshwane University of TechnologyPrivate Bag X680175 Nelson Mandela DriveArcadiaPretoria0001South Africa

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 *** digestion was employed in sample digestion followed by analysis using *** dams,community and garden soil,and stream sediments were further investigated for mercury fractions using a five step sequential extraction *** 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,*** 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,*** sequential extraction procedure showed that most Hg in the tailings dams was largely elemental Hg and Hg bound to *** and sediments were largely dominated by organic bound *** seasonal correlation was observed in tailings dams soil,but weak seasonal correlation in soils collected in the vicinity of ***,a strong seasonal correlationwas observed in sediments and water *** concentrations of Hg obtained largely existed in organic and sulphate bound Hg and there is elevated potential to methylate Hg.

关键词： Mercury concentrations Fractions Gold mining Legacy amalgam Tailing dams Soil Sediment Water Speciation

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Erythrocyte sphingolipid species as biomarkers of Alzheimer's disease

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journal of Pharmaceutical Analysis 2022年第1期12卷 178-185页

作者： jericha Mill Vihar Patel ozioma okonkwo Lingjun Li Thomas Raife Department of Chemistry University of Wisconsin-MadisonMadisonWI53706USA Department of Pathology and Laboratory Medicine University of Wisconsin School of Medicine and Public HealthMadisonWI53705USA Clinical Science Center Wisconsin Alzheimer's Disease Research CenterUniversity of Wisconsin School of Medicine and Public HealthMadisonWI53792USA School of Pharmacy University of Wisconsin-MadisonMadisonWI53705USA

Diagnosing Alzheimer’s disease(AD)in the early stage is *** biomarkers can be of great value for population-based *** studies have been used to find potential biomarkers,but commonly used tissue sources can be difficult to *** objective of this study was to determine the potential utility of erythrocyte metabolite profiles in screening for *** some commonly-used sources such as cerebrospinal fluid and brain tissue,erythrocytes are plentiful and easily ***,erythrocytes are metabolically active,a feature that distinguishes this sample source from other bodily fluids like plasma and *** this preliminary pilot study,the erythrocyte metabolomes of 10 histopathologically confirmed AD patients and 10 patients without AD(control(CTRL))were *** blood was collected post-mortem and erythrocytes were analyzed using ultraperformance liquid chromatography tandem mass *** 750 metabolites were identified in AD and CTRL *** were increased in AD while 24 were decreased(Pjority of the metabolites increased in AD were associated with amino acid metabolism and all of the decreased metabolites were associated with lipid *** among the potential biomarkers were 10 sphingolipid or sphingolipid-related species that were consistently decreased in AD *** have been previously implicated in AD and other neurological ***,previous studies have shown that erythrocyte sphingolipid concentrations vary widely in normal,healthy ***,these observations suggest that certain erythrocyte lipid phenotypes could be markers of risk for development of AD.

关键词： Alzheimer’s disease Neurodegenerative disease Mass spectrometry Erythrocytes Biomarkers Metabolomics

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occurrence and distribution of tetrabromobisphenol A and its derivative in river sediments from Vaal River Catchment,South Africa

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Emerging Contaminants 2017年第3期3卷 121-126页

作者： Tlou B.Chokwe jonathan o.okonkwo Mutshinyalo S.Nwamadi Rand Water Scientific Services 2 Barrage RoadVereeniging1930 South Africa Department of Water Environmental and Earth SciencesTshwane University of Technology175 Mandela RoadPretoria0001 South Africa Spectra Analytical Facility University of JohannesburgKingsway RoadAuckland ParkJohannesburg2006 South Africa

Brominated flame retardants(BFRs)compounds have been widely added in a number of products to reduce their *** the present study,the concentrations and distribution of tetrabromobisphenol A(TBBPA)and its derivatives,*** dibromopropyl ether(TBPDBPE),tetrabromobisphenol A bis-dibromopropyl ether(TBBPA BDBPE),tetrabromobisphenol A bis-allyl ether(TBBPA BAE)were investigated in sediment samples collected from the Vaal River catchment,South *** results showed that all these pollutants were detected in sediments with TBBPA BAE being the most abundant *** TBBPA BAE concentrations ranged from 3.5 to 44.4 ng/g(mean 16 ng/g)while the concentration ranged from not detected(nd)to 2.4 ng/g(mean 0.6 ng/g),nd-21.0 ng/g(mean 6 ng/g)and nd-2.0 ng/g(mean 0.2 ng/g)for TBPDBPE,TBBPA and TBBPA BDBPE;*** concentrations of these pollutants were found in sampling sites receiving effluents of wastewater treatment works(WWTWs)treating some industrial wastewater suggesting effluents might play an important role in the contamination of BFRs in the *** correlation between TBBPA and TBBPA BAE was observed implying different sources or environmental fates between these ***,the results showed a need for further studies to be undertaken in investigating the presence,fate and sources of alternative halogenated flame retardants in the environment.

关键词： Brominated flame retardants Tetrabromobisphenol A derivatives Concentrations Sediments Vaal river

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