7 results on '"Linda A. Lawton"'
Search Results
2. Polyamide microplastics in wastewater as vectors of cationic pharmaceutical drugs
- Author
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Anthony Wagstaff, Linda A. Lawton, and Bruce Petrie
- Subjects
Microplastics ,Environmental Engineering ,Chemistry ,Health, Toxicology and Mutagenesis ,Public Health, Environmental and Occupational Health ,General Medicine ,General Chemistry ,Wastewater ,Pollution ,Dilution ,Nylons ,Adsorption ,Pharmaceutical Preparations ,Desorption ,Environmental chemistry ,Environmental Chemistry ,Sewage treatment ,Water pollution ,Plastics ,Effluent - Abstract
Reported here is the first study to investigate the adsorption of pharmaceutical drugs to microplastics in wastewater. Wastewater is an environmental source of microplastics and pharmaceuticals, which is discharged as treated effluent or combined sewer overflows. In this study, adsorption of cationic pharmaceuticals, with a range of octanol-water distribution coefficients, to polyamide (Nylon 12) microplastics was investigated in real wastewater samples. Significant adsorption was observed for the more hydrophobic pharmaceuticals studied, propranolol, amitriptyline, and fluoxetine, with equilibrium reached within 24 h. Microplastic-wastewater distribution coefficients for these three pharmaceuticals were 191, 749 and 1020 L kg−1, respectively. Favourable wastewater conditions for adsorption of pharmaceuticals to polyamide were at pH > 7, summer temperatures (20 °C), and no stormwater dilution. Adsorption of the more hydrophilic pharmaceuticals atenolol, pseudoephedrine, metoprolol, and tramadol was ≤7% under all conditions and considered insignificant. Limited desorption (7–17%) of propranolol, amitriptyline, and fluoxetine was observed in river water over 24 h. This suggests that microplastics may be able to transport adsorbed pharmaceuticals for considerable distances after discharge. In simulated gastric fluids their desorption increased to 24–27% and 40–58% in cold- and warm-blooded temperatures respectively. The findings demonstrate that wastewater microplastics could act as a vector of pharmaceutical drugs, from wastewater treatment plants to aquatic organisms. However, further research is needed to better appreciate the risks posed by pharmaceuticals adsorbed to microplastics in comparison to other organic particulates found in wastewater.
- Published
- 2022
3. Oxidative stress in the cyanobacterium Microcystis aeruginosa PCC 7813: Comparison of different analytical cell stress detection assays
- Author
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José Capelo-Neto, Christine Edwards, Linda A. Lawton, Indira Menezes, Declan Maxwell-McQueeney, and Carlos J. Pestana
- Subjects
Cyanobacteria ,Environmental Engineering ,Microcystis ,Photosystem II ,Microcystins ,Health, Toxicology and Mutagenesis ,0208 environmental biotechnology ,02 engineering and technology ,Microcystin ,010501 environmental sciences ,Photosynthesis ,01 natural sciences ,chemistry.chemical_compound ,Extracellular ,Environmental Chemistry ,Animals ,Humans ,Microcystis aeruginosa ,Hydrogen peroxide ,0105 earth and related environmental sciences ,chemistry.chemical_classification ,biology ,Public Health, Environmental and Occupational Health ,General Medicine ,General Chemistry ,Hydrogen Peroxide ,biology.organism_classification ,Pollution ,020801 environmental engineering ,Oxidative Stress ,chemistry ,Biophysics ,Intracellular - Abstract
Cyanobacterial blooms are observed when high cell densities occur and are often dangerous to human and animal health due to the presence of cyanotoxins. Conventional drinking water treatment technology struggles to efficiently remove cyanobacterial cells and their metabolites during blooms, increasing costs and decreasing water quality. Although field applications of hydrogen peroxide have been shown to successfully suppress cyanobacterial growth, a rapid and accurate measure of the effect of oxidative stress on cyanobacterial cells is required. In the current study, H2O2 (5 and 20 mg L−1) was used to induce oxidative stress in Microcystis aeruginosa PCC 7813. Cell density, quantum yield of photosystem II, minimal fluorescence and microcystin (MC-LR, -LY, -LW, -LF) concentrations were compared when evaluating M. aeruginosa cellular stress. Chlorophyll content (determined by minimal fluorescence) decreased by 10% after 48 h while cell density was reduced by 97% after 24 h in samples treated with 20 mg L−1 H2O2. Photosystem II quantum yield (photosynthetic activity) indicated cyanobacteria cell stress within 6 h, which was considerably faster than the other methods. Intracellular microcystins (MC-LR, -LY, -LW and -LF) were reduced by at least 96% after 24 h of H2O2 treatment. No increase in extracellular microcystin concentration was detected, which suggests that the intracellular microcystins released into the surrounding water were completely removed by the hydrogen peroxide. Thus, photosynthetic activity was deemed the most suitable and rapid method for oxidative cell stress detection in cyanobacteria, however, an approach using combined methods is recomended for efficient water treatment management.
- Published
- 2020
4. Removal of microcystins from a waste stabilisation lagoon: Evaluation of a packed-bed continuous flow TiO
- Author
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Carlos J, Pestana, Peter, Hobson, Peter K J, Robertson, Linda A, Lawton, and Gayle, Newcombe
- Subjects
Titanium ,Microcystis ,Microcystins ,Marine Toxins ,Wastewater ,Cyanobacteria ,Waste Disposal, Fluid ,Water Pollutants, Chemical - Abstract
Photocatalysis has been shown to successfully remove microcystins (MC) in laboratory experiments. Most research to date has been performed under ideal conditions in pure or ultrapure water. In this investigation the efficiency of photocatalysis using titanium dioxide was examined in a complex matrix (waste stabilisation lagoon water). A flow-through photocatalytic reactor was used for the photocatalytic removal of four commonly occurring microcystin analogues (MC-YR, MC-RR, MC-LR, and MC-LA). Up to 51% removal for single MC analogues in waste lagoon water was observed. Similar removal rates were observed when a mixture of all four MC analogues was treated. Although treatment of MC-containing cyanobacterial cells of Microcystis aeruginosa resulted in no decline in cell numbers or viability with the current reactor design and treatment regime, the photocatalytic treatment did improve the overall quality of waste lagoon water. This study demonstrates that despite the presence of natural organic matter the microcystins could be successfully degraded in a complex environmental matrix.
- Published
- 2019
5. The degradation of microcystin-LR using doped visible light absorbing photocatalysts
- Author
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Linda A. Lawton, Douglas J. L. Graham, Peter K. J. Robertson, and Horst Kisch
- Subjects
Environmental Engineering ,Light ,Microcystins ,Health, Toxicology and Mutagenesis ,Microcystin-LR ,Microcystin ,Photochemistry ,Catalysis ,chemistry.chemical_compound ,Animals ,Humans ,Environmental Chemistry ,Environmental Restoration and Remediation ,Titanium ,chemistry.chemical_classification ,Public Health, Environmental and Occupational Health ,General Medicine ,General Chemistry ,Photochemical Processes ,Pollution ,chemistry ,Titanium dioxide ,Photocatalysis ,Marine Toxins ,Water treatment ,Marine toxin ,Visible spectrum - Abstract
Microcystins are one of the primary hepatotoxic cyanotoxins released from cyanobacteria. The presence of these compounds in water has resulted in the death of both humans and domestic and wild animals. Although microcystins are chemically stable titanium dioxide photocatalysis has proven to be an effective process for the removal of these compounds in water. One problem with this process is that it requires UV light and therefore in order to develop effective commercial reactor units that could be powered by solar light it is necessary to utilize a photocatalyst that is active with visible light. In this paper we report on the application of four visible light absorbing photocatalysts for the destruction of microcystin-LR in water. The rhodium doped material proved to be the most effective material followed by a carbon-modified titania. The commercially available materials were both relatively poor photocatalysts under visible radiation while the platinum doped catalyst also displayed a limited activity for toxin destruction.
- Published
- 2010
6. Biodegradation of microcystins and nodularin in freshwaters
- Author
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Christine Edwards, Nicholas Fowler, Linda A. Lawton, and Douglas J. L. Graham
- Subjects
chemistry.chemical_classification ,Cyanobacteria ,Environmental Engineering ,Microcystins ,biology ,Health, Toxicology and Mutagenesis ,Public Health, Environmental and Occupational Health ,Fresh Water ,General Medicine ,General Chemistry ,Microcystin ,Biodegradation ,biology.organism_classification ,Peptides, Cyclic ,Pollution ,Nodularin ,Hydrolysis ,chemistry.chemical_compound ,chemistry ,Environmental chemistry ,Microcystis ,Environmental Chemistry ,Water treatment ,Amino Acid Sequence ,Demethylation - Abstract
Microcystin-LR (MC-LR) was readily biodegraded on addition to six different water samples irrespective of their previous exposure to microcystins. Subsequent studies with water from three of these water bodies confirmed the degradation of MC-LR and also demonstrated the biodegradation of MC-LF, nodularin and mixture of microcystins and nodularin. Rates of degradation of MC-LR, MC-LF and NOD in individual water samples ranged from a half-life of 4 to 18d. Analysis by HPLC-PDA-ESI+ and MALDI MS/MS revealed novel intermediate degradation products of MC-LF and nodularin which included demethylation, hydrolysis, decarboxylation and condensation of the parent compound(s). Our study suggests a possible diversity of micro-organisms and/or pathways which has not been previously observed.
- Published
- 2008
7. The photocatalytic decomposition of microcystin-LR using selected titanium dioxide materials
- Author
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Detlef W. Bahnemann, Linda A. Lawton, Bernd Proft, Iain Liu, Peter K. J. Robertson, and Lei Liu
- Subjects
Environmental Engineering ,Microcystins ,Photochemistry ,Ultraviolet Rays ,Health, Toxicology and Mutagenesis ,Microcystin-LR ,Microcystin ,Cyanobacteria ,Catalysis ,Water Purification ,chemistry.chemical_compound ,polycyclic compounds ,Environmental Chemistry ,chemistry.chemical_classification ,Titanium ,Public Health, Environmental and Occupational Health ,General Medicine ,General Chemistry ,Cyanotoxin ,Pollution ,Decomposition ,chemistry ,Environmental chemistry ,Titanium dioxide ,Photocatalysis ,Degradation (geology) ,Marine Toxins ,Oxidation-Reduction - Abstract
Microcystins (cyclic heptapeptides) produced by a number of freshwater cyanobacteria are a potential cause for concern in potable water supplies due to their acute and chronic toxicity. TiO(2) photocatalysis is a promising technology for removal of these toxins from drinking water. It is, however, necessary to have a sufficient knowledge of how the catalyst materials cause the degradation of the toxins through the photocatalytic process. The present study reports microcystin degradation products of the photocatalytic oxidation by using a number of commercial TiO(2) powder (P25, PC50, PC500 and UV100) and granular (KO1, KO3, TiCat-C, TiCat-S) materials, so aiding the mechanistic understanding of this process. Liquid chromatography-mass spectrometry analysis demonstrated that the major destruction pathway of microcystin for all the catalysts tested followed almost the same pathway, indicating the physical properties of the catalysts had little effects on the degradation pathway of microcystin-LR.
- Published
- 2009
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