Elucidating mechanisms of sulfamethoxazole sorption onto bentonite in the presence of fresh liquid swine manure dissolved organic carbon
| dc.contributor.author | Hansima, Charitha | |
| dc.contributor.examiningcommittee | Zvomuya, Francis (Soil Science) | |
| dc.contributor.examiningcommittee | Farenhorst, Annemieke (Soil Science) | |
| dc.contributor.examiningcommittee | Indraratne, Srimathie (University of Winnipeg) | |
| dc.contributor.supervisor | Amarakoon, Inoka | |
| dc.date.accessioned | 2023-09-28T18:19:37Z | |
| dc.date.available | 2023-09-28T18:19:37Z | |
| dc.date.issued | 2023-09-11 | |
| dc.date.submitted | 2023-09-12T04:12:33Z | en_US |
| dc.date.submitted | 2023-09-28T17:21:45Z | en_US |
| dc.degree.discipline | Soil Science | en_US |
| dc.degree.level | Master of Science (M.Sc.) | |
| dc.description.abstract | The extensive use of sulfamethoxazole (SMX) as a veterinary antimicrobial in the Canadian swine industry increases its occurrence in manure. Land application of swine manure enhances the dispersal of SMX in the environment, increasing the risk of antibiotic resistance development in bacteria, one of the focal human health emergencies of our times. Humic acid (HA) and fulvic acid (HA) from the dissolved organic carbon (DOC) fraction in fresh liquid swine manure influence the sorption of SMX onto smectite clays, hence the environmental fate. This research aimed to elucidate the effect of fresh liquid swine manure DOC species in fresh liquid swine manure on SMX sorption onto bentonite. Specific objectives were to (i) elucidate the physicochemical characteristics of HA and FA isolated from fresh liquid swine manure DOC and (ii) assess their contribution to the mechanisms controlling SMX sorption onto bentonite clay. Humic substances were extracted and characterized for their physicochemical properties. A batch sorption study with a randomized complete block design was used to quantify the SMX sorption, explicit clay-mineral surface and interlayer sorption, and probe fluorescence quenching in humic substances by SMX. Results showed that FA was the dominant component of DOC in the fresh liquid swine manure examined in this study (10 FA: 1 HA). Thus, FA determined the major portion of organic matter coating on the mineral bentonite and binding of SMX. Spectroscopic analysis revealed that hydrophobicity (53.0% HA, 56.5% FA), hydrophilicity (34.0% HA, 35.1% FA), aromaticity (34.0% HA, 37.2% FA), and aliphaticity (66.0% HA, 62.7% FA) of the two humic substances were similar despite the differences in their functional groups. Solid state 13C-NMR data and X-ray Photoelectron Spectroscopic data revealed that the core and the surface of HA and FA secondary structures were substantially different. The orientation of functional groups in clay mineral-bound HA and FA and free aqueous HA and FA determined SMX sorption mechanisms. The abundance of surface-oriented phenolic functional groups in mineral-bound and free FA resulted in fluorophore quencher π-π electron-donor-acceptor interactions, cation and water bridging, and H-bonding. In contrast, the relatively high surface amide groups in HA structures allowed non-fluorophore quencher H-bonding, cation, and water-bridging mechanisms with SMX. Sorption data suggested the formation of extractable aqueous FA-SMX residues, whereas SMX complexed to aqueous HA is non-extractable. Spectroscopic data revealed a comparatively higher amount of -COOH functional groups in FA colloids, which made FA-SMX unstable and susceptible to breakdown in aqueous environments. SMX complexed with aqueous FA can be transported in rain and snowmelt runoff and leach into aquatic environments and subsequently desorbed. We suggest the storage of fresh liquid swine manure under aerobic conditions in open lagoons to oxidize FA functional groups or composting of the manure to hinder SMX sorption to FA before land application. Further, the transformation of FA to HA through humification under long-term storage may also contribute to reducing the sorption of SMX onto FA. | |
| dc.description.note | February 2024 | |
| dc.description.sponsorship | University of Manitoba Graduate Fellowship (UMGF) Manitoba Zero Tillage Research Association (MZTRA) soil conservation fellowship | |
| dc.identifier.uri | http://hdl.handle.net/1993/37738 | |
| dc.language.iso | eng | |
| dc.rights | open access | en_US |
| dc.subject | Fresh liquid swine manure | |
| dc.subject | Dissolved organic carbon | |
| dc.subject | Humic acid | |
| dc.subject | Fulvic acid | |
| dc.subject | Sulfamethoxazole | |
| dc.subject | Sorption mechanisms | |
| dc.subject | Bentonite clay | |
| dc.title | Elucidating mechanisms of sulfamethoxazole sorption onto bentonite in the presence of fresh liquid swine manure dissolved organic carbon | |
| dc.type | master thesis | en_US |
| local.subject.manitoba | yes | |
| project.funder.identifier | RGPIN-2022-04497 | |
| project.funder.name | Natural Sciences and Engineering Research Council of Canada Discovery Grant |