- Title
- Evaluation of spatial distribution and health risk of pesticide residues in the environmental matrices of buffalo river estuary and their removal using nanosponges and modified cyclodextrins
- Creator
- Mdeni, Nonkululeko Landy
- Subject
- Chemicals
- Subject
- Hazardous substances
- Subject
- Dangerous chemicals
- Date Issued
- 2023-03
- Date
- 2023-03
- Type
- Master's theses
- Type
- text
- Identifier
- http://hdl.handle.net/10353/27629
- Identifier
- vital:69321
- Description
- The contamination of lotic ecosystems caused by agricultural, industrial, and anthropogenic activities has attracted the attention of researchers, authorities, and scientists because these waterbodies are of social and economic importance to human livelihoods. Pesticides and insecticides are a group of compounds that are toxic to pests and insects, respectively. Organophosphate pesticides (OPs) can be released into different environmental matrices through several sources including agricultural and urban runoff. They are one of the three main classes of synthetic organic pesticides that are used in agricultural sector and very often end up in other destinations than their target sites. In this study, four OPs, namely, ronnel, malathion, parathion and Durban were investigated. The Buffalo River Estuary, located in East London, is one of most popular areas and the river is a major source of raw water abstraction for three municipalities in the Eastern Cape Province, South Africa. Sediment samples were collected from six points in the estuary and soil samples were taken from a nearby dumpsite in winter and spring seasons of 2021. The physicochemical parameters of the samples including particle size, moisture content, oil and grease and organic carbon were determined. The samples were then extracted by ultra-sonication, the final extracts were analyzed using GC-μECD and the risk quotient (RQ) method was used to evaluate the risk of OP exposure to aquatic organisms. Polymer modified cyclodextrin (β-CD) for the removal of parathion in sediment and soil was synthesized and the morphology of the modified β-CD and vibrations of the synthesized material were determined using scanning electron microscope (SEM) and Fourier transform infrared (FTIR) spectroscopy, respectively. The limit of detection (LOD) and the limit of quantification (LOQ) of the OPs investigated were in the range of 0.09 to 2.99 and 0.274 to 9.06 μg/L, respectively. OPs gave a good recovery except for malathion, which had a recovery percentage lower than 70%. Calibration curves were plotted for the four OPs and were linear with relative standard deviations (RSD) ranging from 1.02 to 3.50, and correlation coefficients (R2) ranging from 0.9935 to 0.9972. The mean concentrations for sediments and soil in both seasons varied from 0.00231 to 63.8 μg/g in winter and from 0.0017 to 36.6 μg/g in spring, with malathion being the predominant congener and dursban being the least dominant in both seasons. In winter, the particle size percentages of the sediment and soil samples ranged from 34.4 to 79.4 percentage, 15.4 to 23.9 percentage and from 7.77 to 38.3 percentage for coarse, medium, and fine fractions, respectively. While in spring, the particle size for the course, medium and fine mesh fractions ranged from 37.4 to 74.6 percentage, 14.1 to 25.1 percentage and 12.4 to 35.0 percentage respectively; the percentage moisture content varied from 43.0 to 73.1 in winter, and from 57.1 to 63.4 in spring. In the soil samples, the physicochemical properties were lower in winter except for the n- hexane extractable material (HEM), which significantly decreased in spring from 2.6 to 1.63 mg/kg; while for sediments, the oil and grease ranged from 1.77 to 10.3 mg/kg in winter and from 1.63 to 4.28 mg/kg in spring. The risk quotient method was used to determine the risk of OP exposure to sediment-dwelling organisms and the results obtained indicated that the levels of OPs in this study, especially dursban, can pose a high risk to the organisms in sediments, with RQs higher than ten (˃10) in both winter and summer. The Pearson product-moment correlation showed that parathion had a weak correlation with every other variable except for malathion in winter, whereas in spring, parathion correlated very weakly with malathion; suggesting that products containing parathion are mostly used to control pests found in crops, such as corn and mosquitos, which are most active in the spring season. There was a very strong correlation between dursban and ronnel in spring and winter, implying that an increase in dursban concentration resulted in an increase in the concentration of ronnel. To determine the efficiency of the synthesized adsorbent CD-chitosan-alginate for the removal of Parathion from soil and sediment, different parameters such as concentration, time, pH and dose were varied. The adsorption capacity was found to be highest at pH 2 (99.19 percentage), when 3 mL of the adsorbent was used for 30 minutes.
- Description
- Thesis (Msci) -- Faculty of Science and Agriculture, 2023
- Format
- computer
- Format
- online resource
- Format
- application/pdf
- Format
- 1 online resource (xvii, 105 leaves)
- Format
- Publisher
- University of Fort Hare
- Publisher
- Faculty of Science and Agriculture
- Language
- English
- Rights
- University of Fort Hare
- Rights
- All Rights Reserved
- Rights
- Open Access
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UFH Department of Chemistry
| Thumbnail | File | Description | Size | Format | |||
|---|---|---|---|---|---|---|---|
| View Details Download | SOURCE1 | MDENI FINAL DISSERTATION.pdf | 2 MB | Adobe Acrobat PDF | View Details Download |