Saudi Cultural Missions Theses & Dissertations
Permanent URI for this communityhttps://drepo.sdl.edu.sa/handle/20.500.14154/10
Browse
2 results
Search Results
Item Restricted Multimarker Metabarcoding of Prokaryotic and Eukaryotic Communities in Contaminated UK Estuaries(Saudi Digital Library, 2025-06-02) Aleidan, Abdullah; Grant, Alastair; Tolhurst, TrevorAnthropogenic metal contamination, particularly from historic mining, has led to persistent copper enrichment in estuarine sediments of southwestern England. Although this contamination is well documented, its ecological consequences remain less understood, especially in microbial and meiofaunal communities, which can offer early indicators of pollution. This thesis aimed to determine (i) whether a multi-marker metabarcoding strategy (16S, ITS, 18S, 28S, COI) can better detect pollution-induced changes compared with single- marker approaches (ii) which taxa respond most consistently to elevated metal levels and (iii) whether porewater copper more accurately predicts benthic community shifts than sediment copper concentrations. Field sampling encompassed 12- and 34-site datasets across major estuaries, covering porewater Cu concentrations from 4.6 to over 400 µg/L. Sediment DNA was extracted in triplicate at each site. Amplicon sequencing of multiple markers profiled bacterial, archaeal and eukaryotic assemblages. Statistical analyses linked community data to copper levels (porewater and sediment), revealing thresholds for compositional turnover. Bacterial and archaeal communities underwent threshold-like shifts near 20 µg/L porewater Cu, with archaea showed greater sensitivity in more uniform site subsets. Eukaryotic assemblages, particularly nematodes and alveolates, exhibited marked changes at heavily contaminated sites, corroborating previous morphological observations. Multi-primer metabarcoding captured a broader range of taxa than single markers alone but remained limited by primer biases and incomplete reference databases. These results refine pollution threshold estimates and highlight porewater copper as a strong predictor of community disruption. Archaea emerged as potential bioindicators, responding more sharply to contamination than bacteria. The multi-marker approach significantly improves ecological resolution, underscoring the importance of integrating morphological and molecular data. Moving forward, enhancing primer sets, expanding databases and applying functional assays (e.g. metatranscriptomics) will further strengthen the use of metabarcoding in environmental management and remediation efforts.8 0Item Restricted Adsorption of Heavy Metals onto Thermochemically Treated Waste Materials(University of Newcastle, 2024) Alatawi, Rehab; Donne , ScottHeavy metals pose serious environmental threats due to their toxicity, impacting both health and ecosystems. Among the various technologies for removing heavy metals from aqueous solutions, adsorption is widely recognized as one of the most efficient. Biochar, with its remarkable efficiency as an adsorbent for heavy metal removal, has attracted considerable attention This thesis focuses on how biochar, produced under varied pyrolysis conditions, effectively adsorbs heavy metals, offering strong evidence of its efficacy in this regard. Chapter 3 investigates how different pyrolysis conditions, such as temperature, atmosphere, heating time, and activation agents, affect the physical and chemical properties of biochar derived from pine wood chips and sugarcane trash and its ability to adsorb heavy metal ions. Scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) were utilised to analyse the biochar's surface area, pore size, and functional groups. The adsorption capacity for heavy metal ions was evaluated using inductively coupled plasma-optical emission spectroscopy (ICP-OES). Results show that pyrolysis temperature notably impacts the surface areas of biochar, especially above 500°C, significantly affecting carbon surfaces. Consequently, higher pyrolysis temperatures lead to increased adsorption of heavy metal ions. Additionally, longer pyrolysis durations generally result in higher adsorption capacities. Furthermore, pyrolysis gases enhance surface areas and functional groups, making them highly effective at adsorbing heavy metals. Activated biochar with KOH significantly increased the porosity, pore sizes, and oxidative functional groups on its surface, thereby increasing its ability to adsorb heavy metals. In chapter four, the removal of cadmium (Cd (II)), copper (Cu (II)), lead (Pb (II)), and iron (Fe (II)) by biochar produced from pine wood chips and sugarcane trash under optimal (WC600, SC600) and suboptimal (WC300, SC300) pyrolysis conditions, considering factors such as temperature, atmosphere, activation, and duration, as detailed in Chapter 3, has been found to be the initial metal concentration and pH of the solution. The Langmuir isotherm model was employed to determine adsorption parameters. Surface complexation, ion exchange, and precipitation were identified as the primary removal mechanisms. Adsorption isotherm studies revealed that on WC600, the order of adsorption capacities was Pb > Cu > Cd > Fe, while on SC600, it was Cu > Pb > Cd > Fe. Conversely, on WC300 and SC300, the order was Cu > Fe > Pb > Cd due to the specific iv properties of these biochars. The pH of the solution has a significant impact on the adsorption of heavy metal ions onto biochar within the pH range of 1-8. Chapter 5 aimed to study the competitive adsorption of heavy metals in quaternary-metal solutions on KOH-activated biochars from pine wood chips and sugarcane trash (WC600 and SC600), focusing on equilibrium analysis. Batch experimental data fit the Langmuir model. The maximum adsorption capacities of metals by WC600 followed the order Fe (0.0033 mg g -1 ) > Cu (0.00182 mg g-1 ) > Pb (0.00112 mg g-1 ) > Cd (0.00035 mg g-1) , while for SC600, they were in the sequence Fe (0.00295 mg g-1 ) > Cu (0.00177 mg g-1 ) > Pb (0.00098 mg.g-1 ) > Cd (0.00036 mg.g-1 ) in the quaternary- metal adsorption isotherm. Fe exhibited the highest retention, while Cd showed easy exchange with Fe. Adsorption of Fe2+, Cu2+, Cd2+, and Pb2+ on WC600 reached equilibrium within 1 to 24 hours. Surface complexation, cation-cation interaction, precipitation, and ion exchange are crucial in biochar adsorption behaviour. Chapter six details the enhancement of activated pine wood chips and sugarcane trash by KOH through an electrochemical process to improve heavy metal ion removal from water. Treatment was carried out at different potentials (-0.3, -0.6, 0.3, 0.6, 1.5, 2 V) to modify the biochar. FTIR analysis identified oxygen, nitrogen, and carbon-containing functional groups on the modified biochar surface. Results show that higher potentials (1.5, 2 V) led to increased oxygen-containing groups on the biochar surface, improving the removal of heavy metal ions (Cu2+, Cd2+, Pb2+, Fe2+). Lead and iron had the highest adsorption rates, while cadmium had the lowest. Notably, treating with hydrogen peroxide at 2V enhanced cadmium adsorption. Electrochemically modified biochar offers an efficient method for removing heavy metal ions from wastewater, with benefits such as high efficiency, cost-effectiveness, and reduced processing time, making it a valuable tool for environmental remediation. This study's findings provide useful insights into developing biochar-based materials for wastewater treatment applications18 0