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Title: The impact of heavy metal contamination on the soil quality and microbiome of an urban allotment in Greenock, Scotland
Author: Uchegbu, Andrea Munachiso
ISNI:       0000 0004 9351 7577
Awarding Body: University of the West of Scotland
Current Institution: University of the West of Scotland
Date of Award: 2017
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Allotments, which are community gardens owned and managed by the local authority, are in huge demand because of their economic and health benefits but are marred with heavy metal contaminations (PTE) that affect soil, plant and human health. Thus, a study has been designed to catalogue PTE contaminants in an allotment in Greenock, and investigate their impact on prokaryote and eukaryotic microbiome and these parameters were then used to develop a soil health index. The role of a prokaryote and eukaryotic organism in bioremediation and nitrogen recycling to improve soil health was also investigated. All measured parameters belonging to the three class of soil properties were estimated using standardized techniques; the metal contents were measured using two extraction (Palintest and aqua regia) and two analytical (Palintest and ICP-OES) methods. The soil quality of the plots were calculated by incorporating the soil biomass data into existing SQI’s developed by Amacher et al (2007) and Yao et al. (2013). Using molecular biology techniques, the nitrogen recycling pathway in the eukaryote, Acanthamoeba was identified, and Al-resistant bacteria and Acanthamoeba cells were also isolated and identified from plots of the allotment. The results showed that the soil’s microbiome was affected by the concentrations of Al3+ with Mn2+ in low pH soil samples and NO3- with NH4+ producing low and high biomass respectively. The index developed through the use of the soil’s physical, chemical and biological characteristic correlated with both measures of microbiome biomass but not with other indices described previously e.g. BCSR, SLAN, Ca:Al and Ca: Mg ratios. It was demonstrated that the eukaryote, Acanthamoeba while sensitive to Al3+ and Mn2+ but not Fe3+ could use the eukaryotic nitrate reductase pathway in its gene content, identified by bioinformatics, to salvage NO3- from the soil and convert it to NH4+ to improve soil health. However, the amount of NH4+ excreted exceeded the concentration of NO3- salvaged. Interestingly, phylogenetic analysis of Acanthamoeba isolated from this allotment identified a genotype, not previously reported in the literature. Micrococcus luteus isolated from the Al3+ contaminated soil accumulated Al3+ in its cytosol in in-vitro feeding experiments. In conclusion, high concentration of PHEs in urban soils affects the soil’s microbiome leading to a decreased soil quality which can in turn be improved by exploiting the nitrogen metabolic pathway of Acanthamoeba cells or via the introduction of Al-resistant bacteria in the case of Al-contaminated soils. More so, there exists a high possibility of the emergence of a new Acanthamoeba genotype which is proposed to improve soil quality.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available