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Title: Growth studies of an autochthonous drinking water microorganism : Aquabacterium commune
Author: Bachmann, R. T.
ISNI:       0000 0001 3434 8564
Awarding Body: University of Sheffield
Current Institution: University of Sheffield
Date of Award: 2006
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Results from the optimisation of the DPASV technique showed that a drop size of 4 appeared to give the best overall performance in terms of precision in multi-elemental (Zn, Cd, Pb, Cu) trace analysis. A deposition time of 60 s was sufficient to accurately determine the concentration of Zn, Cd, Pb and Cu between 1-200 ppb. It is suggested to use ultrapure 0.1M KNO3 instead of 3M KCI as electrolyte in the reference electrode to minimise sample contamination. 1/10 KM samples for multi-elemental analysis by ICP-MS should be diluted by a factor of 10 to ensure that the total dissolved solids concentration remains well below 0.2 % (w/v). Greater dilution factors may improve the accuracy of Na, Mg and K measurements but may result in a loss of elements present at low ppb concentrations. From studies on 1/1 KM it is concluded that the oxidation of Fe2+ to Fe3+ and subsequent formation of Fe(III)PO4 Fe(III) OOH and Fe2O3 can be considered the dominant precipitation reactions in autoclaved and non-autoclaved 1/1 KM. It was suggested that filter-sterilised FeSO4 should be added separately to the autoclaved, cooled medium in order to minimise the premature formation of Fe3+ precipitates as well as the oxidation of Fe2+ under oxic conditions. ICP-MS and DPASV results indicated that Zn concentration in 1/10 KM increases after autoclaving. Cadmium, Pb and Cu concentrations were found to be less than 0.1 ppb (near LoD). ICP-MS data have also shown that common borosilicate glass components such as B, Ba, Na, A1 and Zn are present at elevated levels. In order to avoid sample contamination in metal uptake studies it is recommended to use PP or Teflon. DPASV experiments with EDTA in a 3M buffer showed that 0.538 μM EDTA complexed 35 % less Pb2+ than theoretically possible. It is likely that heavy metal contaminants were present in the 3M buffer using up the remaining binding sites of the EDTA. The experiment in general demonstrated that DPASV is a suitable technique to study metal complexation and monitor the labile (bioavailable) metal fraction in aqueous solutions. The addition of 4 μM and 10 μM EDTA to non-autoclaved 1/10 KM resulted in a residual labile Zn2+ ion concentration of 0.8 and 0.3 nM, respectively. Labile Cd2+ and Pb2+ ion concentrations after EDTA addition were below the LoD. After autoclaving labile metal ions could not be detected, proving that EDTA retained its metal complexing capability. Based on ICP-MS and Visual MINTEQ results it is concluded that 10 μM EDTA was sufficient to complex Ca and Fe and prevent both from precipitating before and after autoclaving. However, 4 μM EDTA may be sufficient if FeSO4 is added to 1/10 KM after autoclaving.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available