Development of a Time Efficient Method for the Determination of 210Pb, 210Bi and 210Po Activities in Seawater by Liquid Scintillation Spectrometry

Biggin, Colin David (2001) Development of a Time Efficient Method for the Determination of 210Pb, 210Bi and 210Po Activities in Seawater by Liquid Scintillation Spectrometry. PhD thesis, University of Glasgow.

Abstract

A time efficient method has been developed for the determination of the natural decay series radionuclides, 210Pb, 210Bi and 210Po in dissolved and particle associated phases of the marine water column. The disequilibria between parent-daughter pairs of natural decay series radionuclides can provide information on the rates of particle scavenging in the marine environment. The rates of removal of particle reactive radionuclides can be used, by analogy, to determine the rates of removal of particle reactive pollutants in the marine environment. The method utilises state of the art liquid scintillation spectrometry to directly determine 210Pb. Traditional methods rely on the ingrowth of 210Bi (t 1/2 5.013 days) or 210Po (t1/2 = 138.378 d) to determine Pb indirectly. The direct determination of 210Pb allows the whole procedure to be carried out in under 10 days, a significant time saving on the traditional methods. Various techniques for the pre-concentration and purification were investigated during this research. Much of the difficulty in the method development was as a result of trying to obtain a suitable matrix for liquid scintillation spectrometry. The pre-concentration stage was carried out using Fe(OH)3 to scavenge the dissolved metals from solution but the variation in recoveries required yield tracers to be applied. 210Pb (t 1/2= 10.6 hours) was utilised as a tracer for 210Pb and 207Bi was used as a tracer for 210Bi. Liquid scintillation spectrometry was used to determine 210Pb and 210Bi activities. However the requirement of 208Po as a tracer for 210Po meant that 210Po determination had to be carried out using a spectrometry as liquid scintillation spectrometry could not resolve the a peaks of 208Po and 210Po to a sufficient degree. With these problems overcome, the method was applied to a study of nearshore scavenging processes in the Irish Sea. The results obtained from this study were similar to other reported values of 210Pb and 210Po in the nearshore environment. Modelling of the data using a steady-state box model which accounted for atmospheric 210Po inputs allowed dissolved residence times to be determined. The method has the potential for future development to allow 234Th and 238U to be determined in the same sample which would allow rates of processes occurring on a range of timescales to be measured. However, the sample size should be increased for future applications to allow greater sensitivity due to the very low activities of 210Pb, 210Bi and 210Po present in the nearshore marine environment.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Additional Information: Adviser: Gordon Cook
• Keywords: Nuclear physics and radiation, Nuclear chemistry, Chemical oceanography, Analytical chemistry
• Date of Award: 2001
• Depositing User: Enlighten Team
• Unique ID: glathesis:2001-76057
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 19 Nov 2019 17:03
• Last Modified: 19 Nov 2019 17:03
• URI: https://theses.gla.ac.uk/id/eprint/76057