Thesis

A study of potentially toxic elements in the Forth and Clyde Canal, Scotland, UK

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Awarding institution
  • University of Strathclyde
Date of award
  • 2013
Thesis identifier
  • T13623
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Abstract
  • Canal sediments are an important geochemical indicator of the pollutant status of both the waterway itself and the surrounding area. In this study, sediment samples were collected from the Forth and Clyde Canal, Scotland, UK, and analysed for potentially toxic elements (PTE). Pseudototal concentrations of As (5.54 - 219 mg/kg), Cd (< 0.000557 - 11.0 mg/kg), Cr (44.8 - 883 mg/kg), Cu (39.3 - 618 mg/kg), Fe (35.8 - 72.1 g/kg), Mn (720 - 4460 mg/kg), Ni (42.0 - 154 mg/kg), Pb (93.9 - 2740 mg/kg), Sn (5.36 - 122 mg/kg), and Zn (288 - 3640 mg/kg), measured by ICP-MS, were lower than those reported by British Waterways in 1992 but higher than relevant environmental quality standards, as was the Hg concentration (0.589 - 9.19 mg/kg) determined using CVAFS. The concentration of Fe was relatively constant, but an urban/rural divide was evident in the concentrations of the other analytes, indicting significant anthropogenic input, most likely due to runoff of contaminated urban soils. High levels of analytes at particular locations could often be attributed to historical industrial activities. For site-by-site comparisons, PTE concentrations were normalised to account for organic matter content. The modified BCR sequential extraction was applied to fractionate the PTE content (except for Hg) and estimate their potential mobility. A risk assessment code calculation showed that the mobility order was: Cd/Mn/Zn>As/Fe/Pb>Cr/Cu>Ni>Sn. However, levels of Cd were generally low. The analyte of greatest concern was Pb with up to 1960 mg/kg released between the acid exchangeable and reducible fractions. Concentrations of methylmercury (Me-Hg), monobutyltin (MBT), dibutyltin (DBT) and tributyltin (TBT) were measured using GC-ICP-MS. Levels of Me-Hg (3.44 - 14.1 μg/kg) were < 0.58% of the pseudototal Hg content. The likely source is in situ bacteria-mediated methylation of inorganic Hg. Organotin mean concentrations were low at 28.6 - 71.8, 48.7 - 113, and 48.2 - 189 μg/kg for MBT, DBT and TBT, respectively.
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DOI
Date Created
  • 2013
Former identifier
  • 1004066

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