The Occurrence and Spatial Dynamics of Trace Metals in the Topsoil of a Drained Meres and Mosses Habitat Area

Forshaw, C (2025) The Occurrence and Spatial Dynamics of Trace Metals in the Topsoil of a Drained Meres and Mosses Habitat Area. Doctoral thesis, Liverpool John Moores University.

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Abstract

Trace metal pollution is one of the most concerning of anthropogenic impacts on meres and mosses wetland habitats due to their toxicity, persistence and potential for bioaccumulation. The topsoil of these habitats provides a transfer interface for trace metal accumulation in the environment. This study aimed to elucidate the factors driving in-situ trace metal mobility in the topsoil of these habitats once the status of the topsoil of the habitat had been determined. A screening study was undertaken which examined physiochemical properties of the topsoil and determined its trace metal content via Field Portable X-Ray Fluorescence Spectroscopy (FPXRF). This study found there to be enrichment of trace metals within the topsoil of the region being studied and relationships with physiochemical properties, such as pH and organic matter content (OM), were then determined. The enrichment factor analysis results ranged from moderate for Ga, Rb, Co, V, Zn and Sn through to significant for Pb, As and Nb. The trace metal concentrations were then placed into context by examining widely cited soil quality guidelines. The screening study showed that some of these trace metals exceeded ‘target values’ of these soil quality guidelines. Some soil quality guidelines require an alternative analytical methodology, however. Inductively Coupled Plasma Mass Spectrometry (ICP-MS) with reverse aqua regia digestion was therefore implemented due to the analytical methodology having superior limits of detection and adhering to the requirements of the much-cited Finnish Soil Quality Guidelines (Decree 214/2007). Following a method development study to aid in method validity, a comparison study was undertaken so to determine if the results obtained from the acid extraction process (known as pseudo-total result) could be used to indicate the ‘total’ trace metal concentration result obtained via FPXRF. This study found significant relationships for select trace metals between the ‘pseudo-total’ result and the ‘total’ result. A focussed mesocosm study was then conducted on two representative topsoil samples within the sampling area. This study examined the influence of pH and soil organic matter content on the trace metal mobility within the porewater of the topsoil over the course of a calendar year and found that topsoil pH had a direct influence on trace metal mobility for many of the trace metals analysed and that OM content influenced the impact that the change of pH incurs. A chemical fractionation study was conducted on these two representative samples so to ascertain potential for bioavailability and to determine potential risk to the local environment and found that Cu, Pb and Zn reached the ‘Low Risk’ status of the Risk Assessment Code (RAC) in the topsoil. Knowledge garnered from the studies in this thesis will aid in conservation, mitigation and remediation of these environmentally valuable habitat types.

Item Type:	Thesis (Doctoral)
Uncontrolled Keywords:	Trace Metals; XRF; ICP-MS; GIS; PCA; Method Development; Heavy Metals; Soil Quality Standards; Mesocosm Study; Analytical Comparison; Screening Study; Spatial Mapping
Subjects:	G Geography. Anthropology. Recreation > GE Environmental Sciences
Divisions:	Biological and Environmental Sciences (from Sep 19)
Date of acceptance:	24 April 2025
Date of first compliant Open Access:	24 June 2025
Date Deposited:	24 Jun 2025 11:29
Last Modified:	24 Jun 2025 11:29
DOI or ID number:	10.24377/LJMU.t.00026496
Supervisors:	Byrne, P
URI:	https://researchonline.ljmu.ac.uk/id/eprint/26496

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