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Mining impact on stream sediment quality in County Antrim, Northern Ireland

Lass-Evans, S.. 2013 Mining impact on stream sediment quality in County Antrim, Northern Ireland. Edinburgh, UK, British Geological Survey, 19pp. (CR/13/130N) (Unpublished)

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Abstract/Summary

Historical mining activity has in some cases released large quantities of heavy metals into the fluvial environment of many settings around the world. County Antrim is one of the main areas in Northern Ireland known for historical mining, where 780 shafts and adits are associated with iron ore exploration, and where historically, ca. 700,000 tonnes of bauxite were produced. In order to assess the legacy of mining operations, it is important to understand the present (baseline) chemistry of the natural environment. Heavy metals resulting from mining activities need to be distinguished from products of natural variation and geological processes. Using geographic information systems (GIS) and multi-element diagrams ("spidergrams") for analysis, the project modelled the geological background of the area, and was able to distinguish whether high metal concentrations in stream sediments were of mining or of natural origin. Sub-catchments with enhanced sediment element concentrations relative to the geological background were identified; and enrichment factors (EFs), as a classification of the degree of enhancement above natural geological background due to mining activities, were calculated. Results of this study reveal that stream sediment compositions are mainly determined by the underlying geology. Sediment quality guidelines for As, Cd, Cu, Pb and Zn were exceeded by <10% of the samples in most sub-catchments, although 31% of the samples exceeded the guideline for As in the north-eastern coastal Glendun River sub-catchment. By contrast, more than 80% of the samples exceeded the sediment quality guidelines for Cr and Ni in most sub-catchments within the study area. However, these high, Cr and Ni (and also Cu) concentrations do not result from mining activities, and most likely reflect the association with their geological parent material. Mining (mainly iron ore and bauxite) has had no detectable impact on sediment quality in nine sub-catchments, while three coastal sub-catchments showed slight enrichments of either As and Sn or As, Ag, Co, Sb and Sn. However, as the EFs do not exceed 1.5, their enrichment can be classified as minor.

Item Type: Publication - Report (UNSPECIFIED)
Funders/Sponsors: NERC, European Union INTERREG IVA-funded Tellus Border project
Additional Information. Not used in RCUK Gateway to Research.: This item made open by author January 2014. This item has been internally reviewed but not externally peer-reviewed
Date made live: 09 Jan 2014 15:29 +0 (UTC)
URI: http://nora.nerc.ac.uk/id/eprint/504456

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