Geochemistry database audit : historical modifications and conditioning applied to First Series geochemical atlas data

This report describes work undertaken as part of the BGS Information Management Programme, with the aim of improving the quality, metadata attribution and utility of historical regional geochemical data stored in the Geochemistry Database. The particular focus of this report is the status of the earliest geochemical data generated by the ongoing Geochemical Baseline Survey of the Environment (G-BASE) project. Analysis of stream sediment samples collected in northern Scotland between 1969 and 1972 formed the basis of the first four published geochemical atlases covering Shetland, Orkney, Caithness and Sutherland. These four areas form a discrete unit in terms of utilising common sampling and analytical methodologies and are described hereafter as the “First Series” geochemical atlases. The data held in the Geochemistry Database for these areas has until recently been regarded as of unknown quality, with no known documentation regarding quality issues, intra- or inter-atlas modifications to data. The recent commencement of a systematic database audit, also undertaken as part of the Information Management Programme, has allowed these data to be examined in detail, which, in turn, has led to the production of this report, giving information on historical quality issues and modifications made to data in an attempt to provide a contiguous geochemical baseline for the British land area. The first part of the report introduces the project while subsequent sections describe the historical approaches taken to error control in G-BASE, and an element by element analysis of the status and quality of data with a record, where possible, of what modifications have been made in the past. The report appendices show historical documents that record modifications made to data that are relevant to the First Series atlases. The provision of the information presented in this report should lead to improved integrity of the database, and in turn increase the confidence of data users and enable informed treatment/manipulation of data to be undertaken during preparation of key products such as national geochemical maps