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Title: The Natural (Baseline) Quality of Groundwaters in England and Wales - Magnesium Limestone of Yorkshire and Northumbria
Author: (7) British Geological Survey - L J Brewerton
Author: W M Edmunds
Author: Environment Agency
Document Type: Monograph
Annotation: Environment Agency Project ID:EAPRJOUT_973, Representation ID: 290, Object ID: 2260
This document forms one of the regional studies being carried out on representative aquifers or parts of aquifers in England and Wales to provide an improved understanding of the natural baseline quality of groundwaters. It serves as a reference document against which current water quality and future trends (improvements and deteriorations) may be assessed. Section I provides a brief summary of the water quality situation and in section II, further information is given concerning the controls on water quality necessary for an informed interpretation of the hydrogeochemical data. The natural baseline quality of groundwaters. from the Magnesian Limestone is discussed in Section II of this report. The approach adopted is described in Appendix 1. The median concentrations given in Table I.1 of this section may be regarded as the best single value for baseline compositions. Two sets of values are given: one for the Yorkshire area and the other for Northumbria. The upper. baseline value is defined by the 95 percentile. Values in excess of this are likely to be due to pollution. In the Yorkshire Magnesian limestone sources, some 60% of the groundwaters analysed have significant contributions from agricultural nitrate. In Northumbria the number is probably around 20%. The major ion characteristics of the Magnesian Limestone aquifer are summarised in two Piper diagrams. The cations are dominated by Ca and Mg derived from the dolomitic limestone. The anions are dominated by HCO, from carbonate minerals and SO, derived from gypsum. Sulphate concentrations tend to be higher in Yorkshire groundwaters than in Northumbria, probably due to more extensive dissolution of gypsum. Chloride concentrations are generally low but occasional high values occur, probably due to the dissolution of halite. The concentrations of most minor and trace elements are low with the exception of Fe, Mn and F. The median concentration of F in the Northumbria section is 0.7 mg l-l and indicates that a source of F must exist, within the formation probably as traces of fluorapatite in the carbonates. Selenium is detectable in the Yorkshire groundwaters.
Publisher: Environment Agency
Subject Keywords: GroundwaterWater qualityHydrologyBaseline surveysPesticidesNitratesDolomiteCalciumMagnesiumFreshwater ecology
Geographic Keywords: YorkshireNorthumberland
Extent: 39
Total file downloads: 136

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