Title: The Natural (Baseline) Quality Of Groundwaters In England And Wales: The Permo-Triassic Sandstones Of Cumbria, North-West England;
Author: Environment Agency
Author: British Geological Survey
Document Type: Monograph
Annotation: Environment Agency Project ID:EAPRJOUT_325, Representation ID: 77, Object ID: 1670
Abstract:
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 Vale of Eden forms a broad valley situated between the English Lake District and the western edge of the Pennines. The aquifer comprises sedimentary rocks of Permian and Triassic age. The main aquifers are represented by the Permian Penrith Sandstone and the Triassic St Bees Sandstone, separated by the St Bees/Eden Shales. The Permo-Triassic rocks of the area represent an important aquifer in north-west England, supplying water for public supply, local industry and as a bottled mineral water. The groundwaters are mainly of Ca-HCO, type, but other more evolved waters are present including Ca-Mg-SO,, Na-Ca-Cl and Na-HCO, types. The dominant water-rock interactions controlling water chemistry include the dissolution of minerals such as calcite, dolomite, gypsurn/anhydrite or halite. It is likely that the upper parts of the sandstone aquifers have been decalcified and this has led to waters being undersaturated with respect to calcite. The waters are generally oxidising and concentrations of Fe and Mn are generally low. However, where reducing conditions exist in the confined parts of the aquifer Fe is relatively high. Some waters contain extremely high Fe and Mn but these are unfiltered and the high concentrations are considered to represent particulate matter. Trace metal concentrations are generally low reflecting low concentrations in the aquifer rocks as well as the neutral to alkaline conditions in the aquifer, but there is often a correlation between high Fe and Mn and high trace metal concentrations. This is most likely a consequence of the adsorption of metals onto Fe and Mn hydroxide surfaces. Local relatively high concentrations of metals such as Pb and Zn are found associated with high solute Fe and Mn and may relate to the incorporation of metals associated with the dissolution of Fe and Mn oxy-hydroxide phases under reducing conditions. Fluoride concentrations are low reflecting a lack of fluorite in the aquifer. Concentrations of some solutes, particularly Fe and Mn vary significantly with time in some borehole waters, and this most likely relates to the incorporation of particulate matter. Most major elements show much less variation in general, although at some sites variations are significant.
Publisher: Environment Agency
Subject Keywords: Groundwater; Water quality; Baseline surveys; Hydrology; Freshwater ecology
Geographic Keywords: Cumbria
Extent: 48
Permalink: http://www.environmentdata.org/archive/ealit:4408
Total file downloads: 305
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