Orientation studies of stream water hydrogeochemistry for environmental and economic applications in North Wales

Abstract

s 91 Orientation studies of stream water hydrogeochemistry for environmental and economic applications in North Wales P.R. Simpson 1, W.M. Edmunds 2, N. Breward 1, J.M.Cook 3, D. Flight 1 G.E.M. Hall4and T.R. Lister 1 1Geochemistry Group, British Geological Survey Nottingham NG12 5GG. UK 2Hydrogeology Group, British Geological Survey, Wallingford, OXlO 8BB, UK 3Analytical Geochemistry Group, British Geological Survey, Nottingham, NG 12 5GG, UK 4Geological Survey of Canada, 601 Booth Street, Ottawa, Ontario, KIA OE8, Canada The stream water hydrogeochemical database, prepared by the BGS's Geochemical Survey Programme in conjunction with databases for stream sediments , soil samples and mineral concentrates, has recently 'been enhanced for a range of economic and environmental objectives. The density of systematic stream water sampling and analysis has been increased to one sample per km 2 and a much broader spectrum of additional determinands introduced. An orientation suite of coregistered hydrogeochemical maps has been produced from water samples collected at 1,279 sample sites in North Wales. The preliminary results obtained indicate that bedrock geology and mineralisation are the most important variables which influence the surface water chemistry. These primary geological parameters are variously modified by secondary influences which include a tmospher ic (c l imat ic and coastal effects) , a n t h r o p o g e n i c ( ag r i cu l tu re and urban developments) and geomorphological factors. Such regional hydrogeochemical stream water maps have a wide range of economic and environmental appl icat ions, especial ly when interpreted in conjunction with geological data. Results obtained so far indicate that interpretation is likely to be further enhanced in the future by comparison with regional stream sediment , hydrogeolog ica l , geomorphologica l , pedological , agricultural, landuse, climatic and remotely sensed datasets in a GIS environment. Hydrogeochemical sampling and analysis therefore represents a costeffective addition to the Regional Geochemical Survey of the UK. The identification of mining related contamination in the UK using high resolution geochemical mapping: examples from Northeast England and North Wales D.M.A. Flight, T.R. Lister and F.M. Fordyce Geochemistry Group, British Geological Survey, Nottingham NG 12 5GG, UK The Geochemical Survey programme (GSP) of the BGS is currently undertaking the systematic multi-element regional geochemical mapping of the UK landmass° The GSP database presently holds information on the concentration of up to 35 elements determined in stream sediment, stream water, heavy mineral concentrate and soil samples collected at an average aensity of one sample per 1.25 km 2 in an area of northern Britain extending f rom S h e t l a n d to Nor th Wales. R e g i o n a l geochemical maps based on analysis of high density stream sediment samples from Northeast England and North Wales, both of which contain historically important mining fields are considered here. The Northern Pennine Orefield has been worked from Roman times until the early parts of this century primarily for galena but also for associated Zn, Ba and Cu bearing ores. The many historical mining centres of North Wales include Halkyn-Minera (Pb-Zn), Llanlwst (Pb-Zn), Llansannan (Cu-Pb-Zn), Beddgeler t (Cu-Pb-Zn) and Parys Mountain, Anglesey (Cu).