Water samples were collected from six aquifers and three rainstations in the UK. Boron and major cations were determined using inductively coupled plasma - atomic emission spectrometry, while anions were determined using ion chromatography. Prior to boron isotope ratio determination, the boron was separated from the matrix and preconcentrated using ion exchange chromatography. The Inductively coupled plasma mass spectrometer was optimised for preCise and accurate boron isotope ratio determination with repect to nebuliser noise, sample carry over, senSitivity, mass bias and data acquisition. Under optimum conditions a precision of 0.2 %RSD ( 1511] of 20 / 00 ) at a boron concentration of 200 pg.rl was achieved. Major element chemistry identifies that the chalk aquifers of the Isle of Wight and Buckinghamshire, and the Lincolnshire Limestone as Ca HC03-type waters. The Lower Greensand unconfined groundwaters also have Ca HC03- chemistry, whilst the confined zone is characterised by NaCl waters. The Ashdown Sands groundwaters are NaHC03- type waters whilst the continental sands of the Otter Valley are (Ca + Mg) HC03- waters. Generally, boron concentrations in the confined zones of the aquifers are higher than the unconfined. For example, the Lower Greensand unconfined groundwater have a boron concentration ranging from 14 to 49 pg.rl , whilst the confined have a range from 59 to 145 )JgII. The boron isotopic signature (811J3) for the range of waters sampled ranges from -14 to + 48 0/00 , For precipitation samples the ratio is very variable, and the smallest range is seen for the stream samples. The main controls on boron geochemistry in the groundwaters are precipitation, water-rock interaction, mixing with connate waters and isotopiC equilibration. Precipitation is the dominant control on the limestone aquifers, which contrasts with the Lower Greensand and Ashdown Sands where waterrock interaction and mixing with connate waters are most significant. The boron geochemistry of the Otter Sandstone is probably controlled by precipitation and water-rock interaction.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:243580 |
| Date | January 1996 |
| Creators | Porteous, Nicola Claire |
| Publisher | Royal Holloway, University of London |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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