Carbonate chemistry of groundwater from chalk,Givendale, East Yorkshire |
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| Authors: | JI Pitman |
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| Institution: | School of Environmental Sciences, University of East Anglia, Norwich, England |
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| Abstract: | Precipitation, soil and spring waters from an outlier of Chalk were analysed over a one year period for field pH, and contents of Ca+2, Mg+2, HCO3? and other dissolved solids. Measured soil log PCO2 (atm) varied between a minimum of ?2.60 and maximum of ?1.46, and could be predicted from measurements of soil temperature. Soil waters evolved under open system conditions with respect to soil CO2, and were undersaturated with calcite during the winter recharge period.The chemistry of the springs is related to their topographic position. Group 1 springs, located below a feather edge of chalk, had both their minimum and maximum PCO2s predicted by the soil CO2 data, suggesting open system CO2 evolution. Group 2 springs, located along the scarp slope had minimum PCO2s predicted by the soil data, but maximum PCO2s which could only be explained by a closed system evolution from the maximum soil CO2 observed. Group 1 springs were close to calcite saturation, whereas Group 2 springs were significantly undersaturated with calcite. The two groups could be identified by linear discriminant analysis of measured Ca2+, pH and HCO3? concentrations. |
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