『Abstract
　Total dissolved inorganic carbon (TDIC) and its stable isotope ratio δ¹³CTDIC are used to trace the evolution of the carbon system of groundwater in three UK Permo-Triassic sandstone aquifers. Samples were collected from multilevel piezometers, open boreholes and sewer sampling points in the British Midlands (Nottingham, Birmingham and Doncaster) to evaluate both local and regional variations in δ¹³CTDIC. δ¹³C samples of matrix and pore water have also been analysed in each aquifer to further constrain the interpretations. Combining δ¹³CTDIC ratios with measurements of TDIC and pH clearly distinguishes the principal processes underlying the geochemical evolution of groundwater in Triassic sandstone aquifers, where processes can be both natural (e.g. carbonate dissolution) and anthropogenic (sewer-derived recharge). The paper shows that δ¹³CTDIC resolves ambiguities that arise from the interpretation of TDIC and pH measurements in isolation. Field measurements demonstrate that, under natural conditions, the carbonate system evolves similarly in each aquifer. An open-system evolution during recharge largely saturates the groundwater with carbonate depending upon its availability in the sandstone matrix. The contribution of sewer exfiltration to urban recharge is readily distinguished by lower pH and higher TDIC values without significant changes in δ¹³CTDIC.

Keywords: Carbon 13; TDIC; Permo-Triassic sandstone; Sewage; Urban groundwater』

Introduction
Study area
　Doncaster
　Nottingham
　Birmingham
Methodology
　Conceptual model
　Sampling and measurement techniques
Results and discussion
　Sewage
　Doncaster
　Nottingham
　Birmingham
　Synthesis of δ¹³CTDIC inferences in Triassic sandstone aquifers
Conclusions
Acknowledgments
References