THE GEOCHEMISTRY AND EVOLUTION OF NATURAL ORGANIC SOLUTES IN GROUNDWATER

This paper describes the organic carbon cycle of the recharge environment of a shallow, sandy aquifer, with an emphasis on the origin, flux and geochemical evolution of dissolved organic carbon using liquid chromatography, carbon isotopes and GC-MS techniques. The two components of DOC investigated are hydrophobic acids and C1-C-10 hydrophilic compounds. The C-14 activity of these components of the DOC was measured using TAMS. C-14 analyses of DOC components may provide an additional tool for groundwater dating. The initial C-14 activity of DOC in a recharge zone, however, depends mainly on the residence times and cycling of DOC sources in the recharge environment. Using C-14 DOC to estimate groundwater residence times between sampling points along a flow path compares well with residence times estimated on the basis of hydraulic parameters and C-14 DIC under closed system conditions.