GROUNDWATER TRACING WITH INJECTED HELIUM

Helium has several characteristics that make it attractive for use as a tracer in hydrological studies. Two types of experiments were conduc ted to investigate applicability of helium as a tracer of ground-water movement. The experiments included studies using laboratory sand and soil columns and field ground-water tracing in a basaltic aquifer. A w ater helium analyzer comprised of a thin quartz glass membrane and dio de ion pump (making use of the preferential permeation of helium throu gh the quartz glass into an evacuated space) was developed and used fo r the experiments. Results of our studies demonstrated that breakthrou gh curves of specific conductance and helium were similar under satura ted conditions. In the unsaturated sand/soil columns, breakthrough cur ves of helium were retarded relative to specific conductance reducing the usefulness of helium as a tracer.