HYDROGEOCHEMISTRY OF THE PAST 25 AND NEXT 25 YEARS: A REVIEW OF FRANK SCHWARTZ’S CONTRIBUTIONS TO HYDROGEOCHEMISTRY AND THE STATE OF THE SUBDISCIPLINE

Frank Schwartz has covered a wide range of topics in hydrogeology in his productive career over five decades; he has mastered and contributed to both the physics and chemistry of hydrogeology. Geochemical processes occur in every segment of the hydrological cycle. The past 25 years saw a transformation of this scientific discipline from a “witch’s brew” into a credible science, and it has become an indispensable tool. In particular, tremendous progress has been seen in: (1) the use of isotopic and chemical tracers to quantify groundwater flow, recharge, and discharge; (2) kinetics of chemical reactions and geochemical modeling; and (3) mineral-water interfaces and control of contaminant fate and transport. Frank has pioneered or contributed in all these areas.

During the next 25 years, the warming climate, siting of geological repositories for nuclear wastes in many countries, geological carbon sequestration, intensified agriculture, and rapid deterioration of water quality in the less-developed world will all put the sustainability of water resources in peril. Hydrogeochemistry is crucial in addressing these important issues. We will likely see watershed-scale models that closely link hydrogeochemistry to atmospheric processes and biogeochemical cycles. Technological breakthroughs in mass spectrometers, synchrotron-based techniques, remote loggers of geochemical sensors, and big data will make hydrogeochemical data abundant and accessible.