Geochemistry of groundwater: Major and trace elements

This chapter reviews the geochemistry of groundwater systems from near the surface to kilometers depth in various terrestrial environments. Recent advances in sample collection, analysis, interpretation, and modeling are highlighted, along with ongoing challenges. Solute and isotope tracers are integrated to describe how these systems evolved to their specific major ion and trace element chemistries, including water-rock-microbial processes, natural and anthropogenic perturbations, and mixing. New geochemical databases are utilized to provide continental-scale insights into groundwater chemistry. The chapter concludes with geochemical research opportunities on the horizon to help address environmental and societal challenges related to groundwater and the climate crisis.