What is the most abundant anions found in groundwater?

The most abundant anions found in groundwater are typically bicarbonate (HCO3^-), sulfate (SO4^2-), and chloride (Cl^-). Bicarbonate often dominates due to the dissolution of carbonates in the soil and rock, while sulfate and chloride can originate from both natural processes and anthropogenic activities. These anions play a crucial role in the overall chemistry of groundwater and can influence water quality.