Global Analysis and Prediction of Bicarbonate in Groundwater under Climate Change

Bicarbonate (HCO3–) is a major contributor to the alkalinity of groundwater, and low concentrations can reduce buffering capacity and increase the potential susceptibility of water to corrosion-related quality deterioration, particularly in untreated groundwater systems with corrosion-prone infrastructure. Here, we use machine learning and a comprehensive data set of 28,902 groundwater samples from 80 countries to produce a global probability map of HCO3– concentrations below 80 mg/L and estimate the population residing within the Low-Alkalinity Corrosion Risk Potential Zone (LACRPZ). From 2000 to 2020, LACRPZ was mainly concentrated in Southeast Asia and South America, with approximately 704 million people residing within these zones, particularly in Oceania (52.92%) and South America (35.09%). Although the area of LACRPZ is projected to decline under future climate change, the resident population in LACRPZ is expected to increase. This study reveals the evolution of global groundwater bicarbonate concentrations and resident population, underscoring the importance of integrating bicarbonate into water safety management strategies.