Genesis of geogenic contaminated groundwater: As, F and I

Chronic exposure to geogenic contaminated groundwaters (GCGs) has caused serious health problems among billions of people worldwide. The hydrogeological features, main sources of geogenic hazardous substances, dominant hydrogeochemical processes and key factors controlling the occurrence of high arsenic (As ≥ 10 μg/L), high fluoride (F ≥ 1 mg/L), and high iodine (I ≥ 100 μg/L) groundwater are discussed in this review. Although the global and/or regional occurrence, and the environmental and geochemical behaviors of groundwater As, F and I have been well documented in the past three decades, there is still a lack of holistic theoretical analysis to demonstrate the hydrogeological patterns of their (co)occurrence. We here propose four basic genetic types of GCGs by summarizing the characteristics of the distribution and major hydrogeochemical processes: leaching-enrichment type, burial-dissolution type, compaction-release type, and evaporation-concentration type. The complex genetic mechanisms of GCGs are thus integrated into a new theoretical framework to improve our understanding of their genesis and our capability of predicting their spatial and temporal distribution. Moreover, new paradigms of interdisciplinary convergent research are required to find best solutions to ensure the sustainable safe supply of groundwater resources and the well-being of the groundwater-dependent ecosystems and the human society.