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Abstract: Insightful knowledge of geochemical processes controlling fluoride (F) mobility is fundamental to understand the occurrence of elevated F in groundwater. Principal component analysis (PCA) was applied to explore the dominating factors in the F geochemistry in Shanxi and Inner Mongolia, two severely F-affected areas in China. Field sampling results of 111 tubewells showed that 26.1% of drinking water wells, with F concentrations in the range 0.3–5.6mg/L, exceeded WHO standards of 1.5mg/L. PCA with 16 geochemical parameters demonstrated that F occurrence in Shanxi could be the result of mineral weathering and water–rock interactions in the aquifer. Groundwater F concentrations increased with TDS in Shanxi, but not in Inner Mongolia. In agreement with our PCA, the occurrence of F in Inner Mongolia may be attributed to multiple processes including agriculture and mining activities, and water–rock interaction processes in the aquifer. Calcium is the scavenger of fluoride in Shanxi and Inner Mongolia. The results of this study further our understanding of the similarities and differences in the F occurrence and mobility at various locations. [Copyright &y& Elsevier]

Abstract: Insightful knowledge of geochemical processes controlling As mobility is fundamental to understanding the occurrence of elevated As in groundwater. A comparative study of As geochemistry was conducted in the Datong Basin (Shanxi) and Hetao Basin (Inner Mongolia), two strongly As-enriched areas in China. The results show that As concentrations ranged from <1–1160μgL−1 (n =37) in the Datong Basin and <1–804μgL−1 (n =62) in the Hetao Basin. The groundwater is of the Na-HCO3 type in the Datong Basin and Na-Cl-HCO3 type in the Hetao Basin. Silicate mineral weathering and cation exchange processes dominated the groundwater geochemistry in the two study areas. Principal component analysis of 99 groundwater samples using 12 geochemical parameters indicated positive correlations between concentrations of As and Fe/Mn in the Datong Basin, but no correlation of As and Fe/Mn in the Hetao Basin. Phosphate correlated well with As in the Datong Basin and Hetao Basin, suggesting phosphate competition might be another process affecting As concentrations in groundwater. High concentrations of As, Fe, and Mn occurred in the pe range −2 to −4. The results of this study further understanding of the similarities and differences of As occurrence and mobility at various locations in China. [Copyright &y& Elsevier]