Principal component analysis of fluoride geochemistry of groundwater in Shanxi and Inner Mongolia, China By Shan Hu, Ting Luo, Chuanyong Jing

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 0.3–5.6 mg/L, exceeded WHO standards of 1.5 mg/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.