Arsenic pollution in deep drinking wells in Yuncheng Basin, China: occurrence and mechanisms

Arsenic pollution in groundwater caused serious environment and health problem world widely. Few are reported for the occurrence and mechanisms of arsenic pollution in deep aquifers, though it is well documented by numerous study for arsenic enrichment in shallow groundwater. In this study, arsenic pollution was found in deep wells for drinking purpose. A total of 112 drinking groundwater samples, with burying depths 80 620 m, were collected from sedimentary aquifers in Yunchemg Basin, China. Hydrogeochemistry and geochemical statistical methods were conducted together to investigate the occurrence and mechanisms controlling arsenic concentrations in deep aquifers in the area. Our results show that c.a. 13 % of deep groundwater are enriched with arsenic (> 10 μg/L). The arsenic polluted groundwater are concentrated in aquifers with burying depth 200-300 m in low lands and lacustrine deposition areas in the south-central basin. We also find that the major factors responding for As enrichment in groundwater include: 1) desorption of fluoride from the mineral/organic matter surfaces under alkaline condition; 2) anthropogenic contamination, using of pesticides and fertilizer, introducing As into groundwater. Our findings suggest that cautions should be made for the management of deep As contaminated groundwater.