Natural sediment may shield groundwater from arsenic
Contamination of deep groundwater with arsenic from shallower sources may not be as serious as feared — if pumping deep water is limited to domestic use, a study has found. Exposure to arsenic-contaminated groundwater has been linked to almost one in every five deaths in Bangladesh, and some 100,000 deep wells have been constructed to pump deeper, cleaner water. Recent modelling studies have suggested that these cleaner water sources are also being contaminated — from shallower water seeping down to replenish deeper wells.
But a study published in Nature Geoscience yesterday (9 October) found that natural adsorption of arsenic by sediment — sand in the aquifers — reduces contamination risk in most areas.
"Deep groundwater in Bangladesh is at risk from contamination by arsenic from shallow groundwater seeping downwards if not carefully managed," Yan Zheng, who co-authored the study while he was a senior scientist at Columbia University, United States, told SciDev.Net. "The risk is higher if deep groundwater is used for irrigation, which consumes a lot more water than [use for] domestic purposes."