Do arsenic concentrations in groundwater change over time? A fourteen-year follow-up study of 760 tubewells in Bangladesh

Naturally occurring arsenic (As) contamination of shallow groundwater affects numerous tubewells utilized for drinking water in Bangladesh. Long-term exposure to As contaminated water increases the risk of skin lesions and internal cancers. In 2000-2001, water samples from 61 villages distributed within a 25 km area of Araihazar, Bangladesh were collected and tested for As to better understand the spatial distribution of arsenic in groundwater. In 2012, village health workers returned to the same area and performed field kit tests for arsenic and resurveyed well owners. Of the 9,000 tubewells originally sampled in 2000-01, 760 of them have been identified as potentially still in existence by matching GPS coordinates, well depth, and well age information. The goal of this work is to determine whether arsenic concentrations along with groundwater chemistry have changed over the past 14 years in these tubewells. Archived water samples from the 2000-2001 sampling campaign are being assessed for sample storage integrity and village health workers are currently resampling these 760 tubewells. In 2000-2001, these samples were initially analyzed for As using Graphite Furnace Atomic Absorption (GFAA). The 2000-2001 archived water samples are currently being reanalyzed with Inductively Coupled Plasma Mass Spectrometry (ICP-MS) to improve sensitivity, accuracy and precision of arsenic detection. ICP-MS will also be used to analyze for 13 other elements. Comparing ICP-MS with the GFAA As demonstrated that the long-term storage of these samples did not alter the water chemistry. Analysis of the samples currently being collected in Bangladesh will enable us to determine the stability of groundwater chemistry over time.