title: Arsenic contamination of drinking water in Ireland: A spatial analysis of occurrence and potential risk.
abstract: The presence of arsenic in groundwater has become a global concern due to the health risks from drinking water with elevated concentrations. The Water Framework Directive (WFD) of the European Union calls for drinking water risk assessment for member states. The present study amalgamates readily available national and sub-national scale datasets on arsenic in groundwater in the Republic of Ireland. However, due to the presence of high levels of left censoring (i.e. arsenic values below an analytical detection limit) and changes in detection limits over time, the application of conventional statistical methods would inhibit the generation of meaningful results. In order to handle these issues several arsenic databases were integrated and the data modelled using statistical methods appropriate for non-detect data. In addition, geostatistical methods were used to assess principal risk components of elevated arsenic related to lithology, aquifer type and groundwater vulnerability. Geographic statistical methods were used to overcome some of the geographical limitations of the Irish Environmental Protection Agency (EPA) sample database. Nearest-neighbour inverse distance weighting (IDW) and local indicator of spatial association (LISA) methods were used to estimate risk in non-sampled areas. Significant differences were also noted between different aquifer lithologies, indicating that Rhyolite, Sandstone and Shale (Greywackes), and Impure Limestone potentially presented a greater risk of elevated arsenic in groundwaters. Significant differences also occurred among aquifer types with poorly productive aquifers, locally important fractured bedrock aquifers and regionally important fissured bedrock aquifers presenting the highest potential risk of elevated arsenic. No significant differences were detected among different groundwater vulnerability groups as defined by the Geological Survey of Ireland. This research will assist management and future policy directions of groundwater resources at EU level and guide future research focused on understanding arsenic mobilisation processes to facilitate in guiding future development, testing and treatment requirements of groundwater resources.
authors.affiliation: Earth and Ocean Sciences, School of Natural Sciences National University of Ireland, Galway, Ireland; Ryan Institute: Environmental, Marine and Energy Research, National University of Ireland, Galway, Ireland.
authors.forename: Ellen R
authors.initials: ER
authors.lastname: McGrory
authors.affiliation: Ryan Institute: Environmental, Marine and Energy Research, National University of Ireland, Galway, Ireland.
authors.forename: Colin
authors.initials: C
authors.lastname: Brown
authors.affiliation: Department of Mathematics and Statistics, University of Limerick, Ireland.
authors.forename: Norma
authors.initials: N
authors.lastname: Bargary
authors.affiliation: Groundwater Section, Geological Survey of Ireland, Haddington Road, Dublin 4, Ireland.
authors.forename: Natalya Hunter
authors.initials: NH
authors.lastname: Williams
authors.affiliation: Hydrometric and Groundwater Section, Environmental Protection Agency, Richview, Dublin 4, Ireland.
authors.forename: Anthony
authors.initials: A
authors.lastname: Mannix
authors.affiliation: GIS Centre, Ryan Institute and School of Geography and Archaeology, National University of Ireland, Galway, Ireland.
authors.forename: Chaosheng
authors.initials: C
authors.lastname: Zhang
authors.affiliation: Earth and Ocean Sciences, School of Natural Sciences National University of Ireland, Galway, Ireland.
authors.forename: Tiernan
authors.initials: T
authors.lastname: Henry
authors.affiliation: Earth and Ocean Sciences, School of Natural Sciences National University of Ireland, Galway, Ireland.
authors.forename: Eve
authors.initials: E
authors.lastname: Daly
authors.affiliation: Earth and Ocean Sciences, School of Natural Sciences National University of Ireland, Galway, Ireland.
authors.forename: Sarah
authors.initials: S
authors.lastname: Nicholas
authors.affiliation: Earth and Ocean Sciences, School of Natural Sciences National University of Ireland, Galway, Ireland.
authors.forename: Barbara M
authors.initials: BM
authors.lastname: Petrunic
authors.affiliation: Groundwater Section, Geological Survey of Ireland, Haddington Road, Dublin 4, Ireland.
authors.forename: Monica
authors.initials: M
authors.lastname: Lee
authors.affiliation: Earth and Ocean Sciences, School of Natural Sciences National University of Ireland, Galway, Ireland; Ryan Institute: Environmental, Marine and Energy Research, National University of Ireland, Galway, Ireland. Electronic address: liam.Morrison@nuigalway.ie.
authors.forename: Liam
authors.initials: L
authors.lastname: Morrison
mesh_terms: D001151:Arsenic / Q000032:analysis*; D060766:Drinking Water / Q000737:chemistry*; D004784:Environmental Monitoring; D060587:Groundwater / Q000737:chemistry; D007494:Ireland; D062206:Spatial Analysis; D014874:Water Pollutants, Chemical / Q000032:analysis*; D014881:Water Supply / Q000706:statistics & numerical data
chemical_list: D060766:Drinking Water; D014874:Water Pollutants, Chemical; D001151:Arsenic
keywords: Arsenic; Geology; Geostatistics groundwater; Ireland; WFD