Arsenic in Groundwater in South West Ireland: Occurrence, Controls, and Hydrochemistry

Abstract

Globally numerous regions have been identified with elevated arsenic within groundwater which can result in potential adverse health risks. In Ireland, a previous national-scale research assessment of groundwater identified isolated clusters of elevated arsenic and indicated that lithology was a major controlling factor on arsenic in groundwater. Complementary comparisons of national-scale and regional-scale groundwater assessments of arsenic are lacking in Europe when compared to other global regions. The aims of this study were to demonstrate the value of a regional-scale groundwater hydrochemistry dataset with an existing national-scale approach, describe anomalies that can become the focus of attention for public health and economic reasons, and to provide a wider context for arsenic in groundwater within Ireland and Europe. Regional-scale data using 470 locations comprising 1,493 analyses using several hydrochemical parameters (arsenic, pH, conductivity, iron, manganese, sodium, potassium, calcium, magnesium, and total hardness) in south west Ireland were integrated with geological, hydrogeological, and land use datasets. Statistical analysis was performed using a combination of methods including score tests of geological groups using an empirical cumulative distribution function plot in addition to spatial analysis. Results revealed that hydrochemical parameters exhibited different spatial clusters, which was generally associated with lithology. Arsenic was elevated in sandstone derived bedrock. Weak correlation of arsenic with other hydrochemical parameters were observed and redox-sensitive elements like manganese and iron showed a greater diversity in spatial occurrence. This study has shown that the variation of hydrochemical parameters are controlled by regional geology. Finally, the paper focuses on anomalies identified by concentrations of individual ions or statistical associations in the context of, for example, historical mineral exploration and mining in the area and also discusses whether groundwater chemistry sampling on this scale can assist in future mineral exploration, as well as guiding the future development of high quality public and private water supplies.

Occurrence, Geochemistry and Speciation of Elevated Arsenic Concentrations in a Fractured Bedrock Aquifer System

“…Modern boreholes in the Republic of Ireland are designed and constructed with this consideration in mind (Institute of Geologists Ireland 2007; Environmental Protection Agency 2013). Older, or simply constructed boreholes will often yield water that is an uncontrolled blend of shallow groundwater from the overburden and the transition zone and deep groundwater from one or more open joints, fractures or faults in the deep bedrock (refer to McGrory et al 2018 for further information).…”

“…This anomalously high value in comparison with the lower values in the surrounding area arises from the reductive dissolution of Fe and Mn oxyhydroxides (reducing conditions noted while sampling) as the well is not currently in active use. Indeed, concentrations of these trace elements are usually low with higher concentrations found in private wells elsewhere (DeSimone et al 2009;Homoncik et al 2010;McGrory et al 2018).…”

Estimation of redox-sensitive metals in Lafarge cement company’s area in Akamkpa Nigeria: Assessment of ecological health risk

“…A sample of soil may contain multiple chemicals in many situations (McGrory et al, 2018). Chemicals in combination may have unanticipated negative consequences that cannot be expected based on individual exposure to each chemical involved.…”