Assessing threats to shallow groundwater quality from soil pollutants in Glasgow, UK: development of a new screening tool

Abstract

A new GIS-based screening tool to assess threats to shallow groundwater quality has been trialled in Glasgow, UK. The GRoundwater And Soil Pollutants (GRASP) tool is based on a British Standard method for assessing the threat from potential leaching of metal pollutants in unsaturated soil/superficial materials to shallow groundwater, using data on soil and Quaternary deposit properties, climate and depth to groundwater. GRASP breaks new ground by also incorporating a new Glasgow-wide soil chemistry dataset. GRASP considers eight metals, including chromium, lead and nickel at 1622 soil sample locations. The final output is a map to aid urban management, which highlights areas where shallow groundwater quality may be at risk from current and future surface pollutants. The tool indicated that 13% of soil sample sites in Glasgow present a very high potential threat to groundwater quality, due largely to shallow groundwater depths and high soil metal concentrations. Initial attempts to validate GRASP revealed partial spatial coincidence between the GRASP threat ranks (low, moderate, high and very high) and groundwater chemistry, with statistical correlation between areas of high soil and groundwater metal concentrations for both Cr and Cu (r2>0.152; P<0.05). Validation was hampered by a lack of, and inconsistency in, existing groundwater chemistry data. To address this, standardised subsurface data collection networks have been trialled recently in Glasgow. It is recommended that, once available, new groundwater depth and chemistry information from these networks is used to validate the GRASP model further.

Stochastic modelling of hydraulic conductivity derived from geotechnical data; an example applied to central Glasgow

“…Depending on local characteristics it can form either a barrier, or a preferential route for recharge and contamination, and/or it can be a contaminant source in itself (Fordyce et al . 2018; Ó Dochartaigh et al . 2018).…”

“…For example, Fordyce et al . (2018) highlight the high levels of potentially harmful, particularly metallic waste from former industrial sites buried at many locations throughout Glasgow, which if mobilised could have potentially deleterious consequences on the overlying population.…”

Improving understanding of shallow urban groundwater: the Quaternary groundwater system in Glasgow, UK

“…This area also has a significant extent and thickness of artificial ground formed of building rubble and cement, which tends to be alkaline in nature, and is associated with elevated concentrations of many trace metals in soils, including As, Cr, Pb and Fe (Fordyce et al . 2018).…”

“…2010); the development of a tool to assess threats to shallow groundwater from soil pollutants (Fordyce et al . 2018); improving the management of subsurface data (Bonsor et al . 2013); collating and using geotechnical data to model Quaternary hydraulic conductivity (Williams et al .…”

The Geoscience Context for Europe's Urban Sustainability – Lessons from Glasgow and Beyond (CUSP): preface

“…This study, and the development of a tool to assess threats to shallow groundwater quality from soil pollution described in the Fordyce et al . (2018a) GRASP paper, also highlight the extensive anthropogenic alteration of the groundwater system in Glasgow and the impacts of the urban and industrial legacy on groundwater quality in the area.…”