Search

Interest in dissolved methane (CH4) concentrations in aquifers in England, Scotland and Wales (‘Great Britain’ or GB) has grown concurrently with interest in the exploitation of unconventional gas sources (UGS). Experience, mainly from North America, has shown the importance of a pre-production baseline against which changes possibly due to UGS extraction can be compared. The British Geological Survey, aided by water utilities, private users and regulators, has compiled a unique dataset for CH4 in groundwaters of GB. This focuses principally on areas where UGS exploration is considered more likely, as indicated by the underlying geology. All the main water supply aquifers (Principal aquifers) were targeted, plus Secondary aquifers where locally important. The average dissolved CH4 concentration across GB in the aquifers sampled was 45 μg/l. Out of a total of 343 sites, 96% showed dissolved CH4 concentrations b100 μg/l, 80% b10 μg/l, and 43% b 1 μg/l. No site had a CH4 concentration above the US Department of the Interior suggested risk action level of 10,000 μg/l. While most sites were sampled only once, a sub set was monitored quarterly to determine the magnitude of seasonal or other variations. Generally these variations were minor, with 84% of sites showing variations within the range 0.5–37 μg/l, but some aquifers where the porosity was primarily fracture-related showed larger changes (0.5–264 μg/l). This may have been due to the nature of sampling at these sites which, unlike the others, did not have installed pumps. Since the regulatory compliance monitoring attending UGS operations will include the measurement of parameters such as dissolved CH4, it is essential that sampling methods are tested to ensure that reliable and comparable datasets can be obtained.

This paper explores the temporal variation of a broad suite of micro organic (MO) compounds within hydrologically linked compartments of a lowland Chalk catchment, the most important drinking water aquifer in the UK. It presents an assessment of results from relatively high frequency monitoring at a well-characterised site, including the type and concentrations of compounds detected and how they change under different hydrological conditions including exceptionally high groundwater levels and river flow conditions during 2014 and subsequent recovery. This study shows for the first time that within the Chalk groundwater there can be a greater diversity of the MOs compared to surface waters. Within the Chalk 26 different compounds were detected over the duration of the study compared to 17 in the surface water. Plasticisers (0.06–39 μg/L) were found to dominate in the Chalk groundwater on 5 visits (38.4%) accounting for 14.5% of detections but contributing highest concentrations whilst other compounds dominated in the surface water. Trichloroethene and atrazine were among the most frequently detected compounds. The limit for the total pesticide concentration detected did not exceed EU/UK prescribed concentration values for drinking water. Emerging organic compounds such as caffeine, which currently do not have water quality limits, were also detected. The low numbers of compounds found within the hyporheic zone highlight the role of this transient interface in the attenuation and breakdown of the MOs, and provision of an important ecosystem service.

The Chalk aquifer of Northern Europe is an internationally important source of drinking water and sustains baseflow for surface water ecosystems. The areal distribution of microorganic (MO) contaminants, particularly non-regulated emerging MOs, in this aquifer is poorly understood. This study presents results from a reconnaissance survey of MOs in Chalk groundwater, including pharmaceuticals, personal care products and pesticides and their transformation products, conducted across the major Chalk aquifers of England and France. Data from a total of 345 sites collected during 2011 were included in this study to provide a representative baseline assessment of MO occurrence in groundwater. A suite of 42 MOs were analysed for at each site including industrial compounds (n = 16), pesticides (n = 14) and pharmaceuticals, personal care and lifestyle products (n = 12). Occurrence data is evaluated in relation to land use, aquifer exposure, well depth and depth to groundwater to provide an understanding of vulnerable groundwater settings.

The term ‘emerging contaminants’ is generally used to refer to compounds previously not considered or known to be significant to groundwater (in terms of distribution and/or concentration) which are now being more widely detected. As analytical techniques improve, previously undetected organic micropollutants are being observed in the aqueous environment. Many emerging contaminants remain unregulated, but the number of regulated contaminants will continue to grow slowly over the next several decades. There is a wide variety of sources and pathways for these compounds to enter the environment and these include agriculture and urban areas. Some of these contaminants can have human or ecological health effects and there is a need for better understanding of their fate in environmental systems. This report provides a short review of the types of organic micropollutants which can be found in the aqueous environment. These include nanomaterials, pesticides, pharmaceuticals, industrial additives and by-products, personal care products and fragrances, water treatment by-products, flame/fire retardants and surfactants, as well as caffeine and nicotine metabolites and hormones. Many of the compounds are relatively small polar molecules which are not effectively removed by conventional drinking water treatment using activated carbon. Pesticides and some industrial compounds are presently covered by the Water Framework Directive, the Groundwater Regulations and the Drinking Water Directive. Additional parameters, such as bisphenol A and nonyl-phenol are anticipated to be covered by revisions to the Drinking Water Directive. Others are currently unregulated. In order to assess the hazards presented by such compounds, information on usage, persistence, leachability and a robust sensitive analytical method is required. The UK metaldehyde problem was not originally discovered due to lack of an analytical method and was exacerbated by recalcitrance in water treatment. For many pesti