Development of nitrate profiles database

This report describes the continued development of the database of nitrate porewater profiles produced by both BGS and other organisations since the mid 1970s. A large number of sites for which profiles were either partially or completely missing from the first version of the database were identified, including investigations by the Southern Water Authority and the University of Birmingham. It was also considered that it would be desirable to capture other relevant data, primarily other nitrogen species and tritium. All identified profiles were added to the database, using original data where possible and otherwise as scanned and digitised data. A few profiles are outstanding where available plots are of poor quality. Dataholdings have increased from 32,000 to 51,000 individual records of quality data

Pesticides and metabolites in groundwater: examples from two major UK aquifers

Reducing the impact of anthropogenic pollution on groundwater bodies and ameliorating any deterioration of water quality is central to key legislative drivers such as the EU Water Framework Directive and the proposed daughter Directive relating to the protection of groundwater. Pesticide pollution has a direct impact on groundwater quality and an indirect impact on the associated aquatic ecosystems supported by groundwater. There is currently no legislative requirement to monitor pesticide metabolite concentrations in groundwater. Pesticide and metabolite results from two nationally important aquifers are presented, the Trassic Sandstone and the Chalk of Southern England. Aerobic microbial degradation of diuron in the soil can lead to the formation of three compounds; dichlorophenylmethyl urea (DCPMU), dichlorophenyl urea (DCPU) and dichloroanaline (DCA).Median diuron concentrations were significantly higher than each of the metabolites with outliers exceeding the PVC on at least one occasion. At nine sites in Kent, Southern England, (60%) metabolites were more prevalent than diuron. Both aquifers are an important source of water, locally supplying up to 80% of public drinking water. The sandstone site has a predominantly arable landuse with a potential diffuse source of pesticides although soakaways are possible point sources.The chalk site has a mixture of arable and industrial/urban landuse. A significant source has been from excessive applications of diuron (“over-spray”) on a number of public amenities. Data from both aquifers show that pesticide concentrations have a high degree of temporal variability. Elevated pesticide concentrations are associated with recharge events in both aquifer systems regardless of pesticide source terms. Pesticides from amenity use and diffuse agricultural sources both pose a threat to groundwater quality. Pesticide metabolites are present in significant concentrations in groundwaters. Systematic, long-term monitoring (5-10 years) is required to understand trends in groundwater quality

Macronutrient status of UK groundwater: nitrogen, phosphorus and organic carbon

Groundwater is a large, slowly changing pool of the macronutrients nitrogen (N), phosphorus (P) and dissolved organic carbon (DOC), with impacts on receptors, surface waters, dependent wetlands and coastal marine ecosystems. Sources of N to groundwater include fertilisers, animal wastes and septic effluents. N species are well-quantified in groundwater and NO3-N has a wide range of median values (0-12 mg/L). The highest concentrations are in the Chalk of East Anglia and Humberside and the Permo-Triassic Sandstone (PTS) of Staffordshire. The highest concentrations of NH4-N are found in confined aquifers. N concentrations have increased with time peaking during the 1980s. Changes in practice have led to the reduction observed in rapidly-responding aquifers. For the Chalk, where the unsaturated zone is thick, improvements may not be seen for decades. P is less well-characterised in UK groundwater reflecting the lack of historical interest in groundwater P, although it can be significant in some aquifer matrices. Groundwater P concentrations are elevated in sandstone formations compared to other lithology and highest in the PTS of the Midlands and northern England (median values >50 µg/L). Overall half of the aquifers studied in the UK have median TDP >50 g/L, with values of up to 100 µg/L under some urban areas, such as Manchester and Liverpool as well as the Lee Valley. P concentrations in arable areas are variable (20-100 µg/L), whereas under semi-natural conditions they are lower (20-50 µg/L). There is little information on P trends in groundwater. Most DOC is derived from soils, playing an important part in redox processes. The aquifer matrix can contain high OC and contribute significantly to groundwater DOC. Median values range between 0.4 and 9 mg/L, but rarely exceed 5 mg/L, except in the Chalk of Yorkshire and Humberside and PTS of Liverpool which have long legacies of anthropogenic pollution

Temporal variability of micro-organic contaminants in lowland chalk catchments: new insights into contaminant sources and hydrological processes

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

Regulatory practice and transport modelling for nitrate pollution in groundwater

This report forms the first deliverable of a project jointly funded by BGS and the Environment Agency to consider the potential for incorporating the outputs from the BGS unsaturated zone travel time work in assessing the risks to water from nitrate. This is to help to inform the nitrate vulnerable zones (NVZs) designation process. In England, the Environment Agency advises Defra on identifying areas for designation as NVZs. Over time, the designation process has developed and become more complex since the first round of designations in 1996. The designation process for groundwater initially used only public supply monitoring data and the associated source catchment area. In December 2000, the European Court of Justice held that the UK had failed to designate sufficient NVZs for the protection of all waters, not just for drinking water sources. This resulted in the development of revised methodologies for the designation of NVZs which separately address surface waters, groundwater and waters at risk of eutrophication. This was implemented in 2002. Further reviews have been carried out in 2008 and 2012 and as a result, modifications and improvements to methods have been made at each designation round. For groundwater the Environment Agency developed a numerical risk assessment procedure that uses a range of risk factors including both nitrate concentration data and nitrate-loading data to assess the risk of nitrate pollution. The loading data is based on farm census returns made to Defra and combined using the NEAP-N methodology developed by ADAS (Lord and Anthony, 2000). The overall risk assessment considers both current observed concentrations and predicted future concentrations as well as current loadings. However, this approach has a number of disadvantages including a lack of a specific term for the time of travel to the water table and emergence of pollutant both into groundwater and to groundwater discharge points that support surface water features. Instead, these issues are considered at the conceptual level in workshops with local EA hydrogeologists. A key question for Defra and the Agency is how long it will take for nitrate concentrations to peak and then stabilise at an acceptable, lower level, in response to existing and future land management control measures. This is most important for soils, for aquifers, for lakes and for groundwater-fed wetland systems that respond less quickly to changes in loading. Groundwater and lake catchment numerical models can provide first-order estimates of likely response times, but can be difficult and costly to set-up for many different situations and are difficult to apply consistently at the national scale. A previous review of nitrate vulnerable zones suggests a range of further needs: • to understand the recent developments in nitrate pollution simulation and particularly the potential to understand/characterise past nitrate loading from changing land management practices and correlate these with observed nitrate concentrations over time; • to evaluate the retention of nitrate in catchments, particularly in the unsaturated zone of soils and aquifers; • to simulate the recent and future anticipated decreases in nitrate loading by sectors within the UK; • to understand the likely time taken for nitrate concentrations to peak and then stabilise at an acceptable, lower level, in response to existing and future control measures. Without evidence of how long it may take systems to recover it is difficult to evaluate the effectiveness of existing measures or decide whether additional measures are necessary. The aim of this project is to investigate the use of new models to inform decision-making on nitrate pollution in groundwater and the potential for incorporating unsaturated zone processes in future NVZ designations. The work described here forms the first task of this project and aims to review NVZ methodology and recent designation experience. As part of this we will: • collate information from the Agency on the recent application of the methodology; • provide case study examples of designation in different time-lag settings and/or where these are not corroborated by water quality

Estimating the leakage contribution of phosphate dosed drinking water to environmental phosphorus pollution at the national‐scale

Understanding sources of phosphorus (P) to the environment is critical for the management of freshwater and marine ecosystems. Phosphate is added at water treatment works for a variety of reasons: to reduce pipe corrosion, to lower dissolved lead and copper concentrations at customer’s taps and to reduce the formation of iron and manganese precipitates which can lead to deterioration in the aesthetic quality of water. However, the spatial distribution of leakage into the environment of phosphate added to mains water for plumbosolvency control has not been quantified to date. Using water company leakage rates, leak susceptibility and road network mapping, we quantify the total flux of P from leaking water mains in England and Wales at a 1 km grid scale. This is validated against reported leaks for the UKs largest water utility. For 2014, we estimate the total flux of P from leaking mains to the environment to be c. 1.2 kt P/yr. Spatially, P flux is concentrated in urban areas where pipe density is highest, with major cities acting as a significant source of P (e.g. London into the Thames, with potentially 30% of total flux). The model suggests the majority (69%) of the P flux is likely to be to surface water. This is due to leakage susceptibility being a function of soil corrosivity and shrink‐swell behaviour which are both controlled by presence of low‐permeability clays. The location of major cities such as London close to the coast results in a potentially significant flux of P from mains leakage to estuarine environments. The contribution of leakage of phosphate dosed mains water should be considered in future source apportionment and ecosystem management. The methodology presented is generic and can be applied in other countries where phosphate dosing is undertaken or used prior to dosing during investment planning

Phosphate dosing of mains water : novel approaches to water loss reduction through leakage detection and policy [abstract]

Detection and t racing of leakage in the environment are essential component s of water loss reduction strategies. Industry standard techniques for tracing leaks include analysis of chlorine and trihalomethane concentrations, but levels of these determinands can fall belo w detection limits due to their volatile nature 1 . Consequently additional tools to trace leakage in the environment are a useful step to move towards minimum losses

Mapping groundwater denitrification potential : methodology report

An understanding of the fate of nitrate in groundwater is vital for managing risks associated with nitrate pollution, and to safeguard groundwater supplies and groundwater-dependent surface waters. One of the main mechanisms to control nitrate is the designation of nitrate vulnerable zones (NVZs). Recent review of the designation process in England has highlighted that in some locations measured groundwater nitrate concentrations are not as high as might be expected from knowledge of the surface loads of nitrate applied at the ground surface. A possible reason for this is that the nitrate is being transformed through denitrification. The aim of this work was to develop a weight of evidence approach to allow the assessment of denitrification potential across groundwater in England using literature and existing groundwater and other relevant data

Persistent and emerging micro-organic contaminants in Chalk groundwater of England and France

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

Quantification of nitrate storage in the vadose (unsaturated) zone: a missing component of terrestrial N budgets

National terrestrial nitrogen budgets for many developed countries have been calculated as part of the management of impacts of N on the environment, but these rarely represent the subsurface explicitly. Using estimates of vadose zone travel time and agricultural nitrate loading, we quantify, for the first time, the total mass of nitrate contained in the vadose zone of aquifers in England and Wales. This mass peaked in 2008 at 1400 kt N (800 to >1700 kt N from sensitivity analyses) which is approximately 2.5 to 6 times greater than saturated zone estimates for this period and indicates that the subsurface is an important store of reactive nitrogen. About 70% of the nitrate mass is estimated to be in the Chalk, with the remainder split between the Permo-Triassic sandstones, the Jurassic Oolitic limestones and minor aquifers. Current controls on fertiliser application mean that the vadose zone is now a nitrate source and in 2015 we estimate the net flux from the unsaturated zone to groundwater to be 72 kt N/annum. The mass of nitrate in the vadose zone should be included in future terrestrial nitrogen budgets at national and global scales to improve ecosystem management. This article is protected by copyright. All rights reserved