Emerging organic contaminants (EOCs) detected in groundwater may have adverse effects on human health and aquatic ecosystems. This paper reviews the existing occurrence data in groundwater for a range of EOCs including pharmaceutical, personal care, 'life-style' and selected industrial compounds. The main sources and pathways for organic EOCs in groundwater are reviewed, with occurrence data for EOCs in groundwater included from both targeted studies and broad reconnaissance surveys. Nanogram-microgram per litre concentrations are present in groundwater for a large range of EOCs as well as metabolites and transformation products and under certain conditions may pose a threat to freshwater bodies for decades due to relatively long groundwater residence times. In the coming decades, more of these EOCs are likely to have drinking water standards, environmental quality standards and/or groundwater threshold values defined, and therefore a better understanding of the spatial and temporal variation remains a priority.Keywords: emerging contaminants; review; groundwater; pharmaceuticals; occurrence Capsule: A large range of emerging organic contaminants are now being detected in groundwater as a result of recent and historical anthropogenic activities. IntroductionA diverse array of synthetic organic compounds are used by society in vast quantities for a range of purposes including the production and preservation of food, industrial manufacturing processes, as well as for human and animal healthcare. In the last few decades there has been a growing interest in the occurrence of these, so called, 'micro-organic contaminants' in the terrestrial and aquatic environment, their environmental fate and their potential toxicity (Stan and Linkerhagner, 1992;Stan et al., 1994;Halling-Sørensen et al., 1998;Daughton and Ternes, 1999;Schwarzenbach et al., 2006;Kümmerer, 2009). The contamination of groundwater resources by micro-organics is a growing concern and relatively poorly understood compared to other freshwater resources. Groundwater provides the most reliable perennial source of freshwater on Earth. It maintains flows and levels in rivers and lakes, is essential for the health of groundwater-dependant ecosystems, and in many parts of the world is the most important source of drinking water.Of particular concern are 'emerging organic contaminants' (EOCs). This term is used to cover not only newly developed compounds but also compounds newly discovered in the environment -often due to analytical developments (Lindsey et al., 2001;Petrovic and Barceló, 2006;Richardson and Ternes, 2011) and compounds that have only recently been categorised as contaminants. EOCs include a wide array of different compounds (as well as metabolites and transformation products-collectively referred to here as degradates)including; pharmaceuticals and personal care products (PPCPs), pesticides, veterinary products, industrial compounds/by-products, food additives as well as engineered nanomaterials. Because of the vast array of possible comp...

This paper provides a review of the types of emerging organic groundwater contaminants (EGCs) which are beginning to be found in the UK. EGCs are compounds being found in groundwater that were previously not detectable or known to be significant and can come from agricultural, urban and rural point sources. EGCs include nanomaterials, pesticides, pharmaceuticals, industrial compounds, personal care products, fragrances, water treatment by-products, flame retardants and surfactants, as well as caffeine and nicotine. Many are relatively small polar molecules which may not be effectively removed by drinking water treatment. Data from the UK Environment Agency's groundwater screening programme for organic pollutants found within the 30 most frequently detected compounds a number of EGCs such as pesticide metabolites, caffeine and DEET. Specific determinands frequently detected include pesticides metabolites, pharmaceuticals including carbamazepine and triclosan, nicotine, food additives and alkyl phosphates. This paper discusses the routes by which these compounds enter groundwater, their toxicity and potential risks to drinking water and the environment. It identifies challenges that need to be met to minimise risk to drinking water and ecosystems.

across the full extent of the IGB. The aquifer system is usually represented as a single category on 66 hydrogeological maps [6]. However, in practice the system is complex and heterogeneous with large 67 spatial differences in permeability, storage, recharge and water chemistry as well as having an 68 important depth dimension. This complexity strongly influences how each part of the aquifer 69 responds to stresses [7]. The IGB is home to the largest surface water irrigation system in the world, 70 constructed during the 19 th and early 20th century to redistribute water from the Indus and Ganges 71 through a canal network >100,000 km long. Leakage from this irrigation infrastructure has had a 72 profound impact on the current quantity and quality of groundwater resources and is a significant 73 factor governing its response to contemporary and future pressures. Increasing groundwater use for 74 irrigation poses legitimate questions about the future sustainability of abstraction from the basin 75 and future groundwater security of this region is a major social-political concern [8]. 76Recent discussion of water security has been dominated by interpretations of remotely-sensed 77 gravity data from the GRACE mission gathered at a coarse scale of 400x400 km are poorly constrained by ground-based observations; local field studies nonetheless provide partial 82 insight into system dynamics. These include evidence of: declining groundwater levels [11,12,13], 83 groundwater security has been introduced by forecasts of climate change and the potential for 88 significant change to precipitation, river flows and groundwater recharge [20,21,22]. 89Here we present for the first time an analysis of the status of groundwater across the IGB alluvial 90 aquifer based entirely on in situ measurements. We use a statistical analysis of multiyear 91 groundwater-level records from 3652 water-wells and a compilation and interpretation of existing 92 high resolution spatial datasets and studies within Pakistan, India, Nepal and Bangladesh to assess: 93 (1) groundwater-level variations; (2) groundwater salinity; and (3) We find that the water-table within the IGB alluvial aquifer is typically shallow (< 5 m below ground 98 surface) and the long-term trend is relatively stable throughout much of the basin, with some 99 important exceptions. In areas of high groundwater abstraction in northwest India and the Punjab in 100 Pakistan ( Figure 2) the water-table can be >20 m bgl and in some locations is falling at rates of > 1 101 m/a (Figure 3). In areas of equivalent high irrigation abstraction within Bangladesh, the average 102 water-table remains shallow (<5 m bgl) due to greater direct recharge and high capacity for induced 103 recharge. Groundwater levels are deep and falling beneath many urban areas, and particularly in 104 large groundwater dependant cities such as Lahore, Dhaka and Delhi [23]. Shallow and rising water-105 tables are found in the Lower Indus, parts of the lower Bengal basin and in places throughout the 106 IGB aqui...

Groundwater resources are important sources of drinking water in Africa, and they are hugely important in sustaining urban livelihoods and supporting a diverse range of commercial and agricultural activities. Groundwater has an important role in improving health in sub-Saharan Africa (SSA). An estimated 250 million people (40% of the total) live in urban centres across SSA. SSA has experienced a rapid expansion in urban populations since the 1950s, with increased population densities as well as expanding geographical coverage. Estimates suggest that the urban population in SSA will double between 2000 and 2030. The quality status of shallow urban groundwater resources is often very poor due to inadequate waste management and source protection, and poses a significant health risk to users, while deeper borehole sources often provide an important source of good quality drinking water. Given the growth in future demand from this finite resource, as well as potential changes in future climate in this region, a detailed understanding of both water quantity and quality is required to use this resource sustainably. This paper provides a comprehensive assessment of the water quality status, both microbial and chemical, of urban groundwater in SSA across a range of hydrogeological terrains and different groundwater point types. Lower storage basement terrains, which underlie a significant proportion of urban centres in SSA, are particularly vulnerable to contamination. The relationship between mean nitrate concentration and intrinsic aquifer pollution risk is assessed for urban centres across SSA. Current knowledge gaps are identified and future research needs highlighted.

The occurrence of emerging organic contaminants within the aquatic environment in Africa is currently unknown. This study provides early insights by characterising a broad range of emerging organic contaminants (n > 1000) in groundwater sources in Kabwe, Zambia. Groundwater samples were obtained during both the dry and wet seasons from a selection of deep boreholes and shallow wells completed within the bedrock and overlying superficial aquifers, respectively. Groundwater sources were distributed across the city to encompass peri-urban, lower cost housing, higher cost housing, and industrial land uses. The insect repellent DEET was ubiquitous within groundwater at concentrations up to 1.8 μg/L. Other compounds (n = 26) were detected in less than 15% of the sources and included the bactericide triclosan (up to 0.03 μg/L), chlorination by-products - trihalomethanes (up to 50 μg/L), and the surfactant 2,4,7,9-tetramethyl-5-decyne-4,7-diol (up to 0.6 μg/L). Emerging contaminants were most prevalent in shallow wells sited in low cost housing areas. This is attributed to localised vulnerability associated with inadequate well protection, sanitation, and household waste disposal. The five-fold increase in median DEET concentration following the onset of the seasonal rains highlights that more mobile compounds can rapidly migrate from the surface to the aquifer suggesting the aquifer is more vulnerable than previously considered. Furthermore it suggests DEET is potentially useful as a wastewater tracer in Africa. There was a general absence of personal care products, life-style compounds, and pharmaceuticals which are commonly detected in the aquatic environment in the developed world. This perhaps reflects some degree of attenuation within the subsurface, but could also be a result of the current limited use of products containing emerging contaminants by locals due to unaffordability and unavailability. As development and population increases in Africa, it is likely a wider-range of emerging contaminants will be released into the environment.

Tryptophan-like fluorescence (TLF) is an indicator of human influence on water quality as TLF peaks are associated with the input of labile organic carbon (e.g. sewage or farm waste) and its microbial breakdown. Hence, real-time measurement of TLF could be particularly useful for monitoring water quality at a higher temporal resolution than available hitherto. However, current understanding of TLF quenching/interference is limited for field deployable sensors. We present results from a rigorous test of two commercially available submersible tryptophan fluorometers (ex ∼ 285, em ∼ 350). Temperature quenching and turbidity interference were quantified in the laboratory and compensation algorithms developed. Field trials were then undertaken involving: (i) an extended deployment (28 days) in a small urban stream; and, (ii) depth profiling of an urban multi-level borehole. TLF was inversely related to water temperature (regression slope range: -1.57 to -2.50). Sediment particle size was identified as an important control on the turbidity specific TLF response, with signal amplification apparent <150 NTU for clay particles and <650 NTU for silt particles. Signal attenuation was only observed >200 NTU for clay particles. Compensation algorithms significantly improved agreement between in situ and laboratory readings for baseflow and storm conditions in the stream. For the groundwater trial, there was an excellent agreement between laboratory and raw in situ TLF; temperature compensation provided only a marginal improvement, and turbidity corrections were unnecessary. These findings highlight the potential utility of real time TLF monitoring for a range of environmental applications (e.g. tracing polluting sources and monitoring groundwater contamination). However, in situations where high/variable suspended sediment loads or rapid changes in temperature are anticipated concurrent monitoring of turbidity and temperature is required and site specific calibration is recommended for long term, surface water monitoring.

10Eutrophication is a globally significant challenge facing aquatic ecosystems, associated with human 11 induced enrichment of these ecosystems with nitrogen (N) and phosphorus (P). However, the limited 12 availability of inherent labels for P and N has constrained understanding of the triggers for 13 eutrophication in natural ecosystems and appropriate targeting of management responses. This paper 14 proposes and evaluates a new multi-stable isotope framework that offers inherent labels to track 15 biogeochemical reactions governing both P and N in natural ecosystems. importance of abiotic and metabolic processes for the in-river fate of N and P are also explored 27 through the stable isotope framework. Microbial uptake of ammonium to meet metabolic demand for 28 N is suggested by substantial enrichment of δ 15 N NH4 (by 10.2‰ over a 100m reach) under summer 29 low flow conditions. Whilst the concentration of both nitrate and phosphate decreased substantially 30 along the same reach, the stable isotope composition of these ions did not vary significantly, 31indicating that concentration changes are likely driven by abiotic processes of dilution or sorption. 32The in-river stable isotope composition and the concentration of P and N were also largely constant 33 downstream of the waste water treatment works, indicating that effluent-derived nutrients were not 34 strongly coupled to metabolism along this in-river transect. Combined with in-situ and laboratory 35 hydrochemical data, we believe that a multi-stable isotope framework presents a powerful approach 36 for understanding and managing eutrophication in natural aquatic ecosystems. 37 38

Chlorofluorocarbons (CFCs) and sulphur hexafluoride (SF 6 ) provide a technique for dating groundwater up to 50 years old. When used together, CFCs and SF 6 can help to resolve the extent to which groundwater mixing occurs, and therefore provide indicators of the likely groundwater flow mechanisms. Modelling shows that diffusive retardation of these tracers is likely to be low owing to the high moisture content of the chalk unsaturated zone. Data collected from groundwater and surface water from a lowland Chalk catchment in southern England suggest that groundwater movement can be divided into three regimes: on the interfluves of the catchment, 'piston' flow dominates with a bulk groundwater age of several decades; at the valley bottom, there is mixing between shallow groundwater and stream water; and in an intermediate zone between the top and the bottom of the valley there is approximately 3:1 mixing between new and pre-tracer groundwaters. A conceptual model of groundwater movement has been developed to describe the catchment processes. Surface water-groundwater interactions are found to take place down to depths in excess of 10 metres bgl.The nitrate found at the greatest depth are thought to originate from the mid 1950s.