The use of field studies to establish the performance of a range of tools for monitoring water quality
Introduction
The Water Framework Directive (WFD) of the European Union (EU) includes a wide range of measures aimed at achieving good quality status in all waters (surface waters and groundwaters).
Where waters meet this standard, then only surveillance monitoring is necessary, and this could readily be achieved using infrequent spot (bottle) samples analyzed by classical laboratory methods. However, where a water body is failing to achieve the necessary quality due to identified causes or where there are recognized pressures, then operational monitoring will be necessary.
Where the system is complex (e.g., tidal waters) or is subject to temporal fluctuations in levels of pollutants (e.g., due to seasonal use of pesticides or to weather patterns), then infrequent spot samples are unlikely to provide a representative picture of water quality.
Similar considerations apply where there are marked spatial variations in levels of pollutants due to the distribution of point or diffuse sources.
Under these circumstances, it will be necessary to have monitoring campaigns employing either frequent and/or widespread spot sampling, or alternative methods that can provide the equivalent information. Where operational monitoring is applied, the cost will be high because of the labor and transport costs involved in sampling, and the need for a large number of analyses. Some alternative methods may be able to deliver the necessary information at lower cost and or more quickly.
If a water system is failing to meet quality standards and the cause is not known, then investigative monitoring will be necessary. In this case, many of the “emerging” methods could provide the necessary information in a cost-effective manner. The thrust of the EU-funded SWIFT-WFD project was to identify available monitoring tools, evaluate their performance in the field, investigate quality-assurance issues, assess their potential for underpinning the monitoring requirements of the WFD, and research their potential socio-economic impact. This project aims to provide tools from which regulators and end users can select the most appropriate and cost effective to meet specific monitoring needs.
It is unlikely that all of the aims of the WFD will be achieved if regulators focus entirely on comparing concentrations of priority pollutants in infrequent spot samples with Environmental Quality Standards (EQSs). There is a need to consider what information will be necessary in order to measure progress towards achieving good water quality, and how the data can be obtained in a cost-effective way. The emerging methods provide information that may be similar to, or remarkably different from, that derived from the analysis of spot samples by classical analytical methods.
Some of the methods replace only the analytical stage and still depend on spot sampling. However, some can be less expensive, more rapid or portable, and can be used in the field (e.g., on a river bank or a survey boat). These methods include immunoassays, test kits, hand-held sensors, and some spectrophotometric methods. Some of these can be used in situ (e.g., by dipping a screen-printed electrode of a sensor directly into the water body under investigation, thus avoiding the sampling step).
A second set of emerging methods addresses the need for representative sampling and includes biomonitoring (the use accumulation by living organisms, usually bivalve mollusks) and passive sampling to provide time-weighted average (TWA) estimates of concentrations of pollutants to which the organisms or samplers were exposed. These sampling methods are linked to classical laboratory analytical methods.
A further set of methods provides completely different information on water quality: these are based on toxicological assessments, and they include direct toxicity assays (usually laboratory based and depending on spot samples of water) and biomarkers (ranging from changes at cellular levels to changes in behavior of whole organisms). Some biological monitoring systems can be used on-line or in situ, and they include biological early warning systems (BEWSs) (e.g., the mussel monitor, the Daphnia Toximeter, and the algal monitor [1]) that are deployed to provide warnings of changes in water quality in order to safeguard sensitive sites, such as drinking-water-intake points. The various methods provide data with a wide range of associated uncertainties, and, for some of them, the uncertainties are poorly defined.
There is a need to establish the performance criteria for the various emerging methods, to define the uncertainties associated with the data they yield, and to interpret the information that they provide within the context of the WFD. The SWIFT-WFD project addressed these areas for a range of emerging methods representing the categories identified in the previous paragraph. This article aims to provide some illustrative examples of how the information needed by regulators to allow them to assess the utility of the various emerging methods can be obtained in field trials. In order to provide a baseline against which the emerging methods can be compared, they were usually deployed alongside current regulatory methods. We have used the SWIFT-WFD trials to identify areas where further research and development work is necessary.
Section snippets
Monitoring metals with passive sampling devices
The Aller river system is located in the Basin of the River Weser that is situated in central northern Germany, and is one of 10 German river-basin districts. Water management and monitoring in the Aller river system are the responsibility of the State Office for Water Management, Coast and Nature Protection (Niedersächsischer Landesbetrieb für Wasserwirtschaft, Küsten und Naturschutz, NLWKN). The frequency of measurements differs for the different groups of parameters, and ranges from monthly
Conclusions
Some of the emerging tools (e.g., passive samplers, hand-held sensors, and field-test kits) can be used in monitoring programmes for a range of tasks, including mapping wide areas to identify where monitoring efforts should be concentrated. They can provide more representative measures of water quality through increased numbers of samples and frequency of sampling. This should give regulators more confidence in making decisions about frequency and spatial distribution of standard monitoring for
Acknowledgements
We acknowledge financial support from the Sixth Framework Programme of the European Union (Contract SSPI-CT-2003-502492; http://www.swift-wfd.com). We also thank the local Environmental Agencies (in the Ribble, Alsace, and Aller) for permission to work on their rivers. Finally, we thank all the partners in the SWIFT-WFD consortium who carried out the field and reference measurements.
References (16)
- et al.
- et al.
J. Environ. Monit.
(2001) - et al.
J. Environ. Monit.
(2002) - et al.
Environ. Sci. Technol.
(1998) - et al.
Nature (London)
(1994) - et al.
Anal. Chem.
(1995) - et al.
J. Environ. Monitor
(2003) - et al.
Environ. Sci. Technol
(2003)
Cited by (34)
Assessing variability in the ratio of metal concentrations measured by DGT-type passive samplers and spot sampling in European seawaters
2021, Science of the Total EnvironmentDiatoms as indicators of environmental health on Korean islands
2020, Aquatic ToxicologyCitation Excerpt :Significantly higher percentages of deformed frustules have been documented in laboratory and field studies under metal stress conditions (Gautam et al., 2017; Pandey et al., 2014,2015,2016a). Metal toxicity can vary with, among other factors, water pH and the presence of organic matter (Roig et al., 2007). As a consequence, toxicity and hence the frequency of deformities is likely to be more variable under field conditions than under controlled laboratory conditions (Pandey et al., 2017).
Use of spatially distributed time-integrated sediment sampling networks and distributed fine sediment modelling to inform catchment management
2017, Journal of Environmental ManagementCitation Excerpt :This is a direct consequence of the prohibitive costs associated with frequent sampling, and a lack of quantitative criteria specifying suitable sampling designs (Greenwood et al., 2007; Madrid and Zayas, 2007). In order to robustly test the targets of the Water Framework Directive, including ensuring that concentrations of priority substances do not increase within sediments and biota, with negligible discharges by 2025 (Crane and Babut, 2007; Förstner, 2009), alternative monitoring approaches are required (Hering et al., 2010; Roig et al., 2007). Advances in low-cost devices and open-source sensors for hydrological monitoring offer significant potential for the accurate assessment of spatio-temporal dynamics and fluxes of contaminants, with passive sampling technology being used for the determination of time-weighted average concentrations of various analytes including metals and organic contaminants (Allan et al., 2006).
Overview of the Chemcatcher® for the passive sampling of various pollutants in aquatic environments Part A: Principles, calibration, preparation and analysis of the sampler
2016, TalantaCitation Excerpt :Allan et al. [80] also observed the ability of both samplers to respond to highly fluctuating metal concentrations. In Roig et al. [82], a fairly good agreement was found between both passive samplers, except for lead because of a high uncertainty in calibration for this element. During an intercomparison exercise, DGT and Chemcatcher® data were not easy to compare as Chemcatchers® were deployed by only one participant at one site [81].
Overview of the Chemcatcher® for the passive sampling of various pollutants in aquatic environments Part B: Field handling and environmental applications for the monitoring of pollutants and their biological effects
2016, TalantaCitation Excerpt :Rs are calculated as shown in Charriau et al. [4] (Section 2.2) and are then used to determine TWACs for Chemcatcher® field applications. The majority of the studies dealing with quantification took place in river waters [9,10,15,16,18,19,35,38,41,57,71–73]. Applications were also conducted in high salinity media such as seawater [11,23–25,27,29], harbor sites [7,16,17,27,29] or estuarine and brackish waters [16,35].