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Emerald Group Publishing Limited
Copyright © 2012, Emerald Group Publishing Limited
Article Type: Viewpoint From: Sensor Review, Volume 32, Issue 1
.The quality of the ambient environment is recognised as a high priority in most countries throughout the world, as some key anthropogenic pollutants are now recognised as having a global impact. As a consequence, a number of international monitoring programmes have been established. An example is the United Nations Stockholm Convention (2001) on the trans-boundary atmospheric movement of persistent organic pollutants (POPs) such as pesticides and various polychlorinated compounds. Here, large networks of air quality monitoring stations on a continental scale have been established. These provide a harmonized organizational framework for the collection of comparable monitoring data so as to identify changes in levels over time, as well as information on the regional and global environmental transport of POPs. Similarly, within the European Community, efforts have been made to harmonise biological and chemical monitoring activities within the aquatic environment. The European Union’s Water Framework Directive (2000) adopts an integrated river basin management approach within the community for the monitoring of water (surface, including transitional waters and the coastal fringe, and ground), sediments and biota. More recently this concept has been extended to include the coastal and marine zones through the introduction of the EU’s Marine Strategy Directive (2008). Both directives require the attainment of “good environmental status” within set time frames. As a consequence, of these international conventions and policies monitoring activities will need to be increased in the different environmental matrices (air, biota, sediments, soils and water) in order to fulfil the various mandated legislative requirements and to provide evidence of an improvement in environmental quality over time. Owing to the financial constraints that now exist in most countries, it is not expected that new resources will be made available in order to undertake these additional monitoring activities.
Many monitoring campaigns rely on the field collection of individual, discrete or spot samples for subsequent biological or chemical analysis in a remote laboratory. Often this approach to monitoring is expensive due to the manpower needed to collect the sample and the associated transportation costs. There can also be substantial logistic problems in connection with representative sampling over wide areas, e.g. the marine sector using this method. In addition, this monitoring method reflects only the situation at the instant of sampling, and fluctuations associated with episodic events (e.g. a pollution incident) can be missed, or in some cases, conclusions on environmental quality could be drawn on the basis of transitory high levels of a particular pollutant. The cost of incorrect data can be high, particularly if expensive remedial actions are undertaken on the basis of wrong information. As a consequence, there is an urgent need for the development and validation of alternative cost-effective technologies and methodologies that can be widely adopted by end-users for routine monitoring purposes. Such techniques need to be affordable, reliable and produce data that are of comparable quality between times and locations.
A number of potential alternative monitoring tools is now available for inclusion in the “toolboxes” of those charged with managing the environmental quality of air and water. Some of these tools are available commercially, whilst others are still at the laboratory prototype or proof-of-concept stage. These include: bio-monitoring and biological early warning systems, online and in situ monitoring systems, various passive samplers, field test kits, portable toxicological assay equipment and a wide range of biologically and chemically based sensors. Each of these different methods has their own advantages and disadvantages in terms of the type of information they can produce, their environmental applicability, reliability, sensitivity and usability, and most importantly cost. Caution sometimes needs to be taken when using these alternative tools as often they can measure different fractions of a pollutant within the matrix. Some methods will measure the freely available concentration of an analyte in water, whilst others measure the total (i.e. the freely available together with that fraction bound to particulate matter) concentration. This can present problems when comparing data derived from different methods and particularly with historical information obtained by conventional discrete sampling techniques.
Much research effort is being directed (e.g. particularly in Europe via the EU’s various Research Framework Programmes) to further develop and field validate new environmental monitoring tools that can be used by the various groups of end-users, as well as address some of the short-coming of the existing methods. For example, often the field lifetime of these systems is short due to limitations of the operational power supplies or amount of available chemical reagents that are used to initiate reactions in situ, the harshness of the environmental conditions where the devices are deployed and/or (bio)fouling of detection surfaces. Advances are taking place in miniaturisation (using micro-fabrication, micro-fluidics and integrated optics), telemetry and the use of advanced materials of construction that can limit fouling. These approaches can in turn reduce the costs of the sensing apparatus and the end-users are enabled, potentially, to deploy larger numbers of devices and thereby improve the spatial and temporal resolution and extent of monitoring activities. Further work, however, is still needed in a number of important areas, particularly in the establishment of internationally recognised validation protocols and standards, quality assurance and quality control procedures and the setting up of inter-laboratory trials for the use of these monitoring techniques in the different compartments of the environment. It is only by addressing all these latter issues that these different devices and techniques will become fit-for-purpose monitoring tools that can be used with confidence within a legislative framework and all the significant research efforts can be capitalised upon.
Graham A. MillsProfessor of Environmental Chemistry, University of Portsmouth, Portsmouth, UK