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Graphic element Research > Growth > Research projects > Measurements & testing projects > Something in the water
Graphic element Something in the water
    23-11-2001
 
A simple device with a big impact
A simple device with a big impact
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A three-year EU-funded project aimed at improving the measurement of water pollution has developed and tested equipment for passive water sampling over a period of time, a method which eliminates the variation often seen with the widely-used spot sampling method. Partners, including a number of organisations from the UK, the Netherlands and Sweden, say the new method also saves money, as repeated sampling is not needed. It can detect inorganic or organic pollutants, and can be adapted to measure an almost infinite range of compounds in very low concentrations.

Citizens of Europe are increasingly concerned about the quality of their water for drinking and bathing, and want to know that their rivers, lakes, ground water and beaches are adequately protected from pollution from a myriad of sources. The European Union has a number of laws in place, including the recent water policy framework directive , which aims to monitor and limit water pollution. However, to reduce levels of pollution they first have to be measured, and currently available methods leave a lot to be desired.

A point in time
 

Measurements of water pollutants made by spot sampling have a major disadvantage - they assess pollution at a single moment and can easily miss transient higher levels, e.g. shortly after a farmer had sprayed nearby fields, or lower levels, e.g. after heavy rainfall. "It's quite worrying," says project leader Richard Greenwood of the University of Portsmouth, "A lot of national government data, e.g. levels of pollutants moving down rivers, are based on only a few spot samples per year." The new passive sampling system will enable much more meaningful measurements to be taken and time-averaged over a period - between two days and three weeks.

 
So simple
 

The passive sampler is a very simple device containing a solid chromatographic receiving phase, which accumulates the pollutant. A diffusion-limiting membrane, held in place and protected by a mesh, separates the receiving phase from the solution it is to test. The whole device is suspended, membrane downwards to protect from fouling, in the test solution. The membrane must be chosen according to the type of pollutant that is being measured - inorganic, polar or non-polar organic. The receiving phase has a very high affinity for the pollutant substance while the membrane prevents it from becoming saturated too quickly.

To reach the receiving phase, the pollutant must diffuse through the membrane. The driving force for diffusion is the concentration outside the membrane, because the concentration inside is zero as any pollutant inside will immediately be taken into the receiving phase. The amount taken into the receiving phase is then extracted with an acid (inorganics) or an organic solvent (organics), and measured. The system can be calibrated in the laboratory for a given receiving phase and membrane, using solutions of known concentrations. The amount of water sampled over time is independent of external concentration, and once measured for any pollutant this can be used to determine unknown concentrations in the field. "The system will not measure such low concentrations as some other existing devices," says Richard Greenwood, "but the group is more interested in making sure that high levels are not missed, which is of concern to legislators and water supply managers."

 
The system in practice
 

Trials have been carried out comparing the passive sampling method with spot sampling in a variety of sites in different countries, including the Rhine near the Dutch border, storm water in Gothenburg, and two seawater marinas in the UK. In the latter, measurements were made of two herbicides used in ship antifouling paints. In open water, levels were extremely low, but within closed lock gates they were high - concentration of pollutants and accumulation in the sampler are affected by water turbulence and by temperature.

The group is now hoping to carry out further development work to look at determination of a wider range of pollutants. Priority pollutants tend to change over time. Currently, problem substances include detergents, perfumes, fabric conditioners and endocrine disrupters. The partnership now holds a UK patent for the design of the device and its use for non-polar pollutants. For further work on polar pollutants, the group is seeking a licensing agreement with other workers researching similar systems, and now hopes to set up manufacturing arrangements with a company active in environmental monitoring.

 
Members of the project group included:

The University of Portsmouth (UK) (coordinator)
University College London (UK)
Chalmers University of Technology, Gothenburg (Sweden)
Southern Water Services (UK)
Rijksinstituut voor Visserijonderzoek, Ijmuiden (Netherlands)
KM Laboratorierna AB, Linköping (Sweden).

 

A point in time
So simple
The system in practice
   

Key data

Research aimed at developing equipment to measure time-averaged levels of organic and inorganic pollutants in fresh or sea water is currently supported under the Growth Programme's Measurements and testing generic activity .

Projects

'Development of passive sampling systems for use in monitoring of organic and inorganic pollutants in aquatic environments' (project no. SMT4-CT96 2114).

     

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