Several of the methods that are used for calculating how different chemical environmental pollutants impact organisms measure concentrations of such pollutants. But the total concentration is not always relevant. Especially not for determining how long, or to what extent, a chemical can impact organisms in a given environment. Researchers from the Idea Support project Equilibrium sampling through membranes — towards online and onsite exposure measurements of available pollutants have, therefore, developed a technique called balanced testing, with a sampler for measuring chemical environmental pollutants in water. Free concentrations
With this new technique, researchers are measuring the free concentrations of chemicals, i.e., that which is not bound to particles or, for example, soil or sediment. Measuring the free concentration is in principle the same as measuring the chemical activity of a material, which is decisive for understanding a material´s biological availability (how a material is absorbed by different organisms) as well as its toxic, poisonous impacts on the environment. “In this way, one gets better and more specific knowledge about a material´s concentration and, thereby, it´s potential impact on different organisms. Therefore, in many ways it is more interesting to measure the free concentration for performing risk analyses," says Jan Åke Jönsson, project leader and Professor of Analytical Chemistry at LundUniversity.
Thread-thin sampler
The project was initiated during the fall of 2003 and proceeded for just over four years. In total, about 20 researchers participated, and the researchers in Lund collaborated with, amongst others, Denmark´s National Environmental Research Institute in Roskilde.
The actual sampler, a thread-thin permeable tube with a hole-fiber membrane (which captures the material), can be adapted in size and membrane type depending on which materials one is interested in and how large concentrations one desires. Jan Åke Jönsson compares the technology with how a thermometer works.
A thermometer measures temperature in, for example, a container with water. But to avoid having the thermometer influence the sample, the thermometer can´t be too large in relation to that which is being measured, because otherwise it can influence the temperature in the water. “The principle for balanced sampling that we have developed is, therefore, designed so that it won´t influence the sample that will be measured. In that way a sort of balance is achieved," he says.
Tested in Ethiopia
The technique has been tested in Ethiopia, in a project where environmental pollutants in Ethiopian lakes were measured. But, according the Jan Åke Jönsson, it will take time before the technique can be used in full-scale applications. "Before it comes to practical use, it must be accepted as accurate and useful for these types of measurements. We are currently at a stage where we are presenting the principles, primarily to other researchers. In the future we also aim to measure traces of pharmaceuticals in nature, because we believe that balanced sampling is a very relevant method for gaining a deeper understanding of the spread of different pharmaceuticals and their effects in nature," says Jönsson.
