Short-term peak concentrations are severely underestimated

A glimpse inside the measurement trailer (Photo: Eawag) - The mobile and automated MS2field mass spectrometer allows measurements to be taken of harmful substances in surface waters with high temporal resolution. The initial measurements using the device are revealing the extent to which peak concentrations of pesticides, for example, have been underestimated by traditional methods. Although it is actually only a prototype, the fully automated mobile water laboratory known as MS2field is already delivering reliable - and controversial - data. In an article published today in the journal Aqua&Gas, the Eawag researchers responsible for the platform describe not only how it works, but also how they used it to measure pesticide concentrations in a small stream in an agricultural area. MS2field automatically collects, prepares and analyses a sample every 20 minutes, allowing major changes in concentration - by several orders of magnitude in the space of hours or days - to be detected with unprecedented clarity. Over the same measurement period, the researchers also collected conventional composite samples - each of them over a period of 3.5 days - which they analysed in the laboratory in the traditional way. In doing so, the team was able to demonstrate the extent to which the traditional method underestimates peak concentrations because they are missed, or rather diluted.