Real-time monitoring of micropollutants

Article from the Info Day Magazine 2022

The results surprised even the researchers. In a small stream – which, like many others, flows through fields and orchards – pesticide concentrations were measured in early summer 2019 that exceeded the permissible maximum by up to 30 times. This has been made visible by “MS2field”, a mass spectrometer brought into the field.

For environmental engineer Christoph Ort, the limited knowledge about such environmental pollutant peaks in water bodies was the main reason why he together with his colleague, environmental chemist Heinz Singer, developed the MS2field device: “With the previous methods for water testing, you had to invest a lot of time and money in taking, transporting and preparing samples before you could even start measuring. That’s why composite samples are often taken, which cover longer periods of time but say little about short-term dynamics.” If a long time elapses between storage and measurement, there is also the risk that some substances will change and the results will be falsified accordingly. Another disadvantage is that conventional measuring methods often take weeks to months before the final results are available. Should critical substances then show up in the data, valuable time has already passed before any action can be taken.

Live in the field via smartphone

The situation is completely different with MS2field. Using a smartphone, the researchers can follow live which pollutants are present in the water bodies and how their concentration changes. For this purpose, water is continuously pumped from the test water using a hose. Every twenty minutes, a small sample is automatically filtered and processed in the MS2field trailer. The substances contained in the water are separated chromatographically so that they can be analysed qualitatively and quantitatively with the built-in mass spectrometer. Once the measurement is complete, the data is automatically evaluated within a few minutes and transferred to a server, where it can be retrieved at any time via the Internet. If the research question requires it, the measurements can be run for months – and with minimal, usually weekly, on-site maintenance work.

Conventional measured values massively exceeded

In the case of the small stream, the advantages of this first mobile and fully automated water laboratory became particularly clear. As conventional composite samples were also taken over three and a half days during the same measuring period and analysed in the laboratory at Eawag, the data from the two measuring systems could be compared directly. It turned out that the maximum concentrations of the 20-minute MS2field measurements exceeded the mean concentration values from the multi-day composite samples by up to 170 times. As known from other studies, depending on the pesticide, aquatic organisms can already be harmed if they are exposed to too-high concentrations for only one hour – a risk, however, that only became visible with the MS2field water analyses with high time resolution. Thanks to such data, it is now possible to better assess the fluctuations and peak concentrations to which aquatic organisms may be exposed for a wide range of pesticides.

Environmental engineer Christoph Ort and environmental chemist Heinz Singer inside the MS2field.
(Photo: Aldo Todaro, Eawag)

Diverse applications

However, pesticide measurement in streams is only one of the possible applications of MS2field. With the mobile water laboratory, the researchers have, for example, also examined the inflows and outflows of wastewater treatment plants. Here, too, the 20-minute measurements revealed pollution patterns that would otherwise remain undetected. These samples can be used, for example, to draw conclusions about how micropollutants enter the sewage system. In the wastewater from Fehraltdorf-Russikon, for example, it was observed that the concentration of candesartan – a frequently taken antihypertensive drug – fluctuated systematically on a daily basis. The highest values were reached in the morning, which is probably related to the first visit to the toilet in the morning. Pesticides were also detected in the wastewater. Mecoprop, for example, which is supposed to protect bitumen membranes on flat roofs from root penetration, reached its highest concentration after the only rainfall during the measurement period; the rain washed out the herbicide and flushed it into the sewage system.

Prototype has proven its worth

The examples of the small stream and the Fehraltdorf-Russikon wastewater treatment plant demonstrate that even though MS2field is only a prototype, it provides not only reliable but also interesting data. Accordingly, Christoph Ort and Heinz Singer also draw an extremely positive conclusion: “To be honest, we were surprised at how flawlessly MS2field ran almost from the start, and we were delighted that the unit can generally be operated in a very stable manner; our accurate and comprehensive planning paid off. Even operating such a device under constant laboratory conditions is demanding. However, no-one had ever built such an instrument into a trailer to measure directly in the field. We had to think of an enormous number of things that need to be automatically detected and rectified – or set it up so that problems can be reported via text message and resolved remotely.”

Portable minilab as the next objective

And the success story is set to continue in the coming years. It is planned to continuously expand the range of applications. Christoph Ort comments: “We are constantly learning how we can use MS2field in even more diverse ways. It is often young talents who come up with new ideas, and thanks to the competent support of the technical department, these can be implemented and tested promptly in each case with the help of suitable electronics and sensor technology.” In the near future, for example, applications are planned in spring water and in combined water overflows of wastewater treatment plants. Sometimes orders also come from practice, and even from abroad. Nevertheless, MS2field has so far been a research instrument, because despite a lot of automation, it needs plenty of expertise in analytical chemistry to operate the device optimally. Accordingly, Eawag is working to make MS2field even more practical. In addition, the MS2field team's vision goes further: “We want to measure with even higher temporal resolution and make the next version smaller and more autonomous, while consuming less energy. This would allow us to use MS2field in the future at measurement sites without car access and the power grid.”

The most important components in the air-conditioned MS2field trailer: A pump (1) continuously conveys water from the subject body of water. A small part of the flow is diverted through a filter (2) for analysis. For the quantification of the substances, a highly precise dosing syringe (3) adds a mix of isotope-labelled standards (4) to a precisely defined sample volume. At valve position I of the switching valve (5) (blue dotted line), this sample is then passed over a solid phase extraction (SPE) cartridge (6) on which the dissolved substances are extracted. Then, with the valve in position II (pink line), the substances are released from the SPE cartridge with the aid of the LC pump (7), separated by liquid chromatography in the LC column (8) and then measured in the mass spectrometer (9). Together with sensors for monitoring – flows, pressure and temperatures, for example – a programmable logic controller (PLC (10)) regulates all process automatically. The PLC sends warnings to the staff via text messages, allows them to control the process manually via remote PC access (11) and to visually check the inside of the trailer with webcams (12). The course of concentration of the substances in the water body (13) can be monitored online, with a new measuring point being added every 20 minutes.
(Graphic: Peter Penicka, Eawag)

Created by Christine Huovinen for the Info Day Magazine 2022