What first sparked your interest in environmental chemistry and water quality?
I chose to study chemistry, and biochemistry more broadly, because I wanted to understand how nature works: what it’s made of and how it all comes together – from food to the environment.
I went into biochemistry for my master’s thesis, but quickly, I realized I wanted to do something for the environment. That led me to a PhD in environmental sciences in Berlin – which was a fascinating time, not too long after the Berlin Wall came down. I’ve stayed in this field ever since, with a strong desire to contribute to both science and society.
Your research focuses on micropollutants and transformation products in aquatic systems. What drew you to this area – and what keeps you engaged?
There are so many chemicals out there, with more and more constantly introduced into the environment. I’m particularly interested in chemical structures – identifying new chemicals and transformation products. Knowing what they are – as well as working with engineers to develop mitigation methods – is essential. This field combines my interests in chemical structures (organic compounds especially), analytical techniques, and environmental science.
High-resolution non-target screening has become central to your work. What excites you most about its potential, and what are the current limitations?
I started working with HRMS when the Orbitrap came onto the market, back in 2005. With its high resolution for chemical identification, it was an incredibly exciting tool. We often don’t have complete information about the chemicals present in the environment, which makes tools capable of identifying them – even at trace levels – very important. NMR is still the superior method for structure elucidation, but it generally requires pure chemicals and much higher concentrations than we find for micropollutants, which are typically present at trace levels. HRMS offers the sensitivity we need for such analyses.
Of course, there are limitations. Mass spectra are not always sufficiently informative; there isn’t always enough fragment data to make an identification, which makes standards often necessary. Some years ago, we developed a confidence level scoring system, now widely used in environmental science, to help communicate the certainty of an identification when no standard is available. This system defines levels based on the evidence available – whether it’s just the exact mass, the presence of fragments, or additional supporting information, such as results from transformation experiments where parent compounds yield identifiable products. This approach has become a valuable tool for improving transparency and consistency in non-target screening results.
What do you think needs to happen to bridge the gap between non-target screening research and its adoption in regulatory monitoring?
Standardization is difficult for non-target screening, but harmonization is realistic and necessary. We’ve made a start by publishing a ~100-page guidance document in Metrology in Measurement Science Europe via the NORMAN network: a Europe-wide network centered on emerging contaminants, where I lead the non-target screening group. It outlines good practices – both methodological and interpretive – and stresses that although vendor software is improving, users still need expertise to understand what the software is doing and how to set parameters appropriately. More training and clear guidance will help.
On the implementation side, there are already successful regulatory examples. In Switzerland, for about 10 years now, a high-resolution mass spectrometer has been operating at a monitoring station on the River Rhine. Daily non-target analyses flag recurring peaks that exceed thresholds. These are then identified and traced back to industrial sources, followed by engagement with the responsible parties. We helped to establish and train this team in Basel, and they now operate largely independently, asking for expert input only when needed. Similar activities are expanding to other Rhine states.
Beyond Switzerland, several German drinking water labs routinely apply non-target screening to scrutinize raw water. At the EU level, the Partnership for Chemical Risk Assessment is actively exploring how to bring new methods – including non-target screening – into regulation, in dialogue with agencies such as ECHA and EFSA. The remaining challenges are cost (due to expensive instrumentation), sustained training and continued methodological harmonization – but the path from research to practice is already being paved.
Would you say your work is driven more by fundamental questions or real-world environmental concerns – or do those naturally go hand in hand?
I try to connect both. I’m strongly motivated by my desire to ensure better environmental protection for the good of society. Much of our work is done in close contact with the Swiss Federal Office for the Environment, reflecting the applied nature of our institute – although I also teach at ETH. This means we’re often working directly with agencies to apply our findings in practice.
At the same time, I also supervise PhD students pursuing more fundamental research. One project, for example, is investigating how organisms take up pollutants, exploring the mechanisms behind contaminant uptake and toxicity. Balancing these applied and basic research strands allows me to address both immediate environmental concerns and deeper scientific questions, which I find to be very rewarding!
What’s the biggest challenge currently facing environmental analytical science?
In my area, it’s the sheer number of chemicals – and that number is still increasing. Industry is making efforts to design safer chemicals, but “safe-by-design” principles are not yet fully integrated, meaning we still have a huge amount of work to do.
It’s not just the parent chemicals that are a challenge. Many undergo transformation in the environment, creating multiple transformation products, depending on conditions. These can result from both biotic and abiotic reactions, both in organisms or the environment. Some transformation products can have the same – or even greater – toxicity as the parent compound. A major difficulty is that we often don’t have analytical standards for these transformation products, which makes detection and assessment more complex.
We also face a balance between high-throughput analysis and maintaining high data quality. Ten or twenty years ago, we would go through spectra one by one. Now, workflows and automation help process vast numbers of spectra quickly, which is essential given the scale of the problem. However, it remains essential to manually check spectra or use several tools to confirm an identification. If different tools agree, we can be more confident, but it’s not enough to simply list thousands of peaks – many are likely already known, or explained by contamination. The challenge is to identify what truly matters without compromising accuracy.
It’s worth mentioning that these are just the biggest challenges in my field. Of course, in other environmental science areas – such as climate change – the primary challenges are different, but equally pressing.
Has there been a mentor or colleague who’s had a lasting influence on your career?
Not a single individual per se, but I’ve been lucky to work with a number of excellent colleagues who have influenced my work. At our institute, it’s not a top-down model where one professor directs everything – it’s much more team-oriented. We work closely together and inspire each other, and I’m regularly motivated by the feedback and ideas my colleagues bring. We have weekly seminars involving PhD students, postdocs, and six senior scientists, which creates a steady exchange of perspectives.
I also draw inspiration from colleagues in other departments. We work in a highly interdisciplinary way, so engineers, toxicologists, and now increasingly data scientists all contribute to my research. Because my own background spans chemistry, biochemistry, and environmental sciences – and I’ve worked in different institutions, including in medical science. As a result, I’ve been shaped by a broad network of collaborators and disciplines, and now my focus is very much on water research.
What’s the biggest lesson you’ve learned in your career so far?
The biggest lesson has been the importance of working in teams, especially when tackling environmental or applied questions. Solving these kinds of complex challenges requires collaboration across disciplines and perspectives.
It’s enjoyable too. Working alongside others brings diverse expertise, sparks new ideas, and makes the process of research more engaging and rewarding.
What advice would you offer to the next generation of scientists entering the field of environmental chemistry?
Follow your passion and motivation – make sure you genuinely enjoy the science you’re doing. If you’re excited by your work, you’ll have the energy to push through challenges. Keep an open mind about your career path. For me, it was never guaranteed that I would stay in academia, and it’s important not to be fixed on just one route. If that path doesn’t work out, there are many other directions where you can have an influence and make a difference. The key is to remain motivated and flexible, and to find the kind of work that feels right for you.
What’s your overall outlook on the future of environmental chemistry and monitoring?
I believe the field will be increasingly shaped by data science and digital chemistry. Automation in the lab – both for chemical analyses and conducting experiments – will grow, extending into environmental science and risk assessment. High-throughput testing and biodegradation studies will become more common, producing vast datasets.
The ability to handle, evaluate, and interpret this data will be crucial. It’s for this reason that I believe coding and computational skills will become as important as traditional chemistry knowledge for the next generation. These combined capabilities will drive faster, more precise, and more comprehensive environmental monitoring in the years ahead.
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