Understanding Organic Matter in Water: Professor William H. McDowell is Senior Fellow at the Faculty of Environmental Sciences

As a follow up to his first visit last April and May, Professor William H. McDowell researched and taught at the Institute of Soil Science and Site Ecology at the Faculty of Environmental Sciences at the TU Dresden in October and November this year within the Senior Fellowship Programme. William McDowell, who has been Professor of Environmental Sciences at the University of New Hampshire, USA, since 1998, is an internationally well-known expert in the field of ecology and biogeochemistry of flowing waters at the interface between terrestrial and aquatic ecosystems. Continuing his work at the Institute next year in spring, Professor McDowell gave an insight into his research and teaching work as a Senior Fellow.

What are your general research interests?
Prof. McDowell: In general I try to understand how water quality in streams and rivers relates to the processes that go on inside the watershed, things like the functioning of soils and tree health. I've done a lot of work looking at the response of watersheds in Puerto Rico to hurricanes, that knocked down all the trees. I have also examined the effects of urbanization and other drivers within the landscape that can affect water quality.

How does your work as a Senior Fellow look like?
Prof. McDowell: I've given a series of guest lectures, for example at the biogeochemistry course as part of the MSc program in forestry. I will give one more in the spring seminars to the Department of Forestry at TU Dresden. I also work a bit with some of the classes that Professor Kalbitz is teaching.

But my main focus is on developing a shared research agenda with Professor Kalbitz. One of my primary areas of interest is understanding that yellow stuff in water, that we call dissolved organic matter. Professor Kalbitz is a global, world leading expert on organic matter in soil water and I've known him for almost two decades.  This fellowship represents a real opportunity for us to collaborate because he focuses primarily on the soil's end, the processes within soils that control the delivery of this yellow organic matter from land to stream. I really focus on what's in the stream and how it's transported and the biology of what's going on, whereas he focuses more on the chemistry. So it's a nice combination of similar interests but different intellectual approaches, different disciplines, one from soils and chemistry and me more from water, ecology and ecosystem science.

Can you tell us something more about your planned research project?
Prof. McDowell: We're trying to understand some of the long-term drivers, that have resulted in changes in this organic matter in water. There are a lot of hypotheses that have been proposed in the literature, for example changes in climate such as warming and rainfall. All of those may have an effect on what is delivered from the land to the water in terms of the organic matter, but which one is driving the changes is not clear. This represents a big management issue here in Saxony as it is in many places, because this organic matter, when it is in water has a lot of positive aspects in terms of ecosystem health. However, it's also a significant problem for water treatment. If we add chlorine to the water that contains organic matter, we can actually form compounds, variously called trihalomethanes or disinfection by-products. Basically, the chlorine reacts with the organic matter in water and forms some nasty compounds that are bad for human health. The water managers really care if their water supplies are increasing in the amount of this yellow organic matter. Because they have to get rid of it to insure a safe drinking water supply. So they really want to know: What's going to happen? Why is it happening? Why do we see these changes? In many watersheds, though not all by any means, but in many parts of the world, especially in the northern hemisphere, developed parts of the world, we've seen changes in the amount of this organic matter in water and we're not exactly sure why. Maybe it's because of changes in acid rain and other inputs to the soils, maybe it's because of changes in climate or other drivers. So that's why we would like to focus on changes in the organic matter in streams as a broad research topic.

I have study sites and collaborations in the US, in New Hampshire, where it's a very similar climate to here, and then a tropical site in Puerto Rico, and then also collaborations with scientists in Prague. So we have all these different field sites, where we can study the organic matter and how it may be responding to long-term global environmental changes. We want to find out, whether biotic or abiotic processes are most important or interactions between the two. Why in many cases and here in Saxony, why is this organic matter, this yellow stuff in water, increasing over time? Is it going to keep increasing or is it just a pulse of organic matter for five or ten years? Or will it just be a new normal situation with more organic matter in the water than in past years? That is something we want to take a look at because it's important for management and it is also a very interesting biogeochemical puzzle. We are studying together the biology, geochemistry and chemistry of processes in the landscape.

Will your collaboration continue after the Dresden Senior Fellowship Programm?
Prof. McDowell: Yes, our goal is to develop a longstanding collaboration that will go beyond next spring. We both will look for some additional funding to support that research and to allow for exchanges between our groups in terms of students and PostDocs for example. We will write some papers together and present the results at conferences. The Dresden Senior Fellowship Programme gave me the opportunity to begin a serious cooperation with Professor Kalbitz, whom I've known but have not worked with for a number of years. So it is a good opportunity.

Here you can find some more information about the Dresden Fellowship Programme.

Contact
Prof. Dr. Karsten Kalbitz
Professor of Soil Resources and Land Use
Institute of Soil Science and Site Ecology
Phone: +49 351 463-31379