She is originally from New Zealand and gained her PhD on “Stable isotopes as indicators of nitrate attenuation across landscapes” at Lincoln University (New Zealand). Thanks to a Fulbright scholarship, she spent one year of her doctoral research working at the International Rice Research Institute to develop stable isotope-based measures of nitrogen losses in rice paddy systems. About her background, she received her MSc (with distinction) in Soil Science from the University of Aberdeen in the UK and her Bachelor's degree in Environmental Science from Wellesley College in the USA. At present, Naomi is developing “isoflux“ type models to improve estimations of nitrogen loss pathways and rates within complex contaminated aquifers.
Why did you apply for an ER position on ADVOCATE Project? What attracted you to the project?
I was excited by the possibility to continue developing the tools I’d developed during my PhD research and applying them to a new environmental problem (i.e., shifting focus from agriculture sustainability to contaminant remediation). Besides the research, the possibility of working on a ‘big project’ like an ITN was very attractive to me. After working in New Zealand, where you’re probably always a four hour flight away from your closest collaborators, becoming a part of this tightly connected research network was quite novel!
Your work is being developed on-site in Leuna, Germany, with a huge industrial legacy since the agricultural revolution. Can you tell us more about the site background?
Leuna has been a centre of German industry for hundreds of years. There are still many companies operating in the ‘Leuna Werk’ today, including Linde, a company that will probably be familiar to any people working with gas in the laboratory! When I learned that this could potentially be one of my research sites I was actually really excited because I’d recently read Thomas Hager’s excellent 'The Alchemy of Air', which describes how Haber and Bosch discovered the process to make nitrogen fertilisers and began manufacturing them at the Leuna Werk. You’d never guess the pivotal historical events that took place there if you visit today, though… However, the reason that this location has become a focus of contaminant remediation research is actually more closely related to the Second World War, when bombs hit one of the refineries and propelled the entire oil supply straight into the deepest groundwater. Seventy odd years later, it’s still there.
It is well known that nitrogen is an essential element in our lives, a primary nutrient for the survival of all living organisms but how can N become a pollutant?
It’s exactly nitrogen’s importance that makes it such a ubiquitous pollutant! Even though nitrogen is extremely abundant (it makes up 98% of the air around us!), the vast majority of it is not in a biologically available form. The end result is that the growth of most plants, microbes, etc. is limited by the amount of ‘available’ nitrogen around… and that humans spent hundreds of years searching for a way to get more of this available nitrogen to their crops! Now that we have synthetic nitrogen fertilisers (thanks to Haber, Bosch, and the Leuna Werk) agricultural production has massively increased, livestock production has massively increased, the human population has grown… the end result being that the turnover of reactive nitrogen has actually doubled over the past one hundred years.
As this nitrogen moves through the environment it has a dramatic impact on ecosystems. Again, because it’s so important to biology, even small changes in concentration can have a dramatic effect. A good example of this is eutrophication: if too much nitrogen gets up in a water body the plants and microbes start going crazy, and grow so quickly that the oxygen supply is quickly depleted, causing the biology of the system to then collapse.
This issue of the ‘nitrogen cascade’ is covered very well by James Galloway’s work (Galloway et al., 2003; Galloway et al., 2014):
Galloway, J.N., Aber, J.D., Erisman, J.W., Seitzinger, S.P., Howarth, R.W., Cowling, E.B., Cosby, B.J., 2003. The nitrogen cascade. Bioscience 53, 341-356. Galloway, J.N., Winiwarter, W., Leip, A., Leach, A.M., Bleeker, A., Erisman, J.W., 2014. Nitrogen footprints: past, present and future. Environ. Res. Lett. 9, 11.
Also, nitrogen undergoes transformations and they are highly dependent on the activities of a diverse assemblage of microorganisms. However, it is not well identified that if the N concentration on a specific site is decreasing is due to the microorganisms or other factors, why?
Nitrogen is always a tricky (and exciting!) scientific puzzle because it is so reactive, and occurs in many different forms in nature, each of which has a different level of chemical/physical mobility. So it can be very challenging to tell if a change in concentration in one of these forms represents a change in the total concentration, or just a chemical/ biological transformation. When discussing nitrogen as a contaminant, what we’re really interested in is the reactive nitrogen transforming back into its inert form, so we want to be able to distinguish this from more temporary removal pathways like uptake by plants or immobilization in organic matter, etc.
Related to the previous question, you are working on quantifying the importance of in situ nitrogen cycling for the remediation of contaminated groundwater megasites. To do this, you are using advanced N isotopes to detect the microbial populations for developing sensitive indicators of in situ transformations. Can you tell me more about this issue?
The majority of nitrogen atoms have a mass of ‘14’, but a small percentage have an extra neutron (creating an isotope with a mass ‘15’). Because this heavy nitrogen is handled slightly differently, measuring changes in the distribution of heavy v. light nitrogen isotopes in the environment can be used to trace biological reactions. For instance, the microbes that transform nitrate (a very form of nitrogen) into N2 gas (inert nitrogen) preferentially use light isotopes, meaning that the nitrate left behind will get ‘heavier’ the further along the reaction progress. Understanding how different biological (and chemical) reactions affect the isotopic composition of different nitrogen species can therefore provide cool avenue to explore for developing better and more complete ways of tracking nitrogen’s fate in the environment.
About your future, where would you like to develop your professional career? Where do you see yourself?
My career goal from the scientific point of view is to develop an isotope-based tool box’ that I can use to help people tackle the many and varied issues arising from alterations to nutrient cycles. And of course to keep improving our understanding of isotope dynamics to make these tools more precise and flexible along the way! After working in contaminated groundwater, freshwater ecosystems, and agricultural soils, I’m keen to tackle some of the unique challenges to effective nitrogen management in new environments (e.g. water-scarce regions).
If you had to describe yourself in a phrase, what would it be?
Questioning.
