The Whole Range of Environmental Processes

Processes in our environment influence the transport of contaminants in water, soil and air and the behaviour of microscopic particles. Two research groups at the Department of Environmental Geosciences are studying these processes with ground-breaking methods.

Feb. 1, 2016

Sand and gravel are the most commonly used construction materials. However, in an Alpine country like Austria, their supply is limited. Potential extraction sites conflict with other land uses. “For a long time, the excavation of gravel pits was considered problematic because of the supposed negative impact on ground water quality”, Thilo Hofmann, who leads one of the two research groups at the Department, explains. However, a country-wide study allowed the environmental geoscientist and his Research Group to demonstrate that gravel pit ponds can have very positive ecological impacts, which can even improve ground water quality.

Our goal is to understand crucial mechanisms that influence environmental processes and to apply this understanding to the solution of important current and future environmental issues.”

Thilo Hofmann, Professor of Environmental Geosciences

They attract specific animal and plant populations. If water polluted with nitrates or pesticides flows into the pond, the resident flora and fauna can degrade the pollutants. “If certain rules are followed, gravel pit ponds can be an efficient water filtration system,” says Hofmann. With their study, the researchers contributed to a guideline for the protection of ground water in sand and gravel extraction developed with the Austrian Water and Waste Management Association (ÖWAV). As a result, the province of Lower Austria has already revised its resource master plan.

Traces of anthropogenic inputs

In addition to hydrogeology, Thilo Hofmann’s team of environmental geoscientists studies pollutants and their behaviour in the environment. The focus is on contaminations and how to combat them. Current projects, for example, study the impact of microplastic particles on the behaviour of other contaminants in water and the use of biochar in the remediation of lightly contaminated soils. In some cases, anthropogenic pollutants can also make natural processes visible: In a project with a large water supplier, the scientists are using gadolinium as an indicator for interactions between river water and ground water. Gadolinium is used as a contrast agent in magnetic resonance imaging. The extremely stable and highly toxic substance is eliminated by the human body very quickly. “If a river contaminated with waste water infiltrates an aquifer, gadolinium is an ideal signal for our analyses,” says Thilo Hofmann. It allows the researchers to measure how much river water is entering the ground water, how rapidly the river water is moving and which proportion of contaminants it contains.

The Group’s third major area of research is nanogeoscience, i.e. the analysis of environmental processes on the nanoscale (a nanometre is a millionth part of a millimetre). Building on their internationally renowned analysis of natural nanoparticles, the focus of Thilo Hofmann and his colleague Frank von der Kammer is now on engineered nanoparticles.

We want to understand processes involving nanoparticles. After all, in terms of surface area, these tiny particles make up a large part of the reactive surface of our planet.”

Frank von der Kammer, Deputy Head of Department

In an ERA-NET project, the researchers are currently studying the use, behaviour and risk of nanopesticides such as copper oxide nanoparticles in soil. In a recently completed study, they examined the behaviour of technical titanium dioxide (TiO2) – a common component of sunscreen – in surface waters such as the Old Danube, a popular bathing spot in Vienna. They developed a special analysis method for this study. The Group is currently also contributing their experience in the development of methods to a number of international working groups, among them the development of OECD guidelines for the testing of nanoparticles.

“A core question of our research for the last decade has been how to distinguish engineered particles from natural particles in the first place,” says nanogeoscientist Frank von der Kammer, adding: “We have been able to show that it can be done with cerium dioxide, which is sometimes added to fuels.” The researchers found that natural particles often contain impurities. In natural samples, the metal cerium nearly always co-occurs with lanthanum at a 2:1 ratio, while engineered particles have an extremely high purity grade. To prove this, they developed a single-particle multi-element analysis method. The tool required for it, a time-of-flight mass spectrometer, is currently being applied for together with the Department of Analytical Chemistry. Using this method, they are planning to develop a reference database together with ETH Zurich: Natural particles will be analysed to determine their element patterns. This data can then be used as reference material for particles in unknown samples and will help to answer the question whether they are natural or engineered.

Environmental and isotope geochemistry

Environmental geochemistry of nutrients and pollutants is the focus of the second group at the Department led by Stephan Krämer. “The supply of vital micronutrients to bacteria, plants and humans influences our environment in major ways,” says Walter Schenkeveld, a scientist focusing on nutrient acquisition. “For example, the iron acquisition of phytoplankton in the ocean and the copper acquisition of methanotrophic bacteria influence the climate.” The team investigates factors causing a low supply of micronutrients in aquatic systems and soils, and which biogeochemical processes are used by organisms to increase the supply.

Stephan Krämer, Professor of Isotope Chemistry and Biogeochemistry

Krämer’s Research Group Environmental Geochemistry also analyses processes that can mobilise or immobilise inorganic pollutants such as mercury, uranium or chromium. One research question is: Under which conditions can soil contaminated by depleted uranium ammunition pose a risk for the ground water? Depleted uranium (a by-product of the enrichment of natural uranium) is used in armour-piercing shells deployed in many conflict areas. Another “dangerous mineral” is chrysotile. For decades, it was used to produce asbestos cement. The unregulated disposal of asbestos cement waste and its use as recycling material has caused soil contamination. A current project investigates whether and how quickly the natural weathering of chrysotile contributes to a reduction in contamination and whether the weathering process can be accelerated by plants.

The environmental geochemists also study the stable isotope geochemistry of metals in the environment. Most chemical elements of the periodic table consist of a mix of several stable isotopes. The exact isotopic composition of natural materials, i.e. the relative ratio of isotopes to each other, can vary minutely between environmental samples. “The high-precision measurement of the isotopic fingerprints of an element in an environmental sample can tell us about its geochemical history,” Jan Wiederhold, an environmental isotope geochemist in the Krämer Group explains, adding: “The characteristic isotopic signature allows us to distinguish between different contamination sources of heavy metals or different processes in biogeochemical cycles.” Current research in the Group focuses on the isotopic signature of mercury (Hg). Together with partners from Germany and Switzerland, the researchers aim to determine the transport pathways and transformation mechanisms of mercury in contaminated locations and advance the understanding of the behaviour of mercury in the environment. This high-precision analysis of isotope ratios of metals has only become possible recently with new methods such as Multicollector-Inductively Coupled Plasma Mass Spectrometry (MC-ICPMS). This method allows the researchers at the University of Vienna to investigate completely new questions in environmental geochemistry.