Research interests within the Environmental Mineralogy Research Group include:

The list below contains short descriptions of our current research topics, while our publications are here.


Properties and formation mechanisms of carbonate and phosphate minerals in lakes

This line of research developed from our interest in Lake Balaton, a large,  shallow lake that has a distinguished place in Hungarian hearts and culture (including science). We study sediment formation in the lake, with a focus on carbonate precipitation and phosphorus cycling. Our mineralogical work resulted in new knowledge on the heterogeneous nucleation of carbonates and freshwater dolomite formation, all of which have some relevance to lake ecology and lake management. Distinct research topics in this theme are the following:

  • Effects of heterogeneous surfaces (primarily clays) in carbonate and phosphate precipitation. Using an automatic titrator we feed Ca into a carbonate-bearing solution, and measure the dissolved Ca with an ion-selective electrode in order to identify nucleation events and to compare clay-free and clay-containing systems (see Molnár et al. 2021). Similar experiments are performed for phosphates. For studying the precipitated materials, we use TEM. 
  • Protodolomite structure and formation. This topic was initiated by Enikő Magyari (Eötvös University, Budpest) who found two distinct Mg-rich layers (about 5 and 8 ky ago) in the sediment core of Lake Balaton. We use HAADF imaging and elemental mapping to study atomic-scale ordering of Mg and Ca in dolomite-like and calcite-like domains and wish to understand the environmental and climatic changes that caused the formation of abundant protodolomite. 
  • Phosphorus in lakewater sediments, inspired by an algal bloom in Lake Balaton in August 2019, an unexpected event for which a large supply of "internal" phosphorus was necessary.  At the moment we are studying the distribution of phosphorus in our lake sediment samples (it is expected to be bound to carbonates and iron oxides). In addition, we carry out lab experiments to understand how P is bound to sediment minerals and under what conditions will it be released. 
  • Polyphosphate inclusions in aquatic microorganisms and thier potential role in P cycling in lakes. By TEM measurements we found that polyphosphate granules were prolific in various algal species collected during an algal bloom. On the other hand, we detected similar P-rich granules in the sediment. In order to understand whether the two pools of P-rich solid particles are related, and whether they are important components of the P cycle, we study both sediment and algal samples from the lake, and perform controlled experiments with algal cultures (in collaboration with Boglárka Somogyi and Attila Kovács (BLKI Tihany) and Vera Istvánovics (BME)). 


Structures and formation of biominerals

We have been involved for more than 20 years in research on magnetic biominerals produced by magnetotactic bacteria, mainly focusing on the special properties (size, structure, composition, magnetism) of magnetite and greigite nanocrystals that formed inside the cells of bacteria (see our list of publications). Recently, partly motivated by our work on lacustrine carbonates, we started to study the interesting nanostructures of carbonate biominerals.

  • Potential dissolution of spent Dreissena shells in Lake Balaton. Two invasive species of Dreissana populate the bottom of the lake. Despite the presence of aragonitic shells, we hardly found any aragonite in the sediment, according to XRD, raising the possibility of the dissolution of spent shells.  We are performing both field and lab dissolution experiments (in collaboration and with the direction of Csilla Balogh, BLKI Tihany) in order to understand the fate of shells. The topic has general relevance for both lake ecology and carbon dioxide fixation. 
  • Nanostructure of mussel shells and fish otoliths. While working on the above topic (shell dissolution), we discovered that Dreissena shells contain a variety of planar defects in the structure of aragonite. Our goal is to characterize the types of defects and understand whether they have a biological(?) function. Aragonite of fish otoliths also displays interesting structural phenomena that we wish to understand better. For studying structural features in various aragonite samples we are involved in a joint project with Aleksander Recnik and Vesna Ribic (Ljubljana), Pavel Gavryushkin (Novosibirsk) and Péter Németh (CsFK, Budapest).
  • Bullet-shaped magnetite in magnetotactic bacteria. Some strains of magnetotacic bacteria produce magnetite nanocrystals with highly unusual and highly controlled, bullet-shaped morphologies. Despite considerable research, neither the exact crystallographic morphology (faces? curved surfaces? elongations?), nor the growth mechanism is satisfactorily known. We collect bacteria form lakes perform STEM tomography for obtaining the precise morphologies of bullet-shaped magnetosomes and their positions within the cells. 
  • Polyphosphate inclusions in magnetotactic bacteria. Some magnetotactic cocci build enormous polyphosphate inclusions, raising the question whether they play important role in shuttling phosphorus under changing redox conditions. At the moment we are trying to isolate such bacteria from the mud of Lake Balaton. 
  • Biomineralization in genetically modified or cultured magnetotactic bacteria. We perform TEM studies and crystallographic analysis on nanominerals formed by bacteria that were cultured or genetically engineered by our collaborating partners at Bayreuth University (Dirk Schüler and Marina Dziuba) and CEA Cadarache (Damien Faivre and Yeseul Park).
  • Microbial formation of Se and As minerals. We perform TEM studies and crystal chemical anlaysis of solid materials produced by Shewanella from Se- and As-bearing solutions, in order to assist Lucian Staicu (U. Warsaw) in his microbiological experiments. The topic has nanotechnological relevance for the cleanup of wastewater (see Staicu et al. 2022).


Properties of individual atmospheric aerosol particles

A long-time research interest of our group is the TEM study of invidiual atmospheric aerosol particles, in order to understand their physical and chemical properties, and the consequences of these properties for atmospheric processes, climate, and health. Our current themes are mostly concerned with anthropogenic particles from combustion sources:

  • Origin and properties of urban magnetic aerosol particles. We compare magnetically separated particles from three sources: the urban atmosphere, exhaust from internal combustion engine vehicles, and vehicle brakes. The significance of the research is the assumed harmful effect of magnetic particles on human health. 
  • Individual aerosol particles produced by burning household waste. The burning of household waste is one of the major sources of urban air pollution. Members of the Air Chemistry Research Group (András Hoffer, Ádám Tóth) performed controlled burns of specific waste types, and we study and chracterize the particles produced by distinct fuels. We identify certain properties (soot morphology, composition, presence of specific elements) that can be used as markers for tracing the origin of these particles.