Research Projects Soil Science

Forschungsarbeiten im Getreidefeld

Arsenic, Antimony & Mercury in Soils

Arsenic (As), antimony (Sb) and mercury (Hg) have been heavily used throughout the last century and a half as pesticide, chemical weapons, flame retardants, in plastics and in ammunition, as amalgam for gold mining or as chemical catalysts. It was only recently that their negative impacts on the environment and humans have been evaluated. Such investigations almost always originated from reported environmental and human catastrophes. In the case of Hg, it was the Minamata Bay catastrophe in Japan. For As, it was the discovery of very high levels of naturally present As in the groundwater in SE Asia, impacting up to 100 million people. Sb has been much less studied than As or Hg and there is only very little legislation on this element although initial findings show that its behavior and toxicity are similar to As. However, these issues also exist locally. In Switzerland, 15-20t of Sb enters the soil each year through shooting activities while an important Hg pollution exists in Valais between Visp and Raron. Finally, hot-spots of naturally occurring As exist in the Jura, the Valais and in Tessin.

Our main goal is to study the behavior of As, Sb and Hg in soils in Switzerland in order to contribute to the remediation efforts in locally polluted areas. Our research also takes place in polluted areas of Bangladesh and of China so that we can understand the global behavior of these pollutants. Our focus is on assessing the microbial transformation of As, Sb and Hg in soils (e.g. biomethylation and biovolatilisation) by developing new analytical techniques (speciation analysis using chromatography and mass spectrometry). With these techniques we are able to precisely measure the different chemical species of these pollutants. Furthermore, our goal is to evaluate the influence of agricultural practices and climate change on these chemical species.

With rhizon sampler and flow pumps equipped flasks in a growth chamber

Research Projects

Last updated: March 2026

Arsenic

Environmental Drivers of Toxic Organic Arsenic Species Generation and Accumulation in Rice (ENORA). 

Effects of increased temperature and CO2 levels on arsenic species uptake in rice.

This project investigates how a highly toxic organic arsenic compound, dimethyl monothioarsenate (DMMTAV), forms in paddy soils and is taken up and accumulated in rice grains. Whilst current EU and WHO regulations and limits apply only to inorganic arsenic, recent data show that DMMTAV is both widespread in rice and significantly more toxic than inorganic forms of arsenic. One of ENORA’s main objectives is to use climate-controlled growth chambers to simulate future IPCC scenarios in order to test how climate change might alter the production and uptake of DMMTAsV and arsenic in general in rice, with direct implications for: food security, agricultural practices, ensuring climate-resilient agriculture.

Project leader: Prof. Dr. Adrien Mestrot, Dr. Yasmine Ali Farhat

Geogenic Arsenic in Swiss Rice Paddies

Arsenic is a carcinogenic element that occurs naturally in Swiss soils. For some years now, attempts have been made to cultivate paddy rice in waterlogged areas north of the Alps. The paddy rice is grown on formerly drained peatland which is degraded and is now partially wet again due to the close groundwater table. Growing rice in these fields could be an adaptation strategy for affected farmers. However, the cultivation of paddy rice and the associated flooding of the fileds mobilises arsenic and bacterial activity produces methylated arsenic species. The various arsenic species are absorbed by the rice plant and thus incorporated into the rice grain. The toxicity of the methylated species is not well known and not included in the food safety legislation.

Our aim is to determine the concentrations of the different arsenic species occuring in Swiss rice and to identify possible drivers in the Swiss context. For this, we use state-of-the-art analytical speciation techniques and cooperate with local and European experts. This research will allow a better understanding of the occurrence of arsenic species in rice and the impact of the cultivation of rice in Switzerland.

Project leader: Prof. Dr. Adrien Mestrot, Dr. Ikram Bakour

Antimony

Release, biomethylation and biovolatilisation of antimony (Sb) in soils: Drivers, mechanisms and global environmental implications

Sb release upon flooding

Antimony (Sb) can become highly mobile in flooded soils, posing a threat to surrounding environments. The project aims to investigate the mobility of Sb in flooded soils from Swiss shooting ranges and Australian antimony mine surroundings. Through laboratory simulations, we aim to understand the complex geochemistry driving antimony mobility under these conditions. Our analysis includes soil pore water chemistry, various antimony species, and the characterization of antimony-bearing colloids over time. Additionally, we examine volatile antimony and its binding in the soil. By gaining insights into antimony's behavior in flooded soils, this research enhances our ability to assess environmental risks associated with antimony contamination.

Sb Speciation and Biotransformation

The project is also dedicated to advancing analytical methods for investigating the speciation and biotransformation of antimony in soils. This focus involves developing new analytical methods and conducting direct measurements in both laboratory incubations and field environments. These measurements will provide valuable data on methylated and volatile Sb species formation in soils, allowing us to characterise the environmental relevance of biomethylation and biovolatilisation of Sb.

Project leader: Prof. Dr. Adrien Mestrot, Dr. Ikram Bakour

Mercury

Mercury at the Nanoscale: Unveiling HgS Nanoparticles as Hidden Drivers of Environmental Toxicity

Hg contamination remains a significant global environmental concern due to its persistence and toxicity, especially in the form of monomethylmercury (MMHg), a highly neurotoxic compound that poses risks to ecosystems, wildlife and human health.

In environmental systems, Hg occurs in multiple forms, among which mercury sulfide (HgS) nanoparticles are increasingly recognized as widespread in waters, soils, and sediments and as important contributors to MMHg formation. Their properties strongly influence Hg transport and bioavailability. However, their concentration, size, composition and reactivity remain poorly understood due to limited analytical methods and lack of reference materials.

This project aims to address these gaps by developing innovative methods and protocols to characterize HgS nanoparticles in both pristine and contaminated environments. Experimental incubations of soils and sediments will further investigate their environmental fate and role in MMHg production, ultimately advancing our understanding of mercury cycling and its ecological impacts.

 

PhD student: Evangelia Sigala
Project leader: Prof. Dr. Adrien Mestrot

Mercury in terrestrial environment in Switzerland: Bioaccumulation and biomagnification in food chains

Studies on mercury bioaccumulation and biomagnification in terrestrial food chains are scarce compared to aquatic food chains. With reducing global mercury levels in the environment, following the Minamata convention, we aim to monitor mercury in different environmental matrices and update the national database for terrestrial biota in Switzerland. Additionally, we aim to investigate biological factors like age, sex and diet, and environmental factors like proximity to local pollution sources and atmospheric Hg depositions to explain variations in tissue mercury levels.

There are three principal focuses:

  1. Method development for quantification of total, inorganic and organic mercury from different tissue samples.
  2. Study bioaccumulation and biomagnification in barn owl food chain using least-invasive tissue samples. The food chain consists of soil, prey fur collected from pellets, and down feathers of juvenile barn owls.
  3. Study bioaccumulation in wildlife (roe deer, lynx, and wolves) and assess threat to apex predators.

 

PhD student: Sabnam Mahat
Project leader: Prof. Dr. Adrien Mestrot