Research

Soil Science Group

Arsenic, Antimony and Mercury in soils

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

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.

Arsenic biomethylation across microbial phyla

Arsenic, a carcinogenic element, undergoes extensive microbial cycling in soils, including methylation. It is unclear whether this process is an arsenic detoxification mechanism or a strategy to inhibit the growth of competitors. Our overall objective is to shed light on the role of soil microbial arsenic methylation by combining state-of-the-art analytical speciation techniques with microbiological and molecular biological techniques. This research will allow a better understanding of its biogeochemical cycle and may lead to direct applications for bioremediation.

PhD student: Karen Viacava
Project leader: Prof. Dr. Adrien Mestrot, Dr. Rizlan Bernier-Latmani (Environmental Microbiology Laboratory, EPFL)

Organic and inorganic arsenic species

Assessing the cascading effects of arsenic on the health of soils, plants, microorganisms and humans: 2018-2021

see One Health Project

Antimony in Swiss shooting range soils

Antimony is used as a hardening agent in ammunition and is accumulating in shooting range soils. Since antimony is toxic and can cause severe health effects it is necessary to take a closer look at this poorly studied environmental pollutant. Our projects aim to examine the mobilization potential of antimony in soils. We focus on developing method to capture and quantify volatile antimony and on investigating the influence of temperature changes caused by climate change on the mobility of antimony in flooded soils.

PhD student: Jaime Caplette
Coworkers: Lucija Stanisic, Stephanie Pfister
Project leaders: Prof. Dr. Adrien Mestrot, Dr. Moritz Bigalke, Dr. Jen-How Huang (Departement of Environmental Sciences, University of Basel)

Target area of a shooting range

Antimony mobilization in rice paddy fields

The Xikuangshan mining area in Lengshuijiang, Hunan, China, is one of the largest antimony deposits in the world. Our project is a collaboration with the Chinese Academy of Sciences and focuses on understanding antimony mobilization in rice paddy fields. This includes antimony mobilization in paddy soils, rice plant uptake, biomethylation and biovolatilization of antimony. We deployed the first ever set-up to measure volatile antimony production in rice paddy fields and discovered that volatile antimony is indeed produced from rice paddy fields to the atmosphere.

PhD student: Jaime Caplette
Project leader: Prof. Dr. Adrien Mestrot
Collaborators: Profs. Xinbin Feng and Hua Zhang, State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences

Research setup in a rice paddy field

Biomethylation of mercury in a polluted agricultural floodplain

The biomethylation of mercury to methylmercury is a process that drastically increases the toxicity of this trace element. Methylmercury formation happens mainly under the water surface in oxygen poor and organic carbon rich environments. We study the influence of flooding and agricultural practices (e.g. manure amendment) in mercury polluted agricultural floodplain soils between Visp and Raron (VS).

PhD student: Lorenz Gfeller
Project leader: Prof. Dr. Adrien Mestrot

Two people on an agricultural field in Raron

Biomethylation of mercury in rice paddy fields

The biomethylation of mercury to methylmercury is a process that drastically increases the toxicity of this trace element. Methylmercury formation happens mainly under the water surface in oxygen poor and organic carbon rich environments. We study the influence of flooding and agricultural practices (e.g. manure amendment) in regularly submerged rice paddy soils in mercury polluted mining areas, in Wanshan (China).

PhD student: Lorenz Gfeller
Project leader: Prof. Dr. Adrien Mestrot
Collaborators: Profs. Xinbin Feng and Hua Zhang, State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences

Two people in a rice paddy field

Fate of mercury and methylmercury in terrestrial food chain (Switzerland)

Mercury is a toxic heavy metal and methylmercury is the most toxic organic compound of mercury because it bioaccumulates in the environment and biomagnifies in the food chain. The fate of mercury and methylmercury, once in the food chain, is not well understood, especially in the terrestrial environment. This research principally focuses on measuring the baseline mercury concentration and the rate of biomagnification in the terrestrial food chain in Switzerland. With an aim to develop a non-invasive method for conducting long term environmental biomonitoring, the research emphasizes on the suitable matrix and species of the terrestrial animals found in Switzerland. The study will help to answer: if the contamination and bioaccumulation of mercury pose a risk to certain animals of higher trophic levels; which environments are more prone to mercury accumulation; and what are the major sources of mercury to terrestrial animals in Switzerland.

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

Alpine ibex, eurasian lynx and golden eagle connected in a food chain scheme