Dr. Axel Horst

Contact / Addess:



Phone +49 (0) 341 235 1360
Fax +49 (0) 341 235 450822

Helmholtz Centre for Environmental Research - UFZ
Permoserstrasse 15
04318 Leipzig

Dr. Axel Horst

Research topics:

Halogenated organic compounds are ubiquitously distributed in the environment. These compounds are not only human-made but they are also released by multiple biogenic and abiogenic processes including production by terrestrial and marine plants, volcanoes, wildfires, and so on. Many of these halogenated compounds have direct and indirect adverse effects on flora and fauna and increasing efforts have been invested to better understand the fate of these substances. The use of stable isotope analysis was developed in the last decades and this technique has contributed to a better source differentiation and provided additional process level information of halogenated organics. I’m interested in studying the fate of these halogenated contaminants in water and air. My personal expertise is the development of new analytical methods for less-commonly used isotopes such as chlorine and bromine and to use these techniques in conjunction with established isotopic techniques to study the physical and chemical processes of halogenated organics in the environment.

Previous projects:

DEMETROPIS (2016-2018): This project was funded by a Horizon 2020 Marie Słodowska Curie individual fellowship (No. 701350) and aimed at improving our understanding of abiotic degradation mechanisms of ozone depleting methyl halides by using multiple stable isotopes in these substances. Specifically, a new and universal method for the measurement of stable chlorine isotope ratios was established, permitting now the analysis of the stable isotopes of three different elements in these compounds. With these methods a major sink for methyl chloride and methyl bromide was investigated: the abiotic degradation by hydrolysis and halide exchange in ocean water. Isotopic results revealed large isotope fractionation for carbon and chlorine/bromine but relatively small fractionation for hydrogen. These results deliver valuable insights in isotope fractionation effects caused by abiotic degradation mechanisms and may be used in future isotope-based studies for the source apportionment of methyl halides.

Degradation of chlorofluorocarbons (CFC) in groundwater (2013-2016): In this project we investigated the potential of stable carbon isotope analysis to study degradation of CFC in groundwater. A method, capable to extract CFC from up to 500 mL of water was developed and ground-truthed for conservation of the stable carbon isotopic signature. The measurement of first field samples indicated that carbon isotope fractionation of CFC in groundwater was indeed occurring indicating that degradation may be identified and quantified using this technique.

Curriculum Vitae

Postdoctoral Fellow
Helmholtz Centre for Environmental Research – UFZ
Department of Isotope Biogeochemistry
Postdoctoral Fellow
University of Toronto, Earth Sciences, Toronto, Canada
Doctoral degree (Ph.D.)
Deptartment of Applied Environmental Science (ITM), Stockholm University, Sweden
Research assistant
Centro de Estudios del Agua, Instituto Tecnológico y de Estudios Superiores Monterrey (ITESM), Monterrey, Mexico
Diplom (Master)
Technische Universität Bergakademie Freiberg, Germany


Keppler F., Barnes J.D., Horst A., Bahlmann E., Luo J., Nadalig T., Greule M., Hartmann S.C., Vuilleumier S. (2020), Chlorine isotope fractionation of the major chloromethane degradation processes in the environment, Environmental Science & Technology, Vol 54 (3), pp 1634-1645

Phillips E.,  Gilevska T., Horst A., Manna J., Seger E., Lutz E.J., Norcross S., Morgan S.A., West K.A., Mack E.E., Dworatzek S., Webb J., Sherwood Lollar B. (2020), Transformation of chlorofluorocarbons investigated via stable carbon compound-specific isotope analysis, Environmental Science & Technology, Vol 54 (2), pp 870-878, full text (open access)

Horst A., Bonifacie, M., Bardoux, G., Richnow H.-H. (2019), Isotopic characterization (2H, 13C, 37Cl, 81Br) of abiotic degradation of methyl bromide and methyl chloride in water and implications for future studies, Environmental Science & Technology, Vol 53 (19), pp 8813-8822

Renpenning J., Horst A., Schmidt M., Gehre M. (2018), Online isotope analysis of 37Cl/35Cl universally applied for semi-volatile organic compounds using GC-MC-ICPMS, Journal of Analytical Atomic Spectrometry, Vol 33, pp 314-321

Horst A., Renpenning J., Richnow H.-H. and Gehre M. (2017), Compound specific stable chlorine isotope analysis of volatile aliphatic compounds using gas chromatography hyphenated with multiple collector inductively coupled plasma mass spectrometry, Analytical Chemistry, Vol 89 (17), pp 9131-9138, full text (open access)

Horst, A., Lacrampe-Couloume G. and Sherwood Lollar B. (2016): Vapor pressure isotope effects in halogenated organic compounds and alcohols dissolved in water, Analytical Chemistry, Vol 88 (24), pp 12066−12071                 

Thornton, B. F., Horst A., Carrizo D., Holmstrand H. (2016), Methyl chloride and methyl bromide emissions from baking: an unrecognized anthropogenic source, Science of the Total Environment, Vol 551-552:327-33

Horst, A., Lacrampe-Couloume G. and Sherwood Lollar B. (2015): Compound-specific stable carbon isotope analysis of chlorofluorocarbons in groundwater, Analytical Chemistry, Vol 87 (20), pp 10498–10504

Horst A., Andersson P., Thornton B. F., Holmstrand H., Wishkerman A., Keppler F., and Gustafsson O. (2014), Stable bromine isotopic composition of methyl bromide released from plant matter, Geochimica et Cosmochimica Acta, Vol 125, 186-195

Horst A., Thornton B. F., Holmstrand H., Andersson P., Crill P. M., and Gustafsson O. (2013), Stable bromine isotopic composition of atmospheric CH3Br, Tellus B, Vol 65, p. 1-8

Thornton, B. F., Horst A., Carrizo D., Holmstrand H., Andersson P., Crill P. M., and Gustafsson O. (2013), A high-volume cryosampler and sample purification system for halogen isotope studies of methyl halides, Journal of Atmospheric and Oceanic Technology Vol 30, Iss 9, p. 2095-2107

Horst A., Holmstrand H., Andersson P., Andersson A., Carrizo D., Thornton B. F., and Gustafsson O. (2011), Compound-specific bromine isotope analysis of methyl bromide using gas chromatography hyphenated with inductively coupled plasma multiple-collector mass spectrometry, Rapid Communications in Mass Spectrometry, Vol. 25(17), p. 2425–2432,

Horst A., Mahlknecht J., López-Zavala M.A., Mayer B. (2011): The origin of salinity and sulphate contamination of groundwater in the Colima State, Mexico, constrained by stable isotopes. Environmental Earth Sciences Vol 64 (7), p. 1931-1941.

Horst A., Mahlknecht J., Merkel B., Aravena R., Ramos-A. Y.R (2008): Evaluation of recharge processes and the impacts of irrigation on groundwater by using CFCs and radiogenic isotopes in the Silao-Romita basin, Mexico. Hydrogeology Journal Vol.16 (8), p.1601-1614

Mahlknecht J., Horst A., Hernandez-Limon L.G., Aravena R. (2008): Groundwater geochemistry of the Chihuahua City region in the Rio Conchos Basin (Northern Mexico). Hydrological Processes Vol 22 (24) p. 4736 - 4751

Horst A., Mahlknecht J., Merkel B. (2007): Estimating groundwater mixing and origin in an overexploited aquifer in Guanajuato, Mexico using stable isotopes (strontium-87, carbon-13, deuterium, oxygen-18). Isotopes in Environmental and Health Studies Vol 43 (4). p. 323-338


Ph.D thesis: Stable bromine isotopic composition of methyl bromide - Method development and applications

M.Sc. thesis: Use of stable and radioactive isotopes and gaseous tracers for estimating groundwater recharge, time of residence, mixing of the different types of groundwater and origin in the Silao Romita Aquifer, Guanajuato, Mexico