Articles | Volume 23, issue 21
https://doi.org/10.5194/bg-23-7787-2026
© Author(s) 2026. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/bg-23-7787-2026
© Author(s) 2026. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Research article
| 
05 Nov 2026
Research article |
| 05 Nov 2026
| 05 Nov 2026
Divergent mercury accumulation dynamics in tropical dry and moist broadleaf forests
Juan Francisco Morales Arteaga
CORRESPONDING AUTHOR
Department of Environmental Geochemistry, Technische Universität Braunschweig, Brunswick, 38106, Germany
Grace Tatiana Páez-Barrera
Departamento de Ciencias de la Vida y la Agricultura, Universidad de las Fuerzas Armadas ESPE, Sangolquí, 171103, Ecuador
Matthias Beyer
Department of Environmental Geochemistry, Technische Universität Braunschweig, Brunswick, 38106, Germany
Christian Birkel
Department of Ecohydrology and Biogeochemistry, Leibniz Institute of Freshwater Ecology and Inland Fisheries Berlin, Germany
Department of Geography, University of Costa Rica, San José, 11501-2060, Costa Rica
Werner Huber
Department of Botany and Biodiversity Research, University of Vienna, Vienna, 1030, Austria
María Auxiliadora Zúñiga Amador
Escuela de Ciencias Exactas y Naturales, Universidad Estatal a Distancia, Montes de Oca, 474-2050, Costa Rica
Harald Biester
Department of Environmental Geochemistry, Technische Universität Braunschweig, Brunswick, 38106, Germany
Marta Pérez-Rodríguez
CORRESPONDING AUTHOR
Department of Environmental Geochemistry, Technische Universität Braunschweig, Brunswick, 38106, Germany
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Thomas Maier, Sophia Dobkowitz, Wolfgang Jens-Henrik Meier, Matthias Beyer, Mona Quambusch, Ursula Fritsche, Puneetha Dharmapura Shrirama, Subhashmita Roy, Naga Venkata Sai Jitin Jami, Jonas Troles, Thomas Reinfelder, Nikolai Kendzia, Jörg Jaroszewski, Pauline Leonie Christianus, Thomas Roth, Andrea Kodym, Krissa Skogen, Frank Schumacher, Marcel Klaps, Jan Pinski, Nicole Baeumer, Kathrin Scharsich, Lydia Herrmann, Cord Jürgens, Jussi Grießinger, Achim Bräuning, and Björn M. Eskofier
EGUsphere, https://doi.org/10.5194/egusphere-2026-5892, https://doi.org/10.5194/egusphere-2026-5892, 2026
This preprint is open for discussion and under review for Geoscientific Instrumentation, Methods and Data Systems (GI).
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Trees help cities cope with heat, but only if their soil holds enough water. We measured soil moisture at 555 trees in 37 cities in Germany, Austria and Switzerland and studied how the soil responds to rain and watering. Warm weather lets the soil gain less water and dry faster. Watering lasts about three times longer than rain but brings no benefit if the soil is still wet, and open ground around a tree matters more than other site features. Soil sensors can help watering trees in drought.
Johannes Hoppenbrock, Matthias Beyer, Malkin Gerchow, and Matthias Bücker
EGUsphere, https://doi.org/10.5194/egusphere-2026-4818, https://doi.org/10.5194/egusphere-2026-4818, 2026
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Trees in cities cool the air and store carbon, but they need water, and it is important to understand where and when they take it up. We sent weak electric currents through the ground beneath park trees to see how water is distributed in the subsurface. The soil dried during the day, when the trees were taking up water, and recovered at night. The method can therefore follow a tree's daily water use without digging, which could help cities keep their trees healthy through dry summers.
Hyekyeng Jung, Chris Soulsby, Christian Birkel, Songjun Wu, Kristina Yordanova, and Dörthe Tetzlaff
EGUsphere, https://doi.org/10.5194/egusphere-2026-4371, https://doi.org/10.5194/egusphere-2026-4371, 2026
This preprint is open for discussion and under review for Hydrology and Earth System Sciences (HESS).
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A model is built on domain knowledge and improved by analysing its errors, which often leads to new insight about the system being studied. Here, we propose a machine-learning approach that analyses the time series of model errors and separates the information they contain by time step and by the delay to the driving conditions. Applied to an ecohydrological model, it shows how many days earlier a driving factor contributed to the model errors, and how this changes through the seasons.
Alberto Iraheta, Elise Malsch-Fröhlich, Malkin Gerchow, and Matthias Beyer
Hydrol. Earth Syst. Sci., 30, 5005–5021, https://doi.org/10.5194/hess-30-5005-2026, https://doi.org/10.5194/hess-30-5005-2026, 2026
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We present a simple and practical method for sampling water vapor for stable isotope analysis. Tests conducted under various conditions demonstrate that using 250-mL glass bottles, a flow rate of 100 to 125 milliliters per minute, and storage for up to 24 h at a temperature of 20 to 25 °C yields the most stable results. The method is cost-effective, non-destructive, and suitable for remote locations.
John D. Marshall, Maren Dubbert, Teresa E. Gimeno, Ruth-Kristina Magh, Kathrin Kühnhammer, David Dubbert, Paul Koeniger, Matthias Cuntz, and Matthias Beyer
Hydrol. Earth Syst. Sci., 30, 4757–4770, https://doi.org/10.5194/hess-30-4757-2026, https://doi.org/10.5194/hess-30-4757-2026, 2026
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Water transport in forest soils occurs both vertically and horizontally. We added a stable isotope label to a small forest plot and monitored its passage vertically into the soil and horizontally into stems of surrounding trees. The labelled water was detected in the upper layers of the soil and in trees up to 6.7 m away, but was mostly taken up by one tree adjacent to the plot. These results affect how we think about summing over individual trees to describe the water economy of a whole forest.
Lina Oskamp, Marta Pérez Rodríguez, Adelina Calean, Olaf Rienitz, Klaus-Holger Knorr, Kazumasa Oguri, Masashi Tsuchiya, Marco Benkhettab Sindlev, Stephan Krisch, Arianna Olivelli, Frank Wenzhöfer, Ronnie N. Glud, and Harald Biester
EGUsphere, https://doi.org/10.5194/egusphere-2026-3608, https://doi.org/10.5194/egusphere-2026-3608, 2026
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Lead (Pb) isotopes in marine sediments are used as source tracers of Pb in the oceans. Recent studies suggested Pb isotope exchange on sinking particles, but it remained unknown if this affects isotope signatures. Our study on deep-sea sediments of the South Atlantic Ocean reveals that Pb isotope separation occurs in sinking particles and depends on the intensity of primary productivity.
Cong Jiang, Doerthe Tetzlaff, Songjun Wu, Christian Birkel, Hjalmar Laudon, and Chris Soulsby
Hydrol. Earth Syst. Sci., 30, 3715–3739, https://doi.org/10.5194/hess-30-3715-2026, https://doi.org/10.5194/hess-30-3715-2026, 2026
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We used a modelling approach supported by stable water isotopes to explore how forest management – such as conifer, broadleaf, and mixed tree–crop systems – affects water partitioning and drought resilience in a drought-sensitive region of Germany. By representing forest type, forest density, and rooting depth, the model helps quantify and show how land use choices affect water availability and ecohydrological resilience, thereby supporting improved land and water management decisions.
Alexander Land, Aleta Neugebauer, Jürgen Franzaring, Petra Schmidt, and Harald Biester
Biogeosciences, 23, 2803–2813, https://doi.org/10.5194/bg-23-2803-2026, https://doi.org/10.5194/bg-23-2803-2026, 2026
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Trees take up mercury through their leaves and enrich it in their tree-rings. We investigated tree-ring records of oak and Douglas fir in Germany reaching back ~120 years. We have found that the overall magnitude of mercury loads in trees are determined by local atmospheric Hg concentrations while changes in mercury uptake are controlled by climate. Oak and Douglas fir show different Hg records through time as a results of different adaptation strategies to high temperatures and drought.
Hanwu Zheng, Doerthe Tetzlaff, Christian Birkel, Songjun Wu, Tobias Sauter, and Chris Soulsby
Hydrol. Earth Syst. Sci., 30, 1143–1163, https://doi.org/10.5194/hess-30-1143-2026, https://doi.org/10.5194/hess-30-1143-2026, 2026
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Ecohydrological processes in heavily managed catchments are often inadequately represented in models. We applied a tracer-aided model STARR (Spatially distributed Tracer-Aided Rainfall-Runoff) in an ET (evapotranspiration)-dominated region (the Middle Spree, NE Germany) with major management impacts. Water isotopes were useful in identifying runoff contributions and partitioning ET even at sparse resolution. Trade-offs between discharge- and isotope-based calibrations could be partially mitigated by integrating more process-based conceptualizations into the model.
Ann-Marie Ring, Dörthe Tetzlaff, Christian Birkel, and Chris Soulsby
Hydrol. Earth Syst. Sci., 29, 6663–6683, https://doi.org/10.5194/hess-29-6663-2025, https://doi.org/10.5194/hess-29-6663-2025, 2025
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During summer drought, a clear sub-daily cycling of atmospheric water vapour isotopes (δv) and plant xylem water isotopes (δxyl) was observed. δv daytime depletion was driven by evaporation and local atmospheric factors (entrainment). δxyl daytime enrichment was consistent with high vapor pressure deficit and stomatal regulation of transpiration. This sub-daily dataset provides unique insights on sub-daily cycling of stable water isotopes and can help constrain ecohydrological models.
David S. McLagan, Carina Esser, Lorenz Schwab, Jan G. Wiederhold, Jan-Helge Richard, and Harald Biester
SOIL, 10, 77–92, https://doi.org/10.5194/soil-10-77-2024, https://doi.org/10.5194/soil-10-77-2024, 2024
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Sorption of mercury in soils, aquifer materials, and sediments is primarily linked to organic matter. Using column experiments, mercury concentration, speciation, and stable isotope analyses, we show that large quantities of mercury in soil water and groundwater can be sorbed to inorganic minerals; sorption to the solid phase favours lighter isotopes. Data provide important insights on the transport and fate of mercury in soil–groundwater systems and particularly in low-organic-matter systems.
Laura Balzer, Carluvy Baptista-Salazar, Sofi Jonsson, and Harald Biester
Biogeosciences, 20, 1459–1472, https://doi.org/10.5194/bg-20-1459-2023, https://doi.org/10.5194/bg-20-1459-2023, 2023
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Toxic methylmercury (MeHg) in lakes can be enriched in fish and is harmful for humans. Phytoplankton is the entry point for MeHg into the aquatic food chain. We investigated seasonal MeHg concentrations in plankton of a productive lake. Our results show that high amounts of MeHg occur in algae and suspended matter in lakes and that productive lakes are hot spots of MeHg formation, which is mainly controlled by decomposition of algae organic matter and water-phase redox conditions.
David S. McLagan, Harald Biester, Tomas Navrátil, Stephan M. Kraemer, and Lorenz Schwab
Biogeosciences, 19, 4415–4429, https://doi.org/10.5194/bg-19-4415-2022, https://doi.org/10.5194/bg-19-4415-2022, 2022
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Spruce and larch trees are effective archiving species for historical atmospheric mercury using growth rings of bole wood. Mercury stable isotope analysis proved an effective tool to characterise industrial mercury signals and assess mercury uptake pathways (leaf uptake for both wood and bark) and mercury cycling within the trees. These data detail important information for understanding the mercury biogeochemical cycle particularly in forest systems.
Saúl Arciniega-Esparza, Christian Birkel, Andrés Chavarría-Palma, Berit Arheimer, and José Agustín Breña-Naranjo
Hydrol. Earth Syst. Sci., 26, 975–999, https://doi.org/10.5194/hess-26-975-2022, https://doi.org/10.5194/hess-26-975-2022, 2022
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In the humid tropics, a notoriously data-scarce region, we need to find alternatives in order to reasonably apply hydrological models. Here, we tested remotely sensed rainfall data in order to drive a model for Costa Rica, and we evaluated the simulations against evapotranspiration satellite products. We found that our model was able to reasonably simulate the water balance and streamflow dynamics of over 600 catchments where the satellite data helped to reduce the model uncertainties.
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Short summary
Tropical forests help to remove toxic mercury from the air through their foliage, and when leaves fall, the mercury moves into the soil, where it is stored. Our study found that water availability affects this process: dry forests capture more mercury during rainy seasons and less during dry seasons, while rainforests remain stable throughout the year. Climate change and prolonged droughts may weaken this natural process.
Tropical forests help to remove toxic mercury from the air through their foliage, and when...
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