Preprints
https://doi.org/10.5194/bg-2020-466
https://doi.org/10.5194/bg-2020-466

  01 Feb 2021

01 Feb 2021

Review status: this preprint is currently under review for the journal BG.

Mercury mobility, colloid formation and methylation in a polluted fluvisol as affected by manure application and flooding-draining cycle

Lorenz Gfeller1, Andrea Weber1, Isabelle Worms2, Vera I. Slaveykova2, and Adrien Mestrot1 Lorenz Gfeller et al.
  • 1Institute of Geography, University of Bern, Hallerstrasse 12, 3012 Bern, Switzerland
  • 2Environmental Biogeochemistry and Ecotoxicology, Department F.-A. Forel for environmental and aquatic sciences, School of Earth and Environmental Sciences, Faculty of Sciences, University of Geneva, Uni Carl Vogt, Bvd Carl-Vogt 66, CH-1211 Geneva 4, Switzerland

Abstract. Floodplain soils polluted with high levels of mercury (Hg) are potential point sources to downstream eco-systems. Repeated flooding (e.g. redox cycling) and agricultural activities (e.g. organic matter addition) may influence the fate and speciation of Hg in these soil systems. The formation and aggregation of colloids and particles influences both Hg mobility and its bioavailability to methylmercury (MeHg) forming microbes. In this study, we conducted a microcosm flooding-draining experiment on Hg polluted floodplain soils originating from an agriculturally used area situated in the Rhone Valley (Valais, Switzerland). The experiment comprised two 14 days flooding periods separated by one 14 days draining period. The effect of freshly added natural organic matter on Hg dynamics was assessed by adding liquid cow manure (+MNR) to two control soils characterized by different Hg (47.3 ± 0.6 mg kg−1 or 2.38 ± 0.01 mg kg−1) and organic carbon (OC: 1.92 wt. % or 3.45 wt. %) contents. During the experiment, the release, colloid formation and methylation of Hg in the soil solution were monitored. Upon manure addition in the highly polluted soil (lowest OC), an accelerated release of Hg to the soil solution could be linked to a fast reductive dissolution of Mn oxides. The manure treatments showed a fast sequestration of Hg and a higher percentage of particulate (0.02–10 µm) bound Hg. As well, analyses of soil solutions by asymmetrical flow field-flow fractionation coupled with inductively coupled plasma mass spectrometry (AF4–ICP–MS) revealed a proportional increase of colloidal DOM-Hg and inorganic colloidal Hg (+MNR: 70–100 %; control: 32–70 %) upon manure addition. Our experiment shows that net Hg methylation (MeHg/Hg) was highest after the first draining period and decreased again after the second flooding period. No significant effects on methylation upon manure addition was found. The results of this study suggest that manure addition may promote sequestration by Hg complexation on large organic matter components and the formation/aggregation of inorganic HgS(s) colloids in Hg polluted fluvisols with low levels of natural organic matter.

Lorenz Gfeller et al.

Status: open (until 15 Mar 2021)

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Dataset to: Mercury mobility, colloid formation and methylation in a polluted fluvisol as affected by manure application and flooding-draining cycle Lorenz Gfeller, Andrea Weber, Isabelle Worms, Vera I. Slaveykova, and Adrien Mestrot https://doi.org/10.5281/zenodo.4058675

Lorenz Gfeller et al.

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