Water pollution risks by smoldering fires in degraded peatlands

Haojie Liu; Dominik Zak; Nerijus Zableckis; Antje Cossmer; Nicole Langhammer; Björn Meermann; Bernd Lennartz

doi:10.1016/j.scitotenv.2023.161979

Water pollution risks by smoldering fires in degraded peatlands

Sci Total Environ. 2023 May 1:871:161979. doi: 10.1016/j.scitotenv.2023.161979. Epub 2023 Feb 3.

Authors

Haojie Liu¹, Dominik Zak², Nerijus Zableckis³, Antje Cossmer⁴, Nicole Langhammer⁴, Björn Meermann⁴, Bernd Lennartz⁵

Affiliations

¹ Faculty of Agricultural and Environmental Sciences, University of Rostock, Justus-von-Liebig-Weg 6, 18059 Rostock, Germany. Electronic address: haojie.liu@uni-rostock.de.
² Department of Ecoscience, Aarhus University, C.F. Møllers Allé 4-6, 8000 Aarhus, Denmark; Department of Ecohydrology and Biogeochemistry, Leibniz-Institute of Freshwater Ecology and Inland Fisheries, Müggelseedamm 301, 12587 Berlin, Germany.
³ Lithuanian Fund for Nature, Algirdo Str. 22-3, LT-03218 Vilnius, Lithuania.
⁴ Division 1.1 - Inorganic Trace Analysis, Federal Institute for Materials Research and Testing (BAM), Richard-Willstätter-Straße 11, 12489 Berlin, Germany.
⁵ Faculty of Agricultural and Environmental Sciences, University of Rostock, Justus-von-Liebig-Weg 6, 18059 Rostock, Germany.

PMID: 36739030
DOI: 10.1016/j.scitotenv.2023.161979

Abstract

Climate change may increase the overall susceptibility of peatlands to fire. Smoldering fires in peatlands can cause substantial emissions of greenhouse gases. It is, however, less clear how smoldering affects the soil pore water quality. In this study, soil samples were collected from agricultural fen and disturbed bog study sites in Germany and Lithuania to quantify the effect of peat burning on pore water composition. The samples were air dried and smoldered under ignition temperature (approximately 200 °C) with different durations (0, 2, 5, and 10 h). Pore water samples were extracted from the soil to determine dissolved organic carbon (DOC) concentrations, dissolved organic matter (DOM) fractions, fluoride, extractable organically bound fluorine (EOF), and sulfate concentrations. The results showed that soil smoldering changes the peat pore water chemistry and that changes differ between fens and bogs. The smoldering duration is likewise influential. For fen grasslands, 2 and 5 h of smoldering of peat caused a >10-fold increase in DOC (up to 1600 mg L^-1) and EOF concentrations. The fluoride (up to 60 mg L^-1) and sulfate concentrations substantially exceeded WHO drinking water guidelines. In contrast, the temperature treatment decreased the DOC concentrations of samples from raised bogs by 90 %. The fluoride concentrations decreased, but sulfate concentrations increased after smoldering of the bog samples. DOC, fluoride, and sulfate concentrations of bogs varied significantly between the smoldering duration treatments. For all peat samples, the extracted DOM was dominated by humic-like substances before smoldering, but the fraction of low molecular weight substances increased after smoldering combustion. In conclusion, smoldering alters the biogeochemical processes in both peatland types and possibly impair the water quality of adjacent water resources especially in fen peat landscapes.

Keywords: Dissolved organic carbon; Dissolved organic matter fractions; Extractable organically bound fluorine; Fluoride; Peatlands; Smoldering fires.