TY - JOUR

T1 - Rapid remediation of sandy sulfuric subsoils using straw-derived dissolved organic matter

AU - Kölbl, Angelika

AU - Kaiser, Klaus

AU - Thompson, Aaron

AU - Mosley, Luke

AU - Fitzpatrick, Rob

AU - Marschner, Petra

AU - Sauheitl, Leopold

AU - Mikutta, Robert

N1 - Funding Information: We thank Anja Kroner, Alexandra Boritzki, Max Meister and Martin Janz for sample preparation and laboratory analyses. Prof. Dr. Dr. Herbert Pöllmann (Institute of Geosciences and Geography) is acknowledged for providing glove box access, and Dr. Werner Häusler for earlier XRD analysis of the clay-sized fraction. The study was funded by Deutsche Forschungsgemeinschaft (DFG), project “Interactions between organic matter and iron oxyhydroxysulfates / iron sulfides during remediation of acid sulfate soils” (KO 2245/3-2). LM and RF acknowledge the contribution of Australian Research Council Discovery Project funding to this research (DP170104541).

PY - 2022/8/15

Y1 - 2022/8/15

N2 - When acid sulfate soils dry, oxidation of pyrite can cause acidification and formation of iron (Fe) oxyhydroxy sulfate phases such as jarosite. Remediation via re-establishment of reducing conditions requires submergence and addition of biodegradable organic carbon (OC) to stimulate activity of reducing bacteria. Addition of fresh plant litter has been shown to activate reducing bacteria, likely due to the release of readily available soluble organic matter. However, the effectiveness of soluble organic matter from plant residues has not been tested yet. Here, we tested the potential of wheat straw-derived dissolved OC (DOC) for remediation of a sandy sulfuric (pH < 4) soil. In a second set of experiments, we used combinations of wheat straw-derived DOC with lactate, which is a preferred substrate of sulfate reducing bacteria. All incubation experiments were conducted in the dark at 20 °C. The results showed that addition of DOC from wheat straw induces reduction reactions and rapidly increases the pH by 2–3 units after 3 weeks of incubation under submerged conditions. Mössbauer spectroscopy and X-ray diffraction revealed that jarosite was lost after 200 days of anoxic incubation. Short range-ordered FeIII oxyhydroxides were formed, most likely by FeII-catalysed transformation of jarosite. A second addition of DOC, as well as the addition of lactate, resulted in the almost complete loss of jarosite with increased proportions of FeIII oxyhydroxides in the remaining solids, but not in the formation of FeII sulfides. The formation of FeIII oxyhydroxides reduces the risk of both Fe leaching and renewed acidification in the event of future oxidation. The results suggest that deep injection of wheat straw-derived DOC is a promising approach for rapid and sustainable remediation of sandy sulfuric subsoils.

AB - When acid sulfate soils dry, oxidation of pyrite can cause acidification and formation of iron (Fe) oxyhydroxy sulfate phases such as jarosite. Remediation via re-establishment of reducing conditions requires submergence and addition of biodegradable organic carbon (OC) to stimulate activity of reducing bacteria. Addition of fresh plant litter has been shown to activate reducing bacteria, likely due to the release of readily available soluble organic matter. However, the effectiveness of soluble organic matter from plant residues has not been tested yet. Here, we tested the potential of wheat straw-derived dissolved OC (DOC) for remediation of a sandy sulfuric (pH < 4) soil. In a second set of experiments, we used combinations of wheat straw-derived DOC with lactate, which is a preferred substrate of sulfate reducing bacteria. All incubation experiments were conducted in the dark at 20 °C. The results showed that addition of DOC from wheat straw induces reduction reactions and rapidly increases the pH by 2–3 units after 3 weeks of incubation under submerged conditions. Mössbauer spectroscopy and X-ray diffraction revealed that jarosite was lost after 200 days of anoxic incubation. Short range-ordered FeIII oxyhydroxides were formed, most likely by FeII-catalysed transformation of jarosite. A second addition of DOC, as well as the addition of lactate, resulted in the almost complete loss of jarosite with increased proportions of FeIII oxyhydroxides in the remaining solids, but not in the formation of FeII sulfides. The formation of FeIII oxyhydroxides reduces the risk of both Fe leaching and renewed acidification in the event of future oxidation. The results suggest that deep injection of wheat straw-derived DOC is a promising approach for rapid and sustainable remediation of sandy sulfuric subsoils.

KW - Acid sulfate soils

KW - Anoxic incubation

KW - Jarosite transformation

KW - Organic matter addition

KW - Reductive dissolution

UR - http://www.scopus.com/inward/record.url?scp=85128460070&partnerID=8YFLogxK

U2 - 10.1016/j.geoderma.2022.115875

DO - 10.1016/j.geoderma.2022.115875

M3 - Article

AN - SCOPUS:85128460070

VL - 420

JO - GEODERMA

JF - GEODERMA

SN - 0016-7061

M1 - 115875

ER -