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- Title
Consumption and alteration of different organic matter sources during remediation of a sandy acid sulfate soil.
- Authors
Koelbl, Angelika; Bucka, Franziska; Marschner, Petra; Mosley, Luke; Fitzpatrick, Rob; Kögel-Knabner, Ingrid
- Abstract
When acid sulfate soils dry, they generate large amounts of sulfuric acid due to oxidation ofpyrite to form sulfuric material (pH <4). After re-saturation of these sulfuric soilsand thus the re-establishment of reduced conditions, activity of sulfate reducingbacteria (SRB) can lead to a renewed formation of pyrite and pH increase. However,many SRB are heterotrophic and require sufficient available organic matter. Despitethe general knowledge about positive impacts of organic carbon (OC) sources forameliorating sulfuric soils, little is known about OC consumption and changes of OCcomposition of added organic substrates during the amelioration process. To investigateremediation of a sandy, OC-poor sulfuric soil (initial pH = 2.5), a short-term anoxicincubation experiment over a period of approx. 10 weeks was conducted afterre-submerging under controlled laboratory conditions. We tested organic matterquantities between 50% up to 200% of the native soil OC content. Besides wheat straw,we used lactate additions to test if this selectively promotes the activity of SRB,and thus, accelerates sulfate reduction and pH neutralization. The results showedthat OC additions of ≥ 50% of native soil OC content and pre-adjustment of pHto values ≥ 5.0 were sufficient to enable microbial reduction reactions to occur,which increased the pH to values ≥ 5.5. OC additions of ≥ 100% of native soil OCas wheat straw led to quicker changes of redox and pH values when compared toadditions of 50% of native soil OC, and led to higher proportions of newly-formedmineral-associated OC. The addition of OC as lactate solution to promote specificallySRB resulted in highly variable pH and redox values between the replicates. Thiscannot be rated as reliable remediation success. However, in combination withwheat straw addition, the presence of lactate led to the quickest changes of pH andredox values and resulted in pH ≥ 7 and redox values ≤ -300mV, which wasaccompanied by high CO2 release indicating an active microbial population. Theapplication of 1:1 wheat straw-lactate – mixtures led to the quickest remediation success;however, OC losses due to microbial degradation and leaching losses due to highproportions of dissolved OC have to be taken into account and may require repeated OCaddition, especially if this remediation approach is to be transferred to field conditions.
- Subjects
ACID sulfate soils; ORGANIC compounds; BACTERIAL leaching; WHEAT straw; SULFURIC acid
- Publication
Geophysical Research Abstracts, 2019, Vol 21, p1
- ISSN
1029-7006
- Publication type
Article