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- Lu, Lu, et al.
(författare)
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Rhamnolipid Biosurfactants Enhance Microbial Oil Biodegradation in Surface Seawater from the North Sea
- 2023
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Ingår i: ACS - ES & T Water. - : American Chemical Society (ACS). - 2690-0637. ; 3:8, s. 2255-2266
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Tidskriftsartikel (refereegranskat)abstract
- This study provides strong evidence thatthe biosurfactantrhamnolipid is more efficient than the widely used chemical dispersantsCorexit 9500 and Slickgone NS in stimulating oil biodegradation innatural seawater. Biosurfactants arepromising alternatives to chemical dispersantsfor combating marine oil spills; however, the impacts of biosurfactantson microbial community composition and oil biodegradation activitiesremain largely unknown. Here, we conducted a time-course microcosmexperiment mimicking oil spill scenarios with surface seawater fromthe North Sea, amended with either the biosurfactant rhamnolipid ora dispersant (Corexit 9500 or Slickgone NS). Radioactive tracer assaysto track hexadecane and naphthalene oxidation as well as bacterialproduction revealed the highest hydrocarbon oxidation rates and generalmicrobial activities in the rhamnolipid-amended oil microcosms, followedby oil microcosms with Slickgone and Corexit. Impacts on the microbialcommunity composition differed among treatments, and growth of oil-degrading Colwellia was stimulated remarkably in Corexit-amended oiland oil-only microcosms, while potential oil-degrading Oleispira were highly enriched in the presence of oil in combination withrhamnolipid or Slickgone. Furthermore, increased abundances of Colwellia and Oleispira, and stimulatedbacterial production in microcosms with only rhamnolipid, Corexit,or Slickgone, indicated their involvement in biosurfactant/dispersantbiodegradation. Our findings highlight varying microbial impacts resultingfrom rhamnolipid and chemical dispersants and suggest great promisefor the application of biosurfactants in future marine oil spills.
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| 2. |
- Wimmer, Benedikt, et al.
(författare)
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Mechanistic modeling indicates rapid glyphosate dissipation and sorption-driven persistence of its metabolite AMPA in soil
- 2023
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Ingår i: Journal of Environmental Quality. - : Wiley. - 0047-2425 .- 1537-2537. ; 52:2, s. 393-405
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Tidskriftsartikel (refereegranskat)abstract
- Residual concentrations of glyphosate and its main transformation product aminomethylphosphonic acid (AMPA) are often observed in soils. The factors controlling their biodegradation are currently not well understood. We analyzed sorption-limited biodegradation of glyphosate and AMPA in soil with a set of microcosm experiments. A mechanistic model that accounts for equilibrium and kinetic sorption facilitated interpretation of the experimental results. Both compounds showed a biphasic dissipation with an initial fast (up to Days 7–10) and subsequent slower transformation rate, pointing to sorption-limited degradation. Glyphosate transformation was well described by considering only equilibrium sorption. Model simulations suggested that only 0.02–0.13% of total glyphosate was present in the soil solution and thus bioavailable. Glyphosate transformation was rapid in solution (time required for 50 % dissipation of the total initially added chemical [DT50] = 3.9 min), and, despite strong equilibrium sorption, total glyphosate in soil dissipated quickly (DT50 = 2.4 d). Aminomethylphosphonic acid dissipation kinetics could only be described when considering both equilibrium and kinetic sorption. In comparison to glyphosate, the model simulations showed that a higher proportion of total AMPA was dissolved and directly bioavailable (0.27–3.32%), but biodegradation of dissolved AMPA was slower (DT50 = 1.9 h). The model-based data interpretation suggests that kinetic sorption strongly reduces AMPA bioavailability, leading to increased AMPA persistence in soil (DT50 = 12 d). Thus, strong sorption combined with rapid degradation points to low risks of glyphosate leaching by vertical transport through soil in the absence of preferential flow. Ecotoxicological effects on soil microorganisms might be reduced. In contrast, AMPA persists, rendering these risks more likely.
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