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Biodegradation of pyrene in sand, silt and clay fractions of sediment.

Cui X, Hunter W, Yang Y, Chen Y, Gan J - Biodegradation (2010)

Bottom Line: A biodegradation model was modified by imbedding a two-phase desorption relationship describing sequential Tenax extractions.The enhanced bioavailability may be attributed to the higher chemical concentration, higher TOC or larger SSA in the silt and clay fractions, which appeared to overcome the reduced bioavailability of pyrene due to sorption, making pyrene on the silt and clay particles readily available to degrading microbes.This conjecture merits further investigation.

View Article: PubMed Central - PubMed

Affiliation: Department of Environmental Sciences, University of California, Riverside, CA 92521, USA. lizzyc@ucr.edu

ABSTRACT
Microbial degradation is the dominant pathway for natural attenuation of PAHs in environmental compartments such as sediments, which in turn depends on the bioavailability of PAHs. The bioavailability of PAHs has seldom been studied at the sediment particle size scale. We evaluated biodegradation of pyrene by Mycobacterium vanbaalenii PYR-1 as a function of sediment particle sizes, and investigated the relationship between the rate of degradation on sand, silt and clay particles with their individual desorption kinetics measured with the Tenax extraction method. Regression analysis showed that the total organic carbon (TOC), black carbon (BC), and specific surface area (SSA) of the specific particle size fractions, instead of the particle size scale itself, were closely related (P<0.01) with the mineralization rate. While the fraction in the rapid desorption pool (F (rapid)) ranged from 0.11 to 0.38 for the whole sediments and different size groups, the fractions mineralized after 336-h incubation (0.52 to 0.72) greatly surpassed the F (rapid) values, suggesting utilization of pyrene in the slow desorption pool (F (slow)). A biodegradation model was modified by imbedding a two-phase desorption relationship describing sequential Tenax extractions. Model analysis showed that pyrene sorbed on silt and clay aggregates was directly utilized by the degrading bacteria. The enhanced bioavailability may be attributed to the higher chemical concentration, higher TOC or larger SSA in the silt and clay fractions, which appeared to overcome the reduced bioavailability of pyrene due to sorption, making pyrene on the silt and clay particles readily available to degrading microbes. This conjecture merits further investigation.

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Microbial mineralization of pyrene (filled square: observed values) on various sized particles in SP sediment. The solid lines represent the model 1 predicted values, and the dash lines represent the model 2 predicted values
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Fig5: Microbial mineralization of pyrene (filled square: observed values) on various sized particles in SP sediment. The solid lines represent the model 1 predicted values, and the dash lines represent the model 2 predicted values

Mentions: For the SP sediment, the measured mineralization curves for all of the three particle size fractions fell above the predicted line by model 1 (Fig. 5), indicating that the bacteria not only utilized pyrene in the solution phase, but also either enhanced the desorption of pyrene into the solution phase or directly used the sorbed pyrene. The measured mineralization curve for the sand aggregates fell between model 1 and model 2 predicted lines. In comparison, the measured mineralization for the silt fraction closely mimicked the model 2 prediction while that for the clay fraction clearly surpassed that predicted by the model 2 in the later phase of the incubation experiment (Fig. 5). Similar patterns were also observed for the SDC sediment (Fig. 6). Again, while the measured mineralization fell between the two predicted lines for the sand fraction, the cumulative mineralization was similar to that predicted by the model 2 for silt, and was greater than that predicted by the model 2 for clay (Fig. 6). The increased mineralization in relation to that predicted by the model 2 implied that pyrene sorbed on silt and clay particles was probably used directly by the PYR-1 bacteria, that is, without first being desorbed into the solution phase.Fig. 5


Biodegradation of pyrene in sand, silt and clay fractions of sediment.

Cui X, Hunter W, Yang Y, Chen Y, Gan J - Biodegradation (2010)

Microbial mineralization of pyrene (filled square: observed values) on various sized particles in SP sediment. The solid lines represent the model 1 predicted values, and the dash lines represent the model 2 predicted values
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3046355&req=5

Fig5: Microbial mineralization of pyrene (filled square: observed values) on various sized particles in SP sediment. The solid lines represent the model 1 predicted values, and the dash lines represent the model 2 predicted values
Mentions: For the SP sediment, the measured mineralization curves for all of the three particle size fractions fell above the predicted line by model 1 (Fig. 5), indicating that the bacteria not only utilized pyrene in the solution phase, but also either enhanced the desorption of pyrene into the solution phase or directly used the sorbed pyrene. The measured mineralization curve for the sand aggregates fell between model 1 and model 2 predicted lines. In comparison, the measured mineralization for the silt fraction closely mimicked the model 2 prediction while that for the clay fraction clearly surpassed that predicted by the model 2 in the later phase of the incubation experiment (Fig. 5). Similar patterns were also observed for the SDC sediment (Fig. 6). Again, while the measured mineralization fell between the two predicted lines for the sand fraction, the cumulative mineralization was similar to that predicted by the model 2 for silt, and was greater than that predicted by the model 2 for clay (Fig. 6). The increased mineralization in relation to that predicted by the model 2 implied that pyrene sorbed on silt and clay particles was probably used directly by the PYR-1 bacteria, that is, without first being desorbed into the solution phase.Fig. 5

Bottom Line: A biodegradation model was modified by imbedding a two-phase desorption relationship describing sequential Tenax extractions.The enhanced bioavailability may be attributed to the higher chemical concentration, higher TOC or larger SSA in the silt and clay fractions, which appeared to overcome the reduced bioavailability of pyrene due to sorption, making pyrene on the silt and clay particles readily available to degrading microbes.This conjecture merits further investigation.

View Article: PubMed Central - PubMed

Affiliation: Department of Environmental Sciences, University of California, Riverside, CA 92521, USA. lizzyc@ucr.edu

ABSTRACT
Microbial degradation is the dominant pathway for natural attenuation of PAHs in environmental compartments such as sediments, which in turn depends on the bioavailability of PAHs. The bioavailability of PAHs has seldom been studied at the sediment particle size scale. We evaluated biodegradation of pyrene by Mycobacterium vanbaalenii PYR-1 as a function of sediment particle sizes, and investigated the relationship between the rate of degradation on sand, silt and clay particles with their individual desorption kinetics measured with the Tenax extraction method. Regression analysis showed that the total organic carbon (TOC), black carbon (BC), and specific surface area (SSA) of the specific particle size fractions, instead of the particle size scale itself, were closely related (P<0.01) with the mineralization rate. While the fraction in the rapid desorption pool (F (rapid)) ranged from 0.11 to 0.38 for the whole sediments and different size groups, the fractions mineralized after 336-h incubation (0.52 to 0.72) greatly surpassed the F (rapid) values, suggesting utilization of pyrene in the slow desorption pool (F (slow)). A biodegradation model was modified by imbedding a two-phase desorption relationship describing sequential Tenax extractions. Model analysis showed that pyrene sorbed on silt and clay aggregates was directly utilized by the degrading bacteria. The enhanced bioavailability may be attributed to the higher chemical concentration, higher TOC or larger SSA in the silt and clay fractions, which appeared to overcome the reduced bioavailability of pyrene due to sorption, making pyrene on the silt and clay particles readily available to degrading microbes. This conjecture merits further investigation.

Show MeSH
Related in: MedlinePlus