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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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Pyrene degradation kinetics up to 336 h by the PYR-1 strain in SP sediment. a Mineralization in the sediment size aggregates: sand-(filled square), silt-(filled circle), and clay-sized (filled triangle) aggregates. b Observed mineralization values in the whole sediment particles (filled square) and the calculated values from the three sized fractions (filled circle) Bars represent standard deviations (n = 3)
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Fig2: Pyrene degradation kinetics up to 336 h by the PYR-1 strain in SP sediment. a Mineralization in the sediment size aggregates: sand-(filled square), silt-(filled circle), and clay-sized (filled triangle) aggregates. b Observed mineralization values in the whole sediment particles (filled square) and the calculated values from the three sized fractions (filled circle) Bars represent standard deviations (n = 3)

Mentions: Biodegradation of pyrene in the two sediments and their particle size fractions was rapid and progressed without an apparent acclimation phase (Figs. 2, 3). For the SP sediment, mineralization of pyrene followed similar trends among the different particle size fractions. After 336 h of incubation, the percentages of pyrene mineralized by Mycobacterium vanbaalenii PYR-1 were not significantly different among the sand (51.73 ± 8.95%), silt (55.11 ± 2.25%), and clay (55.92 ± 2.83%) fractions (Fig. 2a). For the SDC sediment, mineralization of pyrene appeared to be faster in the sand fraction than in the silt or clay fraction (72.27 ± 14.27% in sand fraction versus 63.38 ± 3.78% and 59.42 ± 4.92% in silt and clay fractions, Fig. 3a). The sum of cumulative mineralization from the different size fractions, calculated after mass normalization over the specific size fractions, closely approximated the mineralization measured independently from the whole sediment for both sediments (Figs. 2b, 3b), suggesting the rigorousness of measurement and also that the physical separation of sediment aggregates did not modify the original availability of pyrene for microbial degradation.Fig. 2


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

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

Pyrene degradation kinetics up to 336 h by the PYR-1 strain in SP sediment. a Mineralization in the sediment size aggregates: sand-(filled square), silt-(filled circle), and clay-sized (filled triangle) aggregates. b Observed mineralization values in the whole sediment particles (filled square) and the calculated values from the three sized fractions (filled circle) Bars represent standard deviations (n = 3)
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC3046355&req=5

Fig2: Pyrene degradation kinetics up to 336 h by the PYR-1 strain in SP sediment. a Mineralization in the sediment size aggregates: sand-(filled square), silt-(filled circle), and clay-sized (filled triangle) aggregates. b Observed mineralization values in the whole sediment particles (filled square) and the calculated values from the three sized fractions (filled circle) Bars represent standard deviations (n = 3)
Mentions: Biodegradation of pyrene in the two sediments and their particle size fractions was rapid and progressed without an apparent acclimation phase (Figs. 2, 3). For the SP sediment, mineralization of pyrene followed similar trends among the different particle size fractions. After 336 h of incubation, the percentages of pyrene mineralized by Mycobacterium vanbaalenii PYR-1 were not significantly different among the sand (51.73 ± 8.95%), silt (55.11 ± 2.25%), and clay (55.92 ± 2.83%) fractions (Fig. 2a). For the SDC sediment, mineralization of pyrene appeared to be faster in the sand fraction than in the silt or clay fraction (72.27 ± 14.27% in sand fraction versus 63.38 ± 3.78% and 59.42 ± 4.92% in silt and clay fractions, Fig. 3a). The sum of cumulative mineralization from the different size fractions, calculated after mass normalization over the specific size fractions, closely approximated the mineralization measured independently from the whole sediment for both sediments (Figs. 2b, 3b), suggesting the rigorousness of measurement and also that the physical separation of sediment aggregates did not modify the original availability of pyrene for microbial degradation.Fig. 2

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