Bioavailability and Biodegradation of Aromatic Compounds in Sediments

1
Bioavailability and Biodegradation of Aromatic
Compounds in Sediments

• Danny Reible, PhD, PE, DEE, NAE
• Smith Chair of Environmental Health Engineering
• University of Texas at Austin

4th Symposium on Biosorption and
Bioremediation August 27. 2007
2
Routes of Contaminant Exposure to Sediments

• Direct flux to water
• Sediment erosion
• Bioturbation and surface release
• Physicochemical processes
• Accumulation in benthic organisms and food chain
  transfer
• Conclusion - In stable (non-erosive environments)
  benthic organisms largely control contaminant
  release and exposure

3
Bioturbation

• Normal life cycle activities of benthic organisms
  leading to sediment mixing and transport
• Dominated by deposit feeders that ingest sediment
  e.g. freshwater oligochaetes
• Densities up to 100,000 worms/m2 or more
• Organisms may process 10-20 times their wt/day
• Controls depth of sediments leading to exposure
• Controls rate of sediment reworking, sediment
  redox conditions and porewater release of
  contaminants
• Bioturbation may lead to degradation via organism
  metabolism
• Bioavailability largely defined by what can be
  moved or metabolized by or accumulate in benthic
  organisms

4
The Bioturbation/Soluble Release Process
5
Current work on biodegradation in sediments

• Characterization of dominant electron acceptor
  transitions due to benthic organism activity
  using sub-mm resolution voltammetry
• Characterization of microbial community changes
  in response to dominant electron acceptor
  transitions
• Special focus on chlorinated benzenes
• Dechlorination of multi-chlorinated benzenes
  under strongly reducing conditions
• Oxidation of monochlorobenzene in transitional
  and aerobic zone created by benthic organisms
• This lecture
• General effects of benthic organism affects on
  sediment and contaminants
• Extension of past laboratory work on assessing
  availability of desorption resistant contaminants
  to benthic organism (i.e. effect of contaminants
  on organisms)

6
Bioturbation Particle Diffusion Rates
Freshwater and Estuarine Systems
7
Bioturbation Mixing Depths
Freshwater and Estuarine Systems
8
Effects of BioturbationMicrocosm Experiments
9
Effects of BioturbationContaminant Fate
10
Effects of Contamination on Benthic
OrganismsWhole Sediment Concentration ???
Non- Toxic
Toxic
Adapted from Dave Nakles, ENSR
11
Effects of Contamination on Benthic
OrganismsInterstitial Water Concentration
EPA H. azteca 28-day test
Survival ()
Non- Toxic
Toxic
Sediment Porewater PAH34 Conc. (Toxic Units)
Adapted from Dave Nakles, ENSR
12
Metrics - Correlation (?) of PCB Uptake with
Whole Sediment Concentration
Anacostia River
13
Accumulation Predicted by Porewater?Predicted vs
Measured BSAF - PCBS
Anacostia River
14
Laboratory Correlation of PAH Uptake with
Interstitial Water Concentration
Anacostia River
Assuming KlipidKoc
Porewater
15
But How to Measure Porewater Concentration?

• Solid Phase MicroExtraction
• Sorbent Polymer PDMS (poly-dimethylsiloxane)
• Thickness of glass core 114-108 µm
• Thickness of PDMS coating 30-31 µm
• Volume of coating 13.55 (0.02) µL PDMS per
  meter of fibre
• Easily capable of measuring ng/L concentrations

16
Field Deployment System
17
Field Deployment with Caged Lumbriculus
18
Does it Work in the Field?Field Deployed SPME
with Accumulation in Caged Lumbriculus
Assuming KlipidKoc
19
Anacostia Sediment Porewater Concentration
Contaminants exhibit low availability compared
to the expected whole sediment concentration
20
SPME Measured Porewater Concentrations
21
Summary and Conclusions

• Bioturbation dominant mechanism for defining
  contaminant fate and transport in non-erosive
  sediments
• Benthic organisms responsible for bioturbation
  define risk (direct and food chain transport) of
  contaminated sediments
• Benthic organisms dramatically affect near
  surface redox conditions and contaminant dynamics
• Interstitial water (porewater) concentrations
  better indicator of exposure and risk than whole
  sediment concentration even for contaminants
  whose uptake is controlled by ingestion
• Field-deployable SPME simple and useful to define
  exposure and risk