Characterization of microbial communities and their anaerobic degradation potential of PAHs in

contaminated riverbank sediments

G. Patricia Johnston

KSU -YSU

Mahoning River

- Steel mills and support industries used the river as a sewer.

- One of the most active industrial zone in the 1800s and 1900s.

Mahoning River

• Intact riparian ecosystem• Contaminated river banks with metals, PAHs, and PCBs.• Considered the 5th most contaminated river (channel + banks) in the U.S. (EPA)

Polycyclic Aromatic Hydrocarbons

(PAHs)

• Organic compounds with multiple closed benzene rings.

• Result from incomplete combustion of carbon (natural and anthropogenic).

• Diverse, recalcitrant, lipophilic, low solubility, high affinity to organic matter.

• Carcinogenic, mutagenic, estrogenic.

Remediation of PAHs

• Demonstrated under denitrifying, sulfate-reducing, and methanogenic conditions.

• Limitations:– Marine systems– Spiked sediments– Few PAHs studied– Lack of information on

river ecosystems– Few studies with

indigenous microbial communities

• Extensive evidence of aerobic microbial degradation in a variety of environments (marine, freshwater & brackish sediments)

• Common degradation pathways

• PAH degraders identified

Various conventional approaches

Microbial transformation* (algae, bacteria , fungi)

Army Corps of Engineers- Remediation Plan

• Dredging sediments in the river channel• Capping river banks

NAVIGATION SERVITUDE LIMITOHW

IN-RIVER

CONTAMINATED SEDIMENTSORIGINAL CONTOUR

BANK CONTAMINANTS

MAXNATURAL CAP TYPICAL DAM / WATER ELEVATION

MIN

Alternative for bioremediation?

• Bacteria can degrade PAHs under various redox conditions.

• Long history of PAH contamination suggests that microbial communities may have adapted and therefore have anaerobic degradation potential.

• Information on microbial ecology of sediments is critical for implementing bioremediation.

Proposed Research Summary

• Biogeochemical characterization of the river bank sediments.– indigenous microbial communities– terminal electron acceptors– physico-chemical parameters

• Determination of the anaerobic PAH degradation potential.

Biogeochemical characterization

o PAHs o pH o Particle size distributiono Moisture contento Organic matter and ash

content

o Fe2+/Fe3+ ratios o Nitrateo Sulfateo Fe3+

o MnIVo Metals

o Microbial activity o Total bacteria o Microbial community o Clone libraries

Redox sensors

• Lack of commercially available redox sensors for sediments.

• Most microelectrodes are custom made in laboratories ( no recipe ???).

• Need to develop disposable probes for in situ measurements.

• Available sensors are designed for water, however low accuracy.

My IGERT Goal

• Research on redox sensors • Develop a redox sensor prototype • Testing • Commercialization?

Mahoning River in fall

Questions