Sungwoo Ahn
Sungwoo Ahn, Ph.D.
Senior Scientist
Environmental & Earth Sciences
  • Seattle

Dr. Ahn specializes in the fate and transport, bioavailability, and environmental chemistry of hydrophobic organic contaminants (HOCs). Dr. Ahn is experienced in matters related to environmental forensics and chemical fingerprinting of polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), and dioxins in support of source identification and contribution quantification. He has expertise in utilizing receptor models (EPA’s Chemical Mass Balance (CMB) and Positive Matrix Factorization (PMF) models) as tools of source allocation of contaminated soil and sediment in complex settings. Further, he has experience in using passive samplers to measure low level PAHs in water compartments, which is simple, economical, and powerful tool for low level aqueous phase HOC measurement.

Before joining Exponent, Dr. Ahn worked as a postdoctoral scholar at Stanford University, where he conducted research on the degradation of flame retardant PBDEs by various forms of nano-scale zerovalent iron particles (nZVI). Dr. Ahn studied the reaction kinetics and the degradation of PBDEs. As a part of the research, he synthesized nZVI as well as catalyzed and carbon supported nZVI in the laboratory, and characterized them using analytical tools such as TEM, SEM, XPS, and XRD.

During his Ph.D. work, Dr. Ahn studied the transport and fate of PAHs in contaminated soil and sediment amended with a carbon sorbents for in situ contaminant stabilization. The study included physicochemical characterization of contamination at micro-scale, assessment of PAH bioavailability and availability to the surroundings, and model simulation of contaminant mass transfer in sediment-sorbent systems, to predict the fate of PAHs and the long-term effect of carbon amendment.

CREDENTIALS & PROFESSIONAL HONORS

  • Ph.D., Civil and Environmental Engineering, Stanford University, 2006
  • M.S., Civil and Environmental Engineering, Stanford University, 2001
  • M.S., Chemical Engineering, Yonsei University, South Korea, 1997
  • B.S., Chemical Engineering, Yonsei University, South Korea, 1995
  • The Ford Fund Fellowship, 2001–2003

LICENSES & CERTIFICATIONS

OSHA 40-hour HAZWOPER Certification

LANGUAGES

  • Korean

Publications

O'Reilly KT, Mohler RE, Zemo DA, Ahn S, Tiwary AK, Magaw RI, Espino Devine C, Synowiec KA. Identification of ester metabolites from petroleum hydrocarbon biodegradation in groundwater using GC×GC-TOFMS. Environmental Toxicology and Chemistry 2015; 34(9):1959–1961.

O'Reilly KT, Ahn S, Pietari J, Boehm PD. Use of receptor models to evaluate sources of PAHs in sediments. Polycyclic Aromatic Compounds 2015; 35:41–56.

Shields WJ, Ahn S, Pietari J, Robrock K, Royer L. Atmospheric fate and behavior of POPs. Chapter 6. In: Environmental Forensics for Persistent Organic Pollutants. O’Sullivan W, Sandau C (eds), Chennai: Elsevier, pp. 199-290, 2014.

Ahn S, Werner D, Luthy RG. Modeling PAH mass transfer in a slurry of contaminated soil or sediment amended with organic sorbents. Water Research 2008; 42:2931–2942.

Yoon TH, Benzerara K, Ahn S, Luthy RG, Tyliszczak T, Brown GE. Nanometer-scale chemical heterogeneities of black carbon materials and their impacts on PCB sorption properties: Soft x-ray spectromicroscopy study. Environmental Science and Technology 2006; 40:5923–5929.

Ahn S, Werner D, Karapanagioti HK, McGlothlin DR, Zare RN, Luthy RG. Phenanthrene and pyrene sorption and intraparticle diffusion in polyoxymethylene, coke, and activated carbon. Environmental Science and Technology 2005; 39:6516–6526.

Ahn S, Werner D, Luthy RG. Physicochemical characterization of coke-plant soil for the assessment of polycyclic aromatic hydrocarbon availability and the feasibility of phytoremediation. Environmental Toxicology and Chemistry 2005; 24:2185–2195.

Presentations

Pietari JMH, O’Reilly K, Ahn S. Boehm, P. Tools for source apportionment: Receptor models and their applications. 31st Annual International Conference on Soils, Sediments, Water and Energy, Amherst, MA, October 20, 2015.

Boehm, P, Pietari JMH, Ahn S. Application of ensemble environmental forensics to PAH source attribution. 8th International Conference on Remediation and Management of Contaminated Sediments. New Orleans, LA, January 12–15, 2015.

Ahn, S; O’Reilly. The influence of source selection on Chemical Mass Balance modeling results: Implications for source control policy. SETAC North America Annual Meeting, Vancouver, Canada, November 2014.

O'Reilly, K. T.; Ahn, S. Receptor Models for PAH Source Characterization: Opportunities and Limitations. SETAC North America Annual Meeting, Vancouver, Canada, November 2014.

Kane Driscoll S, Ahn S, Pietari J, Burgess R. Procedures for derivation of site-specific equilibrium partitioning sediment benchmarks for the protection of benthic organisms: nonionic organics. SETAC North America 32nd Annual Meeting, November 13–17, 2011.

Zhuang Y, Ahn S, Luthy RG. Debromination of polybrominated diphenyl ethers by nano-iron particles and carbon-supported nano-iron particles. 239th American Chemical Society National Meeting, San Francisco, CA, March 2010.

Zhuang Y, Ahn S, Luthy RG. PBDE debromintaion by nano-scale zerovalent iron (nZVI) and carbon supported nZVI. SETAC North America Annual Meeting, New Orleans, LA, November 2009.

Yoon TH Benzerara K, Ahn S, Luthy RG, Tyliszczak T, Brown GE. Soft x-ray spectromicroscopy study of carbonaceous materials: Characterization of their chemical heterogeneities in sub-micrometer scale. 229th American Chemical Society National Meeting, San Diego, CA. March 2005.


Prior Experience

Postdoctoral Scholar, Stanford University, 2006–2010

Professional Affiliations

American Chemical Society

Society of Environmental Toxicology and Chemistry

Project Experience

Petroleum and Polycyclic Aromatic Hydrocarbons (PAHs)

Applied EPA’s CMB model for source identification and contribution quantification of PAHs in lake sediment impacted by multiple sources including petroleum fuel terminals, MGPs, and chemical manufacturing facilities.

Assisted a complex project on forensic investigation to support cost allocation for a Superfund site consisting of former lumber yard with wood treatment operations and a former MGP adjacent to a lake. Used CMB model as a part of multiple-lines-of-evidence approach, utilizing a suite of apportionment models and forensic tools.

Conducted chemical fingerprinting analysis to evaluate the impact of former MGP facilities on soils on the sites and their boundaries in metro urban area. Using PAH histograms, diagnostic ratios, and the review of GC chromatograms, the effort was made to evaluate the impact from MGP-related materials and urban background.

For a major oil company, estimated the water-dissolved fraction of PAHs in the field-collected water samples that contain both non-dissolved and dissolved fractions of oil spill by applying partitioning and equilibrium theories, in junction with toxicity evaluation of the chemicals.

Assisted forensic investigation to support cost allocation for a site where former MGP and fuel terminal were. Reviewed historical and site investigation documents and performed environmental forensics.

Conducted sediment sampling in a river at a Superfund site for evaluation of PAH impact from a fuel terminal facility next to the river.

PCBs

As part of a team of experts, reviewed and critiqued PCB fate and transport models used in multiple modeling studies for a river highly contaminated by PCB. Also, provided theoretical information of PCB’s physicochemical properties in support of new modeling effort of PCB in the river.

Dioxins

Estimated dioxin emission from a secondary copper smelter stack flue gas in US.

Assisted chemical fingerprinting of naturally occurring dioxins in various ball clay samples.

Assisted a project on evaluating dioxin in sediment potentially impacted by the treated wastewater effluent discharged from a pulp and paper mill.

Environmental Chemistry

For a major oil company, performed identification and classification of polar metabolites in groundwater samples from long term monitoring of petroleum fuel terminals and service stations. The multi-faceted project evaluated a potential problem of TPH overestimation due to the presence of polar metabolites, degradation and transformation of the polar metabolites, and toxicity of the polar metabolites.

Reviewed and critiqued reports on methyl mercury in a river marsh and sediment allegedly impacted by a paper mill.


Knowledge

News & Events

CREDENTIALS & PROFESSIONAL HONORS

  • Ph.D., Civil and Environmental Engineering, Stanford University, 2006
  • M.S., Civil and Environmental Engineering, Stanford University, 2001
  • M.S., Chemical Engineering, Yonsei University, South Korea, 1997
  • B.S., Chemical Engineering, Yonsei University, South Korea, 1995
  • The Ford Fund Fellowship, 2001–2003

LICENSES & CERTIFICATIONS

OSHA 40-hour HAZWOPER Certification

LANGUAGES

  • Korean