Geochemistry ~ Environmental Forensics ~ Mineralogy
 

Upcoming Events - Presentations

Title:                    Geochemistry of Contaminants

Where:                Denver, CO (see www.nwetc.org)

When:                 September 12-13, 2007

Sponsor:             Northwest Environmental Training Center

Company Milestones

Forensic Isotope Geochemistry Text

In collaboration with Elsevier Publishers, Dr. Hurst is continuing to write and revise a volume dedicated to forensic geochemistry with applications to timing environmental releases.  The expected date of completion is winter 2007.

Hydrocarbon Releases:  Approaches to Age Dating

The application of stable lead isotopes and the ALAS Model, Anthropogenic Lead ArchaeoStratigraphy (Hurst, 2000, Jour. Environ. Foren. and  Environ. Geosci., 2002) continues to be refined to estimate the age of gasoline releases dating back to the 1920s when tetraethyllead was first introduced.  This research has now added another dimension  to petroleum hydrocarbon-source correlations and provides a foundation for modeling degradation rates of carcinogenic gasoline constituents, such as benzene, in groundwater; the latter application can be used to evaluate, on a case-by-case basis, the time scale of natural attenuation at a site. 

As a result of the release of data pertaining to crude oil geochemistry into the public domain, Gene Schmidt (GW/S Environmental) and Richard W. Hurst (Hurst & Associates, Inc.) have revised and re-evaluated the use of the nC₁₇ to pristane ratio as a means of age dating middle distillate fuel releases (Environ. Geosci, 2005, v. 12, 177-192).  The rate of change in this ratio was evaluated as a function of environmental conditions (aerobic versus anaerobic); additionally, the initial nC₁₇/Pr ratio of nearly 4000 crude oils and 100 refined middle distillate fuels was calculated to assess the expected variability in this ratio.  The paper also addresses regional variations in the ratio as well as the limitations of the use of the so-called Middle Distillate Degradation Model in age dating releases. 

 Advances in  Forensic Investigations Concerning Lead in Paint

Collaborations between Hurst & Associates, Inc. and the Isotope Geochemistry Laboratory at the Massachusetts Institute of Technology (Prof. S. A. Bowring and Dr. F.O. Dudas) have resulted in new, more rigorous approaches to evaluating the potential contribution of lead derived from lead-based paint to the urban lead budget.   The approach integrates high precision lead isotope ratio analyses with electron microprobe/microscopic techniques to more effectively assess the distribution of lead in multiple paint layers on walls and exteriors of older homes.

Forensic Geochemical Workshops

At the request of the Northwest Environmental Training Center based in Seattle, WA, Dr. Hurst developed a two day workshop that introduces participants to forensic geochemical techniques designed to model the fate and transport of contaminants of concern in the environment.  At present, the course (CHEM 405, see the NWETC website at www.nwetc.org for scheduled offerings) is taught ~ 2-3 times per year at different locations throughout the western U.S.  It is scheduled to be offered again September 12-13, 2007 at a location that has yet to be determined.  Contaminants covered include hydrocarbons, nitrates, chlorinated solvents, saline water, and metals---issues concerning landfill gases and PCBs are in the process of being integrated into the course. 

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