On November 17th, the Groundwater Resources Association of California will be hosting an Advanced Tools Workshop in Oakland, CA. The full day workshop will feature Advanced Tools experts discussing their latest tools, research, and findings. Speakers include:
Dr. John T. Wilson, USEPA
Greg Davis, Microbial Insights
Dr. Mike Hyman, NC State University
Joseph Haas, NY State Office of the Attorney General
Dr. Robert Pirkle, Microseeps, Inc.
Dr. Rula Deeb, ARCADIS
Dr. Kerry Sublette, University of Tulsa
Tim Buscheck, Chevron Energy Technology Company
To see the workshop agenda, and to sign up to attend, visit: http://www.advancedtools.us/workshops/
If you are interested in bringing the Advanced Tools Workshop to your city, email: info@advancedtools.us.
The Groundwater Resources Association of California (GRAC) held a symposium on “Environmental Forensics in an Era of Emerging Diagnostic Methods” during which Microseeps collaborated with EWMA to present a poster entitled “Forensic Investigations Using Compound Specific Isotope Analysis.” The poster is available here as a series of slides documenting the following case studies:
- Excerpts from the literature indicating that transport processes do not significantly affect carbon isotopic signatures
- From the literature that draws conclusions by combining both isotopic results for carbon and an assessment of the redox processes based upon interpretation of the groundwater chemistry
- From our own recent work at a site where carbon CSIA data was used at a DNAPL site to help confirm the existence of two distinct sources and to suggest that a third hotspot was a mixture.
The use of CSIA in forensics is very powerful, and new data interpretation techniques render it far more powerful than even these slides suggest. That said, forensics and degradation are very tightly coupled. Degradation blurs or even eliminates the forensic information obtainable through CSIA. Forensic investigation is most successful when multiple techniques are employed, such as CSIA in combination with either qPCR or PLFA’s. It is also important characterize the geochemistry in terms of laboratory-based analyses and field analyses. The laboratory analyses include the distribution of organic contaminant concentrations , electron donors such as TOC, and electron acceptors. Field analyses include parameters such as DO (dissolved oxygen), pH and conductivity.
As always, it is important to control costs. While CSIA of multiple isotopes is often required to make forensic arguments (see chapter 6, “Use of Stable Isotopes for Source Differentiation,” in the USEPA Consensus guide and our presentation), it is often possible to make a sound forensics argument with just carbon and a thorough interpretation of the existing data. Indeed, if a project is promising but needs analyses of additional isotopes to support the conclusions, Microseeps will help you by providing the analyses ourselves or working with our sub-contracts to procure them for you. We can advise you on the necessity of forensic investigation for your project, possibly reducing expenses and providing clear results. If you are considering a forensic investigation please contact us to discuss your ideas and questions.
As remarked in the previous posting, depleted DO (< 1.0 mg/l) and reduced ORP (< -50 mV) is extremely likely at a petroleum base. Most petroleum products participate in biodegradation as electron donors and require an electron acceptor like oxygen. Chlorinated solvents are not electron donors, but electron acceptors like oxygen. Chlorinated solvents require an electron donor to degrade through reductive dechlorination. Reductive dechlorination is the most common biodegradation mechanism used for these solvents. Electron donors may not be present at the site of a chlorinated solvent release so reductive dechlorination can not occur. (The USEPA Technical Protocol for Evaluating Natural Attenuation of Chlorinated Solvents in Groundwater is an excellent resource for discussing this phenomenon and appendix B2 provides a good summary of the basics of biodegradation. At 248 pages with appendices, it’s well worth your time. If you’re looking for a shorter read, Microseeps provides an excellent summary.
We try to talk to practitioners very often. We participate in conferences, symposia and workshops (Battelle’s chlorinated solvents conference, Battelle’s bioremediation symposium, and the Soil, Sediment, Water and Energy conferences put together by AEHS, SERDP/ESTCP Partners workshop) where we have representatives attending talks to hear both the public presentations and staffing booths so they can participate in the private conversations as well. We are active in ITRC so we hear the concerns of regulators, responsible parties and consultants. We helped found and put a lot of effort into preparing many of the workshops and material for the website of ADT. We also spend a lot of time talking to clients over the phone or by email, not just before the sale but also after it, following up on how they apply our analyses and suggesting how they might interpret their results. Indeed, we are still trying to reach out even more and that is a principle reason why we started this blog.
Measuring DO and ORP during a low flow purge is an important and useful first step to test for biodegradation, but it is just that: a first step. In a petroleum release, depleted DO (< 1.0 mg/l) and reduced ORP (< -50 mV) is extremely likely. Petroleum products are a mixture of many components, and invariably some of them will be very biodegradable, especially in the presence of a large supply of DO. The bacteria that carry on this aerobic biodegradation are ubiquitous. This means the biodegradation of at least some of the petroleum products occurs rapidly. During this process, the DO is consumed (as evidenced by the depleted DO) and anoxic conditions are established (as evidenced by the reduced ORP). Observation of those things at a petroleum release provides very little site or risk specific information. Data regarding either the growth or shrinkage of specific contaminant plumes is very important and a “first line of evidence”. If the evolution of the contaminant plumes suggests that in-situ biodegradation should be a component of the remedy, more detailed information about the geochemistry must be collected. Evidence must be gathered to answer the important question: now that the DO is gone, is biodegradation still occurring? read more…
Dr. Robert Pirkle, Microseeps, Inc.
