31st August 2009

Day 2

Good talks; the day started with one from Brian Murphy from Chicago on appropriate methods for detecting sources of chlorinated solvents. Additives, degradation products and the use of isotopes. Isotopes have been used to distinguish manufactured TCE from TCE formed from the degradation of PCE.

The next talk was from Zhendi Wang from Ontario, a world expert on the analysis of spilled oil. There is an oil spill every week, somewhere in the world.  Examples shown were those of the Detroit river spill, and the 2004 HMCE submarine fire accident. He showed how integrated oil fingerprinting methods characterise and distinguish the different hydrocarbon sources in spill oil samples when mixed with other hydrocarbons, such as tracing the sources of the spilled crude oil from Hurricane Katrina.

Marion Stelling, from the Netherlands Forensic Institute, gave a presentation on sampling strategies in criminal cases, and showed the need for experts to work together.

Yvan Razafindratandra, from Adamas in Paris, gave a legal perspective in his talk on environmental law as a two way process, arguing that science and law development must work together. Our legal system has origins in Roman law, guided by two arts: the art of discourse and the art of observation. Environmental forensics belongs to the latter art.

This entails the fact finding, analysis and construction of gathered facts.  The European Liability Directive sets up a system for soils, water and protected species, not the air. The organisation taking decisions on environmental damage and remedial action is vested primarily in the relevant administrative authority, NOT the judge. Discussion about this and the Water Framework Directive stressed the increasing importance of environmental forensics.

My keynote started off the afternoon session and was well received (I think, although it still felt like I was jet lagged).

The next speaker was Paul Philip from Oklahoma. He showed that while stable isotope analysis will not necessarily provide the silver bullet, it can give additional information that will be beneficial. It can provide a tool to identify source discrimination and the extent of natural attenuation particularly for groundwater contaminants. He also showed the benefits of 2D isotope analysis (i.e. C and H isotopes) in evaluating mechanisms of degradation. It can distinguish abiogenic from biogenic sources.

Thomas Boyd, from the naval research labs in Washington DC, talked about hydrocarbon source apportionment using compound specific C isotope analysis to identify apportionment of blame when there is more than one potentially responsible party. He used multivariate statistics at spatial and temporal scales to assess which well most likely released the hydrocarbon contaminant. Challenges are that groundwater models are not helpful, and fractionation due to degradation is not predictable.

Julie Sueker, of the company Aracadis, considered the issue of dealing with small sample sets.  For many constituents, the abiotic and microbial degradation results in a shift in the isotopic composition as the main process is ongoing. Sorption, dilution, and volatalisation have a negligible effect. Predicting this degradation is not yet currently possible.  Using case studies, she showed CSIA for nitrate, sulphate, chromate, benzene, MTBE and chlorinated solvents, and that 15 N and 18 O were good indicators of nitrate reduction.

There is so much work going on in the field of environmental forensics, much of which is directly relevant for our work at the Macaulay. It is good to see that we have much in common.

Talk by Paul Boehm of Exponent Inc, identified that a proper environmental forensic study in soil or sediments depends on a three part approach: 1 the right representative set of samples, 2 the right set of target analytes with the right quality and 3 the right data analysis approach. Up to 53 compounds are now used. The use of tight SOPs is important. Trained operators are important as GC operator must draw the appropriate baseline. Standard reference materials are essential.
Petrogenic, biogenic and pyrogenic sources can often be difficult to ascertain.

Multiple lines of evidence (ie statistical data analysis) provide the best approach for the use of polycyclic aromatic hydrocarbons(PAH) in environmental forensics.
Patterns, PCA plots and ratio and double ratio analyses can all be equally informative. Quantitative apportionment techniques is also another approach - source driven is better than sample driven.

Antoine Assal from Bob Kalin's group at Strathclyde showed the great potential of stable isotopic fingerprints of PAHs by GC IRMS. Working on a tar works case it was illustrated that such methods can help decipher new degradation pathways of lighter PAHs. The use of heavier PAHs are more reliable. They do not fractionate.
Results suggest that C and H are subject to the same degradative processes. Position specific isotope analysis is a new development which will help environmental forensics.  'Isotopic fingerprinting' is this term relevant? It implies that they are unique but they have been shown not to be unique.

The distribution of PAHs in urban soils in the US from over 500 sites and 42 population centres was presented by David Mauro of META environmental Inc. The site use was recorded, most being on municipal and heavy residential. Heavy industrial sites were not focussed on. This background data allows regulators to identify sites outside the background signatures. PAHs come from asphalt, pavement sealers, roofing materials, automobile exhausts (modern) as well as more ancient sources. Fluoranthene to pyrene ratio was helpful for identifying sources. However when it was plotted against benzanthracene to chrysene ratio better groupings were identified. The oil and gas industries have an interest in the ability to predict biodegradation of compounds.

A good day with lots of interesting presentations. Food for thought about how these approaches can transfer from one application such as environmental forensics to criminal forensics.

Tired, I headed home early (for Canada; still late for the UK!) to my hotel and then found myself being chased back by a group of junkies! Yes, I had got myself lost in the Chinese zone of Calgary last night (even in a grid-based city a geographer can get lost!) ..... I crashed out in my room exhausted and slightly scared.  However, it had been a great day of networking. Great people at the meeting! Gwen and Tina were so helpful; thanks both!

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