Igne’s environmental forensic services explained
Every type of hydrocarbon fuel leaves a fingerprint and with Igne’s environmental forensic services, you can understand what your development site is potentially contaminated with and receive comprehensive decontamination advice and support to remediate your land.
This is exactly the comprehensive service we provided to a developer who wanted to transform a mixed-use site into a drive-thru restaurant and car park. Initial site investigation identified hydrocarbons in ground water samples taken from the site, and so Igne’s scientists and engineers collaborated to determine the nature, source, and age of the contaminant, before developing a comprehensive remediation strategy.
Here's how we work:
At Igne, we have an extensive range of chromatographic fingerprints in our library; a library we have built up over the decades. We can compare a customer sample chromatogram to our library and then suggest a possible contaminant.
Each type of hydrocarbon produces a ‘hump or hedgehog.’ This is called the unresolved complex mixture (UCM) of compounds that make-up a fuel. If there are multiple humps, or UCMs, that would indicate to us that there are multiple sources of hydrocarbon contamination e.g., diesel and motor oil say.
This can be useful for identifying a possible source of the contaminant, so that you can isolate a problem. For example, if you were remediating a petrol station: is the underground petrol tank leaking or is the diesel tank leaking, or both? A forensic chromatographic (CG) fingerprint will allow us to tell you.
Another example of how our environmental forensic services can be applied is if a client finds abandoned drums of old fuel. We can easily tell you not only what it is but how old it is.
Age dating a contamination from a hydrocarbon
In terms of age dating a contamination from a hydrocarbon – for example, a diesel spill in soil, we know that diesel weathers over time and by comparing the fingerprint to the weathered diesel standards, we can determine whether the spill is new or historic.
For petrol spills in water, we can assess the ratio of BTEX concentrations (that is Benzene, Toluene, Ethyl Benzene, and Xylenes) – and by doing so, predict the age of the spill. Furthermore, in petrol analysis, if the sample contains lead, then it must be older than when leaded fuels were banned, so this too would indicate an older fuel source.
We can also help clients understand where their polynuclear aromatic hydrocarbons (PAH) come from. PAHs are a by-product of combustion. So, you can find these from fuels, coal, charcoal (barbeques etc.,), coal tar, and soot.
There are 16 PAHs that the US Environmental Protection Agency (USEPA) has set for testing, as these are considered to be more harmful than the others, generally having the highest concentrations in hydrocarbon contamination, and indicative of the hundreds of different types of PAHs that may be present.
Sourcing a contaminant
Depending on the ratio of some of the individual PAHs in the 16 tested, we can provide an indication of the source of the PAHs found.
Further source identification can be achieved by a compound ratio analysis technique (CORAT) plot; if multiple samples have the same contaminant, they will have the same shape on the graph that we plot. So, if you had a site with many samples taken across the site, and they correlate on a CORAT plot, this would indicate that the contaminant is from the same source.
So, in summary, our environmental forensics package can tell you what a contaminant is (GC-Fingerprint ID), where PAHs may have come from (PAH ratio plot), estimate of the age of the contaminant (assess GC-Fingerprint for weathering), and whether the contaminant is from the same source (CORAT plot).
How we helped one client
Returning to the hydrocarbon found in ground water samples on a development site for a drive-thru restaurant and car park, the history of the site was complex. It was undeveloped until a library was built on it in the 1960s, it was then converted to a light engineering factory in the 1970s before metal works were added in the 1980s, and then all the structures were demolished between 2006 and 2010.
The site’s surroundings had been dominated by industrial developments, including brick and gas works, railway lines and railway sidings, which were dismantled by the mid 1970s.
We did a chromatographic fingerprint of the contaminant found in the water samples, and determined that it was predominantly diesel with heavy fuel oils. Then, when comparing the surrounding samples, this displayed the same fingerprint indicating that the source of the contaminant was consistent.
On assessing the chromatographic fingerprint further, the diesel was notably weathered, so unlikely to be fresh, and ultimately, through additional testing, it was attributed to historical onsite activity.
How we can help you
At Igne, we can support your development activity from pre-purchase right through all planning and construction phases to ensure you fully understand and plan around the innumerable challenges that the ground can throw up.
Our geo-environmental, site investigation, testing and unexploded ordnance services ensure you work with clear sight and full awareness of your site’s unique geography and history – and our specialist drilling, water well and geothermal solutions can support your development to be sustainable and successful. Contact the team for more information.