The challenge
A certificate of analysis reports concentrations; it can't say where they came from. With a deadline approaching, the consultancy asked its laboratory whether more could be read from the samples, and Statvis was engaged to interpret them.
The approach
Statvis examined each sample's PAH fingerprint, diagnostic ratios and degree of weathering. The naphthalene homologues were unaltered in every sample, a sign of no weathering, which ruled out weathered fuel oil: naphthalenes are the first compounds to change as fuel weathers. Apart from one anomalous peak, the pattern was typical of bituminous coal.
Statvis then asked for site context. The consultancy had collected a control sample from a coal seam next to the site, and Statvis added it to the comparison. Every site sample matched the coal control at more than 99%, showing that the PAHs on site and in the seam share a source.
The result
The consultancy has a defensible statement that the PAHs come from the same source as the nearby coal seam rather than a facility release, and is taking that position to the provincial regulator. A second sampling program, with more control samples, more site samples and hydrocarbon analysis, is planned to strengthen the record.
For the laboratory, interpretation added value to samples it had already analyzed, without new instruments or accreditation, and led to a larger follow-up program.