Coal Tar Forensics - New ways of understanding an old product Dr Russell Thomas 1 , Dr Laura McGregor 2 , Christopher Gallagher 3 , Dr Caroline Gauchotte- Lindsay 4 and Prof. Robert Kalin 3 - Introduction The manufactured gas industry has left a considerable environmental legacy in Britain and across the world of thousands of former gasworks (manufactured gas plant) sites, ranging in size from large city gasworks to those small gasworks at country houses. In Britain the environmental concerns on many of these sites have been addressed; however, many former gasworks require further investigation and remediation on some or all parts of the site. Historically, the analysis of coal tar has been something commercial laboratories have struggled to provide and often avoided. To provide any detailed analysis required lengthy and costly preparation, separating the coal tar into different fractions, each of which had to be analysed individually. This is traditionally done using a Gas Chromatograph (GC) the column separates out organic compounds depending on their boiling point and polarity. The key innovation described in this paper is the development of an analytical tool which can, in one sample preparation stage, identify thousands of individual compounds of a coal tar sample. By matching this expertise in forensic chemistry with a detailed historical understanding of former gasworks sites, this innovative method can attribute different coal tars found on former gas or coking works to specific gas manufacturing processes - something previously impossible. This is valuable information for investigating groundwater pollution at former coal carbonisation sites. Brief History of Gas Manufacturing in Britain Gas in Britain was once manufactured rather than extracted from gas fields deep below ground. Natural gas has only been available in Britain for about 40 years, whereas gas manufacturing lasted for a period of about 170 years, until the closure of the last coal gasworks in Britain on the Isle of Cumbrae, Scotland, in 1981. The roots of the gas industry were in the provision of lighting, rather than heating as it is primarily used today. Lighting of the ever expanding textile mills and factories of Britain was difficult and dangerous. Candles and oil lamps produced a dull light, required continual attention for trimming wicks and replacement, and were a significant safety hazard. The potential for a cheaper, safer and more effective alternative, in the form of gas, was developed by William Murdoch and his colleagues at the Boulton and Watt Company in Birmingham. The evident need for this new form of lighting led to many gasworks being built. The value of gas lighting for improving the safety of urban streets was realised and with the help of the German entrepreneur Freidrich Winzer gas lighting soon spread to the streets, public and private establishment and houses of the nation. 1 Parsons Brinckerhoff, Bristol, UK, +44 (0) 117 933 9262, thomasru@pbworld.com 2 Markes International Limited, Gwaun Elai Medi Science Campus, Llantrisant, RCT, CF72 8XL 3 Department of Civil and Environmental Engineering, University of Strathclyde Glasgow G1 1XQ 4 School of Engineering, University of Glasgow