Statistics of Lost Historical Coal Tar PAH Contamination in Soils and Sediments

Beginning in the mid-1800s in the United States, coal gasification provided energy for an emergent utility industry. With focus largely on the engineering aspects of manufactured gas production (MGP) mainly for lighting purposes, the energy industry gave little thought to waste management end practices, vestiges of which remain over 100 years later as legacy contamination. As a consequence, in today's energy marketplace, industry's successor companies now carry significant MGP financial and legal liability. Polycyclic aromatic hydrocarbons (PAH), with structures ranging from two to six aromatic rings, are dominant legacy MGP pollutants. Sorting out possible multiple PAH sources at former MGP sites carries significant forensic geochemical challenges. Analyses of PAH data using statistical visualization by multiple linear regression and principal component analysis (PCA) have been shown to address legacy forensic geochemical MGP problems but there are interpretation problems as well. Done properly, statistical analyses will aid in the delineation of former MGP operation loci, provide assessment of multiple PAH sources and mixing effects, and offer clear output graphics for potential legal application. Three case studies will be presented that show how clear statistical presentation can illustrate how different historical gas engineering practices are reflected in modern legacy PAH pollutant distributions.