Appraisal of coal- and coke-derived wastes in soils near a former manufactured gas plant, Jacksonville, Florida

Abstract

Preliminary site assessments revealed visibly-impacted soils in downtown Jacksonville, Florida (USA) suspected to be associated with a historic (1875–1912) manufactured gas plant (MGP) nearby. In this study, 19 soils from 11 borings within the impacted area were collected and analyzed using GC/FID for quantification of total petroleum hydrocarbons (TPH) and GC/MS for quantification of 87 volatiles and 50 parent and alkylated polycyclic aromatic hydrocarbons (PAHs). The results showed soils (up to 11 m deep and spanning ~90 m) containing elevated concentrations of TPH and PAHs, wherein the total PAHs, which were exclusively pyrogenic in character, comprised (on average) 40 ± 10% of the TPH in most (14 of 19) soils. In accord with visual observations of black-to-maroon, viscous non-aqueous phase liquid (NAPL) in some soils, the chemical results confirm the widespread occurrence of variably-weathered MGP tars throughout the area's subsurface. Multiple PAH isomer ratios indicate all but one of the tars likely were produced from the carbureted water gas (CWG) process; the exceptional tar likely was produced via the coal carbonization process. Both processes were historically used by the nearby former MGP. Three soils contained distinct hydrocarbons and pyrogenic PAHs consistent with particulate coke or coal ash (clinker) or heavy (C10 to C22) gas oil, a feedstock for CWG, the latter of which appeared as a yellowish-green NAPL. When interpreted in light of the typical MGP waste management and decommissioning practices, the results demonstrate the area's soils contain MGP wastes consistent with the discharge and/or disposal of wastes and demolition debris from the former MGP.