Origin and Distribution of Polycyclic Aromatic Hydrocarbons in Surficial Sediments from the Savannah River

Surface sediments collected from the Savannah River, located in the southeastern state of Georgia, USA, in June-July 1994 were analyzed for individual polycyclic aromatic hydrocarbons (PAHs). Three subdivisions of the river were identified for the study: upstream from, adjacent to, and downstream from the city of Savannah. There was high spatial variability in the total PAH (ΣPAH) concentrations that ranged from 29 to 5,375 ng/g with an average concentration of 1,216 ± 1,161 (SD). Of the three subdivisions, the highest ΣPAH concentrations were in the middle segment, which was adjacent to urban and industrial areas. To elucidate sources, molecular indices based on indices among phenanthrene versus anthracene and fluoranthene versus pyrene were used to determine pyrogenic and petrogenic sources, respectively. These indices have been used by other authors to differentiate sources. In most cases, PAHs in sediments nearest the city of Savannah were of high temperature and pyrogenic origin. These pyrogenic PAHs were highly associated with toxicity to benthic organisms. The two-ringed naphthalene and substituted naphthalenes, which are petroleum-related PAHs, were significantly higher in the lower section of the river relative to the subdivisions. This river segment receives inputs primarily from shipping and boating traffics Perylene, which is indicative of nonanthropogenic terrestrial inputs of carbon, had the highest concentration among the individual PAHs measured. High perylene concentrations were found at stations located upstream and adjacent to forested terrain and where salinity level was low. To discriminate pattern differences and similarities of individual PAHs among samples, principal component analysis (PCA) was performed on the more hydrophobic and persistent nonalkylated PAHs. These differences and similarities were used to infer perylene origin. PCA was performed on 14 nonalkylated PAHs that was normalized to the sum of nonalkylated PAHs, using a correlation matrix. Generally, the PAHs were separated into group patterns according to chemical and physical properties associated with log K OW , except perylene. Perylene, a five-ringed PAH, was distinctly separated from the other five-ringed PAHs. The sources for perylene are likely from biogenic, terrestrial precursors. The collected data show that pyrogenic PAHs were highly associated with biological effects on benthic organisms, based on bioassay results. Perylene, a nonanthropogenic PAH, was found throughout the river and constituted a large percentage of total PAHs in the upper river.