Source apportionment of PAHs in dated sediments from the Black River, Ohio

Black River, OH, is contaminated with polycyclic aromatic hydrocarbons (PAHs) from coke ovens of a US Steel Corp. Plant. Closing of a coking plant in 1983 and environmental dredging of the sediments during 1989 and 1990 has reduced the PAH levels significantly. This study quantifies the decrease, and consider source apportionment of PAHs in Black River sediments using chemical mass balance modeling. Five vibra cores collected in 1998 and dated using 210Pb and 137Cs, were analyzed for 18 PAHs. The cores had total PAH concentrations between 250 and 0.10 ppm. PAH maxima occur in 1949, 1969, in accordance with regional historical inputs (core BR4), and in 1991 due to remediation (BR6). Coke oven emissions (CO), highway dust (HWY), and wood burning (WB) are likely sources. The CO source (6–92% of total PAHs) is maximal in 1954, and again in 1992–1994 due to the exposure and redistribution of older contaminated sediments during dredging, and decreases thereafter. There is minimal CO content in 1985 (BR4), 2 yr after closure of the coking plant. The HWY contribution (2–86%) is high during 1969–1988, and increases again after 1993. The WB source is less than 23%, and exhibits a minimum (2%) around 1979 (BR4). There is evidence of aerobic biodegradation or photolysis in the sediment of phenanthrene (PhA) at PhA concentrations >500 ppb.