title: Enhanced sorption of PAHs in natural-fire-impacted sediments from Oriole Lake, California.
abstract: Surface sediment cores from Oriole Lake (CA) were analyzed for organic carbon (OC), black carbon (BC), and their δ(13)C isotope ratios. Sediments displayed high OC (20-25%) and increasing BC concentrations from ∼0.40% (in 1800 C.E.) to ∼0.60% dry weight (in 2000 C.E.). Petrographic analysis confirmed the presence of fire-derived carbonaceous particles/BC at ∼2% of total OC. Natural fires were the most likely cause of both elevated polycyclic aromatic hydrocarbon (PAH) concentrations and enhanced sorption in Oriole Lake sediments prior to 1850, consistent with their tree-ring-based fire history. In contrast to other PAHs, retene and perylene displayed decreasing concentrations during periods with natural fires, questioning their use as fire tracers. The occurrence of natural fires, however, did not result in elevated concentrations of black carbon or chars in the sediments. Only the 1912-2007 sediment layer contained anthropogenic particles, such as soot BC. In this layer, combining OC absorption with adsorption to soot BC (using a Freundlich coefficient n = 0.7) explained the observed sorption well. In the older layers, n needed to be 0.3 and 0.5 to explain the enhanced sorption to the sediments, indicating the importance of natural chars/inertinites in sorbing PAHs. For phenanthrene, values of n differed significantly between sorption to natural chars (0.1-0.4) and sorption to anthropogenic black carbon (>0.5), suggesting it could serve as an in situ probe of sorbents.
authors.affiliation: Graduate School of Oceanography, University of Rhode Island, Narragansett, Rhode Island 02882, United States.
authors.forename: Julia
authors.initials: J
authors.lastname: Sullivan
authors.forename: Kevyn
authors.initials: K
authors.lastname: Bollinger
authors.forename: Anthony
authors.initials: A
authors.lastname: Caprio
authors.forename: Mark
authors.initials: M
authors.lastname: Cantwell
authors.forename: Peter
authors.initials: P
authors.lastname: Appleby
authors.forename: John
authors.initials: J
authors.lastname: King
authors.forename: Bertrand
authors.initials: B
authors.lastname: Ligouis
authors.forename: Rainer
authors.initials: R
authors.lastname: Lohmann
mesh_terms: D000327:Adsorption; D002140:California; D004784:Environmental Monitoring; D005390:Fires / Q000706:statistics & numerical data*; D005618:Fresh Water / Q000737:chemistry*; D019015:Geologic Sediments / Q000737:chemistry*; D010616:Phenanthrenes / Q000032:analysis; D011084:Polycyclic Aromatic Hydrocarbons / Q000032:analysis / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000032:analysis / Q000737:chemistry*
chemical_list: D010616:Phenanthrenes; D011084:Polycyclic Aromatic Hydrocarbons; D014874:Water Pollutants, Chemical; C447880:retene