Using Radiocarbon to Apportion Sources of Polycyclic Aromatic Hydrocarbons in Household Soot

Abstract

To determine whether polycyclic aromatic hydrocarbons (PAHs) in household soot were derived from the combustion of scrap wood or creosote that was impregnated in the wood (or some combination of both), the molecular composition and radiocarbon ( 14 C) content of the total carbon and several PAHs in the soot was investigated. The 5730-year half-life of 14 C makes it an ideal marker for identifying creosote-derived PAHs ( 14 C-free) versus those derived from the combustion of wood (contemporary 14 C). The 14 C abundance of phenanthrene, fluoranthene, pyrene, and retene was determined by accelerator mass spectrometry after solvent extraction and purification by preparative capillary gas chromatography. The molecular analysis (presence of retene and 1,7-dimethylphenanthrene) and bulk 14 C content (contemporary) of the soot indicated that wood combustion was a strong source of carbon to the soot. The 14 C of retene in two soot samples was also contemporary, indicating that it was derived from the combustion of the scrap wood. These results are consistent with previous work that has suggested that retene is an excellent marker of wood combustion. However, the 14 C content of phenanthrene, fluoranthene, and pyrene in one soot sample was much lower and revealed that these compounds had a mixed creosote and wood source. Using an isotopic mass balance approach, we estimate that 40 to 70% of phenanthrene, fluoranthene, and pyrene were derived from the combustion of the scrap wood. The results of this study show that molecular marker and bulk 14 C analysis can be potentially misleading in apportioning sources of every PAH, and that molecular-level 14 C analysis of PAHs can be a powerful tool for environmental forensics.

Contribution of Biomass Burning to Atmospheric Polycyclic Aromatic Hydrocarbons at Three European Background Sites

“…The ∆ 14 C of PAHs in air samples of Finokalia and Zadar & Velebit was -914‰ and -888‰, respectively, while much less depleted values were observed for the two Aspvreten samples (-388‰ and -381‰) (Table 1). All chemical species originating from fossil sources have a ∆ 14 C of -1000‰, while the radiocarbon abundance of the compounds emitted from modern biomass should be in the vicinity of +225‰ (40). The latter value is approximately equivalent to the 14 C signal previously measured in soft wood (41), while a ∆ 14 C value of +235‰ has been attributed to plant waxes (42).…”

Compound Class Specific 14C Analysis of Polycyclic Aromatic Hydrocarbons Associated with PM10 and PM1.1 Aerosols from Residential Areas of Suburban Tokyo

“…PAHs Source Apportioning. On the basis of the ∆ 14 C data, the relative contribution of biomass burning and fossil fuel combustion as sources of the PAH burden in residential areas of suburban Tokyo were calculated using an isotopic mass balance approach as described and applied previously (7,13,33) where ∆ 14 CPAH is the 14 C abundance measured for PAHs in APM samples and ∆ 14 Cfossil is the characteristic radiocarbon abundance of fossil material (-1000‰). Fbiomass and 1-Fbiomass are the fraction of the PAHs derived from biomass burning and fossil fuel combustion (including those directly emitted from fossil sources), respectively.…”

Source apportionment of elevated wintertime PAHs by compound-specific radiocarbon analysis

“…An isotopic mass balance equation was applied to the TOC and PAH 14 C results to calculate fractional contribution of wood burning (f biomass ) and fossil fuel combustion (f fossil =1-f biomass ) (Reddy et al, 2002;Currie et al, 1999;Mandalakis et al, 2004a;Reddy et al, 2003):…”