Influence of Soot Carbon on the Soil−Air Partitioning of Polycyclic Aromatic Hydrocarbons

Abstract

Soil-air partitioning is one of the key processes controlling the regional and global cycling and storage of polycyclic aromatic hydrocarbons (PAHs). However, the specific processes dominating the partitioning of PAHs between these two environmental compartments still need to be elucidated. Stable and distinct atmospheric conditions paralleling different soil properties are found at Tenerife island (28 degrees 18'N, 16 degrees 29'W), which is located in permanent inversion layer conditions, and they provide interesting model cases for the study of air-soil partitioning. Analysis of phenanthrene, pyrene, fluoranthene, and chrysene showed concentrations 4- to 10-fold higher below than above the inversion layer. Similarly, soil total organic carbon (TOC) and black carbon (BC) were 11 and 3 times higher, respectively, below the inversion layer than above. The octanol-air partition coefficient (K(OA)) derived model provides a good description of PAH soil-air partitioning coefficients (K(P)) below the inversion layer but underpredicts them in the area dominated by deposition of long-range transported aerosols without inputs of organic matter from local vegetation. Inclusion of soot carbon in the soil-air partitioning model results in good agreement between predicted and measured K(P) in this area but in overpredicted K(P) values for the soils under the vegetation cover, which shows that the influence of soil soot carbon on PAH air-soil partitioning depends on its abundance relative to soil organic carbon. Absorption into organic matter is the dominant process in soils containing high organic carbon concentrations, whereas adsorption onto soot carbon becomes relevant in soils with low organic carbon and high soot content.

Atmospheric Concentrations and Phase Partitioning of Polycyclic Aromatic Hydrocarbons in Izmir, Turkey

“…The values measured in the present study were similar to these, however, they were higher than those typically assumed in modeling studies (10-20%) [22,35]. It was assumed that a EC /a AC ¼ 1, f OM ¼ 1.6 f OC , and f OC /f EC ¼ 3 where f OC is the fraction of total organic carbon [39,42]. Dachs et al [43] have suggested that the thermodynamics-based model recently reported by van Noort [44] can be used to estimate K SA values for PAHs as a function of supercooled liquid vapor pressure (P L , Pa) and elemental carbon specific surface area (a EC , m 2 g À1 ):…”

Determination of octanol–air partition coefficients and supercooled liquid vapor pressures of PAHs as a function of temperature: Application to gas–particle partitioning in an urban atmosphere

“…The a EC value (62.7 m 2 g À1 ) was taken from a recent study by Jonker and Koelmans (2002). It was assumed that a EC /a AC ¼ 1, f OM ¼ 1.6f TOC , and f OC /f EC ¼ 3 where f TOC is the fraction of total organic carbon (Dasch and Eisenreich, 2000;Ribes et al, 2003). Under these assumptions, modeled K p values were calculated using Eq.…”

Quantification of sedimentary black carbon using the chemothermal oxidation method: an evaluation of ex situ pretreatments and standard additions approaches

“…For instance, BC may be an important component of sedimentary carbon preservation (Goldberg 1985;Gustafsson and Gschwend 1998;Masiello and Druffel 1998;Dickens et al 2004) and thereby constitutes a valuable record of the global fire history (e.g., Bird and Cali 1998). Sorption of aromatic compounds to BC is 10 to 1000 times stronger than to nonpyrogenic sedimentary organic matter (e.g., Bucheli and Gustafsson 2000;Accardi-Dey and Gschwend 2002;Jonker and Koelmans 2002;Cornelissen and Gustafsson 2004) and frequently governs the environmental distribution of many organic pollutants (Gustafsson et al 1997;Gustafsson and Gschwend 1997;Dachs and Eisenreich 2000;Persson et al 2002;Ribes et al 2003). In the atmosphere, BC affects Earth's radiative heat balance (e.g., Jacobson 2001) and BC in urban air particles has been implicated as the culprit of epidemiological respiratory diseases and human deaths (Dockery et al 1993;Künzli et al 2000;Gerde et al 2001).…”