Polycyclic aromatic hydrocarbons in different forest soils: Mineral horizons

authored by: Georg Guggenberger, Martin Pichler, Robert Hartmann, Wolfgang Zech
Abstract: The objective of this study was to assess the behavior of PAH in mineral soil horizons of different forest soils (Allersdorf, All: Inceptisol, mull humus type; Geisberg, Geis: Entisol, mull; Hohe Matzen, HoM: Spodosol, mor). At the mor site, the highest PAH loading was observed in the forest floor (HoM L to Oh, Σ 20 PAH: 829 g ha^-1), whereas at the mull sites the humified mineral soil horizons were the main sink for PAH (All aAxh, Σ 20 PAH: 522 g ha^-1). In all soils, there was a significant PAH translocation into subsoil horizons (Σ 20 PAH in the subsoil: 76-195 g ha^-1). In order to delineate possible transport mechanisms, double-logarithmic relationships were established between the translocation of the distinct PAH from the surface soil to the subsoil and the PAH's K_ow values. The data suggested that transport of low-molecular PAH into the subsoil was primarily a function of the water solubility of each compound. In the biologically active All and Geis soils, high-molecular PAH were translocated independently from their K_ow value, and particle-bound transport probably by soil burrowing animals was assumed to control translocation of the penta- and hexacyclic PAH. In contrast, at HoM transfer of high-molecular PAH increased with increasing hydrophobicity, suggesting dissolved organic matter (DOM)-mediated transport of PAH. Fractionation of soil into a floatable fraction and into sand-(20-2000 μm), silt- (2-20 μm), coarse clay- (0.2-2 μm), and fine clay-sized (< 0.2 μm) separates revealed that more than 80% of the PAH loading could be assigned to silt-and coarse clay-sized separates, irrespective of the soil's texture (loamy sand to silty clay loam). Silt generally showed the highest C_org-related PAH concentrations. PAH profiles (relative proportion of each PAH on the sum of 20 PAH) revealed increasing proportions of high-molecular, more refractory PAH from the floatables and the sand-sized separates to the finer particles, corresponding with an increasing degree of SOM alteration in the same direction. At HoM, depth gradients of high-molecular PAH suggested co-transport of penta- and hexacyclic PAH with DOM and subsequent co-sorption selectively to the silt- and coarse-clay sized separates of the Bsh horizon.
External Organisation(s): University of Bayreuth
Type: Article
Journal: Zeitschrift fur Pflanzenernahrung und Bodenkunde
Volume: 159
Pages: 565-573
No. of pages: 9
ISSN: 0044-3263
Publication date: 12.1996
Publication status: Published
Peer reviewed: Yes
ASJC Scopus subject areas: Soil Science
Electronic version(s): https://doi.org/10.1002/jpln.1996.3581590607 (Access: Closed)

BibTeX

@article{654601bb3cfa42a7bd4032f146f47c86,
title = "Polycyclic aromatic hydrocarbons in different forest soils: Mineral horizons",
abstract = "The objective of this study was to assess the behavior of PAH in mineral soil horizons of different forest soils (Allersdorf, All: Inceptisol, mull humus type; Geisberg, Geis: Entisol, mull; Hohe Matzen, HoM: Spodosol, mor). At the mor site, the highest PAH loading was observed in the forest floor (HoM L to Oh, Σ 20 PAH: 829 g ha-1), whereas at the mull sites the humified mineral soil horizons were the main sink for PAH (All aAxh, Σ 20 PAH: 522 g ha-1). In all soils, there was a significant PAH translocation into subsoil horizons (Σ 20 PAH in the subsoil: 76-195 g ha-1). In order to delineate possible transport mechanisms, double-logarithmic relationships were established between the translocation of the distinct PAH from the surface soil to the subsoil and the PAH's Kow values. The data suggested that transport of low-molecular PAH into the subsoil was primarily a function of the water solubility of each compound. In the biologically active All and Geis soils, high-molecular PAH were translocated independently from their Kow value, and particle-bound transport probably by soil burrowing animals was assumed to control translocation of the penta- and hexacyclic PAH. In contrast, at HoM transfer of high-molecular PAH increased with increasing hydrophobicity, suggesting dissolved organic matter (DOM)-mediated transport of PAH. Fractionation of soil into a floatable fraction and into sand-(20-2000 μm), silt- (2-20 μm), coarse clay- (0.2-2 μm), and fine clay-sized (< 0.2 μm) separates revealed that more than 80% of the PAH loading could be assigned to silt-and coarse clay-sized separates, irrespective of the soil's texture (loamy sand to silty clay loam). Silt generally showed the highest Corg-related PAH concentrations. PAH profiles (relative proportion of each PAH on the sum of 20 PAH) revealed increasing proportions of high-molecular, more refractory PAH from the floatables and the sand-sized separates to the finer particles, corresponding with an increasing degree of SOM alteration in the same direction. At HoM, depth gradients of high-molecular PAH suggested co-transport of penta- and hexacyclic PAH with DOM and subsequent co-sorption selectively to the silt- and coarse-clay sized separates of the Bsh horizon.",
author = "Georg Guggenberger and Martin Pichler and Robert Hartmann and Wolfgang Zech",
year = "1996",
month = dec,
doi = "10.1002/jpln.1996.3581590607",
language = "English",
volume = "159",
pages = "565--573",
journal = "Zeitschrift fur Pflanzenernahrung und Bodenkunde",
issn = "0044-3263",
publisher = "Wiley-VCH Verlag",
number = "6",
}