Predictivity Strength of the Spatial Variability of Phenanthrene Sorption Across Two Sandy Loam Fields

Soares, António; Paradelo, Marcos; Moldrup, Per; Delerue-Matos, Cristina; de Jonge, Lis W.

Predictivity Strength of the Spatial Variability of Phenanthrene Sorption Across Two Sandy Loam Fields

2015

Soares, António | Paradelo, Marcos | Moldrup, Per | Delerue-Matos, Cristina | de Jonge, Lis W.

Sorption is commonly agreed to be the major process underlying the transport and fate of polycyclic aromatic hydrocarbons (PAHs) in soils. However, there is still a scarcity of studies focusing on spatial variability at the field scale in particular. In order to investigate the variation in the field of phenanthrene sorption, bulk topsoil samples were taken in a 15 × 15-m grid from the plough layer in two sandy loam fields with different texture and organic carbon (OC) contents (140 samples in total). Batch experiments were performed using the adsorption method. Values for the partition coefficient Kd(L kg⁻¹) and the organic carbon partition coefficient KOC(L kg⁻¹) agreed with the most frequently used models for PAH partitioning, as OC revealed a higher affinity for sorption. More complex models using different OC compartments, such as non-complexed organic carbon (NCOC) and complexed organic carbon (COC) separately, performed better than single KOCmodels, particularly for a subset including samples with Dexter n < 10 and OC <0.04 kg kg⁻¹. The selected threshold revealed that KOC-based models proved to be applicable for more organic fields, while two-component models proved to be more accurate for the prediction of Kdand retardation factor (R) for less organic soils. Moreover, OC did not fully reflect the changes in phenanthrene retardation in the field with lower OC content (Faardrup). Bulk density and available water content influenced the phenanthrene transport mechanism phenomenon.

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