Polycyclic aromatic hydrocarbons (PAH) in different forest humus types.

Area of Science:

• Environmental Chemistry
• Soil Science
• Organic Geochemistry

Background:

• Polycyclic Aromatic Hydrocarbons (PAHs) are persistent organic pollutants found in various environmental compartments.
• Soil organic matter plays a crucial role in the fate and transport of PAHs.
• Understanding PAH behavior in different soil types is essential for environmental risk assessment.

Purpose of the Study:

• To investigate the distribution and enrichment of 20 Polycyclic Aromatic Hydrocarbons (PAHs) in different organic soil layers (L mull, Of mull, mor).
• To determine the influence of soil organic matter decomposition and particle size on PAH concentrations.
• To elucidate the role of microbial activity in differentiating low- and high-molecular-weight PAHs.

Main Methods:

• Soil profile study across L, Of, and Oh horizons of mull and mor soil types.
• Analysis of particle-size separates (< 0.05 mm, > 2 mm) to assess PAH distribution.
• Correlation analysis between PAH enrichment, organic matter decomposition gradient, and octanol-water partition coefficient (KOW).

Main Results:

• PAH concentrations increased with depth in the mor soil profile, indicating selective enrichment during organic matter decomposition.
• PAHs were significantly enriched in finer soil particle-size separates across all soil types.
• A positive correlation between PAH enrichment and KOW was observed in L horizons, with the degree of differentiation influenced by microbial activity.

Conclusions:

• Soil organic matter decomposition and particle size are key factors controlling PAH behavior in organic soil layers.
• Microbial breakdown significantly influences the differentiation of low- and high-molecular-weight PAHs, with greater differentiation in biologically active L mull soils.
• Decomposition processes in L horizons lead to changes in organic matter morphology and chemistry, enriching high-molecular-weight PAHs.