Relationships between aging of PAHs and soil properties

Area of Science:

• Environmental Chemistry
• Soil Science
• Geochemistry

Background:

• Polycyclic Aromatic Hydrocarbons (PAHs) are persistent organic pollutants found in soils.
• Understanding PAH sequestration and diffusion is vital for environmental risk assessment.
• Soil properties significantly affect the fate and transport of organic contaminants.

Purpose of the Study:

• To investigate the sequestration and diffusion of three PAHs in seven Chinese soils.
• To determine the influence of soil properties and aging time on PAH behavior.
• To elucidate the mechanistic basis of organic contaminant sequestration and diffusion in soils.

Main Methods:

• Experiments were conducted in sterile soil microcosms over 200 days.
• PAH aging was assessed using a mild extractant targeting the labile fraction.
• Soil properties analyzed included organic carbon content, organic carbon fractionation, and meso- and micropore distribution.

Main Results:

• PAH aging exhibited biphasic diffusion behavior: rapid diffusion from labile to nonlabile domains and slow diffusion.
• Rapid diffusion was primarily dependent on meso- and micropore fraction and total organic carbon content.
• Slow diffusion decreased with increasing soil organic carbon (especially hard organic carbon), meso- and micropore fraction, and PAH molecular size.

Conclusions:

• Soil organic carbon fractionation and porosity are critical factors in PAH sequestration and diffusion.
• These soil characteristics provide a mechanistic basis for understanding organic contaminant behavior.
• Accurate assessment of soil properties is essential for predicting the environmental fate of PAHs.