Comprehensive Multi-compartment Sampling for Quantification of Long-Term Accumulation of PAHs in Soils

Area of Science:

• Environmental Chemistry
• Soil Science
• Atmospheric Science

Background:

• Polycyclic aromatic hydrocarbons (PAHs) are persistent organic pollutants that accumulate in soils over time.
• Understanding the movement and distribution of PAHs across environmental compartments is key to assessing contaminant fate.
• Quantifying gas-phase concentrations between soil and atmosphere is challenging but crucial for fate assessment.

Purpose of the Study:

• To quantify the phase distribution and fluxes of PAHs in soil and atmosphere.
• To evaluate different methods for determining aqueous and gas-phase PAH concentrations from soil solids.
• To investigate seasonal variations in PAH concentrations and deposition patterns.

Main Methods:

• Combined passive sampling, sorption isotherms, and empirical relationships to estimate PAH phase distribution.
• Measured PAH concentrations in the atmosphere, bulk deposition, and soil solids.
• Analyzed seasonal trends in atmospheric PAH concentrations and fluxes.

Main Results:

• Methods for estimating PAH concentrations agreed within one order of magnitude, except for ex situ passive samplers in soil slurries.
• Atmospheric PAH concentrations exhibited seasonality, with summer revolatilization and winter deposition, but dry deposition dominated annual fluxes.
• PAH distribution patterns across gas, atmospheric, deposition, and soil phases confirmed compound-specific behavior.

Conclusions:

• Topsoil PAH loads are expected to increase due to ongoing wet and dry deposition, with minor summer revolatilization.
• Accurate quantification of PAH phase distribution is essential for understanding long-term soil contamination.
• Environmental monitoring and risk assessment must consider the continuous accumulation of PAHs in topsoils.