Developing a Black Carbon-Substituted Multimedia Model for Simulating the PAH Distributions in Urban Environments

Area of Science:

• Environmental Chemistry
• Multimedia Environmental Fate Modeling
• Urban Scale Pollution Dynamics

Background:

• Traditional multimedia fugacity models rely on organic carbon (OC) to simulate pollutant behavior.
• Polycyclic Aromatic Hydrocarbons (PAHs) like phenanthrene (Phe), pyrene (Pyr), and benzo[α]pyrene (BaP) are significant urban pollutants.
• Black carbon (BC) is increasingly recognized as a crucial sorbent for PAHs in the environment.

Purpose of the Study:

• To develop and validate a spatially resolved multimedia fugacity model at an urban scale.
• To investigate the impact of replacing organic carbon (OC) with black carbon (BC) on PAH distribution simulations.
• To assess the fate and spatial distribution of specific PAHs (Phe, Pyr, BaP) in Nanjing, China.

Main Methods:

• Development of a multimedia fugacity model incorporating black carbon (BC) as a key parameter.
• Simulation of phenanthrene (Phe), pyrene (Pyr), and benzo[α]pyrene (BaP) distributions using OC-Model, dual C-Model, and BC-Model.
• Validation of model predictions against measured environmental concentrations of Phe, Pyr, and BaP.

Main Results:

• The black carbon (BC)-inclusive model (BC-Model) demonstrated improved accuracy in predicting PAH concentrations compared to the original OC-Model.
• Lighter PAHs were found to be more sensitive to the substitution of OC with BC in the model.
• Spatial mapping revealed soil as the primary sink for PAHs in terrestrial systems and sediment in aquatic systems.

Conclusions:

• Sorption with black carbon (BC) is a critical factor for accurately modeling the fate of lighter PAHs in multimedia environments.
• The developed BC-Model provides a rational basis for mapping urban PAH concentrations across different environmental phases.
• Future multimedia fate modeling for lighter PAHs should prioritize the inclusion of black carbon sorption processes.