PARENT SESSION

7A (2) - Simulation and Modelling
Hall 8
8:30 AM - 10:15 AM, Wednesday, 30 April 2003
Chair: Jischa, M.¹, ¹
Co-chair: Tulbure, I.², ²

(WE8/1) Relative concentration as a measure to evaluate a multimedia model (POPsME) for PAHs.

Lee, Yoon Ah¹, Lee, Dong Soo¹, ¹ GSES, Seoul National University, Seoul, Korea

ABSTRACT- A dynamic multimedia model with spatial grids, POPsME (Persistent Organic Pollutants in Multimedia Environments), was evaluated by comparing predicted relative concentrations (e.g. Cair/Csoil if soil is chosen as a reference medium) with those measured. Lack of adequate emission information has often hindered the performance evaluation of multimedia models for POPs. Use of the relative concentration, rather than just concentration, was proposed as the model outcome is nearly insensitive to rate or type of emission. As the relative concentration contains a notion of media distribution, it could serve a good measure to evaluate the performance of multimedia models. Evaluation was conducted for 12 polycyclic aromatic hydrocarbons (PAHs; phenanthrene, anthracene, fluoranthene, pyrene, chrycene, benzo(a)anthracene, benzo(b)fluoranthene, benzo(k)fluoranthene, benzo(a)pyrene, dibenzo(a,h)anthracene, benzo(g,h,i)perylene, and indeno(1,2,3-c,d)pyrene) in Seoul and neighboring area (150km x 150km). Multimedia concentrations were measured at 7 sites and used to calculate relative concentrations. Values of Cair/Csoil, Cdissolved/Csoil, Csuspended solids/Csoil, and Csediment/Csoil seasonally varied by 10³, 10², 10² and 10¹ times, respectively. Model outcomes should carefully be compared to field data of such wide variations. Spatial variations were within a factor of 10 for all the PAHs. For Cair/Csoil, Csuspended solids/Csoil and Csediment/Csoil , prediction by POPsME changed gradually with molecular weight from underestimation to overestimation. The model consistently overpredicted Cdissolved/Csoil for all the PAHs. The disparities for Cair/Csoil and Csediment/Csoil were within or near of a factor of 10. Those for Cdissolved/Csoil and Csuspended solids/Csoil increased by a factor of 10³. Large uncertainties involved in the processes related to suspended solids (e.g. dissolved-suspended solids partitioning, suspended solids mass balance and settling dynamics) warrant further research to improve the capability of the model prediction.

Key words: multimedia model, relative concentration, evaluation, PAHs