Analysis of atmospheric behavior of PCDDs/PCDFs by a one-compartment box model

The overall atmospheric behavior of PCDDs/PCDFs in the Kanto region, Japan, was simulated by a one-compartment box model. For each homologue the relative significance and temperature dependences of dry deposition, wet deposition, degradation, and advection in both gas and particulate phases were examined and compared. The results of the model calculation suggested that the rates for dry deposition are comparable to those for wet deposition, and the rates for advection are comparable to those for bulk (dry+wet) depositions in the Kanto region. On the other hand, the rates of degradation for PCDDs/PCDFs in the atmosphere in the Kanto region would be negligible. The emission rates and the bulk deposition fluxes in the entire Kanto region estimated by the model calculation based on observed air concentrations were 0.084-0.90 kg-TEQ/month and 0.045-0.43 kg-TEQ/month, respectively. These estimated emission rates and bulk deposition fluxes were slightly higher than the estimated emission rate based on observed emission concentrations and the estimated bulk deposition fluxes based on observed deposition fluxes collected on water deposition surface, respectively. This study showed the model calculation can be available for understanding of the overall atmospheric behavior, verification of the source inventory, and estimation of deposition flux on the actual environment including various deposition surfaces.