2022 Volume 57 Issue 2 Pages 66-76
From May 2016 to March 2021 in Sowa, Niigata pref., a parallel measurement was conducted between the traditional Open-faced Filter-Pack (OFP) and PM2.5 Impactor-fitted Filter-Pack (IFP) methods to compare the influence of both chemical reactions and overestimation by particles and gas collected on filters, which are the so-called ‘artifacts’. Also, the degree of coincidence and data continuousness between the two methods was tested for contributing to potential long-term trend analyses. As for the particulate ions, the nss-SO42− quantity (qty.) showed a high degree of coincidence between the two methods, while the coincidence of the Cl− qty. highly depended on whether or not Cl− of the Impactor adherent matter was included. Plus, the coincidence degree of the NO3− and NH4+ qty. varied from season to season, and this seasonal fluctuation of the coincidence degree was almost opposite to that of each gas counterpart (HNO3, NH3), which supported the possibility that artifacts could occur during the OFP/IFP methods at different levels. Furthermore, particulate ingredients from sea salt and soil were collected on the Impactor surface, and the conc. of these ingredients showed correlations to the wind speeds, suggesting that artifacts by unintentionally collecting rain drops and ambient particles could occur during the OFP method under the strong wind conditions. The sum qty. of each ion and gas counterpart (HNO3+NO3−, NH3+NH4+, HCl+Cl−, SO2+nss-SO42−) showed a high degree of coincidence between both methods, and the coincidence degree of HCl+Cl− was remarkably higher when adding the Impactor adherent matter. Thus, with overestimation of the OFP method corrected, and using the sum qty. as the evaluation values, data continuousness between the two methods is likely to be retained.
