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In order to evaluate the positive and negative artifacts in the measurements of the water-soluble organic nitrogen (WSON) in the aerosols by filter sampling, comparative experiments between the filter sampling and denuder-filter sampling were conducted during both the warm and cold seasons. The results suggest that the traditional filter sampling underestimates the concentrations of the particulate WSON due to its volatilization loss, but this effect on the ratio of the WSON to the water-soluble total nitrogen (WSTN) was small probably because inorganic nitrogen species were also lost during the filter sampling. Approximately 32.5% of the WSON in the PM 2.5 was estimated to be lost during the filter sampling. The denuder–filter sampling also demonstrated the existence of the WSON in the gas phase with approximately quarter concentrations of the WSON in the PM 2.5 . On the other hand, the filter sampling would overestimate the gaseous WSON concentration due to the loss of the WSON from the aerosol collection filter. [ABSTRACT FROM AUTHOR]

The WSON in the gas phase and aerosols were simultaneously measured by the denuder–filter pack method. Approximately 33 ± 18% of the WSON in the atmosphere existed in the gas phase. A large portion (approximately 76 ± 33%) of the gaseous WSON collected in the present sampling method was occupied by basic species. The gaseous basic and acid WSON showed about one-sixth of the nitrogen concentrations of the gaseous NH3 and HNO3, respectively. These results indicate that the gaseous WSON is also an important fixed nitrogen species in the atmosphere. [ABSTRACT FROM AUTHOR]