To assess the impact of the atmospheric deposition of air pollutants on ecosystems, it is important to accurately estimate the deposition amounts. Compared to wet deposition, it is difficult to estimate the amounts of dry deposition, and there is still considerable uncertainty in the estimation accuracy. In this review, I provided an overview of a study on dry deposition and atmosphere-surface exchange mechanisms by flux observations, and assessments of atmospheric deposition by the inferential method, along with relevant studies from around the world. Flux observations were done by the gradient method or relaxed eddy accumulation method for ozone, sulfur dioxide, PM_2.5 sulfate, PM_2.5 nitrate, nitric acid, and ammonia sequentially carried out from 2002 to 2021. The observations were carried out above forest sites located in temperate, cool temperate, and tropical regions. Regarding the nitrogen components, observations were also carried out in agricultural fields. The large uncertainties of the deposition velocities of submicron particles above forests were specifically discussed considering some processes that are not considered in dry deposition models. The uncertainties of the observed deposition velocities were also discussed. Furthermore, I showed some results of the assessment of sulfur and nitrogen deposition in Japanese remote areas, and finally considered future atmospheric deposition study.

Methylaminium (MA), ethylaminium (EA), dimethylaminium (DMA), diethylaminium (DEA), trimethylaminium (TMA), and triethylaminium (TEA) in the PM_2.5 were observed at an urban site in Kofu, Yamanashi, for three years. The MA showed the highest average concentration among these six aminiums. These six aminiums accounted for 5.6% of the water-soluble organic nitrogen (WSON) concentration in the PM_2.5. The MA, DMA, and DEA showed seasonal trends with higher concentrations in the summer. During the warm season, the volatilization of the gaseous amines from agricultural lands and/or forest soils and subsequent conversion to the particulate aminiums were considered to be important sources, especially for the MA and DMA in the PM_2.5. In addition, the transport of anthropogenic aerosols from the Tokyo metropolitan area may also be important for the DEA. Biomass burning, on the other hand, was an important source for these three aminiums during the cold season, especially for the MA.

To confirm the contribution of ingredients derived from living things, the protein included in the PM_2.5 collected in the urban and mountain areas of Kanagawa Prefecture during different seasons was determined by the micro BCA protein assay method. As a result, a certain amount of protein was detected in samples from both the urban and mountain areas. In addition, the protein concentrations of the PM_2.5 showed daily fluctuations, and similar daily fluctuations were observed between the urban and mountain areas in the spring and summer, but different in the autumn and winter. On the other hand, the protein concentrations in the PM_2.5 in the urban area tended to be higher than those in the mountain area in the autumn and winter. When the contribution rates of the protein to the mass concentrations of the PM_2.5 were calculated, they were around 20% on average. Furthermore, the correlation between the protein concentrations and the concentrations of the organic carbon (OC) component and the correlation between the protein concentrations and the concentrations of the water soluble organic carbon (WSOC) component in PM_2.5 tended to always be high regardless of the sampling locations and seasons. When OC and WSOC analyses were conducted using bovine serum albumin, as the common protein, quantitative responses were observed. Therefore, it was concluded that a considerable amount of the OC and WSOC components detected in PM_2.5 originated from the protein. The importance of conducting research on the premise that the PM_2.5 contains biologically-originated components such as protein was suggested, for a future study.