Particulate matter (PM) and ozone were measured on Fukue Island, Nagasaki, during the spring season. The concentrations of PM_2.5 and those of sulfate and nitrate in the PM during 2020 decreased compared to those measured in the previous years. The ozone concentration also decreased during the higher PM_2.5 concentration period (over 35 μg/m³). These results suggest that the concentrations of transboundary air pollutants decreased due to the reduction of emissions of air pollutants in China which may be caused by COVID-19 that occurred in the early period of 2020.

In this study, metallic elements (mainly trace elements of crust), mineral composition and loss on ignition for certified reference materials (CRMs) of aerosol, sediment, ash and crude oil were analyzed. The enrichment factor (EF) versus the average upper continental crust of As, Se, and Sb in urban aerosol CRMs and the EF of Zn, Mo, Ag, Cd, Sb, and Pb in tunnel dust CRMs are higher than 10². In the CRMs of simulated aerosol, soil and loess, enriched elements are not observed. The EF of Sb, W, and Pb is higher than 10² in the road dust CRM. However, in the other road dust CRMs, enriched elements are not observed. Coal fly ash CRMs include mullite which is a rare mineral in nature. In the coal fly ash CRM, enriched elements are not observed. The EF of Zn, Se, Ag, Cd, Sb, and Pb in fly ash CRMs and the EF of V, Ni, As, Se, Ag, Cd, and Mo are higher than 10². The observed values of noncertified elements of the analyzed CRMs in this study need to be verified by other institutes for improvement of the observed value’s reliability. After this verification, the observed values would help the quality control of metallic element analysis of environmental aerosol samples.

In order to prevent the spread of COVID-19, the Chinese government imposed a lockdown. During this period, anthropogenic emissions will be reduced; therefore, the trans-boundary air pollution will be changed. The analysis of surface observations by the automated aerosol chemical speciation analyzer (ACSA) showed that the dramatic reduction with 30–50% of PM_2.5, sulfate (SO₄²⁻), and nitrate (NO₃⁻) on February–March 2020 compared to 2018–2019. The results of the chemical transport model suggested that the reduction of SO₄²⁻ was mostly caused by SO₂ emission reduction whereas that of NO₃⁻ was dominated by the meteorological variability. The record high warm winter on 2020 was related to the unfavorable condition to produce NO₃⁻.