The lung deposited surface area (LDSA) measured by diffusion charging (DC) method has been recently receiving increased attention as it is believed to accurately represent the surface reactivity of the particles, including ultrafine particles. To characterize regional and seasonal behaviors of the LDSA in the atmosphere and the factors controlling them, we measured the LDSA concentrations, using the DC method, and other physicochemical properties at three sites in Japan, including urban and rural areas. Comparisons among the three sites in the same season showed the highest LDSA concentration at the urban site Fukuoka, due to high concentrations and low particle sizes. In addition, this urban site frequently recorded high LDSA concentrations with high specific LDSAs, which represents the high contribution of ultrafine particles to the LDSA concentration. This is because the site was dominated by ultrafine black carbon particles emitted from surrounding cities, along with low contribution of long-range transported particles from the continent. In contrast, the dominance of these transported particles, which is typically observed at the three sites during this season, caused the specific LDSA to fall within a low and narrow range. However, even at rural areas, the active formation of organic particles in the summer caused high specific LDSAs, although their concentrations were low. Thus, the particles in urban areas, where ultrafine particles are probably emitted with high concentration from surrounding cities, have the potential to cause a greater adverse effect on human health even for the identical LDSA concentration. In addition, our observations showed that the LDSA of atmospheric aerosol particles measured by the DC method can be roughly represented by the theoretical LDSA of particles assuming spherical shape. Our characterizations using the specific LDSAs provide useful information for applying the LDSAs as the toxicity indicator of atmospheric aerosol particles, including ultrafine particles.

通过扩散充电 (DC) 方法测量的肺沉积表面积 (LDSA) 最近受到越来越多的关注，因为它被认为可以准确地代表颗粒的表面反应性，包括超细颗粒。为了表征大气中 LDSA 的区域和季节性行为及其控制因素，我们使用 DC 方法测量了日本三个地点（包括城市和农村地区）的 LDSA 浓度和其他物理化学特性。同一季节三个站点之间的比较显示，由于高浓度和低粒径，城市站点福冈的 LDSA 浓度最高。此外，这个城市站点经常记录到高 LDSA 浓度和高特定 LDSA，这代表了超细颗粒对 LDSA 浓度的高贡献。这是因为该场地主要是从周边城市排放的超细黑碳颗粒，以及来自大陆的远程传输颗粒的低贡献。相比之下，这些运输粒子的主导地位（通常在本季节在三个地点观察到）导致特定的 LDSA 落在低而窄的范围内。然而，即使在农村地区，夏季有机颗粒的活跃形成也会导致高特定 LDSA，尽管它们的浓度很低。因此，城市地区的颗粒物可能是从周边城市高浓度排放的超细颗粒物，即使 LDSA 浓度相同，也有可能对人类健康造成更大的不利影响。此外，我们的观察表明，DC方法测量的大气气溶胶颗粒的LDSA可以粗略地用假设球形的颗粒的理论LDSA来表示。我们使用特定 LDSA 的表征为将 LDSA 用作大气气溶胶颗粒（包括超细颗粒）的毒性指标提供了有用的信息。