Measurements of atmospheric aerosols with diameters greater than 10 μm and their contribution to fixed nitrogen deposition in coastal urban environment

Annual measurements of the number concentrations and chemical composition of the particles with diameters greater than 10 μm (PM>10) were conducted at a coastal urban site in Japan. The number concentrations of the PM>10 showed an annual mean of 2.14 × 103 m-3, and synchronously varied with those of the particles with diameters greater than 3 μm (PM>3). The PM>10 mainly consisted of sea-salt and soil particles. NO3− and nss-SO42− were detected in the PM>10 at high concentrations. The chemical composition of the PM>10 was similar to that of the particles with diameters of 2–10 μm (PM2–10). The PM>10 would have similar sources and removal processes with the PM2–10. y deposition flux of the particle mass was mostly (approximately 67%) contributed by the PM>10. The PM>10 has a significant contribution to the dry deposition flux of the particulate substances. Approximately 42% of the dry deposition flux of particulate nitrate–nitrogen (NO3−–N) was contributed by the PM>10, although only 9.5% of the NO3−–N concentration was detected in the PM>10. During the summer period, especially, the contribution of the PM>10 to the dry deposition of the NO3−–N increased to approximately 51%. The present study demonstrates that the PM>10 are significant carriers for NO3−–N from the atmosphere to the earth’s surface.