Evaluation of particulate matter deposition in the human respiratory tract during winter in Nanjing using size and chemically resolved ambient measurements
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© 2019, Springer Media B.V., onderdeel van Springer Nature. Size-segregated ambient aerosols were collected by a five-stage impactor at a suburban Nanjing site during the winter of 2016–2017 to estimate the chemical composition and size distribution of particles deposited in different parts of the human respiratory tract. Chemical compositions of carbonaceous aerosols, water-soluble ions, and trace heavy metals were measured. Particulate matter (PM) mass deposited in nasopharyngeal (NOPL), tracheobronchial (TB), and pulmonary (P) was obtained by integrating the size-dependent deposition fractions. During the sampling period, the average PM10 and PM2.5 concentrations were 108.8 ± 30.8 and 77.2 ± 24.2 μg/m3, respectively. Organic matter and water-soluble ions were major components in fine particles. The fine particles had a significant contribution to the particulate pollution in winter Nanjing. The mass concentration of particles increases significantly from the clean days to the pollution days, especially for particles in 1–2.5 μm. The proportion of NO3− and undetected components in particulate matter increases on pollution days, while the proportion of elemental carbon (EC), SO42−, and NH4+ decreases. During the study period, the total particulate matter deposit per minute in the NOPL, TB, and P was 1.06 ± 0.35, 0.10 ± 0.03, and 0.42 ± 0.14 μg, respectively, assuming normal respiration of tidal volumes of 1450 cm3 per breath and 15 breaths per minute. Particles in 2.5–10 μm had the highest deposition mass in NOPL of 0.57 ± 0.16 μg, while particles in < 0.5 μm had the highest deposition mass in TB (0.03 ± 0.01 μg), and particles in 1–2.5 μm had the highest deposition mass in P (0.14 ± 0.06 μg). The total particulate matter deposited in the NOPL, TB, and P increased from 0.79 ± 0.25, 0.08 ± 0.02, and 0.30 ± 0.09 μg on the clean days to 1.23 ± 0.29 μg, 0.12 ± 0.03 μg, and 0.49 ± 0.11 μg on the pollution days. More secondary inorganic aerosol (SNA) and metals (especially Zn, Cr, and Cu) were in the PM deposited in TB and P than in the ambient PM, while more undetected components in the PM deposited in NOPL. The chemical composition fractions deposited in a specific region were different from those measured in the ambient atmosphere, indicating that health effect studies of PM should consider the deposition rates of PM in the human respiratory tract, in addition to the ambient size and chemical characteristics of ambient PM.
author list (cited authors)
Liu, X., Nie, D., Zhang, K., Wang, Z., Li, X., Shi, Z., ... Hu, J.