Evaluation Of Particulate Matter Deposition In The Human Respiratory Tract In Nanjing Using Size And Chemically Resolved Ambient Measurements

Size-segregated ambient aerosols were collected by a five-stage impactor at a suburban Nanjing site during the 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 PM_2.5 concentrations were 91.5±28.9μg/m3and59.1±20.5μg/m3,respectively,the concentration of particulate matter collected is the highest in winter,and the lowest in summer.Organic matter and water-soluble ions were major components in fine particles.The fine particles had a significant contribution to the particulate pollution in Nanjing.The mass concentration of particles increases significantly from the clean days to the pollution days,especially for particles in 1–2.5μm.The increase in the concentration of water-soluble ions on the pollution day is mainly caused by the accumulation of secondary ions(NH₄⁺、NO₃^-and SO₄^2-)in the fine particles,and the contribution of primary ions(Ca²⁺、Na⁺、Mg²⁺,etc.)is less.The mass concentration of Al in heavy metal elements in Nanjing atmospheric particulates is the highest,followed by Zn,Al is relatively large in coarse particles,and Zn is mainly present in fine particles.From the cleaning day to the pollution day,the mass concentration of Al is reduced.During the study,the total particulate matter deposit per minute in the NOPL,TB,and P was 0.948±0.335μg,0.090±0.030μg and 0.350±0.127μg,respectively,assuming normal respiration of tidal volumes of 1450 cm3 per breath and 15 breaths per minute.The coarse particles are mainly deposited in NOPL,and the fine particles are mainly deposited in P.In winter,the mass of particles deposited in each region is the largest,and the summer is the smallest.From the cleaning day to the pollution day,the mass of particulate matter deposited in each region of the human increased significantly per minute,but the deposition mass of Al was slightly reduced.The proportion of each component in the atmospheric particulates differs from the proportion of components in the particulates deposited in each region of the respiratory tract per minute.In different seasons or different pollution days,the proportion of particulate matter is different in the environment and deposition.This study will help to learn the difference in chemical properties between environmental particles and particles deposited in the human respiratory tract.