Sources, Size-Resolved Deposition in the Human Respiratory Tract and Health Risks of Submicron Black Carbon in Urban Atmosphere in Pearl River Delta, China

Abstract

The black carbon (BC) has a significantly negative impact on air quality, climate and human health. Here we investigated the sources and health effects of BC in urban area of the Pearl River Delta (PRD) based on online data measured by Aerodyne soot particle high resolution time of flight aerosol mass spectrometer (SP-AMS). In urban PRD, BC particles mainly came from vehicle emissions especially heavy duty vehicle exhausts (contributing 42.9% of total BC mass concentration), long range transport (27.6%), and aging biomass combustion emissions (22.3%). Indicated by source analysis using simultaneous aethalometer data, BC associated with local secondary oxidation and transport may also be originated from fossil fuel combustion, especially traffic sources in urban and surrounding areas. Size-resolved BC mass concentrations provided by SP-AMS, for the first time to our best knowledge, were used to calculate BC deposition in the human respiratory tract (HRT) of different populations (children, adults, and the elderly) by the Multiple-Path Particle Dosimetry (MPPD) model. We found that submicron BC deposited more in the pulmonary (P) region (49.0-53.2% of the total BC deposition dose), while less in tracheobronchial (TB, 35.6-37.4%) and the head (HA, 10.7-13.9%) regions. Adults suffered the highest BC deposition (1.19 µg day-1) than the elderly (1.09 µg day-1) and children (0.25 µg day-1). BC deposition rate was greater at night (especially 18:00-24:00) than that at daytime. The maximum deposition in the HRT was found for BC particles around 80 nm, mainly in deeper respiratory regions (TB and P), which may cause more serious health effects. Adults and the elderly group confronted with notable carcinogenic risk of BC in the urban PRD, up to 29 times higher than the threshold. Our study emphasizes the need to control BC pollution in the urban area, especially the nighttime vehicle emissions.

Note:
Funding Declaration: This work was supported by the National Natural Science Foundation of China (No. 41807302, 41877302, 41875156), Guangdong Natural Science Foundation (No. 2018A030313384, No. 2019A1515011153), Guangdong Pearl River Talents Program (2019QN01L948), Special Fund Project for Science and Technology Innovation Strategy of Guangdong Province (No. 2019B121205004), and Guangdong Innovative and Entrepreneurial Research Team Program (No. 2016ZT06N263).

Conflicts of Interest: None

Keywords: Black carbon, source apportionment, Inhaled particle deposition, Size distribution, health risk