Embedded information of aerosol type, hygroscopicity and scattering enhancement factor revealed by the relationship between PM2.5 and aerosol optical depth.

Satellite aerosol optical depth (AOD) provides an alternative way to depict the spatial distribution of near-surface PM2.5. In this study, a mathematical formulation of how PM2.5 is related to AOD is presented. When simplified to a linear equation, a functional dependence of the slope on the aerosol type, scattering enhancement factor f(RH), and boundary layer height is revealed, while the influence of the vertical aerosol profile is embedded in the intercept. Specifically, we focus on the effects of aerosol properties and employ a new aerosol index (Normalized Gradient Aerosol Index, NGAI) for classifying aerosol subtypes. The combination of AOD difference at shorter wavelengths over longer-wavelength AOD from AERONET data could distinguish and subclassify aerosol types previously indistinguishable by AE (i.e., urban-industrial pollution, U/I, and biomass burning, BB). AOD-PM2.5 regressions are performed on these aerosol subtypes at various relative humidity (RH) levels. The results suggest that BB aerosols are nearly hydrophobic until the RH exceeds 80 %, while the AOD-PM2.5 regressions for U/I depend on RH levels. Moreover, the scattering enhancement factor f(RH) can be calculated by taking the ratio of intercepts between dry and humidity conditions, which is proposed and tested for the first time in this study. Our results show an f(RH ≥ 80 %) of ∼2.6 for U/I-dominated aerosols, whereas the value is not over 1.5 for BB aerosols. The f(RH) can be further used to derive the optical hygroscopicity parameter (κsca), demonstrating that the NGAI can be used to exploit differences in aerosol hygroscopicity and improve the AOD-PM2.5 relationship.

The effects of hydrogen treatment in a cigarette smoke solution-induced chronic obstructive pulmonary disease-like changes in an animal model.

Background: Molecular hydrogen, with its antioxidant and anti-inflammatory properties, may be suitable for the prevention and treatment of chronic obstructive pulmonary disease (COPD). This study aims to investigate the therapeutic efficacy of hydrogen-oxygen (H2/O2) treatment in cigarette smoke solution (CSS)-induced COPD-like injury in a female BALB/c mouse model. Methods: Thirty mice were randomly assigned to three groups: Control (n=8), COPD (n=10), and COPD + H2/O2 (n=12). CSS was administered by intraperitoneal (IP) injection twice weekly for 6 weeks during the COPD induction phase. Simultaneously, the COPD + H2/O2 group started received 75 minutes of inhalation therapy (42% H2) delivered by the Oxy-Hydrogen Generator twice daily for 9 weeks. Mice body weights and survival were measured throughout the study period. Neutrophil elastase (NE) activity and lung histopathological changes were also evaluated. Results: The results showed a higher survival rate in the COPD + H2/O2 group compared to the COPD group (100% vs. 80%) during the induction phase. Slight decreases in body weight gains were observed in the COPD and COPD + H2/O2 groups during the first 15 days of the induction phase, but there was no significant difference in mean body weights among the three groups throughout the study period. NE activity was numerically lower in the COPD + H2/O2 group compared to the COPD group. The histopathological evaluation showed significant improvements in the H2/O2-treated mice with respect to mean linear intercept (MLI) and lesion (inflammation and emphysema) scores. Improvements in goblet cell hypertrophy and hyperplasia of airway epithelium were not significant. Conclusions: A 9-week H2/O2 inhalation therapy delivered by the Oxy-Hydrogen Generator to CSS-induced COPD-like injury in mice showed improvement in survival rate, alveolar structural changes, and histopathological lesion scores of the lung.