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Volatile organic compounds (VOCs) are representative indoor air pollutants that negatively affect the human body owing to their toxicity. One of the most promising methods for VOC removal is photocatalytic degradation using TiO2. In this study, the addition of carbon black (CB) and heavy metal nanoparticles (NPs) was investigated to improve the efficiency of a TiO2-based photocatalytic VOC decomposition system combined with ultrasonic atomization and ultraviolet irradiation, as described previously. The addition of CB and Ag NPs significantly improved the degradation efficiency. A comparison with other heavy metal nanoparticles and their respective roles are discussed. [ABSTRACT FROM AUTHOR]

Every year, Hanoi suffers from several episodes (periods with daily concentration of PM2.5 higher than 50 µg m−3 during at least two consecutive days). These episodes are of health concern because of the high concentration of PM2.5 and/or PM0.1 and the presence of PM-bound toxic components, such as, PAHs. In this study, the concentrations of PAHs bound to PM2.5 and PM0.1 in night-time and day-time samples during episode and non-episode periods in December 2021 were determined. The concentrations of PAHs bound to PM2.5 were found to increase significantly from day-time samples of 3.24 ± 0.83 ng m−3 to night-time samples of 10.8 ± 4.45 ng m−3 in episode periods. However, PAHs bound to PM0.1 increased slightly from day-time samples of 0.58 ± 0.12 ng m−3 to night-time samples of 0.89 ± 0.30 ng m−3 in episode periods. Diagnostic ratios of PAHs indicate that biomass/coal combustion and vehicular emission are the primary sources of PAHs. The incremental lifetime cancer risk was estimated to vary from 8.7E-09 to 2.5E-08 for children and 6.7E-08 to 2.2E-07 for adults, respectively. Accordingly, loss of life expectancy was estimated at 0.11 min and 0.82 min for children and adults, respectively. These findings imply that the carcinogenic impact induced by PAHs via inhalation is negligible during the episode period. [ABSTRACT FROM AUTHOR]

The chemical composition studies of indoor particulate matter (PM2.5 and PM0.1) are lacking in the developing world, yet the attention to indoor air pollution and occupant health risks is rising. This study therefore aims to investigate the chemical compositions of indoor and outdoor PM2.5 and PM0.1 in residential and school buildings in Vietnam during different seasons and the effects of emission sources on particle characteristics. The results show that the concentration of indoor PM2.5 in the residential house was higher than that outdoors, and the indoor-to-outdoor ratios (I/O) exceeded 1, indicating the contribution of indoor sources. The peak concentration of indoor particles was observed during the incense burning days, whereas a higher indoor organic carbon concentration may be due to cooking activities. A similar variation of indoor and outdoor PM2.5 indicates the penetration of outdoor particles. In the school building, seasonal variations in indoor PM0.1 and its chemical species were observed, suggesting outdoor sources had a significant effect. Several factors may affect I/O and the infiltration factor of PM0.1, such as indoor sources, air exchange rate, cracks in the door and window, and particle deposition rate. The reason for the I/O value slightly above 1 for PM0.1 in this study remained unclear. Further investigations are recommended to obtain knowledge regarding the penetration of particles, particularly PM0.1. The findings provide a better understanding of the chemical components of indoor particles and the effects of emission sources, which is crucial to developing management measures for indoor air quality and mitigating exposures. [ABSTRACT FROM AUTHOR]

The study aims to determine the concentration, size distribution and analyze the relationship of indoor and outdoor particles in urban area, in Vietnam. One thousand two hundred daily samples of PM0.1, PM0.1-0.5, PM0.5-1, PM1-2.5, PM2.5-10, PM>10 were taken simultaneously at four residential houses in summer and winter by nano sampler (Model 3182, Kinomax). The average concentrations of indoor PM0.1, PM0.5, PM1, PM2.5 and PM10 were in range of 5.3-8.9 μg/m3; 10.8-20.1μg/m3; 20.5-47.6 μg/m3; 33.7-105.9 μg/m3 and 44.7-135.0 μg/m3 among four houses, respectively. The concentrations of outdoor PM2.5, PM10 were considerately higher than those of indoor PM, whereas negligible differences on concentrations of PM0.1, PM0.5 and PM1 were observed. The significantly seasonal variation was observed for indoor PM1, PM2.5 and PM10, but not for PM0.1 and PM0.5. Majority of indoor fractions were origin from outdoor sources. Unimodal distributions of indoor particles determined the super-micron size (1 to 2.5 μm) with highest concentration and PM10 with lowest concentration. Fine particles with interval sizes (PM0.5-1 and PM1-2.5) contributed to the predominance to coarse particles in both indoors and outdoors, suggesting serious threat on human health.

In this study, we investigated concentrations and profiles of polycyclic aromatic hydrocarbons (PAHs) in rainwater and surface water samples collected in Saitama, an urban city located in Japan. The volume-weighted mean concentration of total PAHs in rainwater samples (dissolved + particulate) was 108.8 ng L−1 with a range of 17.6–192.9 ng L−1. Two and three benzene ring PAHs were predominantly detected, occupying 67.0% of the total concentration in rainwater samples. Individual PAH concentrations were negatively correlated with their Kow, suggesting that low-molecular-weight PAHs are preferentially scavenged owing to the higher hydrophilicity. The toxic equivalent calculated based on the relative potencies of individual PAHs showed high toxic contributions by chrysene and benz[a]anthracene in the rainwater samples. Those PAHs levels in rainwater were comparable or higher than those in adjacent river water. Correlation coefficient of PAH signatures between rainwater and surface water samples was high particularly in the dissolved phase, supporting the source/sink relationships of PAHs between wet deposition samples and receiving waters. The mean deposition flux of PAHs was 2000 ng m−2 and considered to increase with precipitation amounts. [ABSTRACT FROM AUTHOR]