Temporal Trend of Polycyclic Aromatic Hydrocarbons in Atmosphere: A Case Study within 24 h after Snowfall.

Based on air samples within 24 h after snowfall, gaseous and particulate concentrations of 16 priority PAHs were obtained, which provided a good opportunity to study the temporal trend of atmospheric PAHs. An obvious temporal trend with atmospheric concentration was observed, which was mainly influenced by emission sources. It was found that the maximum concentration (Σ16PAHs) was 272.8 ng/m3, appeared in the rush hour of traffic. To the contrary, the minimum concentration was 82.39 ng/m3 at the period with the least anthropogenic activities. The values of particle-phase fraction[Formula: see text]) and G/P partitioning quotient (log K P) were increased along with molecular weight of PAHs. However, for individual PAHs, the differences with [Formula: see text] and log K P were not obvious within 24 h. Furthermore, similar statistically significant positive correlations were found between log K P and log K OA among different periods. According to the short sampling program, chemical properties should be the major influencing factor for the temporal trend of G/P partitioning. The results of the case study provided new insights into the research field of G/P partitioning of PAHs.

[Temporal Trend of Polycyclic Aromatic Hydrocarbons in Atmosphere Within 24 Hours After Snowfall].

The atmosphere is a significant medium for the transportation and diffusion of volatile and semi-volatile pollutants. Furthermore, the atmosphere is the primary exposure route for pollutants to enter the human body. Therefore, the study of the environmental fate of pollutants in the atmosphere is essential. In this study, 16 polycyclic aromatic hydrocarbons (PAHs) were analyzed in snow samples and air samples within 24 hours after a snowfall, and the temporal trend of PAHs in the atmosphere was comprehensively studied. The results indicated that the detection rate of the 16 PAHs in snow was 100%, and the concentration of phenanthrene (538.3 ng·L-1) was the highest, followed by naphthalene (509.1 ng·L-1) and fluoranthene (429.9 ng·L-1), indicating that snowfall can remove PAHs from the atmosphere. After the snowfall, a falling-rising-falling temporal trend of the concentrations of PAHs in the atmosphere was observed. Higher concentrations appeared during rush hour, with the largest automobile exhaust emissions, while lower concentrations appeared during periods with the lowest human activity. The results indicated that the atmospheric concentrations of PAHs were predominantly influenced by human activities. Within 24 hours after snowfall, the ratio of PAHs between the gas phase and particle phase, which depends primarily on the physical and chemical properties of PAHs, had not changed substantially. The diagnostic ratios indicated that within 24 hours after snowfall, the PAHs in the atmosphere originated mostly from the emissions of solid fuel and liquid fuel combustion.