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Dry deposition of particulate matter (PM) indicates the capacity of atmosphere self-depuration. To investigate seasonal dry deposition of PM in an urban forest, the concentration and ionic composition of PM2.5(particulate matter with aerodynamic equivalent diameters less than 2.5 μm) and the deposition of PM and ions in PM at different layer were measured at three canopy heights in the Beijing Olympic Forest Park. Results showed that diurnal trends in PM concentration varied with height and that concentrations tended to be highest in the understory. During winter, when the absorption ability of plants, which withered, was reduced, and anthropogenic emissions, primarily from coal combustion, ion concentrations tended to be highest in the forest canopy. The anions SO42−, NO3−, and Cl−were the dominant ionic species, accounting for 82% of the total mass of water-soluble ions in PM2.5. Results showed a lower mass ratio of NO3−/SO42−(mean = 0.29, SD = 0.24), relative to previous studies, implying that vehicle emissions may have reduced in Beijing. The chemical forms of sulfate and nitrate were likely NH4NO3and (NH4)2SO4; however, Ca(NO3)2was the only chemical form detected based on the correlation coefficient between Ca2+and NO3−. Concentrations of PM were negatively related to temperature and wind speed, and positively related to relative humidity. Within the forest canopy, the deposition velocity was low (high) during summer (winter). Furthermore, ion deposition fluxes were higher in the forest understory (1.5–6 m) during summer and in the canopy (6–10 m) during winter. This was attributed to seasonal trends in PM concentration. The objective of this study was to compare the diurnal variations of the particulate matter (PM) concentrations in an urban forest, and quantify dry deposition flux of PM and ions at three heights during the four seasons, also determine the chemical composition and possible origin of water-soluble ions in PM2.5, and analyze the influence of meteorological factors on the PM concentration.Few studies have investigated PM deposition at different heights within the forest canopy and understory, and previous researches have seldom studied the deposition of ions in PM2.5 in different layer. To address this limitation, this study aims to quantify the PM and ions in PM2.5 deposition and explore the dry deposition fluxes in different layers of forest and seasons to achieve the following objectives: (1) to quantify and compare seasonal dry deposition of PM and ions at three heights in an urban forest, and (2) to determine the chemical composition and possible origins of water-soluble ions in PM2.5. Our analysis will provide information to facilitate effective forestation initiatives to mitigate particle pollution, improving air quality and regional microclimates.

Forkhead box M1 (FoxM1), a transcription factor of the Forkhead family, is demonstrated to be critical for proliferation, apoptosis, migration and invasion of lung cancer. In this study, we extensively investigated the anticancer effect of siomycin A, which was identified as an inhibitor of FoxM1 transcriptional activity, on human lung adenocarcinoma A549 cells. Our study indicated that treatment with siomycin A resulted in the suppression of FoxM1 expression, which consequently contributed to its effect of cell growth inhibition and cell apoptosis induction in A549 cells. Then the molecular mechanism of siomycin A's apoptotic action on A549 cells was further investigated. The results revealed that siomycin A induced apoptosis by influencing the downstream events of FoxM1, including inhibiting the expression of Bcl-2 and Mcl-1, as well as leading to caspase-3 cleavage. Taken together, our findings may be useful for understanding the mechanism of action of siomycin A on lung cancer cells and provide new insights into the possible application of such a compound in lung cancer therapy in the future.