To estimate the deposition effect of PM2.5 (particle matter with aerodynamic diameter <2.5 µm) in forests in northern China, we used the gradient method to measure the deposition velocity of PM2.5 during the winter and spring above a deciduous forest in Olympic Forest Park and above a coniferous forest in Jiufeng National Forest Park. Six aerosol samplers were placed on two towers at each site at heights of 9, 12 and 15 m above the ground surface. The sample filters were exchanged every four hours at 6∶00 AM, 10∶00 AM, 2∶00 PM, 6∶00 PM, 10∶00 PM, and 2∶00 AM. The daytime and nighttime deposition velocities in Jiufeng Park and Olympic Park were compared in this study. The February deposition velocities in Jiufeng Park were 1.2±1.3 and 0.7±0.7 cm s−1 during the day and night, respectively. The May deposition velocities in Olympic Park were 0.9±0.8 and 0.4±0.5 cm s−1 during the day and night, respectively. The May deposition velocities in Jiufeng Park were 1.1±1.2 and 0.6±0.5 cm s−1 during the day and night, respectively. The deposition velocities above Jiufeng National Forest Park were higher than those above Olympic Forest Park. The measured values were smaller than the simulated values obtained by the Ruijgrok et al. (1997) and Wesely et al. (1985) models. However, the reproducibility of the Ruijgrok et al. (1997) model was better than that of the Wesely et al. (1985) model. The Hicks et al. (1977) model was used to analyze additional forest parameters to calculate the PM2.5 deposition, which could better reflect the role of the forest in PM2.5 deposition.

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ABSTRACT:Methyl radical complexes H 3 C . . . HCN and H 3 C . . . HNC have been investigated at the UMP2(full)/aug-cc-pVTZ level to elucidate the nature of hydrogen bonds. To better understand the intermolecular H-bond interactions, topological analysis of electron density at bond critical points (BCP) is executed using Bader's atoms-in-molecules (AIM) theory. Natural bond orbital (NBO) analysis has also been performed to study the orbital interactions and change of hybridization. Theoretical calculations show that there is no essential difference between the blue-shift H-bond and the conventional one. In H 3 C . . . HNC complex, rehybridization is responsible for shortening of the NOH bond. The hyperconjugative interaction between the single electron of the methyl radical and NOH antibonding orbital is up to 7.0 kcal/mol, exceeding 3.0 kcal/mol, the upper limit of hyperconjugative n(Y)3*(X-H) interaction to form the blue-shifted H-bond according to Alabugin's theory.

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