Air pollution causes serious problems in spring in northern China; therefore, studying the ability of different plants to accumulate particulate matter (PM) at the beginning of the growing season may benefit urban planners in their attempts to control air pollution. This study evaluated deposits of PM on the leaves and in the wax layer of 35 species (11 shrubs, 24 trees) in Beijing, China. Differences in the accumulation of PM were observed between species. Cephalotaxus sinensis, Euonymus japonicus, Broussonetia papyriferar, Koelreuteria paniculata and Quercus variabilis were all efficient in capturing small particles. The plants exhibiting high amounts of total PM accumulation (on leaf surfaces and/or in the wax layer), also showed comparatively high levels of PM accumulation across all particle sizes. A comparison of shrubs and trees did not reveal obvious differences in their ability to accumulate particles based on growth form; a combination of plantings with different growth forms can efficiently reduce airborne PM concentrations near the ground. To test the relationships between leaf traits and PM accumulation, leaf samples of selected species were observed using a scanning electron microscope. Growth forms with greater amounts of pubescence and increased roughness supported PM accumulation; the adaxial leaf surfaces collected more particles than the abaxial surfaces. The results of this study may inform the selection of species for urban green areas where the goal is to capture air pollutants and mitigate the adverse effects of air pollution on human health.

The adsorption of isopropanol on Gobi dust was investigated in the temperature (T) and relative humidity (RH) ranges of 273-348 K and <0.01-70%, respectively, using zero air as bath gas. The kinetic measurements were performed using a novel experimental setup combining Fourier-Transform InfraRed spectroscopy (FTIR) and selected-ion flow-tube mass spectrometry (SIFT-MS) for gas-phase monitoring. The initial uptake coefficient, γ, of isopropanol was measured as a function of several parameters (concentration, temperature, relative humidity, dust mass). γ was found independent of temperature while it was inversely dependent on relative humidity according to the empirical expression: γ = 5.37 × 10/(0.77+RH). Furthermore, the adsorption isotherms of isopropanol were determined and the results were simulated with the Langmuir adsorption model to obtain the partitioning constant, K, as a function of temperature and relative humidity according to the expressions: K = (1.1 ± 0.3) × 10 exp [(1764 ± 132)/T] and K = 15.75/(3.21+RH). Beside the kinetics, a detailed product study was conducted under UV irradiation conditions (350-420 nm) in a photochemical reactor. Acetone, formaldehyde, acetic acid, acetaldehyde, carbon dioxide, and water were identified as gas-phase products. Besides, the surface products were extracted and analyzed employing HPLC; Hydroxyacetone, formaldehyde, acetaldehyde, acetone, and methylglyoxal were identified as surface products while the formation of several other compounds were observed but were not identified. Moreover, the photoactivation of the surface was verified employing diffuse reflectance infrared fourier transform spectroscopy (DRIFTs).

[1] Ground-based measurement of total reactive nitrogen (NO y ), NO y(g) (gas phase NO x + HNO 3 ), and particulate NO 3 À was carried out at the Cape Hedo Atmosphere and Aerosol Monitoring Station (CHAAMS) in Okinawa, Japan, from spring to winter in 2006. The concentrations of NO y , NO y(g) , and particulate NO 3 À were simultaneously high in spring but low in summer. This difference was mainly caused by air mass history, which was strongly associated with the typical weather pattern observed in the east Asian region for each season. The chemical transformation process of particulate NO 3 À during transport was examined using the data measured at Qingdao, China, in spring 2006. As the transport time of air masses increased, particulate NO 3 À continuously shifted from fine mode to coarse mode. It was found that the chemical transformation of particulate NO 3 À was mainly associated with the transport time of air masses, the geographical position of CHAAMS, and the transition from NH 4 NO 3 to gas phase HNO 3 . In air masses from Qingdao, China, the ratio of NO y concentration observed at CHAAMS to that at Qingdao was about 0.1, which was lower than that of SO y (SO 2 + nss-SO 4 2À ). Sulfate was found in fine particles at CHAAMS in contrast to particulate NO 3 À . As the lifetimes of NO y and SO y depend on the particle size, the difference in chemical transformation process during transport largely influences the abundance of transported NO y . The variations of NO y(g) and particulate NO 3 À were analyzed when dust plumes reached CHAAMS. The presence of dust causes the formation of particulate NO 3 À in coarse mode from NO y(g) and an increase of its fraction in NO y . The effect of volcanic activity on particulate NO 3 À concentration was also analyzed. It is suggested that particulate NO 3 À escaped to gas phase HNO 3 through the uptake of abundant volcanic H 2 SO 4 by aerosols.

a b s t r a c tThe exchange fluxes of nitrous oxide (N 2 O), nitrogen oxides (NO x ) and ammonia (NH 3 ) from a maize field with three different treatments were simultaneously measured using static and dynamic chambers in the North China Plain (NCP) from June 28 to October 11, 2009. The three treatments included control plot (CK, without crop, fertilization and irrigation), fertilizer N plot (NP) and wheat straw returning plus fertilizer N plot (SN). N-fertilizer application greatly stimulated the emissions of N 2 O, NO x and NH 3 , with durations of about 10 days for N 2 O and NO, and about 7 days for NH 3 . Fertilizer loss rates were 1.08% (NP plot) and 1.20% (SN plot) as N 2 OeN, were 1.93% (NP plot) and 0.76% (SN plot) as NOeN, and were 5.24% (NP plot) and 3.03% (SN plot) as NH 3 eN. In comparison with the NP plot, the significant low fertilizer loss rates as NOeN and NH 3 eN from the SN plot indicated that the wheat straw returning to the field could reduce NO x and NH 3 emissions. The molar ratio of NO/N 2 O was greater than unity for most data during the pulse emission periods induced by fertilization, and thus, nitrification was the dominant process for N 2 O and NO emissions during these periods. Considering the significant amount (>80%) of N 2 O and NO x emissions occurred during the pulse emission periods, the emissions of NO x and N 2 O from the investigated field were mainly ascribed to nitrification process.

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