A vehicle-mounted dual-smog chamber:Characterization and its preliminary application to evolutionary simulation of photochemical processes in a quasi-realistic atmosphere

Smog chambers are the effective tools for studying formation mechanisms of air pollution.Simulations by traditional smog chambers differ to a large extent from real atmospheric conditions,including light,temperature and atmospheric composition.However,the existing parameters for mechanism interpretation are derived from the traditional smog chambers.To address the gap between the traditional laboratory simulations and the photochemistry in the real atmosphere,a vehicle-mounted indoor-outdoor dual-smog chamber(JNUVMDSC)was developed,which can be quickly transferred to the desired sites to simulate quasi-realistic atmosphere simultaneously in both chambers using“local air”.Multiple key parameters of the smog chamber were characterized in the study,demonstrating that JNUVMDSC meets the requirements of general atmospheric chemistry simulation studies.Additionally,the preliminary results for the photochemical simulations of quasi-realistic atmospheres in Pearl River Delta region and Nanling Mountains are consistent with literature reports on the photochemistry in this region.JNU-VMDSC provides a convenient and reliable experimental device and means to study the mechanism of atmospheric photochemical reactions to obtain near-real results,and will make a great contribution to the control of composite air pollution.

Simulation investigations on the marble deterioration by sulphur dioxide

This paper deals with investigations on corrosion of marble SO2. We have simulated oxidation of SO2 by photochemical process in the atmosphere. The experiments indicate that formation of SO3 aerosols is related to the concentration of SO2, the UV light intensity, the time of irradiation and the humidity of the air. The corrosion feature of surfaces of the marble and the depth profiles of sulphur were obtained by SEM (Scanning electron microscope), EDXA (Energy-dispersive X-ray analyzer) and SIMS (Secondary ion mass spectrometer). The results of experiments show the corrosive extent of marble depends on its compositions and microareas of marble, which contain lower silicon content can be easily corroded by SO2.

Water transport and water use efficiency differ among Populus euphratica Oliv. saplings exposed to saline water irrigation

Populus euphratica Oliv.is a unique woody tree that can be utilized for vegetation restoration in arid and semi-arid areas.The effects of saline water irrigation(0.00, 2.93, 8.78 and 17.55 g/L NaCl solutions) on water transport and water use efficiency(WUE) of P.euphratica saplings were researched for improving the survival of P.euphratica saplings and vegetation restoration in arid and semi-arid areas of Xinjiang, China in 2011.Results showed that hydraulic conductivity and vulnerability to cavitation of P.euphratica saplings were more sensitive in root xylem than in twig xylem when irrigation water salinity increased.Irrigation with saline water concentration less than 8.78 g/L did not affect the growth of P.euphratica saplings, under which they maintained normal water transport in twig xylem through adjustment of anatomical structure of vessels and kept higher WUE and photosynthesis in leaves through adjustment of stomata.However, irrigation with saline water concentration up to 17.55 g/L severely inhibited the photochemical process and WUE of P.euphratica saplings, resulting in severe water-deficit in leaves and a sharp reduction in water transport in xylem.Thus, it is feasible to irrigate P.euphratica forest by using saline groundwater for improving the survival of P.euphratica saplings and vegetation restoration in arid and semi-arid areas of Xinjiang, China.

Effect of atmospheric aerosol on surface ozone variation over the Pearl River Delta region

Our analysis of the surface aerosol and ultraviolet （UV） measurements in Pearl River Delta （PRD） region shows that the surface UV radiation is reduced by more than 50% due to high aerosol concentrations. This has important impacts on urban ecosystem and photochemistry, especially on ozone photochemical production over the region. The quantitative effect of aerosols on surface ozone is evaluated by analyzing surface observations （including ozone, ultraviolet radiation, aerosol radiative parameters） and by using radiative and chemical models. A case study shows that the aerosol concentrations and UV radiation are significantly correlated with ozone concentrations. The correlation coefficient between the aerosol optical depth （AOD） and the PM10 mass concentration is very high, with a maximum of 0.98, and the AOD and UV radiation/ozone is anti- correlated, with a correlation coefficient of-0.90. The analysis suggests that ozone productivity is significantly decreased due to the reduction of UV radiation. The noon-time ozone maximum is considerably depressed when AOD is 0.6, and is further decreased when AOD is up to 1.2 due to the reduction of ozone photochemical productivity. Because the occurring probability of aerosol optical depth for AOD550m≥0.6 and AOD340mm ≥1.0 is 47, and 55% respectively during the dry season （October, November, December, January）, this heavy aerosol condition explains the low ozone maximum that often occurs in the dry season over the Guangzhou region. The analysis also suggests that the value of single scattering albedo （SSA） is very sensitive to the aerosol radiative effect when the radiative and chemical models are applied, implying that the value of SSA needs to be carefully studied when the models are used in calculating ozone production.