For the 2008 Beijing Olympic Games full‐scale control (FSC) of atmospheric pollution was implemented to improve the air quality from 20 July to 20 September 2008, resulting in a significant decrease in the emission of pollutants in urban Beijing, especially vehicular emissions. The combination of reduced emissions and weather condition changes provided us with a unique opportunity to investigate urban atmospheric chemistry. Hydrogen peroxide (H 2 O 2 ) and organic peroxides play significant roles in atmospheric processes, such as the cycling of HO x radicals and the formation of secondary sulfate aerosols and secondary organic aerosols. We measured atmospheric H 2 O 2 and organic peroxides in urban Beijing, at the Peking University campus, from 12 July to 30 September, before and during the FSC. The major peroxides observed were H 2 O 2 , methyl hydroperoxide (MHP), and peroxyacetic acid (PAA), having maximal mixing ratios of 2.34, 0.95, and 0.17 ppbv (parts per billion by volume), respectively. Other organic peroxides were detected occasionally, such as bis‐hydroxymethyl hydroperoxide, hydroxymethyl hydroperoxide, ethyl hydroperoxide, and 1‐hydroxyethyl hydroperoxide. On sunny days the concentrations of H 2 O 2 , MHP, and PAA exhibited pronounced diurnal variations, with a peak in the afternoon (1500–1900) and, occasionally, a second peak in the evening (2000–0200). The night peaks can be attributed to local night production from the ozonolysis of alkenes, coupled with the reaction between NO 3 radicals and organic compounds. Sunny‐day weather dominated during 16–26 July, and we found that the concentrations of H 2 O 2 , MHP, and PAA increased strikingly on 22–26 July, compared with the concentrations during 16–19 July. This effect was mainly attributed to the NO x (NO and NO 2 ) decline because of the FSC, due to (i) the suppressing effect of NO and NO 2 on the production of peroxides and (ii) the indirect effect of reduced NO x on the concentration of peroxides via O 3 production in the volatile organic compound‐sensitive area. Although the time period from 29 July to 15 August fell within the FSC, the concentrations of H 2 O 2 , MHP, and PAA decreased significantly. This can be explained by a combination of chemical and physical factors during this period, when rainy‐ and cloudy‐day weather dominated. Weaker irradiation and lower temperatures resulted in a lower photochemical production of peroxides; the higher humidity resulted in their greater loss through their aqueous‐phase oxidation of S(IV) and through heterogeneous removal, and lower temperatures and higher nighttime humidity resulted in a quicker surface deposition of peroxides. Furthermore, our observations seem to imply that the heterogeneous removal of H 2 O 2 is faster than that of MHP, as indicated by the strong negative correlation between the H 2 O 2 ‐to‐MHP ratio and the aerosol surface area.
The heterogeneous reactions of methacrolein (MAC) and methyl vinyl ketone (MVK) on α-Al2O3 surfaces have been studied in a flow reactor using transmission-Fourier Transform Infrared (T-FTIR) spectroscopy to monitor the reaction progress. Unlike SiO2 particles where MAC and MVK are weakly physisorbed, the results in this work demonstrate that on α-Al2O3 particles MAC and MVK are irreversibly adsorbed and can rapidly react on the surface to form various products such as aldehydes, organic acids, hydrogen peroxide, and even higher molecular weight compounds. The initial uptake rates and initial uptake coefficients for MAC and MVK on α-Al2O3 under dry conditions were determined to explore the reactivity of the particles. Furthermore, the effect of water vapor on the heterogeneous reactions was also investigated as a function of relative humidity. Both the heterogeneous uptake and transformation of MAC and MVK on α-Al2O3 were largely suppressed under humid conditions due to the depletion of surface active sites by water molecules. On the basis of experimental results, atmospheric implications of heterogeneous reactions of MAC and MVK were discussed. Our work suggests that heterogeneous reactions on α-Al2O3 can be important sinks for MAC and MVK as well as possible contributors to atmospheric organic aerosol.
Background-In the past two decades, China is experiencing the most rapid and dramatic changes in indoor environment exposure. Coincidently, the prevalence rate of asthma among children increased by 10%. Aims-To understand associations between the home environment in China and asthma and allergy among Chinese children. Methods-China, Children, Homes, Health (CCHH), Phase I study, is a cross-sectional questionnaire survey including 48219 children aged 1-8 years old in 10 major cities (Beijing, Changsha, Chongqing, Harbin, Nanjing, Shanghai, Taiyuan, Urumqi, Wuhan, Xi'an) of China during 2010-2011. The questionnaire used included the core questions in the International Study of Asthma and Allergies in Childhood (ISAAC) and validated questions regarding housing, life habits and outdoor environment, which has been adapted to Chinese customs and building characteristics, from the questions used in Sweden, Denmark, Bulgaria, USA, Taiwan, Singapore, and South Korea. Results-The average prevalence of asthma across China was 6.8% (range 1.7%-9.8%), hay fever 8.6% (2.2%-11.6%), current wheeze 19.2% (13.9%-23.7%), current rhinitis 41.3% (24.0%-45.5%), current eczema 12.1% (4.8%-15.8%). Rates of visible mold on indoor surfaces ranged from 4% (Xi'an; Beijing) to 12% (Harbin), condensation on windowpane in winter from 14.3% (Chongqing) to 32.2% (Nanjing), moldy odor from 0.4% (Nanjing) to 1.9% (Harbin). On average, 59% of families had environmental tobacco smoke exposure. The asthma prevalence was positively associated with the economic status indexed by Gross Domestic Production per capita of a city, but not with ambient air pollution. Conclusions- The data and information collected in this study will be helpful in finding the associations between children's health and indoor environment exposures.
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