Trifluoromethane (CHF3, HFC-23) is one of the hydrofluorocarbons (HFCs) regulated under the Kyoto Protocol with a global warming potential (GWP) of 14 800 (100-year). China's past, present, and future HFC-23 emissions are of considerable interest to researchers and policymakers involved in climate change. In this study, we compiled a comprehensive historical inventory (1980-2012) and a projection (2013-2050) of HFC-23 production, abatements, and emissions in China. Results show that HFC-23 production in China increased from 0.08 +/- 0.05 Gg/yr in 1980 to 15.4 +/- 2.1 Gg/yr (228 +/- 31 Tg/yr CO2-eq) in 2012, while actual HFC-23 emissions reached a peak of 10.5 +/- 1.8 Gg/yr (155 +/- 27 Tg/y CO2-eq) in 2006, and decreased to a minimum of 7.3 +/- 1.3 Gg/yr (108 +/- 19 Tg/yr CO2-eq) in 2008 and 2009. Under the examined business-as-usual (BAU) scenario, the cumulative emissions of HFC-23 in China over the period 2013-2050 are projected to be 609 Gg (9015 Tg CO2-eq which approximates China's 2012 CO2 emissions). Currently, China's annual HFC-23 emissions are much higher than those from the developed countries, while it is estimated that by year 2027, China's historic contribution to the global atmospheric burden of HFC-23 will have surpassed that of the developed nations under the BAU scenario.
To evaluate the variations in temporal and spatial distribution of biogenic volatile organic compound (BVOC) emissions in China, historical BVOC emission inventories at a spatial resolution of 36 km × 36 km for the period of 1981–2003 were developed firstly. Based on the time-varying statistical data and Vegetation Atlas of China (1:1,000,000), emissions of isoprene, 37 monoterpenes, 32 sesquiterpenes, and other volatile organic compounds (OVOCs) were estimated using MEGANv2.1 driven by WRF model. Results show China's BVOC emissions had increased by 28.01% at an annual average rate of 1.27% from 37.89 Tg in 1981 to 48.50 Tg in 2003. Emissions of isoprene, monoterpenes, sesquiterpenes, and OVOCs had increased by 41.60%, 34.78%, 41.05%, and 4.89%, respectively. With fixed meteorological variables, the estimated BVOC emissions would increase by 19.25%, resulting from the increasing of vegetation biomass during the last 23 years. On average, isoprene, monoterpenes, sesquiterpenes, and OVOCs were responsible for 52.40%, 12.73%, 2.58%, and 32.29% of the national BVOC emissions, respectively. β-pinene and α-pinene, farnesene and caryophyllene were the largest contributors to the total monoterpene and sesquiterpene emissions, respectively. The highest emissions were found over northeastern, southeastern, southwestern China, Qinling Mountain, and Hainan and Taiwan provinces. The regions with high emissions had been expanding over the years, especially in the Changbai Mountain, southern China, and southwestern forest regions. The lowest emissions in southern China occurred in 1984–1988. Almost all the provinces had experienced increasing emissions, but their contributions to the national emissions differed significantly over the past 23 years. Yunnan, Guangxi, Heilongjiang, Jiangxi, Fujian, Guangdong, and Sichuan provinces always dominated the national BVOC emissions, excluding in 1977–1981, when the three northeastern provinces had relatively lower emissions.
Housing price has increased dramatically in China during the past decade. The appreciation of house value could relax credit constraint and thus encourage entrepreneurship. However, a house serves as both an important investment channel and a prerequisite for marriage in China. The continuous high return of investment in housing and intensified marriage market competition make house purchase a priority for young people and their parents, which would crowd out entrepreneurial activities. Using two large datasets, we find that high housing price in general discourages entrepreneurial activities for urban adults. For house owners, while house value appreciation has a positive wealth effect, the ratio of mortgage over income has a negative effect. For non-owners, a higher ratio of housing price over income corresponds to a lower probability of entrepreneurship. This study highlights the negative consequences of surging housing price on entrepreneurship in developing countries.
Heterogeneous oxidation of oxygenated volatile organic compounds (OVOCs) serves as an important sink of OVOCs as well as a source of secondary organic material. However, the roles of gas phase oxidants in these reactions are poorly understood. In this work, we present the first laboratory study of the heterogeneous reactions of methacrolein (MACR) on various mineral dust particles in the presence of gaseous H2O2. It is found that the presence of gaseous H2O2 significantly promotes both the uptake and oxidation of MACR on kaolinite, α-Al2O3, α-Fe2O3, and TiO2, but not on CaCO3. The oxidation of MACR produces organic acids as its major low-molecular-weight product, whose yields are enhanced by a factor of 2−6 in the presence of H2O2. In addition, organic peroxides such as methyl hydroperoxide, peroxyformic acid, and peroxyacetic acid are only formed in the presence of H2O2, and the formation of methyl hydroperoxide indicates that MACR oxidation on the surface involves reaction with OH radicals. A probe reaction using salicylic acid verifies the production of OH radicals from H2O2 decomposition on kaolinite, α-Al2O3, α-Fe2O3, and TiO2, which rationalizes the enhanced MACR oxidation observed on these particles. The uptake coefficients of MACR on kaolinite, α-Fe2O3, and TiO2 in the presence of H2O2 are on the order of 10−5−10−4. Our results provide new insights into the formation and chemical evolution of organic species in the atmosphere.
IEEE 1857, Standard for Advanced Audio and Video Coding, was released as IEEE 1857-2013 in June 2013. Despite consisting of several different groups, the most significant feature of IEEE 1857-2013 is its surveillance groups, which can not only achieve at least twice coding efficiency on surveillance videos as H.264/AVC HP, but also should be the most recognition-friendly video coding standard till to now. This article presents an overview of IEEE 1857 surveillance groups, highlighting the background model based coding technology and recognition-friendly functionalities. We believe that IEEE 1857-2013 will bring new opportunities and drives to the research communities and industries on smart video surveillance systems.
The IEEE audio- and video-coding standards family includes updated tools that can be configured to serve new applications, such as surveillance, Internet, and intelligent systems video.
