Characteristics and sources of formic；acetic and oxalic acids in PM2.5 and PM10 aerosols in Beijing；China

IEECAS SKLLQG

Impacts of land use change and climate variations on annual inflow into Miyun Reservoir,Beijing, China

The Miyun Reservoir, the only surface water source for Beijing city, has experienced water supply decline in recent decades. Previous studies suggest that both land use change and climate contribute to the changes of water supply in this critical watershed. However, the specific causes of the decline in the Miyun Reservoir are debatable under a non-stationary climate in the past 4 decades. The central objective of this study was to quantify the separate and collective contributions of land use change and climate variability to the decreasing inflow into the Miyun Reservoir during 1961–2008. Different from previous studies on this watershed, we used a comprehensive approach to quantify the timing of changes in hydrology and associated environmental variables using the long-term historical hydrometeorology and remote-sensing-based land use records. To effectively quantify the different impacts of the climate variation and land use change on streamflow during different sub-periods, an annual water balance model (AWB), the climate elasticity model (CEM), and a rainfall–runoff model (RRM) were employed to conduct attribution analysis synthetically. We found a significant (p  <  0.01) decrease in annual streamflow, a significant positive trend in annual potential evapotranspiration (p  <  0.01), and an insignificant (p  >  0.1) negative trend in annual precipitation during 1961–2008. We identified two streamflow breakpoints, 1983 and 1999, by the sequential Mann–Kendall test and double-mass curve. Climate variability alone did not explain the decrease in inflow to the Miyun Reservoir. Reduction of water yield was closely related to increase in actual evapotranspiration due to the expansion of forestland and reduction in cropland and grassland, and was likely exacerbated by increased water consumption for domestic and industrial uses in the basin. The contribution to the observed streamflow decline from land use change fell from 64–92 % during 1984–1999 to 36–58 % during 2000–2008, whereas the contribution from climate variation climbed from 8–36 % during the 1984–1999 to 42–64 % during 2000–2008. Model uncertainty analysis further demonstrated that climate warming played a dominant role in streamflow reduction in the most recent decade (i.e., 2000s). We conclude that future climate change and variability will further challenge the water supply capacity of the Miyun Reservoir to meet water demand. A comprehensive watershed management strategy needs to consider the climate variations besides vegetation management in the study basin.

The evolution of national level historic district registration and conservation in China: the Beijing Yandaixiejie and Beijing Guozijian districts in Beijing, China

From the 1980s, Chinese experts from some mainland universities, such as Tongji Universtiy in Shanghai and Tsinghua University in Beijing, commenced research into heritage management and historic architectural conservation in China. With the announcement of the First and Second Lists of 10 Chinese Historic and Cultural Districts in 2009 and 2010, the conservation of historic districts was generally received and elevated in agreements from state-level government to local level governments. This paper considers literature about international and Chinese regulations and presents the evolution of historic district conservation in China. The paper explores the effective and ineffective results of the “Selection Contest of Chinese Top 10 Historic and Cultural Districts” in two cases selected from the First and Second Lists of 10 Chinese Historical and Cultural Districts during upon recent research and investigations. In each example, the paper provides a detailed examination of public awareness and their evaluation of conservation effectiveness through questionnaires.

Access to social insurance in urban China: a comparative study of rural-urban and urban-urban migrants in Beijing

 Since 1958 the hukou (household registration) system has assigned Chinese citizens either a rural or urban status. Some studies argue that the rural-to-urban migrants in China who do not have urban hukou are not entitled to urban social insurance schemes, due to institutional discrimination, which applies differing treatment to urban and rural hukou (chengxiang fenge). Although rural-urban migrants participate less in the social insurance system than their counterparts with urban hukou, a closer examination of recent policy developments shows that migrants actually do have the legal right to access the system. This implies that discrimination between rural and urban workers has been declining, and distinctions based on household registration status are less able to explain China's current urban transition. This paper provides a new way of examining Chinese migrants' social insurance participation, by adopting a framework that includes both rural-to-urban migrants and urban-to-urban migrants, which are an important, but less studied, migrant group. Among our key findings are that urban migrants are more likely to sign a labour contract than rural migrants; urban migrants have higher participation rates in social insurance than rural migrants; having a labour contract has a greater impact than hukou status in determining whether Beijing's floating population accesses social insurance; and urban migrants who have signed a labour contract have higher participation rates in social insurance than either rural migrants or urban migrants without a labour contract. © 2013 Elsevier Ltd.

Source apportionment of elemental carbon in Beijing, China: insights from radiocarbon and organic marker measurements

Elemental carbon (EC) or black carbon (BC) in the atmosphere has a strong influence on both climate and human health. In this study, radiocarbon (14C) based source apportionment is used to distinguish between fossil fuel and biomass burning sources of EC isolated from aerosol filter samples collected in Beijing from June 2010 to May 2011. The 14C results demonstrate that EC is consistently dominated by fossil-fuel combustion throughout the whole year with a mean contribution of 79% ± 6% (ranging from 70% to 91%), though EC has a higher mean and peak concentrations in the cold season. The seasonal molecular pattern of hopanes (i.e., a class of organic markers mainly emitted during the combustion of different fossil fuels) indicates that traffic-related emissions are the most important fossil source in the warm period and coal combustion emissions are significantly increased in the cold season. By combining 14C based source apportionment results and picene (i.e., an organic marker for coal emissions) concentrations, relative contributions from coal (mainly from residential bituminous coal) and vehicle to EC in the cold period were estimated as 25 ± 4% and 50 ± 7%, respectively, whereas the coal combustion contribution was negligible or very small in the warm period.

Imaging Land Subsidence Induced by Groundwater Extraction in Beijing (China) Using Satellite Radar Interferometry

Beijing is one of the most water-stressed cities in the world. Due to over-exploitation of groundwater, the Beijing region has been suffering from land subsidence since 1935. In this study, the Small Baseline InSAR technique has been employed to process Envisat ASAR images acquired between 2003 and 2010 and TerraSAR-X stripmap images collected from 2010 to 2011 to investigate land subsidence in the Beijing region. The maximum subsidence is seen in the eastern part of Beijing with a rate greater than 100 mm/year. Comparisons between InSAR and GPS derived subsidence rates show an RMS difference of 2.94 mm/year with a mean of 2.41 ± 1.84 mm/year. In addition, a high correlation was observed between InSAR subsidence rate maps derived from two different datasets (i.e., Envisat and TerraSAR-X). These demonstrate once again that InSAR is a powerful tool for monitoring land subsidence. InSAR derived subsidence rate maps have allowed for a comprehensive spatio-temporal analysis to identify the main triggering factors of land subsidence. Some interesting relationships in terms of land subsidence were found with groundwater level, active faults, accumulated soft soil thickness and different aquifer types. Furthermore, a relationship with the distances to pumping wells was also recognized in this work.