Kuang Cen

The effect of mitigation measures on size distributed mass concentrations of atmospheric particles and black carbon concentrations during the Olympic Summer Games 2008 in Beijing

The period of the 2008 Olympic Summer Games in Beijing can be considered as a unique opportunity to study the influences of emission reduction measures on air quality improvement. Within this study atmospheric particles of different size classes (2.5 to 80 μm) were investigated before, during, and after the Olympic Games period in order to observe and assess the success of short-term measures to mitigate extreme urban aerosol pollution and also to investigate, which particle size classes were reduced most effectively. Furthermore, black carbon (BC) concentrations in fine particles (PM(2.5)) during the source control period were compared to those of the previous years in order to investigate the decrease of combustion-derived aerosols. It is shown that besides the implemented mitigation measures precipitation decisively contributed to a considerable decrease of particulate air pollution in Beijing compared to the respective concentrations during the time directly before and after the Olympic Games, and also compared to average August concentrations during the previous years and the following year 2009. Particles of the fine fraction of the coarse mode (2.5 to 5 μm), which have a residence time in the order of several days and which, therefore, are typically transported over long distances from outside of Beijing, were less efficiently reduced than coarser particles. This indicates that long-range transport of atmospheric particles is difficult to control and that presumably the established mitigation area was not large enough to also reduce the fine fraction of the coarse mode more efficiently. Furthermore, the study showed that coarse geogenic particles, which originated to a high percentage from construction sites and resuspension processes due to traffic seemed to be reduced most efficiently during the Olympic Games period.

Spatio-temporal variations of black carbon concentrations in the Megacity Beijing

The spatial and temporal distribution and the flux of black carbon (BC) concentration in Beijing were continuously investigated over a two-year period at five sites to highlight the relative influence of contributing sources. The results demonstrate firstly that there is significant spatio-temporal variability of BC in Beijing. Highest concentrations occurred during winter primarily due to stagnant meteorological conditions, and seasonal BC sources, such as coal combustion for heating purposes. Biomass burning was identified as a minor seasonal source during the summer months. BC also varied spatially with higher concentrations in the SE of Beijing and lower concentrations in the NW, due to the differing emission intensity of various local BC sources such as traffic and industry. Frequently, overnight BC concentrations were higher due to specific meteorological conditions, such as the lower urban mixing layer height and various anthropogenic activities, such as exclusive night-time heavy duty vehicle traffic in the inner-city.

μ‐Scale Variations Of Elemental Composition In Individual Atmospheric Particles By Means Of Synchrotron Radiation Based μ‐XRF Analysis

Atmospheric pollution poses a huge challenge especially for densely populated urban areas. Although a tremendous knowledge already exists on atmospheric particulate pollution, only very limited knowledge is available on mineral and chemical composition of single atmospheric particles because most studies on air pollution focus on total mass concentrations or bulk elemental analysis. However, it is of particular importance to investigate the properties of single particles since according to their individually composition they differ in their specific impact on climate change, negative environment and health effects, as well as accelerating the weathering of stone buildings in urban areas. Particles with sulfate and nitrate coatings together with sufficient moisture increase metal solubility and possibly catalyze further surface reactions on stone facades of buildings. From the viewpoint of health effects of aerosols it is important to consider agglomerations processes of fine anthropogenic and highly toxic...

Meteorological Influences Within the Context of Air Quality in Beijing

Daily PM2.5 samples were collected continuously with two high-volume samplers at the ground of CUGB from 06/2010 until 06/2011. The site is very near to the instrumentation for long-term investigation of the inorganic composition of PM2.5 (DWD, KIT/IMG). The daily filter samples are analyzed for carbon fractions, organic compound speciation (HMGU, UR), inorganic (KIT/IMG) and isotopic composition. Gaseous pollutants like NO, NO2 and O3 and compounds which are of interest for secondary aerosol formation like SO2 were measured by a DOAS with three retroreflectors from 04/2009 until 03/2011 in Beijing at LAPC. By path-integrated measurements at different directions information about emission sources (motorway, small street) can be provided. The emitter/receiver unit is in 20 m distance to an air pollution monitoring station. The diurnal development and variation of the mixing layer height (MLH) is determined by a ceilometer. It is shown that the variations of the observed SO2 and NO2 as well as PM2.5 concentrations are influenced by the MLH, apart from the meteorological (e.g. wind), emission (e.g. SO2) and photochemistry dependences. High air pollution is coupled significantly with MLH lower than 1,000 m.

Mobility of trace metals in urban atmospheric particulate matter from Beijing, China

Total suspended particles (TSP) and particulate matter ≤ 2.5 µm (PM2.5) from Beijing, China, were studied for a time period of three years (2005– 2008). Beside the total mass and the element concentrations, also the chemical fractionation and bioavailability of various elements was investigated by applying a four-step sequential extraction scheme.

Source Identification and Seasonal Variations of Carbonaceous Aerosols in Beijing—A Stable Isotope Approach

Carbonaceous aerosols constitute an important part of atmospheric particles in urban areas. Within this study, total carbon (TC) was investigated in total suspended particulates (TSP) and fine particles (PM2.5) collected in the megacity Beijing, China. Beside mass and TC concentrations, also stable C isotopes were analyzed by isotope ratio mass spectrometry (IR-MS) coupled to an element analyzer (EA). Carbon isotope ratios (δ13C) can serve as a fingerprint for source identification, because different source materials have characteristic δ13C values.