ALBERT

Description: A special period in Beijing from 6 August to 17 September 2015, during which the World Athletics Championships and Victory Day military parade took place, and which involved measures to restrict traffic and reduce factory emissions, was selected to analyze the aerosol optical properties and the impact of meteorological conditions on pollution levels. The study was based on AERONET observational and retrieval data, particulate matter measurements (TEOM 1405), meteorological data, and then the HYSPLIT model was used to analyze the pollution sources. The study period was divided into three sub-periods according to the different stages of implementation of the control measures, and the main conclusions can be summarized as follows. During the period in which the restrictive measures were applied, the air quality improved significantly, with the average value of the AOD being 0.34 ± 0.20, about 69% less than before. Meanwhile, the average Ångström exponent was about 9.5% higher than before, with an average value of 1.38 ± 0.25, indicating that the main pollutants were fine particles. Single scattering albedo decreased as wavelength increased, being higher than in the other two stages (mean value of 0.944 ± 0.045). This showed that the strong scattering capacity and absorption aerosol optical depth was at its lowest, at about 0.008 ± 0.009. The peaks of aerosol volume concentration in the fine and coarse mode were significantly reduced. Meteorological conditions also had a certain effect on the aerosol optical properties, with the blowing of clean and dry wind and the occurrence of precipitation contributing to the overall improvement in air quality.

Description: An extreme haze event occurred in the Beijing area from 17 to 23 December 2015. Ground-based measurements and satellite observations during this event were used to further our understanding of the formation process of haze pollution and aerosol optical properties. The results suggest that high relative humidity, poor diffusion conditions (low wind speed and stable stratification) and favorable secondary transformation conditions under the hygroscopic growth of aerosol and high emissions led to this serious haze episode. During the haze period, the daily average value was 1.15 and 0.42 for aerosol optical depth (AOD500nm) and columnar water-vapor (CWV, in cm), respectively. On 19 December, the correlation coefficient between CWV and AOD500nm was 0.91, indicating the effect of hygroscopic growth of fine-mode articles. The daily average values for Ångström exponent, fine-mode fraction, aerosol absorption optical depth, and Ångström absorption exponent were 1.19, 0.81, 0.11 and 1.47, respectively, which suggests that fine aerosol particles were dominant in the atmosphere and fine-mode particles were the dominant contributor to atmospheric extinction during the haze period. Moreover, it also reflects that there were more absorbing aerosol particles during the haze period. Compared with other polluted periods with a bimodal distribution, there was an obvious trimodal distribution on 19 December. There were three peaks at radii of about 0.1 μm, 0.5–0.8 μm and 4 μm. Satellite observations show that there was an obvious aerosol layer in the Beijing area during the haze period, concentrated at ground level to within 2 km in the upper layers. The types of aerosol were mainly composed of mixed pollution aerosols.

Description: Grouting materials are used frequently in grouting reinforcement projects, such as mining and coastal engineering. Double liquid grouting materials are mostly used because of the fast setting and high early strength properties when the two slurries are mixed together but high fluidity when the two slurries are separated. In our study, double liquid grouting materials were developed from CSA cement (slurry A), quicklime and fluorgypsum (slurry B). Aluminum sulfate was added in slurry B in order to counteract any adverse effects caused by the fluorgypsum, such as the decreased early compressive strength and the prolonged setting time. The effects of aluminum sulfate content and the quicklime/fluorgypsum ratio on the setting time, hydration heat, and compressive strength of the double liquid grouting materials were investigated, and the hydration products were characterized through thermogravimetry-differential thermal analysis (TG-DTA), X-ray Diffraction (XRD), and Scanning Electron Microscope (SEM) tests. The results show that the addition of aluminum sulfate can shorten the setting time and increase compressive strength at both early and later ages. Considering the setting time and compressive strength of double liquid grouting material at the same time, the optimum content of aluminum sulfate was found to be 2%, and the optimum ratio of quicklime/fluorgypsum was found to be 2:8. The values of the optimum content of aluminum sulfate and ratio of quicklime/fluorgypsum were verified from theoretical analysis.