Characterization of carbonaceous aerosols including CC （carbonate carbon）, OC （organic carbon）, and EC （elemental carbon） were investigated at Xi＇an, China, near Asian dust source regions in spring 2002. OC var...Characterization of carbonaceous aerosols including CC （carbonate carbon）, OC （organic carbon）, and EC （elemental carbon） were investigated at Xi＇an, China, near Asian dust source regions in spring 2002. OC varied between 8.2 and 63.7μgm^- 3, while EC ranged between 2.4 and 17.2 μ m^-3 during the observation period. OC variations followed a similar pattern to EC and the correlation coefficient between OC and EC is 0.89 （n=31）. The average percentage of total carbon （TC, sum of CC, OC, and EC） in PM2.5 during dust storm （DS） events was 13.6%, which is lower than that during non-dust storm （NDS） periods （22.7%）. CC, OC, and EC accounted for 12.9%, 70.7%, and 16.4% of TC during DS events, respectively. The average ratio of OC/EC was 5.0 in DS events and 3.3 in NDS periods. The OC-EC correlation （R^2=0.76, n=6） was good in DS events, while it was stronger （R^2=0.90, n=25） in NDS periods. The percentage of watersoluble OC （WSOC） in TC accounted for 15.7%, and varied between 13.3% and 22.3% during DS events. The distribution of eight carbon fractions indicated that local emissions such as motor vehicle exhaust were the dominant contributors to carbonaceous particles. During DS events, soil dust dominated the chemical composition, contributing 69% to the PM2.5 mass, followed by organic matter （12.8%）, sulfate （4%）, EC （2.2%）, and chloride （1.6%）. Consequently, CC was mainly entrained by Asian dust. However, even in the atmosphere near Asian dust source regions, OC and EC in atmospheric dust were controlled by local emission rather titan the transport of Asian dust.展开更多
Coal burst is caused by a dynamic and unstable release of energy within the overstressed rock mass/coal during the mining process.Although the occurrence of coal burst is a result of the complex impacts of many factor...Coal burst is caused by a dynamic and unstable release of energy within the overstressed rock mass/coal during the mining process.Although the occurrence of coal burst is a result of the complex impacts of many factors,a major component of coal burst mechanism is associated with energy storage and release.This study reviewed the sources of energy that can contribute to a coal burst,principally strain and potential energy stored in the coal mass around excavations,and radiated seismic energy released by geological discontinuities.The energy balance concept proposed by[1]was utilised in numerical modellings to compute the radiated seismic energy in a modelling system and the kinetic energy of ejected rock/coal for a given burst scenario.The modelling results showed that the strain energy density(SED)around excavations increases with increasing mining depth and the maximum SED area migrates deeper into the coal.For the effect of geological features on both roadway and longwall face,the coal burst risk proneness can be assessed considering the proposed energy terms.According to the results of energy changes in excavations,the modelling predicts that for depths of ejection 2 m and 3 m the kinetic energy of a burst increases as the mining depth increases from 100 m to 1000 m,but for depth of ejection 1 m only increases until mining depth reaches 700 m and then decreases.The proposed energy-based model indicators can deepen the understanding of energy changes and the associated coal burst risks for different mining conditions.展开更多
基金the National Natural Science Foundation of China(Grant No. 0675081)the National Key Project of BasicResearch (Grant No. 2004CB720203).
文摘Characterization of carbonaceous aerosols including CC （carbonate carbon）, OC （organic carbon）, and EC （elemental carbon） were investigated at Xi＇an, China, near Asian dust source regions in spring 2002. OC varied between 8.2 and 63.7μgm^- 3, while EC ranged between 2.4 and 17.2 μ m^-3 during the observation period. OC variations followed a similar pattern to EC and the correlation coefficient between OC and EC is 0.89 （n=31）. The average percentage of total carbon （TC, sum of CC, OC, and EC） in PM2.5 during dust storm （DS） events was 13.6%, which is lower than that during non-dust storm （NDS） periods （22.7%）. CC, OC, and EC accounted for 12.9%, 70.7%, and 16.4% of TC during DS events, respectively. The average ratio of OC/EC was 5.0 in DS events and 3.3 in NDS periods. The OC-EC correlation （R^2=0.76, n=6） was good in DS events, while it was stronger （R^2=0.90, n=25） in NDS periods. The percentage of watersoluble OC （WSOC） in TC accounted for 15.7%, and varied between 13.3% and 22.3% during DS events. The distribution of eight carbon fractions indicated that local emissions such as motor vehicle exhaust were the dominant contributors to carbonaceous particles. During DS events, soil dust dominated the chemical composition, contributing 69% to the PM2.5 mass, followed by organic matter （12.8%）, sulfate （4%）, EC （2.2%）, and chloride （1.6%）. Consequently, CC was mainly entrained by Asian dust. However, even in the atmosphere near Asian dust source regions, OC and EC in atmospheric dust were controlled by local emission rather titan the transport of Asian dust.
基金Australian Coal Industry's Research Program.Grant/Project Number:C26066.
文摘Coal burst is caused by a dynamic and unstable release of energy within the overstressed rock mass/coal during the mining process.Although the occurrence of coal burst is a result of the complex impacts of many factors,a major component of coal burst mechanism is associated with energy storage and release.This study reviewed the sources of energy that can contribute to a coal burst,principally strain and potential energy stored in the coal mass around excavations,and radiated seismic energy released by geological discontinuities.The energy balance concept proposed by[1]was utilised in numerical modellings to compute the radiated seismic energy in a modelling system and the kinetic energy of ejected rock/coal for a given burst scenario.The modelling results showed that the strain energy density(SED)around excavations increases with increasing mining depth and the maximum SED area migrates deeper into the coal.For the effect of geological features on both roadway and longwall face,the coal burst risk proneness can be assessed considering the proposed energy terms.According to the results of energy changes in excavations,the modelling predicts that for depths of ejection 2 m and 3 m the kinetic energy of a burst increases as the mining depth increases from 100 m to 1000 m,but for depth of ejection 1 m only increases until mining depth reaches 700 m and then decreases.The proposed energy-based model indicators can deepen the understanding of energy changes and the associated coal burst risks for different mining conditions.
