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Campaigns were conducted to measure Organic Carbon (OC) and Elemental Carbon (EC) in PM2.5 during winter and summer 2003 in Beijing. Modest differences of PM2.5 and PM10 mean concentrations were observed between the winter and summer campaigns. The mean PM2.5/PM10 ratio in both seasons was around 60%, indicating PM2.5 contributed significantly to PM10. The mean concentrations of OC and EC in PM2.5 were 11.2±7.5 and 6.0±5.0μg m-3 for the winter campaign, and 9.4±2.1 and 4.3±3.0 μg m-3 for the summer campaign, respectively. Diurnal concentrations of OC and EC in PM2.5 were found high at night and low during the daytime in winter, and characterized by an obvious minimum in the summer afternoon. The mean OC/EC ratio was 1.87±0.09 for winter and Z39±0.49 for summer. The higher OC/EC ratio in summer indicates some formation of Secondary Organic Carbon (SOC). The estimated SOC was 2.8 μg m-3 for winter and 4.2μg m-3 for summer. 相似文献
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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 63.7 μg m-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 coeflcient 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 (R2=0.76, n=6) was good in DS events, while it was stronger (R2=0.90, n=25) in NDS periods. The percentage of water-soluble 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 than the transport of Asian dust. 相似文献
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地球三四十亿年的生命交响乐,它的主旋律是碳的化学演变。没有碳,就没有生命。碳,是生命世界的栋梁之材。我们来自何方?将去往何处?从远古的蛮荒直至今天的文明,这种疑问始终与人类相伴相随。几乎每一个人,在他有限的一生之中,或多或少都给过类似的问题以思考时间。或许因为,对于绝大多数人来说,这类思考不能解决任何实际问题,而流于一时无所事事的灵光乍现。所以迄今为止,有关生命的来源,我们仍然知之甚少。 相似文献
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Chemical Characteristics of Carbonaceous Aerosols During Dust Storms over Xi'an in China 总被引:1,自引:0,他引:1
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. 相似文献
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Yuqiao GAO Li LIU Qi'an MENG Yan XU Xiyu QU Xianmei JIN 《东北亚地学研究》2007,10(2):148-155
Dawsonite, NaAlCO3(OH)2, is widespread as a cement, replacement and cavity filling in Hailaer Basin in China and Bowen-Gunnedah-Sydney (BGS) basin system in Australia. The origin of dawsonite is emphatically contrasted and analyzed through stable isotopic composition. Dawsonite δ13C values ranging from -4.0×10-3 to 4.1×10-3 are remarkably consistent through the BGS basin system. The calculated δ13C values of CO2 gas in isotopic equilibrium with dawsonite range from -11.3×10-3 to -4.6×10-3. These values indicate carbon of dawsonite came from inorganic CO2 gas accompanied by magmatic activity. In Hailaer Basin, the Dawsonite δ13C values ranging from -4.64×10-3 to 2.12×10-3 are also consistent. The calculated δ13C values of CO2 gas in isotopic equilibrium with dawsonite range from -11.82×10-3 to -5.11×10-3. According to the coincidence of dawsonite-bearing well and CO2 gas well with mantle source,lying along deep fracture within or adjacent to Yanshanian granite,it is concluded that CO2 gas forming dawsonite is derived from mantle related to magmatic process during the Yanshanian. A little biologic origin carbon owing to petroleum charging intervened when dawsonite formed. 相似文献
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Stable carbon isotopic composition of soil organic matter in the karst areas of Southwest China 总被引:1,自引:1,他引:0
This study dealt with the distribution characteristics of soil organic carbon (SOC) and the variation of stable carbon isotopic composition (δ^13C values) with depth in six soil profiles, including two soil types and three vegetation forms in the karst areas of Southwest China. The δ^13C values of plant-dominant species, leaf litter and soils were measured using the sealed-tube high-temperature combustion method. Soil organic carbon contents of the limestone soil profiles are all above 11.4 g/kg, with the highest value of 71.1 g/kg in the surface soil. However, the contents vary between 2.9 g/kg and 46.0 g/kg in three yellow soil profiles. The difference between the maximum and minimum δ^13C values of soil organic matter (SOM) changes from 2.2‰ to 2.9‰ for the three yellow soil profiles. But it changes from 0.8‰ to 1.6‰ for the limestone soil profiles. The contrast research indicated that there existed significant difference in vertical pattems of organic carbon and δ^13C values of SOM between yellow soil and limestone soil. This difference may reflect site-specific factors, such as soil type, vegetation form, soil pH value, and clay content, etc., which control the contents of different organic components comprising SOM and soil carbon turnover rates in the profiles. The vertical variation patterns of stable carbon isotope in SOM have a distinct regional character in the karst areas. 相似文献
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The redox sensitive elements, molybdenum (Mo) and uranium (U), in marine sediments from the latest Permian Dalong (大隆) Formation at the Shangsi (上寺) Section, Northeast Siehuan (四川), South China, were analyzed by inductively coupled plasma mass spectrometry (ICP-MS) to determine their response to a range of redox conditions, and to estimate the organic carbon burial rate. On the basis of the correlation between authigenic Mo abundance and organic carbon content in modern oceans, the organic carbon burial rates were calculated for the rocks at Dalong Formation, ranging from 0.48-125.83 mmol/(m2-d), which shows a larger range than the mineralization rate of organic carbon at the continental margins (1.6-4.23 mmol/(m2.d)). The Zr-normalized Mo and U abundances show large fluctuations in the entire section. The maxima of Zr-normalized Mo abundance and thus the maxima of the organic carbon burial rates were observed at the interval between the 155th and 156th beds (404-407 m above the base of Middle Permian). A decrease (the minimum) in U/Mo ratios is present in this interval. It is speculated that the oxygen-limited conditions and ultimately anoxia or euxinia may develop within this depth interval. In contrast, an enhanced enrichment of Zr-normallzed U abundance is found, in association with less enrichment in Zr-normnllzed Mo abundance in the interval from the I51st to 154th beds (395-404 m above the base of Middle Permian), inferring the dominance of a suboxic/anoxic depositional condition (denitrifying condition), or without free H2S. The presence of small quantities of dissolved oxygen may have caused the solubilization and loss of Mo from sediments. It is proposed that the multiple cycles of abrupt oxidation and reduction due to the upwelllng at this interval lead to the enhanced accumulation of authigenic U, but less enrichment of Mo. A decrease in the contents of U, Mo, and TOC is found above the 157th bed (407 m above the base of Middle Permian), in association with the enhanced U/Mo ratio, suggesting the overall oxic conditions at the end of the Dalong Formation. 相似文献
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