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Analysis of Precipitation Characteristics and Its Causes in Central Yunnan City
HE Ping, LI Jinxiao, FU Yongmei, LIU Shuhua
Acta Scientiarum Naturalium Universitatis Pekinensis    2019, 55 (4): 626-634.   DOI: 10.13209/j.0479-8023.2019.040
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Basing on the nearly 50-year precipitation data of 4 major city (Kunming, Qujing, Yuxi, Chuxiong) in urban agglomeration of central Yunnan, this paper analyzes the variation of precipitation in annual, seasonal, and monthly time scale by using methods including the statistical analysis, the wavelet analysis, accumulative leveling method, and the grey relational analysis. The result shows that the average precipitation in past 50 years is 928.1 mm. The trend of precipitation is declining, and a mutation appears in 2009. Besides, precipitation has a dry and wet season in these region, and the wet season is between May and October but the dry season is between November and April of next year, There are more precipitation in the rainy season and less precipitation in dry season. The maximum of precipitation (184.0 mm) appears in July, but the minimum of precipitation (13.8 mm) appears in December. According to the wavelet analysis, the change of annual precipitation is about 22 years, the summer precipitation has a 19-day increase-decrease cycle with more precipitation and smaller variation, and the winter precipitation has a 20-day increase-decrease cycle with less precipitation and larger variation. The grey relational analysis show that the temperature and the specific humidity are dominant natural factors, and the population and the city size are dominant human factors. Besides, the natural factors play greater role than the artificial factors.
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Origin of Cherts during the Ediacaran-Cambrian Transition in Hunan and Guizhou Provinces, China: Evidences from REE and Ge/Si
WEI Shuaichao, CHEN Qifei, FU Yong, CUI Tao, LIANG Houpeng, GE Zhihua, ZHANG Peng, ZHANG Yong
Acta Scientiarum Naturalium Universitatis Pekinensis    2018, 54 (5): 1010-1020.   DOI: 10.13209/j.0479-8023.2018.035
Abstract806)   HTML    PDF(pc) (5222KB)(140)       Save

Two types of Liuchapo Formation cherts, bedded cherts and mounded cherts, were deposited in Bahuang section of Tongren in Guizhou Province and Ganziping section of Zhangjiajie in Hunan Province. The origin of the cherts was discussed by analyzing the characteristics of major, trace elements and REE compositions and Ge/Si ratios. It was revealed that the content of SiO2 in bedded cherts was range from 96.06% to 99.61%, and the content of SiO2 in mounded cherts was range from 98.62% to 99.56%, averaging 99.13%, and the contents of other chemical components were very low. Thus, two types of cherts are pure cherts. Moreover, the ΣREE of the bedded cherts in Bahuang section is ranged from 20.14 to 248.56 μg/g (averaging 100.62 μg/g), and no obvious abnormality in Eu/Eu* which is ranged from 0.90 to 1.10 (averaging 1.06), and the ratio of Ge/Si is 0.13−0.98 μmol/mol (averaging is 0.50 μmol/mol), indicating that the origin of bedded cherts affected terrigenous input. Whereas, the ΣREE of the mounded cherts in Ganziping district is ranged from 3.75 to 7.24 μg/g (averaging 5.73 μg/g), the ratio of Ce/Ce* is 0.46−0.66 (averaging 0.57) which shows a negative abnormal, Eu/Eu* is ranged from 2.28 to 11.07 (averaging 4.60) which shows a positive abnormal, and Ge/Si ratio is 1.09−1.43 μmol/mol, (averaging 1.25 μmol/mol) all of which reflect a hydrothermal origin of the mounded cherts. Otherwise, the relationship between Al2O3 and ΣREE in the bedded cherts has an excellent correlation, while in the mounded cherts has a poor correlation. It also illustrates that continental substance plays an important role in controlling the formation of bedded cherts, and the mounded cherts is originated from submarine volcanic or hydrothermal activity. The relationship between Al2O3 and Ge/Si also reflect the origin of cherts. Combined with the paleogeographic environment, it can conclude that the mounded cherts were deposited in syngenetic fault at the margin of the basin, originated from submarine hydrothermal activity, while the bedded cherts were deposit in the deep basin, mainly influenced by terrigenous input. What’s more, using 1 μmol/mol as the critical value of Ge/Si may provide a new way to trace the material sources of cherts.

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