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《地质学报(英文版)》 2016-02
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Normal Alkane Distributions in Soil Samples along a Lhasa-Bharatpur Transect

JIA Qiuhuan;SUN Qing;XIE Manman;SHAN Yabing;LING Yuan;ZHU Qingzeng;TIAN Mingzhong;School of the Earth Sciences and Resources, China University of Geosciences;National Research Center for Geoanalysis;Key Laboratory of Cenozoic Geology and Environment, Institute of Geology and Geophysics, Chinese Academy of Sciences;  
We present n-alkane distributions in the soil samples along a transect from Lhasa on the Tibetan Plateau to Bharatpur in Nepal, which covers a large geographical area and a wide range of climatic conditions. These data allow us to assess the significance of n-alkane distributions in different vegetation types and their relationships to temperature and precipitation. In the tropical rainforest and broadleaved forest zones, n-alkanes exhibit a bimodal distribution pattern with dominant homologues around n-C_(31) and n-C_(23). The bimodal distribution of tropical rainforest n-alkanes may be a general pattern because of the presence of many lianas, epiphytic plants, algae and the strong microbial activity and degradation involved in the postdepositional process. In the warm-temperate mixed forest and needle-leaved forest zones, the long-chain alkanes have a pattern of n-C_(31) n-C_(33) n-C_(27). In the alpine shrub and grassland zone, although the most abundant homologue is n-C_(31) , relatively high n-C_(23) concentrations have also been observed in some samples. The statistical results show a good correlation between n-alkane proxies and climatic factors. The average chain length(ACL) values are positively correlated with precipitation and temperature across the transect. The carbon preference index(CPI) values show a negative correlation with temperature and precipitation along a Lhasa–Bharatpur transect. Although there is a positive relationship between ACL and temperature, it is difficult to separate the two climatic variables(temperature and precipitation) because they are well coupled in the monsoon region.
【Fund】: supported by the National Natural Science Foundation of China(Grant nos.41302141 and 41272198);; the Geological Research Program of China Geological Survey(No.12120113015400)
【CateGory Index】: S151.9
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