A comparative study of chemical weathering intensity and element transport features of loess-palaeosol in the upper reaches of Hanjiang and Weihe river valleys, China
Loess-palaeosol profile in the Chinese Loess Plateau has been regarded as one of the best media that can reflect global paleo- climatic changes. Previous studies chemical weathering intensity of loess-palaeosol are mainly conducted on the Loess Plateau, lower reaches of Yangtze River, Xinjiang Autonomous Region, as well as western Sichuan province, but fewer on the difference between the loess-palaeosol weathering intensity in the Hanjiang River Valley and Loess Plateau. So a comparative study of chemical weathering intensity and element transport features of loess-palaeosol in the upper reaches of Hanjiang and Weihe river Valleys was carried out in the paper, the differences and similarities of pedogenic strength and chemical weathering intensity between the Hanjiang and Weihe river valleys were discovered as follows: (1) The loess-palaeosol composition of Hanjiang River valley and Weihe River valley is quite similar to the UCC (upper continental crust) average composition that indicates the loess of two regions came from multiple sources and mixed well. The above evidences showed that the loess of the two regions was aeolian loess. (2) Compared with the morphological and color characters, chemical index (CIA/CIW), the leaching rate of Na and Ca, the mobility of major elements, the loess of the Hanjiang River Valley underwent stronger chemical weathering intensity. (3) Both the two loess-palaeosol profiles of YHC and MTS record the cold and dry event which occurred during 6000-5000 a BP.