STUDIES OF ELEMENTAL COMPOSITION AND UV VISIBLE SPECTROSCOPIC PROPERTIES OF DISSOLVED FULVIC ACIDS FROM SALINE SOILS AROUND WULIANGSUHAI LAKE, CHINA

摘要

The elemental composition and UV visible spectro-scopic properties of dissolved fulvic acids (FA) isolated from salined flavo-aquic soils around Wuliangsuhai Lake in Hetao Irrigation District were examined to evaluate humi-fication levels of FA and salinisation processes of soils. Composite soil samples of different depths (0-20cm, 20-40cm, 40-60cm and 60-80cm) were collected from four different halophyte communities along a saline-impact gradient around Wuliangsuhai Lake, namely, Comm. Salicor-nia europaea (CSE), Comm. Suaeda glauca (CSG), Comm. Kalidium foliatum (CKF) and Comm. Sophora alopecur-oides (CSA). Seven humification indices (HIX) (C/N, SUVA, E_2/E_3, E_2/E_4, E_4/E_6, S_(275-295) and S_(350-400)), deduced from elemental analysis and UV visible spectroscopy of FA, were used to assessing humification degree. Humificaiton levels of FA from the CSA soils were the highest, followed by the CKF, CSG and CSA. There were significant relationships between seven HIX (P<0.05), except E_4/E_6. Exchangeable sodium percentage (ESP) showed good correlations with the HIX, and humification degree increased with the decreasing ESP. Therefore the HIX can not only be used to assessing humification levels of FA, but also be used as a surrogate for ESP and an indicator for soil salinisation processes.