典型岩溶槽谷区土壤水δD和δ^(18)O时空分布特征:以重庆市中梁山岩溶槽谷为例

Temporal and Spatial Distribution of the Soil Water δD and δ^(18)O in a Typical Karst Valley: A Case Study of the Zhongliang Mountain,Chongqing City

为了揭示岩溶槽谷区土壤水氢氧同位素的时空分布特征,以重庆市北碚区中梁山为研究基地,于2017年5月和2017年9月收集降水及3种不同土地利用方式(耕地、草地和林地)不同深度的土壤水,利用稳定同位素技术研究不同土地利用方式下0~15 cm、15~45 cm土壤剖面的土壤水氢氧同位素时空变化特征.结果表明:(1)土壤水δD和δ^(18)O的平均值分别为-50.0‰±33.6‰和-7.9‰±4.3‰,其值均在大气降水线(LMWL)周围,说明降水是该区土壤水的主要补给来源;(2)土壤水δD和δ^(18)O具有明显的季节变化,5月(土壤水δD和δ^(18)O的平均值-19.4‰±6.8‰和-4.1‰±1.0‰)>9月(土壤水δD和δ^(18)O的平均值-82.2‰±14.0‰和-11.9‰±2.2‰);(3)土壤水δD和δ^(18)O在不同土地利用方式下没有表现出明显差异;(4)土壤水δD和δ^(18)O随土壤深度呈梯度变化,5月耕地、草地和林地土壤水稳定同位素以垂直递减趋势为主,9月耕地和林地以递增趋势为主,草地以递减的趋势为主.

In this study, we （cultivated land, grass land, analyzed the stable hydrogen and forest land） at 0-15 cm District, Chongqing） in May 2017 and September 2017 to and oxygen isotopes of precipitation and three different land use patterns and 15-45 cm in a karst ridge-trough area （Zhongliang Mountain, Beibei investigate the spatial and temporal variation of stable isotopes in different soil profiles using the isotope tracer technique. The results show that： ①The average values of the soil water δD and δ^18O are -50.0‰ ± 33.6‰ and -7.‰ ±4. 3‰, respectively, and all plot around the local meteoric water line （LMWL） , indicating that precipitation is the main source of the soil water supply in this area. ②The seasonal variations of δD and δ^18O of the soil water are significant in different months of the rainy season, May （ - 19.4‰ ±.8‰ and -4. 1‰ ± 1.0‰） 〉 September （ -82.2 ‰±14.‰ and - 11.9‰ ±2.2‰）. ③However, there is no significant difference in the soil water 8D and g^SO under different land use patterns. ④ The soil water 8D and g^SO change with soil depth gradients, which decrease along the depth in vertical direction for all types of soil land use in May but mainly increase/decrease in the cultivated land and woodland/grassland in September, respectively.