| 关中平原降水氢氧稳定同位素特征及其水汽来源 |
| 摘要点击 1223 全文点击 516 投稿时间：2019-11-07 修订日期：2020-01-14 |
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| 中文关键词 关中平原 杨凌地区 氢氧稳定同位素 水汽来源 d-excess 17O-excess |
| 英文关键词 Guanzhong Plain Yangling area hydrogen and oxygen stable isotope water vapor source d-excess 17O-excess |
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| 中文摘要 |
| 为探究关中平原降水氢氧稳定同位素特征及其水汽来源，本研究选取关中腹地的杨凌站点次降水为研究对象，利用当地2015~2018年间的98场次降水样品及同期气象资料，分析该地区降水氢氧稳定同位素（δ2H、δ18O和δ17O）组成特征及其影响因素，建立当地大气降水线和三氧同位素大气降水线方程，并利用δ18O、d-excess和17O-excess指标尝试探讨当地可能存在的降水水汽来源，定量描述海洋和内陆源水汽对区域降水的贡献.结果表明，杨凌地区降水氢氧稳定同位素存在明显的季节性变化，同位素组成雨季（5~10月）贫化，旱季（11月~次年4月）富集；当地大气降水线的斜率和截距分别为7.7和9.1，说明研究区降水受到一定程度的蒸发分馏影响；三氧同位素大气降水线斜率为0.528，介于海水平衡分馏斜率（0.529）与水汽扩散斜率（0.518）之间，表明研究区处于海洋气团向内陆干旱区迁移的路径上.综合分析δ18O、d-excess和17O-excess，发现研究区降水受到来自东南季风的暖湿气团和来自西风的干冷气团的共同贡献，其中约有55%~79%的降水水汽来源于海洋，主要集中于6~8月；21%~45%的水汽来源于内陆和局地蒸发，主要集中于10月~次年4月.5月和9月降水水汽来源复杂，可能受海洋水汽和内陆水汽的共同补给. |
| 英文摘要 |
| To improve the understanding of hydrogen and oxygen stable isotope characteristics and vapor sources in the Guanzhong Plain, we collected 98 precipitation samples and corresponding meteorological data between 2015 and 2018 in Yangling, Shanxi Province, which is located in the central area of the Guanzhong Plain. The composition characteristics of the local hydrogen and oxygen stable isotopes of precipitation (δ2H, δ18O, and δ17O) and their environmental controls were analyzed, and the local meteoric water line (LMWL) and the meteoric water line of the triple oxygen isotopes were established. Three indicators (δ18O, d-excess, and 17O-excess) were used to explore the possible vapor sources of local precipitation and to quantify the contributions of ocean-source and inland-source water vapor to the precipitation. The results showed that there were obvious seasonal changes in the hydrogen and oxygen stable isotopes of precipitation in the Yangling area:water isotopes were depleted in the wet season (May to October) and enriched in the dry season (November to April of the next year). Both the slope (7.7) and intercept (9.1) of the LMWL were lower than those of the global meteoric water line (GMWL), indicating that the annual precipitation in the research area experienced variable degrees of secondary evaporation under cloud cover. The slope of the meteoric water line of the triple oxygen isotopes is 0.528, which is between that of seawater equilibrium fractionation (0.529) and water vapor diffusion into dry air (0.518), consistent with the fact that the Guanzhong area is located on the migration path of marine air mass to inland arid regions. Comprehensive analysis of δ18O, d-excess, and 17O-excess confirmed that the precipitation in the study area is jointly contributed to by the warm and humid air mass from the southeast monsoon and the dry and cold air mass from the westerly wind. Of these, approximately 55%-79% of the precipitation water vapor comes from the ocean, mainly in June to August, and about 21%-45% of the water vapor comes from inland and local evaporation, mainly from October to April. The water vapor sources of precipitation in May and September are complex and may intermittently originate from ocean and inland water vapor. |
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