【作者】 黄一民；

【导师】 章新平；

【作者基本信息】 湖南师范大学 ， 自然地理学， 2013， 博士

【摘要】 当代,水稳定同位素已成功应用于水循环机理研究,如水汽来源、降雨径流关系、干旱半干旱区的水资源评价、地表水与地下水的相互作用、地下水起源及测年、湖泊蒸发量及换水周期、水体污染物的来源、地热资源以及气候变化和人类活动对水循环的影响。应用氢氧稳定同位素示踪技术研究水循环机理时,有两个必要前提：一是需了解参与水循环过程的不同水体中D和18O组成的变化特征,二是需揭示影响同位素变化的机制。本文以洞庭湖流域作为研究区域,于2010至2012年在流域内多地进行了降水事件、地表径流(河水)以及地下径流(井水、泉水)的长时间取样,采用液态水同位素分析仪测定了上述水样的氢、氧同位素,同时结合同期卫星反演同位素资料以及模拟资料,对流域水循环过程不同水体(水汽、降水、地表径流以及地下径流)同位素的变化特征以及影响机制进行了研究。研究发现：1)亚洲季风区大气水汽δD在夏季风盛行期间明显要高于冬季风盛行期间,陆地上的这种变化要比海洋上明显。2)流域内降水同位素、过量氘具有明显的季节变化,表现出冬春高、夏秋低的特征。3)对日尺度上降水同位素与降水量、相对湿度、可降水量以及气温的关系统计表明,全年中,降水同位素表现出降水量效应、湿度效应以及反温度效应。另外,我们发现月尺度下降水同位素与上述气象要素的相关性较日尺度都大幅下降。4)日尺度下水汽、降水中δD显示冬春波动要大于夏秋。这可能受冬春较夏秋气温变化大,水汽来源复杂的影响。5)我们认为降雪样与降雨样分别生成的大气水线存在差异的原因不能完全归于降雨过程中同位素云下二次蒸发引起的同位素分馏较降雪明显,还应包括凝华、凝结过程中,凝华同位素分馏效应比要大于凝结。6)通过2010、2011、2012年各年的夏季水汽通量与同期流域降水同位素的分析,我们看到当西南季风输送的印度洋远源水汽较强时,流域内降水同位素为低值,当东南季风输送的太平洋近源水汽较强时,流域内降水同位素为高值。这又一次验证了环流效应的可信性。7)通过比较GNIP长沙观测站实测的,ECHAM4、GissE、 MUGCM三个模式模拟的降水同位素,发现三个模式模拟的降水δ’8O、过量氘以及大气水线的能力有着较大差异：MUGCM模拟月降水δ18O随时间变化的效果最好,ECHAM4模拟大气水线的效果最好,ECHAM4模拟过量氘的能力最强。8)流域内河水、井水、泉水一年中变化幅度要比降水小许多。流域内河水同位素表现出夏秋低、冬春高的季节变化特点,这与降水同位素的季节变化特点一致,这也从同位素角度证实了流域河流补给以降水为主。另外,埋藏深的井水同位素季节性变化非常小且富集明显(长沙井水只是代表了浅层地下水),这说明它们经历了强烈蒸发且有稳定的补给源。更多还原

【Abstract】 Currently, stable water isotopes have been successfully applied to the water cycle mechanism research, such as moisture sources, rainfall-runoff relationship, evaluation of water resources in the arid and semi-arid regions, the interaction of surface water and groundwater, groundwater origin and age, lake evaporation and water change cycle, the source of water pollutants, geothermal resources and climate change and human activities on the water cycle. Application of hydroxide stable isotope tracer technique to study the water cycle mechanism, there are two essential premises:Firstly, we need to understand variations of stable water isotope composition in different water bodies that involved in the water cycle. Secondly, we need to reveal the mechanisms that affect the isotopic variation. We choose the Dongting Lake Basin as the study area. During the period of2010to2012, we have collected event precipitation, surface runoff (river water), and underground runoff (well water, spring water) samples. After that, we measured all the samples’ hydrogen and oxygen isotope with liquid water isotope analyzer. In addition, water vapor HDO that retrieved from Aura satellite and simulated stable isotopes by GCMs have been used in this study. Variations of stable water isotopes in different water as well as the impact mechanism were studied. We found that:1) Atmospheric water vapor δD in the Asia monsoon region during summer monsoon is significantly higher than during the winter monsoon, and this to be more obvious over the land than the ocean.2) Precipitation stable isotopes, deuterium excess have obviously seasonal variation, showing high values in winter and spring, and low in summer and autumn.3) On daily scale, correlations of precipitation stable isotopes with precipitation amount, relative humidity, precipitable water and temperature were statisticed:precipitation isotope showed precipitation amount effect, humidity effect and anti-temperature effect in the entire year. In addition, we found that the correlation of precipitation stable isotopes with the above meteorological elements in monthly scale drop significantly than that in daily scale.4) On daily scale, the fluctuation of both water vapor and precipitation8D in winter and spring to be more significant than in summer and fall. We thought that it is mainly affected by significant temperature variation and complex moisture sources in winter and spring, when compared with summer and fall.5) The differnce of MWLs generated from snow samples and rainfall samples should not be entirely attributed to the secondary evaporation that under cloud, we believed that the ratio of fractionation effect for sublimation greater than condensation should be taken in mind.6)Considering water vapor flux in summer with precipitation stable isotope during the same period in2010,2011and2012, when the moisture, transported by southwest monsoon, which from the Indian Ocean, named as the far source moisture, is strong, precipitation isotopes shows low values in the Dongting Lake Basin, when the moisture, transported by southeast monsoon, from the Pacific Ocean, named as the near source moisture, precipitation isotopes shows high values in the Basin. Once again, we verified the credibility of the isotope circulation effect.7) Comparing monthly precipitation isotopes observed by GNIP with them simulated by ECHAM4, GissE and MUGCM, we found that the ability of simulating δ18O, deuterium excess and MWL are different, MUGCM is the best for δ18O, ECHAM4is the best for MWL and ECHAM4is best for deuterium excess.8) Considering the variation extent of isotopes in different water bodies, precipitation is the largest. River water isotopes in the Basin show low values in summer and fall, higth in winter and spring, which is consistent with the characteristics of the seasonal variation of precipitation isotopes, this confirmed that surface runoff is mainly recharged by precipitation in the Basin. Isotopes in well water that buried deep are with very small variations in time and significantly enriched, which shows that they have experienced a significant evaporation history and have a stable water supply.更多还原