同位素技术解析安阳河与地下水相互作用

河流与地下水相互作用研究是水文学研究的难点和热点。安阳河与地下水相互作用研究,对于安阳市水资源科学开发与管理具有重要意义。安阳河冲洪积扇地表水与地下水转化率为17%～27%。潜水位标高为80 m,向下游逐渐变成多层含水层（水位40 m）。当地降水环境同位素监测数据表明,当地大气降水线与全球大气降水线接近平行,表明该线代表本地区大气降水的氢氧同位素特征。地表水同位素值较集中,2016年8月δ18O值变化范围为-9‰~-8.7‰,δD值变化范围为-65‰~-63‰,2017年1月δ18O值变化范围为-8.5‰~-8.2‰,δD值变化范围为-63‰~-61‰,河水水化学类型为HCO3·SO4—Ca型,表明流域内地表水的同位素值受距离的影响较小。地下水稳定同位素值变化较大,2016年8月δ18O值范围为-10.4‰~-5.5‰,δD值范围为-75‰~-46‰,2017年1月δ18O值范围为-10.2‰~-5.4‰,δD值范围为-75‰~-45‰,即从接近降水值到最大值形成一条“蒸发”线。河流出山口一带地下水同位素值呈现最大蒸发值,表明地表水补给地下水,地下水化学类型为HCO3·SO4·Cl—Ca,存在明显人为污染成分。下游为大气降水补给浅层地下水,中深层地下水主要来源于中游侧向径流,水化学类型主要为HCO3—Ca·Mg型,综合分析表明,安阳河中下游（冲洪积扇）地带“三水”转换积极,并影响其水质、水量。     

Hydrogeochemical and isotopic evidence of groundwater evolution and recharge in aquifers in Beijing Plain, China

An investigation was conducted in Beijing to identify the groundwater evolution and recharge in the quaternary aquifers. Water samples were collected from precipitation, rivers, wells, and springs for hydrochemical and isotopic measurements. The recharge and the origin of groundwater and its residence time were further studied. The groundwater in the upper aquifer is characterized by Ca-Mg-HCO₃ type in the upstream area and Na-HCO₃ type in the downstream area of the groundwater flow field. The groundwater in the lower aquifer is mainly characterized by Ca-Mg-HCO₃ type in the upstream area and Ca-Na-Mg-HCO₃ and Na-Ca-Mg-HCO₃ type in the downstream area. The δD and δ¹⁸O in precipitation are linearly correlated, which is similar to WMWL. The δD and δ¹⁸O values of river, well and spring water are within the same ranges as those found in the alluvial fan zone, and lay slightly above or below LMWL. The δD and δ¹⁸O values have a decreasing trend generally following the precipitation → surface water → shallow groundwater → spring water → deep groundwater direction. There is evidence of enrichment of heavy isotopes in groundwater due to evaporation. Tritium values of unconfined groundwater give evidence for ongoing recharge in modern times with mean residence times <50 a. It shows a clear renewal evolution along the groundwater flow paths and represents modern recharge locally from precipitation and surface water to the shallow aquifers (<150 m). In contrast, according to ¹⁴C ages in the confined aquifers and residence time of groundwater flow lines, the deep groundwater is approximately or older than 10 ka, and was recharged during a period when the climate was wetter and colder mainly from the piedmont surrounding the plain. The groundwater exploitation is considered to be “mined unsustainably” because more water is withdrawn than it is replenished.     

北京市永定河流域地下水^14C年龄的初步分析

应用同位素方法初步分析北京郊区永定河流域地下水的演化特点。沿永定河冲洪积扇地下水流动方向布置取样剖面，共有取样点14个，对采集的水样进行^14C和氚含量分析，并确定地下水同位素年龄。浅层孔隙水的^14C年龄的变化范围为730～4900a，深层孔隙水为13420-22480a；^14C年龄在垂直方向上由浅部至深部逐渐增大，最大变化幅度为从3010a增至22480a；浅层孔隙水的氚含量都在14．99～30．56TU之间，深层孔隙水大部分在0．51～4．71TU之间。运用地下水^14C和氚年龄在垂向和水平方向变化的结果，验证了地下水的流向并计算了地下水的流速变化范围为5．02～62．63m／a，从山前至平原浅层地下水径流速度逐渐变小，反映了地下水水平径流强度逐渐减弱，地下水交替逐渐变差，浅层孔隙水以垂向交替为主，深层孔隙水以水平径流为主。     

Environmental isotopic study on the recharge and residence time of groundwater in the Heihe River Basin, northwestern China

The recharge and origin of groundwater and its residence time were studied using environmental isotopic measurements in samples from the Heihe River Basin, China. δ¹⁸O and δD values of both river water and groundwater were within the same ranges as those found in the alluvial fan zone, and lay slightly above the local meteoric water line (δD=6.87δ¹⁸O+3.54). This finding indicated that mountain rivers substantially and rapidly contribute to the water resources in the southern and northern sub-basins. δ¹⁸O and δD values of groundwater in the unconfined aquifers of these sub-basins were close to each other. There was evidence of enrichment of heavy isotopes in groundwater due to evaporation. The most pronounced increase in the δ¹⁸O value occurred in agricultural areas, reflecting the admixture of irrigation return flow. Tritium results in groundwater samples from the unconfined aquifers gave evidence for ongoing recharge, with mean residence times of: less than 36 years in the alluvial fan zone; about 12–16 years in agricultural areas; and about 26 years in the Ejina oasis. In contrast, groundwater in the confined aquifers had ¹⁴C ages between 0 and 10 ka BP.     

新疆焉耆盆地水环境氢氧同位素特征及其指示作用

根据焉耆盆地开都河水及其两岸地下水中的氢氧稳定同位素资料及氘过量参数(d)值,分析了焉耆盆地内不同水体的δ(D)、δ(18O)和d值的分布规律,并得到地下水的主要补给来源及其与开都河水的相互作用关系;地下水的δ(D)在-87.60‰～-61.82‰间,δ(18O)在-10.90‰～-9.73‰间;开都河水的δ(D)在-71.95‰～-58.58‰间,δ(18O)在-9.57‰～-8.64‰间。结果表明:焉耆盆地内地下水和地表水同源于山区的降水和冰雪融水,且经历了较强的蒸发作用;地下水与地表水之间的直接水力联系较弱,深层地下水主要接受开都河水在洪积扇区的入渗补给,浅层地下水主要接受河流引水灌溉入渗;不同深度地下水之间的水力联系较为密切,为统一的地下水系统。     

新疆喀什三角洲地下水流系统的水化学和同位素标记

新疆喀什三角洲地下水“水质型”缺水问题较为突出，开展地下水流系统研究具有实际意义.采用水化学和环境同位素年龄测试法，在对喀什三角洲地下水含水系统划分基础上，对地下水化学和循环更新特征进行了分析研究.结果表明:三角洲含水系统由山前倾斜冲洪积平原潜水、河流冲积平原潜水和河流冲积平原承压水构成.沿地下水流向，水化学类型演化为HCO₃·SO₄-Ca→SO₄-Ca→SO₄·Cl-Mg·Na→SO₄·Cl-Na，TDS增高，水质趋向盐化.山前倾斜冲洪积平原为溶滤-径流区，河流冲积平原为径流-累盐区.研究区地下水更新速率为0.03%~16.35%·a-1，具有山前倾斜冲洪积平原潜水>河流冲积平原潜水>河流冲积平原承压水的特征.利用3H估算得出，山前倾斜冲洪积平原潜水年龄为8~49 a，平均值为29 a；河流冲积平原潜水年龄为14~>50 a，其中上部潜水平均年龄为24 a，下部潜水平均年龄大于50 a.利用14C估算得出，河流冲积平原潜水为476~33 623 a，平均值为8 106 a；河流冲积平原承压水为5 186~34 578 a，平均值为30 043 a，与潜水比为“更古老”的水.综合以上特征得出，喀什三角洲地下水含水系统可以划分为2个更新速率较快的局部水流系统（Ⅰ₁和Ⅰ₂）和一个循环滞缓的区域水流系统（Ⅱ）.      

Hydrochemical and isotopic investigation of groundwater of Al-Batin alluvial fan aquifer,Southern Iraq

Major ions and important trace elements in addition to δ¹⁸O and δ²H were analysed for 43 groundwater samples sampled from the Al-Batin alluvial fan aquifer, South Iraq. The most dominant ions (with respect to molarity) were: Na⁺ > Cl^? > SO₄ ^2? > Ca²⁺ > Mg²⁺ > NO₃ ^? > HCO₃ ^?, with total dissolved solids (TDS) averaging 7855 mg/L. High concentrations were found for the trace elements U, Mo, V, B, Sr, and Cr. This study suggests a hydraulic connection exists near the fan apex between the uppermost part of the Al-Batin aquifer and the underlying Dammam aquifer by means of the Abu-Jir fault system. Except for the effects of extensive irrigation, fertilizer use, and poorly maintained sewers, the groundwater chemistry is mainly controlled by geological processes such as dissolution of evaporites and the enrichment of dissolved ions as a result of the high evaporation and low recharge rate. Furthermore, it is shown that the Kuwaiti fuel–oil burning during Gulf War in 1991 contributed to the enrichment of V and Mo in the studied aquifer. The spatial distribution of most ions appears to generally increase from the south-west towards the north-east, in the direction of groundwater flow. The stable isotopes show heavier values in groundwater with a gradually increasing trend in the direction of groundwater flow due to the decreasing depth to groundwater and thus increasing of evaporation from both groundwater or irrigation return water. Additionally, the stable isotope signature suggests that rainfall from sources in the Arabian Gulf and the Arabian Sea is the major source of recharge for the Al-Batin aquifer. Except for two samples of groundwater, all samples were not suitable for potable use according to the WHO standards. Most of the groundwater is suitable for some agricultural purpose and for livestock water supply. Apart from the high salinity, boron represents the most critical element in the groundwater with respect to agricultural purposes.     

Recharge and sustainability of a coastal aquifer in northern Albania

The River Mati in Albania has formed a coastal plain with Holocene and Pleistocene sediments. The outer portion of the plain is clay, with three underlying aquifers that are connected to an alluvial fan at the entry of the river into the plain. The aquifers supply water for 240,000 people. Close to the sea the aquifers are brackish. The brackish water is often artesian and found to be thousands of years old. Furthermore, the salinity, supported by δ¹⁸O results, does not seem to be due to mixing with old seawater but due to diffusion from intercalated clay layers. Heavy metals from mines in the upstream section of River Mati are not an immediate threat, as the pH buffering of the river water is good. Moreover, the heavy metals are predominantly found in suspended and colloidal phases. Two sulphur isotope signatures, one mirroring seawater sulphate in the brackish groundwater (δ³⁴S >21 ‰) and one showing the influence of sulphide in the river and the fresh groundwater (δ³⁴S <10 ‰), indicate that the groundwater in the largest well field is recharged from the river. The most serious threat is gravel extraction in the alluvial fan, decreasing the hydraulic head necessary for recharge and causing clogging of sediments.     

Environmental isotopic and hydrochemical study of water in the karst aquifer and submarine springs of the Syrian coast

The groundwater of major karst systems and submarine springs in the coastal limestone aquifer of Syria has been investigated using chemical and isotopic techniques. The δ¹⁸O values of groundwater range from ?6.8 to ?5.05‰, while those for submarine springs vary from ?6.34 to +1.08‰ (eastern Mediterranean seawater samples have a mean of +1.7‰). Groundwater originates from the direct infiltration of atmospheric water. Stable isotopes show that the elevation of the recharge zones feeding the Banyas area (400–600 m a.s.l.) is higher than that feeding the Amrit area (100–300 m a.s.l.). The ¹⁸O_extracted (¹⁸O content of the seawater contribution) for the major submarine springs suggests a mean recharge area elevation of 600–700 m a.s.l., and lower than 400 m a.s.l. for the spring close to Amrit. Based on the measured velocity and the percentage of fresh water at the submarine springs outlet, the estimated discharge rate is 350 million m³/year. The tritium concentrations in groundwater (1.6–5.9 TU) are low and very close to the current rainfall values (2.9–5.6 TU). Adopting a model with exponential time distribution, the mean turnover time of groundwater in the Al-sen spring was evaluated to be 60 years. A value of about 3.7 billion m³ was obtained for the maximum groundwater reservoir size.     

Prediction of the run-out distance of the debris flow based on the velocity attenuation coefficient

Our aim is to determine the run-out distance of the debris flow that is crucial in the assessment, prevention and control of the debris flow hazard. Based on the variation characteristic of debris flow velocity in the alluvial fan, this paper proposes the calculation method of the velocity attenuation coefficient of the debris flow. By defining the velocity attenuation coefficient and deducing its calculating formula, this paper puts forward a new method to determine the run-out distance of the debris flow based on the velocity attenuation coefficient, and Gangou debris flow in Luding County, Sichuan Province is selected as a case for calculation and verification. Having 10 m as its measuring spacing, this paper measured 19 sections at the alluvial fan of the Gangou debris flow (among them, 11 sets of data are valid). And based on the measurement, this paper analyzes the characteristic of the velocity attenuation and calculates its velocity attenuation coefficient after the 2005 debris flow. The study indicates that when the velocity of Gangou debris flow at the alluvial fan is greater than 12 % of the initial velocity (at the mouth of gully), the attenuation is quite remarkable. But when the velocity at the alluvial fan is less than 12 % of the initial velocity, the attenuation is quite slow. Besides, when Gangou debris flow rushes out of the gully mouth (the initial velocity is 10 m/s) and when it attenuates to the 32 time, its velocity is less than 0.1 m/s, the debris flow is considered to stop flowing, and the run-out distance of Gangou debris flow is calculated to be 320 m. But the present alluvial fan of Gangou debris flow is measured to be 285 m in length, and the calculated run-out distance is 320 m, which is 35 m longer than its present length. This means when the debris flow runs out in 2005, it blocked up the main river (Dadu River) in some extent. And this finding is generally in accordance with that from the field survey. The findings can be of theoretical and practical significance in the debris flow hazard assessment, as well as its prevention and mitigation.     

Evolution of the groundwater system under the impacts of human activities in middle reaches of Heihe River Basin (Northwest China) from 1985 to 2013

Investigation of the evolution of the groundwater system and its mechanisms is critical to the sustainable management of water in river basins. Temporal and spatial distributions and characteristics of groundwater have undergone a tremendous change with the intensity of human activities in the middle reaches of the Heihe River Basin (HRB), the second largest arid inland river basin in northwestern China. Based on groundwater observation data, hydrogeological data, meteorological data and irrigation statistical data, combined with geostatistical analyses and groundwater storage estimation, the basin-scaled evolution of the groundwater levels and storage (from 1985 to 2013) were investigated. The results showed that the unbalanced allocation of water sources and expanded cropland by policy-based human activities resulted in the over-abstraction of groundwater, which induced a general decrease in the water table and groundwater storage. The groundwater level has generally fallen from 4.92 to 11.49 m from 1985 to 2013, especially in the upper and middle parts of the alluvial fan (zone I), and reached a maximum depth of 17.41 m. The total groundwater storage decreased by 177.52?×?10⁸ m³; zone I accounted for about 94.7 % of the total decrease. The groundwater balance was disrupted and the groundwater system was in a severe negative balance; it was noted that the groundwater/surface-water interaction was also deeply affected. It is essential to develop a rational plan for integration and management of surface water and groundwater resources in the HRB.     

北京平原区地下水位预警初步研究

借鉴美国地质调查局在宾夕法尼亚的地下水位预警方法,从统计学的角度,探索了北京平原区地下水预警方法。对监测井多年长期监测资料进行百分位统计分析,把同一时间(月平均、旬平均、日平均)地下水水位(头)标高值的最小值至百分位5、百分位5至百分位10、百分位10至百分位25、百分位25至百分位75范围内的地下水位分别定义为红色、橙色、黄色和蓝色预警,形成地下水位预警判据。根据地下水水位实时监测数据,实时判定监测井代表区域的地下水预警等级,同时修正和完善地下水位预警判据,称之为监测井单点预警,监测井代表的同一层位的区域的集合,构成不同含水层的地下水位区域预警。对北京平原区2009年12月的地下水位预警结果为:潮白河冲洪积扇顶部和中部潜水含水层地下水位为红色预警,前缘为黄色预警,冲洪积平原为蓝色预警区;城区以南地区为红色预警,海淀山后的西北部地区为红色预警,永定河冲积扇和冲积平原大部分地区黄色和蓝色预警,大石河冲洪积扇地区均为蓝色预警;承压水含水层在潮白河冲洪积扇的前缘为红色预警,冲洪积平原为蓝色预警,北运河山前地带均为橙色预警,城区东、东南地区为橙色和黄色预警,少数地区为橙色预警,除上述地区以外,承压水均为蓝色预警。北京市平原区主要地下水开采地区地下水位已经处于历史的较低水位处,特别是潮白河冲积扇中上部地区以及平谷盆地,地下水位几乎全部处于红色预警区。该预警方法原理明确,方法简便,有望在地下水主要开采区推广应用。     

Investigation on the hydrodynamics of Ganga Alluvial Plain using environmental isotopes: a case study of the Gomati River Basin, northern India

An investigation using environmental isotopes (δ¹⁸O and δD) was conducted to gain insight into the hydrological processes of the Ganga Alluvial Plain, northern India. River-water, shallow-groundwater and lake-water samples from the Gomati River Basin were analyzed. During the winter season, the δ¹⁸O and δD compositions of the Gomati River water ranged from ?1.67 to ?7.62 ‰ and ?25.08 to ?61.50 ‰, respectively. Deuterium excess values in the river water (+0.3 to ?13 ‰) and the lake water (?20 ‰) indicate the significance of evaporation processes. Monthly variation of δ¹⁸O and δD values of the Gomati River water and the shallow groundwater follows a similar trend, with isotope-depleted peaks for δ¹⁸O and δD synchronized during the monsoon season. The isotopically depleted peak values of the river water (δ¹⁸O?=??8.30 ‰ and δD?=??57.10 ‰) can be used as a proxy record for the isotopic signature of the monsoon precipitation in the Ganga Alluvial Plain.     

衡水地区咸水层沉积物粒度及氘氧同位素的古气候指示

衡水地区的咸水层特征一直备受关注.为了探讨咸水层分布区的沉积环境与咸水形成期的古气候特征,利用钻孔(深度130 m)采集了衡水地区咸水层沉积物,进行了沉积物粒度和粘性土孔隙水氘氧同位素测试.沉积物粒度标准偏差显示,剖面上由深至浅,沉积时期水动力呈由弱到强再到弱的变化趋势,其中水动力强段为90~65 m,为厚层砂砾层.孔隙水TDS和δ18O特征显示在6 m以上受到大气降水和人类活动的影响,并且主要是以淡水灌溉影响为主.剖面上粘性土孔隙水的δ18O在130~90 m平均值为-11.5‰,65~29 m平均值为-12.1‰,23~0 m为-10.6‰,而下部淡水含水层地下水δ18O为-9.8‰,上部咸水含水层地下水δ18O为-8.2‰,粘性土孔隙水δ18O明显偏负于含水层的地下水,反映保存记录了古气候信息.130~90 m,δ18O先增大后减小反映温度先升高后降低;65~29 m,δ18O反映温度偏低的气候特征;23~0 m,δ18O相对比较稳定,总体偏正,反映了全新世为一个相对较为稳定但较高的温度.      

Hydrogeochemistry and possible sulfate sources in karst groundwater in Chongqing, China

Groundwater from karst subterranean streams is among the world’s most important sources of drinking water supplies, and the hydrochemical characteristics of karst water are affected by both natural environment and people. Therefore, the study of karst groundwater hydrochemistry and its solutes’ sources is very important to ensure the normal function of life support systems. This paper focused on the major ion chemistry and sulfate isotope of karst groundwater in Chongqing for tracing the sulfate sources and related hydrochemical processes. Hydrochemical types of karst groundwater in Chongqing were mainly of the Ca-HCO₃ type or Ca(Mg)-HCO₃ type. However, some hydrochemical types were the K + Na + Ca-SO₄ type (G25 site) or Ca-HCO₃ + SO₄ type (G26 and G14 sites), indicating that the hydrochemistry of these sites may be strongly influenced by anthropogenic activities or unique geological characteristics. The δ³⁴S-SO₄ ^2? of collected karst groundwater sample fell into a range of ?6.8 to 21.5 ‰, with a mean value of 5.6 ‰. In dolomite aquifer, the δ³⁴S-SO₄ ^2? value ranges from ?4.3 to 11.0 ‰, and in limestone aquifer, it ranged from ?6.8 to 21.5 ‰. The groundwater samples from different land use types showed distinctive δ³⁴S-SO₄ ^2? value. The δ³⁴S-SO₄ ^2? value of groundwater samples had range of ?6.8 to 16.7 ‰ (mean 4.0 ‰, n = 11) in cultivated land areas, 1.5–21.5 ‰ (mean 7.2 ‰, n = 20) in forested land areas, and ?4.3 to 0.8 ‰ (mean ?1.7 ‰, n = 2) in coalmine areas. The δ³⁴S-SO₄ ^2? values of groundwater samples collected from factory area and town area were 2.2 and 9.9 ‰, respectively. According to the δ³⁴S information of potential sulfate sources, this paper discussed the possible sulfate sources of collected karst groundwater samples in Chongqing. The variations of both δ³⁴S and 1/SO₄ ^2? values of the groundwater samples indicated that the atmospheric acid deposition (AAD), dissolution of gypsum (GD), oxidation of sulfide mineral (OS) or anthropogenic inputs (SF: sewage or fertilizer) contributed to sulfate in karst groundwater. The influence of oxidation of sulfide mineral, atmospheric acid deposit and anthropogenic inputs to groundwater in Chongqing karst areas was much widespread. For protecting, sustaining, and utilizing the groundwater resources, the sewage possibly originating from urban, mine or industrial area must be controlled and treated, and the use of fertilizer should be limited.     

Factors responsible for high arsenic concentrations in two groundwater catchments in Taiwan

High As contents in groundwater were found in two neighboring catchments – the Chianan plain and the southern Choushui river alluvial fan in Taiwan. The groundwater quality, the redox potential and the As distribution of the Chianan plain were characterized using factor analysis, redox zoning and a geochemical program. The results were compared with those of the southern Choushui river alluvial fan. Possible As release mechanisms are also elucidated. Factors 1 and 2 of the groundwater in the Chianan plain – the salinization factor and the As enrichment factor – are similar to those in the southern Choushui river alluvial fan. However, the spatial distribution of reductive tendency in the Chianan plain is different to that in the Choushui river alluvial fan, and yields spatially distinct hydrogeochemical environments in these two neighboring areas. The reduction potential in the Chianan plain is stronger than that in the Choushui river alluvial fan. The difference between the reduction potentials in these two vicinal areas influences the concentrations of As in groundwater. The reductive dissolution of As-rich Fe oxyhydroxide is suggested to be the major mechanism for release of As to the groundwater in the Chianan plain and the Choushui river alluvial fan of Taiwan.     

Malibogazi groundwater dam: an alternative model for semi-arid regions of Turkey to store and save groundwater

In central Turkey, there are serious groundwater quality problems in the main river valleys and plains, and even in the lower parts of the secondary basins due to the underlying evaporitic geological formations. Groundwater quality improves towards the upstreams in the alluvium aquifers in most secondary valleys; however, groundwater potential decreases as well due to the reduced basin area, areal extent and thickness of the aquifers. The Malibogazi valley is situated to some 100 km north of Ankara. The dam constructed in the narrowest section of the valley has an average storage coefficient of 0.2 and the total and active storage capacities of 110,000 and 55,000 m³, respectively. The 20-m-thick aquifer extends for 6–7 km till the dam site within valley with an average width of 50–70 m. It mostly comprises sandy–gravely alluvial deposits. Malibogazi groundwater dam is a valve-controlled gravity flow dam. When the valves are opened, the water from the aquifer reservoir flows by gravity through supply pipe to the main irrigation channel, but when the valves are closed the water is stored in the aquifer and groundwater level begins to rise. Average groundwater discharge was about 20 l/s in 2005–2006 irrigation period. In this period, groundwater levels were about 2 m higher compared to the groundwater levels in the same seasons before the construction of the groundwater dam. Because the dam is of gravity flow type, it means an important contribution to the farmers since the operation cost is quite low. Malibogazi groundwater dam represents one of the first experiences of Turkey in the field of groundwater storage. Although the dam has small storage capacity, it may be a model for Turkey from the viewpoints of investigation, construction, dam wall, intake facility and measurements etc.     

Groundwater mixing and mineralization processes in a mountain–oasis–desert basin,northwest China: hydrogeochemistry and environmental tracer indicators

Hydrogeochemistry and environmental tracers (²H, ¹⁸O, ⁸⁷Sr/⁸⁶Sr) in precipitation, river and reservoir water, and groundwater have been used to determine groundwater recharge sources, and to identify mixing characteristics and mineralization processes in the Manas River Basin (MRB), which is a typical mountain–oasis–desert ecosystem in arid northwest China. The oasis component is artificial (irrigation). Groundwater with enriched stable isotope content originates from local precipitation and surface-water leakage in the piedmont alluvial–oasis plain. Groundwater with more depleted isotopes in the north oasis plain and desert is recharged by lateral flow from the adjacent mountains, for which recharge is associated with high altitude and/or paleo-water infiltrating during a period of much colder climate. Little evaporation and isotope exchange between groundwater and rock and soil minerals occurred in the mountain, piedmont and oasis plain. Groundwater δ²H and δ¹⁸O values show more homogeneous values along the groundwater flow direction and with well depths, indicating inter-aquifer mixing processes. A regional contrast of groundwater allows the ⁸⁷Sr/⁸⁶Sr ratios and δ¹⁸O values to be useful in a combination with Cl, Na, Mg, Ca and Sr concentrations to distinguish the groundwater mixing characteristics. Two main processes are identified: groundwater lateral-flow mixing and river leakage in the piedmont alluvial–oasis plain, and vertical mixing in the north oasis plain and the desert. The ⁸⁷Sr/⁸⁶Sr ratios and selected ion ratios reveal that carbonate dissolution and mixing with silicate from the southern mountain area are primarily controlling the strontium isotope hydrogeochemistry.     

北京市城近郊区地下水的环境同位素研究

应用环境同位素方法,研究北京城近郊区地下水演化规律。沿北京市永定河冲洪积扇地下水流动方向取样15组(D、18O、T、14C及全分析),对所取水样进行D、18O、T、14C分析,并确定地下水同位素年龄。运用地下水14C和T含量在垂向和水平方向变化的结果,验证了地下水的流向并计算了地下水的流速变化范围为5·02~62·63m/a,从山前至平原浅层地下水径流速度逐渐变小,反映了地下水水平径流强度逐渐减弱,地下水交替逐渐变差;浅层孔隙水以垂向交替为主,深层孔隙水以水平径流为主。对地下水D、18O之间的关系进行分析,从而判断地下水的补给来源等。     

黑河干流浅层地下水与地表水相互转化的水化学特征

通过分析黑河干流地表水与地下水的水化学特征,识别沿黑河干流不同地带地下水与地表水的相互转化关系.研究结果表明:(1)在祁连山区,地下水与地表水的转化以地下水向河流排泄为主.(2)南部盆地,在山前戈壁带,出山河水入渗转化为地下水;溢出带地下水以泉的形式转化为地表水;进入细土平原后,汛期河水补给地下水,非汛期地下水补给河水;在农灌区引河水通过田间入渗补给地下水.(3)北部盆地,在金塔灌区,地下水主要接受引水灌溉入渗补给;在金塔灌区到额济纳旗,河流入渗转化为地下水.