Nitrate pollution of groundwater in the Yellow River delta,China

Nitrate pollution of groundwater in the Yellow River delta, China is an important issue related not only to nitrate dispersion and health concerns but also to mass transport and interactions of groundwater, sea, and river waters in the coastal area. The spatial distribution of nitrate, nitrate sources, and nitrogen transformation processes were investigated by field surveys and geochemical methods. Nitrate occurred mainly in shallow layers and had a spatial distribution coinciding with geomorphology and land/water use. Irrigation water from the Yellow River and anthropogenic waste are two main nitrogen sources of nitrate in the delta, and both denitrification and mixing processes could take place according to characteristics identified by ionic and isotopic data.     

Management scenarios for the Jordan River salinity crisis

Recent geochemical and hydrological findings show that the water quality of the base flow of the Lower Jordan River, between the Sea of Galilee and the Dead Sea, is dependent upon the ratio between surface water flow and groundwater discharge. Using water quality data, mass-balance calculations, and actual flow-rate measurements, possible management scenarios for the Lower Jordan River and their potential affects on its salinity are investigated. The predicted scenarios reveal that implementation of some elements of the Israel–Jordan peace treaty will have negative effects on the Jordan River water salinity. It is predicted that removal of sewage effluents dumped into the river (∼13 MCM/a) will significantly reduce the river water’s flow and increase the relative proportion of the saline groundwater flux into the river. Under this scenario, the Cl content of the river at its southern point (Abdalla Bridge) will rise to almost 7000 mg/L during the summer. In contrast, removal of all the saline water (16.5 MCM/a) that is artificially discharged into the Lower Jordan River will significantly reduce its Cl concentration, to levels of 650–2600 and 3000–3500 mg/L in the northern and southern areas of the Lower Jordan River, respectively. However, because the removal of either the sewage effluents or the saline water will decrease the river’s discharge to a level that could potentially cause river desiccation during the summer months, other water sources must be allocated to preserve in-stream flow needs and hence the river’s ecosystem.     

The thermal springs of Jordan

The thermal springs alongside Wadi Araba, Dead Sea and Jordan valley, Jordan, were investigated and sampled in a comprehensive field study of 2 weeks. Conventional physicochemical properties were measured in situ; dissolved solids and isotopic composition were analyzed. Two main spring locations on the east side of the Dead Sea were mapped. It became evident, that the hottest springs are among the closest to prominent faults; some springs are controlled by gas lift. Jordan’s hot springs are described by means of a broad hydrochemical and physicochemical data set and several figures are presented. Based on their hydrochemistry, the thermal springs are classified into four thermal provinces. Water genesis is discussed. Several geothermometers are applied to estimate reservoir temperatures. Observed discharge rate, water temperature and isotopic composition are compared with data from the literature. Although discharge and water temperature are reported to be constant over the last decades, groundwater overexploitation led to a shift of the isotopic composition, what is documented for the first time in Jordan. Thus, the effect of groundwater mining on Jordan’s hot springs can be stated as a fact.     

Groundwater Recharge and Mixing in Arid and Semiarid Regions: Heihe River Basin, Northwest China

A sound understanding of groundwater recharged from various sources occurring at different time scales is crucial for water management in arid and semi-arid river basins. Groundwater recharge sources and their geochemical evolution are investigated for the Heihe River Basin(HRB) in northwest China on the basis of a comprehensive compilation of geochemical and isotopic data. Geochemical massbalance modeling indicates that mountain-block recharge accounts for a small fraction(generally less than 5%) of the shallow and deep groundwater sustaining the oasis, whereas infiltration of rivers and irrigation water contribute most of the groundwater recharge. Dedolomitization is the primary process responsible for the changes in groundwater chemical and carbon isotope compositions from the piedmont to the groundwater discharge zone, where the dedolomitization is very likely enhanced by modern agricultural activities affecting the shallow groundwater quality. Analysis of radioactive isotopes suggests that these primary recharge sources occur at two different time scales. Radiocarbon-derived groundwater age profiles indicate a recharge rate of approximately 12 mm/year, which probably occurred during 2000–7000 years B.P., corresponding to the mid-Holocene humid period. The recharge of young groundwater on the tritium-dated time scale is much higher, about 360 mm/year in the oasis region. Infiltration from irrigation canals and irrigation return flow are the primary contributors to the increased young groundwater recharge. This study suggests that groundwater chemistry in the HRB has been influenced by the complex interaction between natural and human-induced geochemical processes and that anthropogenic effects have played a more significant role in terms of both groundwater quantity and quality.     

珠江口盆地珠江组混积岩中有孔虫的矿化特征与机制

珠江口盆地白云凹陷是我国现今深水油气勘探的重要地区,在其南侧的荔湾X构造的珠江组在3 000~3 281 m以混积岩沉积为主.以荔湾X构造内含有孔虫混积岩为研究对象,通过开展岩石学和同位素地球化学研究,确定了有孔虫宿主岩石类型以及有孔虫矿化的岩相学特征,重点探讨了有孔虫的矿化机制,并最终建立了有孔虫的矿化模式.荔湾X构造珠江组混积岩的生物碎屑以有孔虫碎屑为主,有孔虫壳由刃状、等径状方解石或铁方解石组成.有孔虫的房室可分为未充填、半充填和全充填3种类型.根据有孔虫房室充填的主要自生矿物类型、产状及相互关系,可将有孔虫矿化按其形成的先后分为黄铁矿化、铁方解石化、片钠铝石化和铁白云石化4种类型,其中黄铁矿的形成可能与有孔虫软体组织的生物降解有关,铁方解石可能与有机质热脱羧作用有关,片钠铝石和铁白云石中的“碳”有深部来源的岩浆成因CO₂的贡献.      

云南水富地热钻孔水的地质地球化学特征

本文讨论了金沙江河谷区云南水富地段内地热带的区域地质背景和主要地质构造格局,并通过对区内地热钻孔水及邻近的地表泉点、地表水的同位素与水化学分析研究,地热水的形成和成藏的地质地球化学过程探讨,指出地热区位于多方向构造的复合部位,发育的断裂构造利于富集和提供良好的热源和深部地下水循环通道,属中低温对流型地热系统;源于大气降水,补给区系区内最高,运移途径长,循环深度大,在含水层内的滞留时间最长,与热储层的能量交换充分.地热水具有水温稳定、水量大及承压的特点,有较大的开发潜力.     

Uranium isotopes (234U/238U) in rivers of the Yukon Basin (Alaska and Canada) as an aid in identifying water sources, with implications for monitoring hydrologic change in arctic regions

The ability to detect hydrologic variation in large arctic river systems is of major importance in understanding and predicting effects of climate change in high-latitude environments. Monitoring uranium isotopes (²³⁴U and ²³⁸U) in river water of the Yukon River Basin of Alaska and northwestern Canada (2001?C2005) has enhanced the ability to identify water sources to rivers, as well as detect flow changes that have occurred over the 5-year study. Uranium isotopic data for the Yukon River and major tributaries (the Porcupine and Tanana rivers) identify several sources that contribute to river flow, including: deep groundwater, seasonally frozen river-valley alluvium groundwater, and high-elevation glacial melt water. The main-stem Yukon River exhibits patterns of uranium isotopic variation at several locations that reflect input from ice melt and shallow groundwater in the spring, as well as a multi-year pattern of increased variability in timing and relative amount of water supplied from higher elevations within the basin. Results of this study demonstrate both the utility of uranium isotopes in revealing sources of water in large river systems and of incorporating uranium isotope analysis in long-term monitoring of arctic river systems that attempt to assess the effects of climate change.     

Geochemical characterization of the Biga Peninsula thermal waters (NW Turkey)

Thermal water chemistry from the Biga Peninsula (NW Turkey) was investigated in order to discriminate among hydrochemical facies, and isotopic groups and identify the major geochemical processes. A systematic hydrogeochemical survey was carried out, incorporating new data as well as results from the previous studies. Results were used to further develop hydrogeological and geochemical models. Thermal water compositions were classified into four groups and the processes affecting evolution of water compositions were interpreted. Types 1, 2 and 3 are representatives of water corresponding to sulfate dominant fluids (mainly NaSO₄-type), chloride dominant fluids (mainly NaCl-type), and bicarbonate dominant fluids (Na- or CaHCO₃-type), respectively. Group 4 comprises the fluids with compositions that are not dominated by any distinctive anion. Groundwater infiltrates and circulates through the marbles of the Paleozoic basement. The isotopic composition of thermal waters revealed that deep infiltration of meteoric water took place in periods of changed climatic conditions.     

河套灌区西部浅层地下水咸化机制

浅层地下水水位埋深浅、含盐量高,是导致河套灌区土壤次生盐渍化的重要原因.以河套灌区西部地区为研究区,通过对浅层地下水的水化学和氢氧同位素特征分析以及水文地球化学模拟,探讨了灌区浅层地下水的补给来源和主控水-岩作用过程,并定量估算了蒸发作用对浅层地下水含盐量的影响.研究区内浅层地下水为弱碱性咸水,pH为7.23~8.45,总溶解性固体（total dissolved solids,TDS）变化范围为371~7 599 mg/L;随着地下水咸化程度增大,水化学类型由HCO₃-Na·Mg·Ca型向Cl-Na型过渡.引黄灌溉和大气降水是浅层地下水的主要补给来源,径流过程中浅层地下水受蒸发作用和植物蒸腾作用影响,地下水化学组分主要来源于蒸发盐溶解和硅酸盐风化水解,并受强烈的蒸发作用和离子交换作用影响.水文地球化学模拟和主成分分析结果显示,蒸发作用和岩盐溶解作用对区内浅层地下水咸化贡献最大,石膏和白云石等矿物的溶解、硅酸盐的水解、Na-Ca离子交换以及局部地形起伏对地下水咸化过程也有较大贡献.      

Chemical and strontium isotopic characteristics of shallow groundwater in the Ordos Desert Plateau,North China: Implications for the dissolved Sr source and water–rock interactions

In this study, the chemical and Sr isotopic compositions of shallow groundwater and rainwater in the Ordos Desert Plateau, North China, and river water from the nearby Yellow River, are investigated to determine the dissolved Sr source and water–rock interactions, and quantify the relative Sr contribution from each end-member. Three groundwater systems have been identified, namely, GWS-1, GWS-2 and GWS-3 according to the watershed distribution in the Ordos Desert Plateau. Ca²⁺ and Mg²⁺ are the most dominant cations in GWS-1, while Na⁺ is dominant in GWS-3. In addition, there is more SO₄²⁻ and less Cl⁻ in GWS-1 than in GWS-3. The shallow groundwater in GWS-2 seems to be geochemically between that in GWS-1 and GWS-3. The ⁸⁷Sr/⁸⁶Sr ratios of the shallow groundwater are high in GWS-1 and GWS-2 and are low in GWS-3. By geochemically comparing the nearby Yellow River, local precipitation and deep groundwater, the shallow groundwater is recharged only by local precipitation. The ionic and isotopic ratios indicate that carbonate dissolution is an important process controlling the chemistry of the shallow groundwater. The intensity of the water–rock interactions varies among the three groundwater systems and even within each groundwater system. Three end-members controlling the groundwater chemistry are isotopically identified: (1) precipitation infiltration, (2) carbonate dissolution and (3) silicate weathering. The relative Sr contributions of the three end-members show that precipitation infiltration and carbonate dissolution are the primary sources of the shallow groundwater Sr in GWS-3 whereas only carbonate dissolution is responsible for the shallow groundwater Sr in GWS-1 and GWS-2. Silicate weathering seems insignificant towards the shallow groundwater's chemistry in the Ordos Desert Plateau. This study is helpful for understanding groundwater chemistry and managing water resources.     

用氢氧稳定同位素评价闽江河口区地下水输入

通过分析闽江河口区降水、地表水和地下水的氢氧稳定同位素特征,揭示降水的环境同位素效应和地下水的形成演化规律,定量评价河口区多种水体的混合过程及地下水输入量。夏季的降水氢氧同位素组成相对贫化,呈现出降雨量效应。在δ18O与δD关系图上,闽江北岸基岩裂隙水、平原及丘陵区浅层地下水均落在福州降水线上,而南岸平原及丘陵区浅层地下水大部分落在福州降水线右下方,其拟合线与降水线交点与5~9月农灌期降水氢氧同位素加权值接近,表明北岸地下水主要来自降水补给,而南岸地下水同时接受灌溉水和降水补给,并在入渗过程中经历了不同程度的蒸发作用。闽江河口段除接受两岸地下水补给外,局部河段还接受断裂带裂隙水补给。将线性端元混合模型、数字高程模型和地下水文分析法结合起来定量评价地下水的输入和各水体的混合过程,结果显示,在河口段淡水区,地下水混合比率上限为8.8%,其中包括0.4%的断裂带裂隙水;在河口段淡咸水混合区,淡水(河水、地下水)和海水的混合比为53:47,其中地下水的保守混合比率为1.7%;枯水期闽江河口段地下水保守输入量为87.0 m3/s,是闽江径流量的12.8%。     

莺歌海盆地乐东区片钠铝石特征及其对浅层CO2充注的指示

作为天然CO₂的示踪矿物,片钠铝石的形成与CO₂充注密切相关.莺歌海盆地乐东区乐东X构造莺歌海组-黄流组CO₂气藏内发育含片钠铝石砂岩,在开展的岩石学和地球化学研究基础上,确定了研究区片钠铝石的产状和纵向分布特征,分析了形成片钠铝石的“碳来源”和气水条件,进而探讨了与片钠铝石具有成因联系的CO₂的成因.乐东X构造含片钠铝石砂岩为细—极细粒长石石英砂岩和岩屑石英砂岩,片钠铝石主要以充填孔隙及交代颗粒的形式产出,是成岩共生序列中形成较晚的自生矿物之一.在纵向上,片钠铝石仅集中发育于高含CO₂气层的底部以及其下的水层中,这一分布特征以地质实例的形式证实了片钠铝石的形成需要水的参与.研究区浅层CO₂充注后形成的碳酸盐矿物为片钠铝石和铁白云石.片钠铝石的碳氧同位素特征表明形成片钠铝石的“碳”与LDX构造气层中CO₂具有相同的碳来源,以无机幔源成因CO₂为主.红河断裂以及莺歌海盆地中央坳陷内一系列底辟构造及伴生的垂向裂隙可能为CO₂的运移通道.      

珠江三角洲经济区农业地质与生态地球化学调查成果综述

2005年中国地质调查局与广东省人民政府联合开展珠江三角洲经济区农业地质与生态地球化学调查项目。通过开展多目标区域地球化学调查、区域生态地球化学评价、局部生态地球化学评价和总体综合评价,系统完成了珠江三角洲经济区47 954 km²(包括10 m水深以浅的近岸海域)的生态地球化学调查与评价。按照双层网格化方法系统采集了陆域土壤、近岸海域和珠江水系主要河流沉积物表层和深层样品,测试了71项元素和指标,建立了珠江三角洲经济区土壤、沉积物地球化学背景值和基准值,全面查明了珠江三角洲经济区土壤环境质量状况。定量计算了镉、铅、汞等主要异常元素经河流、成土过程等自然来源和大气干湿沉降、施肥、灌溉、使用农药等人为来源贡献量,阐明了其迁移转化途径及生态安全性。项目紧密结合本地区特点,在国内首次开展了三角洲形成演化过程地球化学研究、区域辐射环境质量评价、酸雨对土壤质量影响的模拟实验、土壤环境质量地方标准研究与制订等工作。     

珠江三角洲经济区生态地球化学评价

土壤重金属污染是珠江三角洲地区主要的生态环境问题之一,直接影响到区域生态系统的稳定和食品安全。通过开展多目标区域地球化学调查、区域生态地球化学评价、局部生态地球化学评价和总体综合评价,系统完成了珠江三角洲经济区47954 km²(包括10 m水深以浅的近岸海域)的生态地球化学调查与评价。按照双层网格化方法系统采集了陆域土壤、近岸海域和珠江水系的主要河流沉积物表层和深层样品,测试了71项元素和指标,建立了珠江三角洲经济区土壤、沉积物地球化学背景值和基准值,首次对珠江三角洲地区区域地球化学特征进行了系统全面的调查,全面查明了珠江三角洲经济区土壤环境质量状况,区内一级和二级土壤分别占总面积的19.9%和57.3%,三级和三级以上土壤占22.8%。定量计算了镉、铅、汞等主要异常元素经河流、成土过程等自然来源和大气干湿沉降、施肥、灌溉、使用农药等人为来源贡献量,阐明了其迁移转化途径及生态安全性。结合研究区特点,系统开展了三角洲形成演化过程的地球化学研究,并在国内首次制定了符合地区特点的珠江三角洲经济区土壤环境质量地方标准。     

黄土高原丘陵沟壑区包气带土壤水运移过程

包气带土壤水运移过程是黄土高原生态修复中亟需回答的关键科学问题。环境同位素方法可获取其他方法难以获取的水文过程信息。通过对黄土高原丘陵沟壑区羊圈沟小流域降水、包气带0~150 cm土壤水和绣线菊（Spiraea salicifolia）木质部水等样品的同位素δD和δ18O进行测定。结果表明:羊圈沟小流域降水同位素组成受蒸发作用影响较大,呈现明显分馏效应。包气带土壤水、降水与木质部水同位素组成存在明显月份变化特征。降水是土壤水的主要补给来源,灌丛的水分利用来源主要为降水和土壤水,符合降水-土壤水-植被水的运移特征。灌丛木质部水和20~40 cm土壤水δD和δ18O最为接近,20~40 cm土壤水是灌丛水分利用的主要来源。研究揭示了包气带土壤水运移过程及植物水分利用来源,为土壤水运移过程、模型结构与参数识别等提供科学依据。     

Composition and Origin of Shallow Biogenetic Gases in the Baise Basin, South China

Based on the analytical data of over 30 gas samples, combined with geochemical and geological backgrounds, the composition and distribution characteristics of shallow biogenetic gases in the Baise Basin, a Tertiary residual basin in southern China, were extensively investigated, and the origin and formation mechanism tentatively approached. The shallow gases are primarily composed of gaseous hydrocarbons, generally accounting for over 90%. The abundances of methane and C2＋ homologues show a relatively wide range of variation, mainly 50%-100% and 0%-50%, respectively, depending on the mixing proportions between biogenetic and thermogenic gases. A highly negative carbon isotope is the significant signature for the shallow gases with δ^13C1 values of -55‰ to -75‰. According to molecular and isotopic compositions and light hydrocarbon parameters, the shallow gases in the basin can be classified into three types of origins： biogenetic gas, biogenetic/thermogenic mixed gas, and oii-biodegraded gas. They exhibit regular distribution both spatially and temporally, and are believed to be associated with the maturity of adjoining gas source rocks and biodegraded oil accumulation. The Baigang and Nadu source rocks can be considered to have experienced early and late gas generation during early burial and after basin uplift respectively. A late accumulation mechanism of multiple gas sources is put forward for the formation of the shallow gas reservoirs, which is responsible for the variations in chemical and isotopic composition of the gases in depth profile.     

Defining the dynamics of groundwater in Serra da Estrela Mountain area, central Portugal: an isotopic and hydrogeochemical approach

In a multidisciplinary approach, geological, geomorphologic, structural, hydrogeochemical and isotopic surveys were conducted on the Serra da Estrela groundwater system (central Portugal) in order to establish/develop a conceptual circulation model of the Caldas de Manteigas thermomineral system. A detailed study of the isotopic and geochemical composition of surface waters (e.g. Zêzere River), shallow groundwaters (cold dilute springs), and thermomineral waters was carried out to characterize the distribution of isotopes in waters of this mountainous region, and to determine the origin and possible recharge locations of the thermomineral system. Special attention was dedicated to isotopic tracers and their role in the definition of the thermomineral waters??conceptual model, considering: (1) the δ¹⁸O fractionation gradient; (2) the mean isotopic composition of the thermomineral waters in the region; and (3) the estimation of snowmelt contribution as a source of groundwater recharge at Serra da Estrela. The recharge of the thermomineral aquifer takes place on the more permeable zones of the granitic massif, associated with the main tectonic structures, whereas the recharge of the shallow aquifers seems to take place mostly in the plateaus, although another part of the recharge may occur in the slopes of the Zêzere River valley.     

A geochemical study of the impact of irrigation and aquifer lithology on groundwater in the Upper Yakima River Basin,Washington, USA

The Yakima River, a major tributary of the Columbia River, is currently overallocated in its surface water usage in part because of large agricultural water use. As a result, groundwater availability and surface water/groundwater interactions have become an important issue in this area. In several sub-basins, the Yakima River water is diverted and applied liberally to fields in the summer creating artificial recharge of shallow groundwater. Major ion, trace element, and stable isotope geochemistry of samples from 26 groundwater wells from a transect across the Yakima River and 24 surface waters in the Kittitas sub-basin were used to delineate waters with similar geochemical signatures and to identify surface water influence on groundwater. Major ion chemistry and stable isotope signatures combined with principal component analysis revealed four major hydrochemical groups. One of these groups, collected from shallow wells within the sedimentary basin fill, displays temporal variations in NO₃ and SO₄ along with high δ¹⁸O and δD values, indicating significant contribution from Yakima River and/or irrigation water. Two other major hydrochemical groups reflect interaction with the main aquifer lithologies in the basin: the Columbia River basalts (high-Na groundwaters), and the volcaniclastic rocks of the Ellensburg Formation (Ca–Mg–HCO₃ type waters). The fourth major group has interacted with the volcaniclastic rocks and is influenced to a lesser degree by surface waters. The geochemical groupings constrain a conceptual model for groundwater flow that includes movement of water between underlying Columbia River basalt and deeper sedimentary basin fill and seasonal input of irrigation water.     

Sr isotopic signature of the Ganga Alluvial Plain and its implication to Sr flux of the Ganga River System

The influx of Sr responsible for increase in marine Sr has been attributed to rise of Himalaya and weathering of the Himalayan rocks. The rivers draining Himalaya to the ocean by the northern part of the Indian sub-continent comprising the Ganga Alluvial Plain (GAP) along with Central parts of the Himalaya and the northern part of the Indian Craton are held responsible for the transformation of Sr isotopic signature. The GAP is basically formed by the Himalayan-derived sediments and serves as transient zone between the source (Himalaya) and the sink (Bay of Bengal). The Gomati River, an important alluvial tributary of the Ganga River, draining nearly 30,500 km² area of GAP is the only river which is originating from the GAP. The river recycles the Himalayan-derived sediments and transport its weathering products into the Ganga River and finally to Bay of Bengal. 11 water samples were collected from the Gomati River and its intrabasinal lakes for measurement of Sr isotopic composition. Sr concentration of Gomati River water is about 335 μg/l, which is about five times higher than the world’s average of river water (70 μg/l) and nearly three times higher than the Ganga River water in the Himalaya (130 μg/l) The Sr isotopic ratios reported are also higher than global average runoff (0.7119) and to modern seawater (0.7092) values. Strong geochemical sediment–water interaction appearing on surface is responsible for the dissolved Sr isotopic ratios in the River water. Higher Sr isotopic rations found during post-monsoon than in pre-monsoon season indicate the importance of fluxes due to monsoonal erosion of the GAP into the Gomati River. Monsoon precipitation and its interaction with alluvium appear to be major vehicle for the addition of dissolved Sr load into the alluvial plain rivers. This study establishes that elevated ⁸⁷Sr/⁸⁶Sr ratios of the Gomati River are due to input of chemical weathering of alluvial material present in the Ganga Alluvial Plain.     

白云凹陷断裂作为天然气运移通道的地质-地球化学证据

通过对白云凹陷区域地质特征分析,并依据天然气的气体成分和甲烷与乙烷的碳同位素关系,对天然气的母源进行分析。结果表明,本区天然气的母质类型主要为II—III有机质生源。对坡折带断层活动的时限进行分析,发现白云凹陷的断裂活动可分为I—IV4个区,每个区的断裂活动均有差异。从I区到IV区,断裂活动依次减弱。番禺低隆起反向断层东西向和南北向活动性存在差异:第三排反向断层活动性强于第二排、第四排又强于第三排。反向断层的主活动期对油气的垂向运移具有重要控制作用,而结束期对油气的封堵圈闭有重要意义。依据录井天然气的同位素特征和流体包裹体的分析证实了断裂是本区天然气垂向运移的主要通道,断层的活动与罐装岩屑录井气地球化学特征完全一致。PY34-1-1断层活动微弱,热成因气没有运移到浅层,说明该区天然气的运移主要发生在深层T5层。LH19-1-1在T4—T5、T2层均发生了天然气的运移,甚至在1000m的浅层,也发现了甲烷碳同位素很重(-30‰)的热成因甲烷。这说明在LH19-1-1区块,热成因气已经运移到浅层。与此同时,流体包裹体均一化温度的直方图与罐装岩屑录井气中的非常吻合,断层活动越强,包裹体均一化温度的峰值越多,这同样表明天然气的垂向运移和分布主要受断裂的活动控制。