河北汤泉地热流体水文地球化学特征及其成因

提要：汤泉位于河北省遵化市西北部,为山前丘陵地貌,地热资源丰富。本文通过对该地区地热流体研究发现：Na⁺、Ca²⁺、K⁺、Mg²⁺与SO^2-₄、HCO^-₃、Cl^-、NO^-₃是该地区地下热水的主要成分,水化学类型主要为SO^2-₄-Na⁺型,属于未污染的天然弱碱性水;流体中F^-含量平均为9.36 mg/l,远高于国家地下水质量标准ⅴ级;可溶性SiO₂的含量可作为地热温标;地热流体总矿化度平均为782.33 mg/l,属于淡水;为中等腐蚀型水,不结碳酸钙垢,无CaSO₄?2H₂O垢和SiO₂垢生成的可能;地热流体属于含岩盐地层溶滤的陆相沉积水;根据氢氧稳定同位素可知,河北汤泉地热流体主要来源于大气降水。     

关中盆地深部地下热水残存沉积水的同位素证据

应用环境同位素水文地球化学方法,结合区域沉积演化史,对关中盆地固市凹陷、咸阳-礼泉断阶和西安凹陷深部地下热水成因类型进行了探讨,并就残存沉积水存在的可能性,寻找氢氧同位素关系、硫氧同位素关系、碳氧同位素关系、N(87Sr)/N(86Sr)与古盐度的关系等环境同位素证据,rNa/rCl值、ρ(Cl-)/ρ(Br-)、rBr/rI值与ρ(Cl-)的关系等水文地球化学证据以及沉积演化史证据。结果表明:固市凹陷华阴地下热水的同位素、水文地球化学特征已基本符合沉积水的特征,推测其为混有古入渗水的残存沉积水;固市凹陷华阴之外的其他构造单元、咸阳—礼泉断阶和西安凹陷地下热水的同位素和水文地球化学特征部分接近沉积水的特征,部分介于古入渗水和沉积水之间;咸阳—礼泉断阶东部地下热水可能为古入渗水或残存沉积水与后期入渗水的混合;西安凹陷及咸阳—礼泉断阶西部地下热水属于现代入渗水与古入渗水的混合水。     

Hydrogeochemical evaluation of high-fluoride groundwaters: a case study from Mehsana District,Gujarat, India

Abstract

Groundwater quality problems have emerged in many geographical areas due to natural environmental processes and human intervention in the geosystems. Hydrogeochemical appraisal of fluoride contaminated groundwater in Mehsana District, Gujarat State, India is carried out by means of groundwater quality investigations together with X-ray diffraction analysis of soil samples in the delineated high fluoride areas. Results show that fluoride has negative relationships with calcium, whereas relationships with sodium, alkalinity and sulphate are positive. Results obtained from aqueous speciation modelling using PHREEQC reveal that the groundwater is undersaturated with fluorite and oversaturated with calcite. The factor analysis indicates that sodium plus potassium bicarbonate groundwater have high factor loading for fluoride, whereas that for calcium chloride and magnesium chloride groundwater is low. The plausible geochemical reactions in the study area are precipitation of calcite and dissolution of dolomite, carbon dioxide and sulphate minerals with ion exchange.     

内蒙古托克托县潜水与承压水中氟化物的空间分布特征及形成机理

氟是维持人体健康所必需的微量元素,过多或过少的摄入都会造成相应的健康问题。本研究从氟的来源、迁移和富集等角度,揭示了内蒙古呼和浩特市托克托县高氟地下水的空间分布规律及其在潜水和承压水中富集的原因。对研究区60个水样(30个潜水和30个承压水)进行了统计分析、水化学特征研究、聚类分析以及相关性分析。结果表明：潜水中F^- 浓度为0.40~7.20(2.30±1.80) mg/L,承压水中F^- 浓度为0.29~12.70(1.67±2.48) mg/L;地下水中F-浓度与HCO^-₃、Na⁺、溶解性总固体(TDS)和电导率(EC)呈正相关,与Ca²⁺呈一定的负相关关系。高氟水的水化学类型主要为HCO₃·Cl-Na型。受地下水流场的控制,高氟潜水(>5 mg/L)主要分布在地下水的排泄区;承压水中F^- 的富集主要受含水层岩性的影响,氟高浓度(>1.5 mg/L)分布区主要集中在研究区南部的湖积台地区域。     

Hydrogeological and hydrogeochemical control of groundwater salinity in an arid inland basin: Dunhuang Basin,northwestern China

High groundwater salinity has become a major concern in the arid alluvial plain of the Dunhuang Basin in northwestern China because it poses a significant challenge to water resource management. Isotopic and geochemical analyses were conducted on 55 water samples from springs, boreholes and surface water to identify potential sources of groundwater salinity and analyse the processes that control increasing salinity. The total dissolved solid (TDS) content in the groundwater ranged from 400 to 41 000 mg/l, and high TDS values were commonly associated with shallow water tables and flow‐through and discharge zones in unconfined aquifers. Various groundwater contributions from rainwater, agricultural irrigation, river water infiltration and lateral inflows from mountains were identified by major ions and δD and δ¹⁸O. In general, HCO₃^? and SO₄^2? were the dominant anions in groundwater with a salinity of <2500 mg/l, whereas Cl^? and SO₄^2? were the dominant anions in groundwater with a salinity of >2500 mg/l. The major ion concentrations indicated that mineral weathering, including carbonate and evaporite dissolution, primarily affected groundwater salinity in recharge areas. Evapotranspiration controlled the major ion concentration evolution and salinity distribution in the unconfined groundwaters in the flow‐through and discharge areas, although it had a limited effect on groundwater in the recharge areas and confined aquifers. Agricultural irrigation increased the water table and enhanced evapotranspiration in the oasis areas of the basin. TDS and Cl became more concentrated, but H and O isotopes were not enriched in the irrigation district, indicating that transpiration dominated the increasing salinity. For other places in the basin, as indicated by TDS, Cl, δD and δ¹⁸O characteristics, evaporation, transpiration and water–rock interactions dominated at different hydrogeological zones, depending on the plant coverage and hydrogeological conditions. Groundwater ages of ³H, and δD and δ¹⁸O compositions and distributions suggest that most of the groundwaters in Dunhuang Basin have a paleometeoric origin and experienced a long residence time. These results can contribute to groundwater management and future water allocation programmes in the Dunhuang Basin. Copyright © 2015 John Wiley & Sons, Ltd.     

贵州七星洞系统中水文地球化学特征对滴水δ~(13)C_(DIC)的影响及其意义

2003年4月至2004年5月,笔者对贵州七星洞(QXD)进行了较为详细的监测,逐月采集了土壤水和洞穴滴水等样品,分别测定了样品的稳定碳同位素组成和水文地球化学参数。结果显示,9个滴水点同期的溶解无机碳同位素值(δ13CDIC)之间存在着大的差异,最大达6.9‰;δ13CDIC值偏重的Ⅰ组滴水,其Ca、Sr、HCO3、电导率(EC)和方解石饱和指数(SIC)等水文地球化学指标偏小,而Mg/Ca比值偏大,Ⅱ组则相反;不同滴水点的δ13CDIC值分别与相应滴水的Ca、Sr、HCO3、EC、Mg/Ca和SIC等水文地球化学指标之间存在较好的相关关系。进一步分析表明,与土壤水δ13CDIC平均值-9.9‰相比,Ⅰ组1#、2#、6#、7#和8#滴水点δ13CDIC值偏重4.5‰～5.7‰,主要是由大量的基岩溶解以及前期方解石沉积(prior calcite precipitation,PCP)共同作用的结果;Ⅱ组3#、4#、5#和9#滴水点δ13CDIC值偏重0.6‰～1.6‰,受基岩溶解和PCP过程影响较小,尤其是9#滴水点受影响最小。因此,若不考虑基岩溶解和PCP过程影响作用,将会极大地影响洞穴化学沉积物碳同位素记录的准确解释。     

应用铀同位素研究砂岩型铀矿中的若干问题探讨

笔者通过对512铀矿床含矿层岩石中铀同位素分布特征的研究,对砂岩型铀矿床铀同位素组成的分区进行了讨论。根据不同氧化还原分带中样品铀同位素组分的分布特征,对Osmond铀钍同位素组成分区模式提出了补充修改意见,认为A区应定名为“地球化学（氧化还原）矛盾区”更宜。该砂岩型铀矿床的铀同位素组成分区特征不仅是预测铀矿化定位的依据,而且也充分说明了铀富集成矿过程的滚动性。     

祁连山黑河源区八一冰川-黄藏寺段河水水文地球化学特征

黑河源区河水水文地球化学特征的研究有助于了解黑河源区河水沿流域水质变化概况,对黑河源区生态环境的保护具有积极意义。以黑河源区干流为研究对象,对河水进行取样检测,结果显示：河水化学组成以K⁺、Na⁺、Ca²⁺、Mg²⁺和Cl^-、NO₃^-、HCO₃^-、SO₄^2-为主。通过聚类分析、舒卡列夫分类和Piper三线图分析发现主要离子中,阳离子主要来源于石灰岩风化产物,SO₄^2-主要来源于蒸发岩矿物风化产物和人类活动,HCO₃^-主要来源于纯碳酸盐风化产物。通过对重金属污染调查发现,V、Co、Cu、Pb、Cr、Mn和Zn含量较高,矿山开采是重金属污染的主要来源。     

Groundwater geochemistry,hydrogeology and potash mineral potential of the Lake Woods region,Northern Territory,Australia

We collected 38 groundwater and two surface-water samples in the semi-arid Lake Woods region of the Northern Territory to better understand the hydrogeochemistry of this system, which straddles the Wiso, Tennant Creek and Georgina geological regions. Lake Woods is presently a losing waterbody feeding the underlying groundwater system. The main aquifers comprise mainly carbonate (limestone and dolostone), siliciclastic (sandstone and siltstone) and evaporitic units. The water composition was determined in terms of bulk properties (pH, electrical conductivity, temperature, dissolved oxygen, redox potential), 40 major, minor and trace elements, and six isotopes (δ¹⁸O_water, δ²H_water, δ¹³C_DIC, δ³⁴S_SO4^2–, δ¹⁸O_SO4^2–, ⁸⁷Sr/⁸⁶Sr). The groundwater is recharged through infiltration in the catchment from monsoonal rainfall (annual average rainfall ～600?mm) and runoff. It evolves geochemically mainly through evapotranspiration and water–mineral interaction (dissolution of carbonates, silicates and to a lesser extent sulfates). The two surface waters (one from the main creek feeding the lake, the other from the lake itself) are extraordinarily enriched in ¹⁸O and ²H isotopes (δ¹⁸O of +10.9 and +16.4‰ VSMOW, and δ²H of +41 and +93‰ VSMOW, respectively), which is interpreted to reflect evaporation during the dry season (annual average evaporation ～3000?mm) under low humidity conditions (annual average relative humidity ～40%). This interpretation is supported by modelling results. The potassium (K) relative enrichment (K/Cl^– mass ratio over 50 times that of sea water) is similar to that observed in salt-lake systems worldwide that are prospective for potash resources. Potassium enrichment is believed to derive partly from dust during atmospheric transport/deposition, but mostly from weathering of K-silicates in the aquifer materials (and possibly underlying formations). Further studies of Australian salt-lake systems are required to reach evidence-based conclusions on their mineral potential for potash, lithium, boron and other low-temperature mineral system commodities such as uranium.     

桂西大型岩溶地下河系统离子来源及碳稳定同位素信息——以坡心地下河流域为例

为探讨坡心地下河系统内地表和地下水体的水化学离子特征、来源及其控制因素,无机碳来源及其稳定性。运用水化学计量法和同位素法对采自坡心地下河流域的38个采样点的水化学和碳稳定同位素样品数据进行分析。结果表明,地下河干流沿程受到局部岩性和支流稀释作用的影响明显,各水化学离子均有所变化。化学离子比例分析发现:大气降水对部分泉水的Cl~-和Na~+影响较大;碳酸盐岩溶解类型主要以灰岩溶解为主,地表水和地下河天窗的Mg~(2+)/Ca~(2+)摩尔比值与HCO_3~-呈负相关,说明在宏观上灰岩溶解程度越强烈,HCO_3~-值就越高,并且H_2SO_4和HNO_3积极参与流域内碳酸盐岩风化。硅酸盐岩的风化对地表和地下水体的Ca~(2+)、Mg~(2+)、Na~+、K~+有一定的贡献。此外,人为采矿活动和农业活动对SO_4~(2-)和NO_3~-的产生有较大的影响。质量平衡正推模型结果显示:受到区域岩性和水文条件的影响,地表和地下河天窗水体主要受碳酸盐岩溶解影响,硅酸盐岩溶解和大气输入也有一定的贡献,三大来源的相对比例在空间上变化较大。水体内的可溶性无机碳(DIC)主要来源于碳酸盐岩的溶解和土壤内CO_2的贡献。地表水和地下水的DIC浓度和δ~(13)C_(DIC)值差别较大,DIC值与δ~(13)C_(DIC)呈反相关关系,这说明来自土壤CO_2贡献的DIC越多,其对碳酸盐岩矿物的溶解能力越强。根据本研究区的数据与前人在西江干流的上、中、下游进行对比,结果表明碳酸盐岩风化产生的DIC可以被西江干流的水生植物利用,从而形成稳定的碳汇。