六盘山地区泉水地球化学特征

根据六盘山地区泉水的化学组成和氢、 氧同位素数据, 讨论了该区地下水的化学类型、 成因及其动态变化特征。 2012年11月和2014年7月在六盘山地区采集10处泉水样品, 氢氧同位素由液态水同位素分析仪测定, 离子组分浓度由离子色谱和化学滴定法测定。 水样的TDS范围为218~27508 mg/L, δ¹⁸O和δD值分别为-12.0‰~ -8.5‰, -88.5‰ ~-61.3‰。 δ¹⁸O和δD指示该区泉水来源于大气降水, 并受水循环条件及水岩反应程度的影响。 根据舒卡列夫分类法, 所采水样可划分为10种水化学类型, 受含水层岩性控制, 宁南地区的水化类型主要为SO₄-Na型, 渭北西部地区的水化类型主要为HCO₃-Ca·Mg型。 两次所采水样的离子浓度显示多数水样点的HCO^-₃具有夏高冬低的季节性变化特征, 千川村(QC)、 双井村(SJ)等因含水层赋存环境较封闭, 受降水干扰小; 硝口村(XKH)泉水的离子毫克当量比值变幅最大, 说明该泉点水岩反应程度变化较大, 易受断层带活动的影响。 研究结果确定了六盘山地区水文地球化学背景和水的来源, 为该区流体地球化学地震监测、 预测提供了背景资料。     

贺兰山东麓断裂地下水水文地球化学特征

以贺兰山东麓断裂带内地下水为研究对象,运用Piper三线图、离子比值等方法对研究区内丰水期与枯水期地下水的水化学特征进行分析,探讨了断裂与水化学组成及地震活动的关系,并建立贺兰山东麓地区地下水成因模型。结果表明：(1)区域地下水总体偏弱碱性,阳离子以Ca²⁺和Na⁺为主,阴离子以HCO^-₃和SO^2-₄为主;(2)区域地下水主要受大气降水补给,补给高程为1.07～2.04 km。Na-K-Mg三角图显示,研究区地下水为“未成熟水”。绝大多数水样的矿物饱和指数SI<0,表明区域地下水中各个离子含量大体处于未饱和状态。利用温标法估算该区域地下水的热储温度为74.6℃～114.1℃,循环深度为1.7～2.8 km;(3)地下水样中的Sr、Ba、Li等微量元素富集因子EF>1,富集程度高,其余大部分微量元素含量较低,说明当地地下水为未成熟水,矿化度低,水岩反应程度不强。(4)研究区地下水出露点主要沿贺兰山东麓断裂展布,水温、矿化度、矿物饱和指数及水循环深...     

甘肃东南地区温泉流体地球化学特征

根据氢、 氧、 氦同位素与水化学组分资料, 讨论了甘肃东南地区温泉水的来源、 地球化学变化及其与2008年汶川M_S8.0地震的关系。 测定结果表明: 样品的溶解性固体总量(TDS)范围为241.7~2 372.1 mg/L。 采集的7处温泉(通渭汤池河温泉、 清水地震台、 天水地震台、 武山地震台、 武山22号井、 成县地震台、 武都地震台)水样可归为四种化学类型: Na·Ca-SO₄、 Ca·Mg-SO₄、 Na-HCO₃·SO₄、 Ca·Mg-SO₄·HCO₃。 地下热水的化学类型与裂隙深度和围岩的岩性有关, 离子浓度和断裂深度基本成正相关。 通渭汤池河温泉和武都地震台的δ18O和δD值分别在-11.4‰ ~ -7.6‰和-85.7‰ ~ -57.1‰的范围内, 通渭汤池河温泉和武都地震台中³He/⁴He的值分别为0.4×10^-7和12.7×10^-7。 氢、 氧、 氦同位素组成特征表明温泉水源于大气降水, 在循环过程中经历了水岩反应, 且可能有地表水的混入。 2008年汶川M_S8.0地震发生后, 研究区域内温泉水中K⁺、 Ca²⁺含量总体上升, SO^2-₄、 Cl^-含量总体下降, Na⁺含量变化不明显; 热水循环深度受地震影响发生变化。 本文确定了甘肃东南地区温泉来源、 水化学类型成因及其与汶川M_S8.0地震的关系。     

内蒙古—辽宁交界地区地下水化学类型及其成因分析

通过对内蒙古东部—辽宁西部地区主要活动断裂带及其周边25个泉、井、河流、水库取样点的氢氧同位素组成及主要离子含量进行测试,讨论了该地区地下水的物质来源及其与地震活动的关系。结果表明：(1)研究区地下水主要来源于大气降水。水样TDS范围为40.14～1 720.87 mg/L,低矿化度(TDS<200 mg/L)水样的离子主要来源于岩石溶解和大气输入,而其它水样的离子主要来源于岩石溶解和深部流体,大气输入相对很小,但各测区深部流体的贡献有明显差别;(2)低温热水、中温热水及高温热水均为花岗岩裂隙水,其水化学类型为硫酸型和重碳酸型,富含碱性长石的火成岩溶解导致地下水富Na⁺,周围构造活动相对活跃。其中,RST水样更接近深部储水层的热水特征,表明其受深部流体影响为主;(3)NS和AES水样位于阴山北部高原区,为CO₂过饱和水,属重碳酸钠型;AES受干旱区季节性降水淋滤表层可溶盐、水体的蒸发以及深部富CO₂流体混入造成其矿化度最高;(4)KZHQ和BYNE水样分别处于碳酸盐岩含水层和含砾砂岩含水层,由于Ca^2+<...     

大凉山断裂带温泉水文地球化学特征

2010—2021年对大凉山断裂带10个温泉开展采样,测定了15个水样中的常量元素和氢氧同位素,进行温泉水文地球化学特征研究,建立了温泉水文地球化学循环模型。研究结果表明：(1)δD、δ¹⁸O的测量值分别为-86.8%～-100.54%和-11.7%～-13.7%,分布于大气降水线附近,表明大凉山断裂带温泉水主要为大气降水补给,其补给高程为2.1～2.5 km;(2)温泉水化学类型主要有HCO₃-Ca·Mg、SO₄·HCO₃-Ca·Mg、HCO₃-Ca、HCO₃-Na·Ca、HCO₃-Na和SO₄·HCO₃-Ca;(3)主量元素来自碳酸盐矿物和硅酸盐矿物的水-岩反应;(4)Na-K-Mg三角图表明该区温泉水样均为未成熟水;(5)运用硅-焓模型图解法得到该区热储温度为105.9℃～203℃,冷水混入比例约为68%～86%,其循环深度为1.9～3.9 km;(6)循环深度越深,地震活动性越强。     

2012年6月30日新源Ms6.6地震前后北天山泥火山及温泉的水化学变化

2012年6月30日新源-和静M_s6.6地震前后,新疆北天山地区的泥火山及温泉出现了明显的水化学异常。在地震前后4天内,采集了两批泥火山和温泉水样品,测定了泥火山和温泉水样的水化学参数。资料表明,泥火山喷溢水属于低温、弱碱性咸水或盐水,水化类型为CI-Na,来源于储存在封闭构造中并与干旱海相、河湖相沉围岩发生了漫长而复杂水岩作用的大气降水。温泉水为中温、弱碱性SO₄·CI-Na型淡水,形成于地表水沿断裂深循环过程中的水岩作用。安集海泥火山出现同震喷溢,震后泥水温度(T)、总矿化度(TDS)、K+、Na+及Ca2+大幅上升;独山子、白杨沟及AM02泥火山为震前喷溢,独山子、白杨沟泥火山表现为T.TDS、EC、Na+、CI的升高和K⁺、Ca²⁺、Mg²⁺的降低;AM02泥火山K⁺、Mg⁺明显降低,Ca²⁺上升达223%。震后沙湾25号泉T降低7℃, TDS、电导率(EC)、K⁺、Na⁺、 Ca²⁺、 .Mg²⁺、CI^-及$SO_{4}^{2-}$升高。研究结果可用于北天山地区的地震趋势分析和改进利用各泥火山、温泉进行北天山地区地震活动性监测的水化学方法。     

昆明地震台流体观测井水文地球化学特征

以昆明地震台井水、渔塘水为研究对象,通过水质、同位素分析方法并结合水文地质、构造地质等资料,探究井水地球化学特征及意义,以及井水与渔塘水之间的水力关系。研究结果显示：昆明地震台井水、渔塘水水化学类型为HCO₃—Ca型,水质受含水层和隔水层岩性控制,与2018年相比2020年井水水化学特征发生了显著变化,K⁺、HCO₃^-浓度降低,这反映了昆明地震台井—含水层渗透性有所增加;SO₄^2-、Cl^-浓度的增加则表明昆明地震台井水会受到人为干扰。研究区构造活动平稳,井水为未成熟水,演化程度较低,因含水层渗透性增强和人为干扰,自2018年7月至2020年11月昆明地震台井水—岩作用有所增强,表现为δD、δ¹⁸O富集,Mg²⁺浓度升高。井水补给来源为大气降水,补给区位于观测井正北的石关一带。渔塘水与昆明地震台井水间存在水力关系,在分析地表水对昆明地震台井的影响时应予以考虑,但渔塘水不是影响井水的主要因素。     

江西九江2号井地震水文地球化学特征及成因

对江西省九江地震台2号观测井井水、大气降水、马尾水泉水及天花井水库水的常量化学组分、氢氧同位素及氚活度数据进行分析,讨论九江台地下水的水化学类型、成因及补给循环过程,揭示九江地震台2号井对构造活动响应灵敏的地球化学特征。研究发现九江台2号井水水化学类型为HCO₃-Ca·Mg型;氢氧同位素指示九江台2号井水属于大气降水成因型,补给高程为647 m;氚活度分析给出的地下水年龄显示九江台2号井既有老水补给又有近10年的新水补给。分析结果表明,九江台2号井既有浅表水特征又有深循环水的特征,暗示两个不同补给源的含水层通过不同循环路径上升至浅表,而深部含水层可能携带部分深部构造活动的氡,并在瑞昌—阳新M_S4.6地震前出现较显著的异常信息。     

松原MS5.1地震前断层土壤气H2、Hg地球化学特征与热红外异常响应研究

利用多种气体开展联合观测是捕捉地震前兆异常的有效途径。氢、汞观测作为地震短临预测主要手段和前兆指标,在揭示地下(断裂带)流体与地震孕育、发生关系中发挥着重要的作用。通过在黑龙江肇东观测井开展断裂带土壤气H₂、Hg野外定点联合观测试验,对2019年5月18日吉林松原宁江M_S5.1主震及其余震序列的震兆关系进行对比分析,结果表明：(1)断裂带土壤气H₂、Hg浓度在宁江M_S5.1地震前分别存在3个月的短期异常和3天的临震异常,二者在主震前后表现形式以及频谱特征均存在较大差异,这可能与氢、汞特性和孕震机理有关;(2)断裂带土壤气H₂、Hg浓度在宁江M_S5.1主震及余震时段均存在高值异常,主要表现为“高值异常—恢复正常—发生主震—震后高值异常—恢复正常—发生较强余震”,具有持续性、可重复性和配套性的特点;(3)吉林松原宁江M_S5.1地震前后肇东断裂带土壤气H₂、Hg地球化学特征与震中区附近热红外异常具有响应特征,主要表现为...     

三轴压力下水与砂岩反应的实验研究

通过饱水砂岩的三轴压缩实验, 研究了含水层砂岩的破裂过程及其伴随的水化学变化, 并探讨了砂岩在蠕变和剪切破裂过程中地震水化异常现象的形成机理。 用离子色谱仪(IC)和等离子原子发射光谱仪(ICP-OES)测定了不同压力条件下实验溶液的F^-、 Cl^-、 NO^-₃、 SO^2-₄、 Ca²⁺、 Mg²⁺、 Na⁺浓度。 饱水砂岩在差应力作用下, 随着蠕变时间延长和剪切作用的强化实验, 溶液中主要离子的浓度均有不同程度的增大, 仅Mg²⁺浓度是降低的。 F^-和Cl^-浓度变化最明显, 在2~12小时的蠕变时间内分别增大约10倍和4倍, 而随剪切作用的强化分别增大约5倍和3倍。 这种变化主要与矿物的溶解和流体包裹体的混入有关。 实验结果表明, F^-、 Cl^-和Ca²⁺可作为砂岩含水层地震水化前兆监测的灵敏组分。     

High concentration of solutes at the upper part of the saturated zone (water table) of a deep aquifer under sewage-irrigated land

The water-table region (upper 50 cm of the saturated zone) of a 25 m deep phreatic sandstone aquifer, lying under fields irrigated with sewage effluents for up to 22 yrs, was monitored in 1971 and 1984. Average concentrations of NO⁻₃, Cl⁻ and SO²⁻₄ of up to 225, 307 and 155 mg l⁻¹, respectively, were detected in the upper 50 cm of the saturated region in two research wells in 1984. These concentrations, which are related to effluent and fertilizer input to groundwater, were two to four times higher than those found deep (37–55 m) below the water table in nearby (1000 m distant) production wells. Nitrate data and the estimated transit time through the unsaturated zone (2 m yr⁻¹) support the model suggesting that the major source of nitrate pollution in the past should be related to the oxidation of soil organic matter. The SO²⁻₄/Cl⁻ ratio is found to be a useful indicator for the arrival of SO²⁻₄-fertilizers at the groundwater interface. The observations presented in this paper question the suitability of plans for using effluents as a water source for agriculture in regions which are the replenishment areas of phreatic aquifers.     

Open-system degassing of sulfur from Krakatau 1883 magma

We present the first sulfur and oxygen isotopic data for tephra from the catastrophic 1883 eruption of Krakatau. Sulfur isotopic ratios in unaltered Krakatau tephra erupted August 26–27, 1883 are markedly enriched in ³⁴S relative to mantle sulfur. High δ³⁴S values of +6.3 to +16.4‰ can best be explained by open-system or multi-stage degassing of SO₂ from the oxidized rhyodacitic and gray dacitic magmas with ³⁴S enrichment of SO²⁻₄ remaining in the melt. Lower whole-rock δ³⁴S values of +2.6‰ and +4.0‰ in two oxidized gray dacitic samples indicate more primitive subarc mantle sulfur in the 1883 magma chamber. Initial δ³⁴S of the rhyodacitic magma was probably in the +1.5‰ to +4.0‰ range and similar to δ³⁴S values measured in arc volcanic rocks from the Mariana Arc.     

Causes of acidity in the River Lillån in the coastal zone of central northern Sweden

Factors controlling acidity were studied in the acidic River Lillån in the coastal zone of central northern Sweden. The stream drains the hilly wave-washed terrain and the sediment-covered coastal plain which are the dominating types of landscape in the region. A synoptic study of 38 small streams, representing both types of landscape was also made. Acidity in all streams is caused by organic acids in combination with catchment sources of sulfate. The most acidic streams occur in the hilly terrain because of a high terrestrial export of organic acids and low buffering capacity. Acidic episodes during snowmelt were associated with strongly decreased base cation concentrations, decreased SO²⁻₄ and slightly increased organic acids concentrations. Frequently occurring acid episodes caused by rainstorms and associated outwash of organic acids from forest soils are typical for events in late summer and autumn. It is suggested that, in all essential aspects, the acidity in surface waters in this part of Sweden is of natural origin.     

The seasonal variation of streamwater chemistry in three forested Mediterranean catchments

Streamwater chemistry is described for three streams draining undisturbed, evergreen broad-leaved forested catchments on phyllites in NE Spain: two streams with no or negligible flow in summer are located in the Prades massif, and one perennial stream is in the wetter Montseny mountains. Weekly data for a study period of 2–4 years are provided to (1) describe the seasonal variations in streamwater chemistry, (2) analyse the relationship between stream discharge and solute concentrations using a two-component mixing model and (3) search for patterns of temporal variation in stream solute concentrations after discounting the effects of discharge. At Prades, concentrations of all analysed ions, except NO⁻₃, showed marked seasonal variations in stream water, whereas at Montseny only ions related to mineral weathering (HCO⁻₃, Na⁺, Ca²⁺ and Mg²⁺) showed strong seasonality. Ion concentrations were more closely dependent on instantaneous discharge at Montseny than at Prades. The residuals of the relationship between solute concentrations and discharge retained a strong seasonality at Prades, but not at Montseny. These differences are related to the major hydrochemical processes that determine the streamwater chemistry at each site. The same processes are probably operative in the three catchments, but are of varying relative importance. At Montseny, the mixing of waters of different chemical composition seems to be the major process controlling streamwater chemistry, although the soilwater end-member composition predicted by the mixing model applied did not match the measured soilwater chemistry. In the drier Prades catchments, the two major hydrochemical processes determining the seasonal variation of streamwater chemistry are (1) the restart of flow after the summer drought, which flushes out the solutes accumulated during the dry period, and (2) the seasonal changes in groundwater chemistry that result from the interplay of water residence time, temperature and CO₂ partial pressure. In Mediterranean catchments with relatively high precipitation, such as Montseny, the seasonal variation in the streamwater chemistry is largely determined by the same processes as at humid-temperate sites, whereas in drier Mediterranean catchments, such as Prades, the major hydrochemical processes are clearly distinct.     

Sources of Ground Water Salinization in Parts of West Texas

Abstract
Determination of chemical constituent ratios allows distinction between two salinization mechanisms responsible for shallow saline ground water and vegetative-kill areas in parts of west Texas. Mixing of deep-basin (high Cl) salt water and shallow (low Cl) ground water results in saline waters with relatively low Ca/Cl, Mg/Cl, SO₄4/ Cl, Br/Cl, and NO₃/Cl ratios. In scattergrams of major chemical constituents vs. chloride, plots of these waters indicate trends with deep-basin brines as high Cl end members. Evaporation of ground water from a shallow water table, in contrast, results in saline water that has relatively high Ca/Cl, Mg/Cl, SO₄/Cl, and Br/CL ratios. Trends indicated by plots of this water type do not coincide with trends indicated by plots of sampled brines. Leaching of soil nitrate in areas with a shallow water table accounts for high NO₃ concentrations in shallow ground water.     

Isotope geochemistry of Pantelleria volcanic fluids, Sicily Channel rift: a mantle volatile end-member for volcanism in southern Europe

Chemical and isotopic ratio (He, C, H and O) analysis of hydrothermal manifestations on Pantelleria island, the southernmost active volcano in Italy, provides us with the first data upon mantle degassing through the Sicily Channel rift zone, south of the African–European collision plate boundary. We find that Pantelleria fluids contain a CO₂–He-rich gas component of mantle magmatic derivation which, at shallow depth, variably interacts with a main thermal (100°C) aquifer of mixed marine–meteoric water. The measured ³He/⁴He ratios and δ¹³C of both the free gases (4.5–7.3 R_a and −5.8 to −4.2‰, respectively) and dissolved helium and carbon in waters (1.0–6.3 R_a and −7.1 to −0.9‰), together with their covariation with the He/CO₂ ratio, constrain a ³He/⁴He ratio of 7.3±0.1 R_a and a δ¹³C of ca. −4‰ for the magmatic end-member. These latter are best preserved in fluids emanating inside the active caldera of Pantelleria, in agreement with a higher heat flow across this structure and other indications of an underlying crustal magma reservoir. Outside the caldera, the magmatic component is more affected by air dilution and, at a few sites, by mixing with either organic carbon and/or radiogenic ⁴He leached from the U–Th-rich trachytic host rocks of the aquifer. Pantelleria magmatic end-member is richer in ³He and has a lower (closer to MORB) δ¹³C than all fluids yet analyzed in volcanic regions of Italy and southern Europe, including Mt. Etna in Sicily (6.9±0.2 R_a, δ¹³C=−3±1‰). This observation is consistent with a south to north increasing imprint of subducted crustal material in the products of Italian volcanoes, whose He and C (but also O and Sr) isotopic ratios gradually evolve towards crustal values northward of the African–Eurasian plate collision boundary. Our results for Pantelleria extend this regional isotopic pattern further south and suggest the presence of a slightly most pristine or ‘less contaminated’, ³He-richer mantle source beneath the Sicily Channel rift zone. The lower than MORB ³He/⁴He ratio but higher than MORB CO₂/³He ratio of Pantelleria volatile end-member are compatible with petro-geochemical evidence that this mantle source includes an upwelling HIMU–EM1-type asthenospheric plume component whose origin, according to recent seismic data, may be in the lower mantle.     

辽宁省地震监测站地下水化学类型及成因分析

通过测试辽宁省15个地震监测站泉水或井水的氢、氧同位素组成及主要离子组分含量,讨论了泉水或井水的化学类型及其成因.测得泉水或井水的δD和δ~(18)O值范围分别为-82.5‰--54.4‰和-11.4‰—-7.3‰,表明所测泉水和井水的主要来源为大气降水.研究区低温泉水为低矿化度的Ca-SO_4·HCO_3型或Ca-HCO_3·SO_4型;而较高温度的花岗岩裂隙水中溶解了较多的钠硅酸盐矿物,水化学类型主要为Na-HCO_3·SO_4型;碳酸盐岩及含砾砂岩含水层分别分布于辽宁省西部及中部地区,水温略低于高温花岗岩裂隙水,水化学类型为Na·Ca-HCO_3型.水中F~-含量较高,且F~-含量与温度、pH值、Na~+和HCO_3~-的浓度呈正相关,表明泉水或井水的化学类型是深部富CO_2流体及大气降水与花岗岩反应的结果.     

Hydrochemical and stable isotope evidence for the extent and nature of the effective Chalk aquifer of north Norfolk, UK

In eastern England the Chalk aquifer is covered by extensive Pleistocene deposits which influence the hydraulic conditions and hydrochemical nature of the underlying aquifer. In this study, the results of geophysical borehole logging of groundwater temperature and electrical conductivity and depth sampling for major ion concentrations and stable isotope compositions (δ¹⁸O and δ²H) are interpreted to reveal the extent and nature of the effective Chalk aquifer of north Norfolk. It is found that the Chalk aquifer can be divided into an upper region of fresh groundwater, with a Cl concentration of typically less than 100 mg l⁻¹, and a lower region of increasingly saline water. The transition between the two regions is approximately 50 m below sea-level, and results in an effective aquifer thickness of 50–60 m in the west of the area, but less than 25 m where the Eocene London Clay boundary is met in the east of the area. Hydrochemical variations in the effective aquifer are related to different hydraulic conditions developed in the Chalk. Where the Chalk is confined by low-permeability Chalky Boulder Clay, isotopically depleted groundwater (δ¹⁸O less than −7.5‰) is present, in contrast to those areas of unconfined Chalk where glacial deposits are thin or absent (δ¹⁸O about −7.0‰). The isotopically depleted groundwater is evidence for groundwater recharge during the late Pleistocene under conditions when mean surface air temperatures are estimated to have been 4.5°C cooler than at the present day, and suggests long groundwater residence times in the confined aquifer. Elevated molar Mg:Ca ratios of more than 0.2 resulting from progressive rock-water interaction in the confined aquifer also indicate long residence times. A conceptual hydrochemical model for the present situation proposes that isotopically depleted groundwater, occupying areas where confined groundwater dates from the late Pleistocene, is being slowly modified by both diffusion and downward infiltration of modem meteoric water and diffusive mixing from below with an old saline water body.