Distribution and speciation of heavy metals and their sources in Kumho River sediment,Korea

The interaction between heavy metals and river sediment is very important because river sediment is the sink for heavy metals introduced into a river and it can be a potential source of pollutants when environmental conditions change. The Kumho River, the main tributaries of the Nakdong River in Korea, can be one of the interesting research targets in this respect, because it runs through different geologic terrains with different land use characteristics in spite of its short length. Various approaches were used, including mineralogical, geochemical, and statistical analyses to investigate the distribution and behavior of heavy metals in the sediments and their sources. The effect of geological factor on the distribution of these metals was also studied. No noticeable changes in the species or relative amounts of minerals were observed by quantitative X-ray diffraction in the sediments at different stations along the river. Only illite showed a significant correlation with concentrations of heavy metals in the sediments. Based on an average heavy metal concentration (the average concentrations of Cd, Co, Cr, Cu, Ni, Pb, and Zn were 1.67, 20.9, 99.7, 125, 97.6, 149, 298 ppm, respectively), the sediments of the Kumho River were classified as heavily polluted according to EPA guidelines. The concentrations of heavy metals in the sediments were as follows: Zn > Pb > Cu > Ni > Cr > Co > Cd. In contrast, contamination levels based on the average I _geo (index of geoaccumulation) values were as follows: Pb > Cd > Zn > Cu > Co = Cr > Ni. The concentrations of heavy metals increased downstream (with the exception of Cd and Pb) and were highest near the industrial area, indicating that industrial activity is the main factor in increasing the concentrations of most heavy metals at downstream stations. Sequential extraction results, which showed increased heavy metal fractions bound to Fe/Mn oxides at the downstream stations, confirmed anthropogenic pollution. The toxicity of heavy metals such as Ni, Cu, and Zn, represented by the exchangeable fraction and the fraction bound to carbonate, also increased at the downstream stations near the industrial complexes. Statistical analysis showed that Pb and Cd, the concentrations of which were relatively high at upstream stations, were not correlated with other heavy metals, indicating other possible sources such as mining activity.     

Hydrogeochemical and nitrate isotopic evolution of a semiarid mountainous basin aquifer of glacial-fluvial and paleolacustrine origin (Lake Titicaca,Bolivia): the effects of natural processes and anthropogenic activities

Hydrogeology Journal - A hydrogeochemical and stable isotopic ( $${\updelta }^{15}{\mathrm{N}}_{{\mathrm{NO}}_{3}}$$ and $${\updelta }^{18}{\mathrm{O}}_{{\mathrm{NO}}_{3}}$$ ) multitracer approach...     

Hydrogeochemical and isotopic investigation of the Bursa-Oylat thermal waters, Turkey

The Oylat spa is located 80 km southeast of Bursa and 30 km south of Ineg?l in the Marmara region. With temperature of 40°C and discharge of 45 l/s, the Oylat main spring is the most important hot water spring of the area. Southeast of the spa the Forest Management spring has a temperature of 39.4°C and discharge of 2 l/s. The G?z spring 2 km north of the spa, which is used for therapy of eye disease, and cold waters of the Saadet village springs with an acidic character are the further important water sources of the area. EC values of Main spring and Forest Management hot spring (750–780 μS/cm) are lower than those of Saadet and G?z spring waters (2,070–1,280 μS/cm) and ionic abundances are Ca > Na + K > Mg and SO₄ > HCO₃ > Cl. The Oylat and Sızı springs have low Na and K contents but high Ca and HCO₃ concentrations. According to AIH classification, these are Ca–SO₄–HCO₃ waters. Based on the results of δ¹⁸O, ²H and ³H isotope analyses, the thermal waters have a meteoric origin. The meteoric water infiltrates along fractures and faults, gets heated, and then returns to surface through hydrothermal conduits. Oylat waters do not have high reservoir temperatures. They are deep, circulating recharge waters from higher enhanced elevations. δ¹³C_DIC values of the Main spring and Forest Management hot spring are −6.31 and −4.45‰, respectively, indicating that δ¹³C is derived from dissolution of limestones. The neutral pH thermal waters are about +18.7‰ in δ³⁴S while the sulfate in the cold waters is about +17‰ (practically identical to the value for the neutral pH thermal waters). However, the G?z and Saadet springs (acid sulfate waters) have much lower δ³⁴S values (~+4‰).     

Hydrogeochemical and isotopic investigation of the Kolan geothermal field, southeastern Turkey

The Kolan geothermal field is located 24 km northwest of the Karakoçan area of Elaz city in southeastern Turkey. The Keban crystallized limestone of Permo-Carboniferous age is the oldest unit in the area. This unit is overlain by the middle-upper Eocene Krkgeçit formation consisting of conglomerate, sandstone, limestone and marl alternations. The youngest unit in the area is the Upper Miocene-Lower Pliocene Karabakr formation consisting of basalt, andesite and tuffs. Thermal Springs in the Kolan field issue along two major fault zones. The temperature of the hot springs is between 38°C and 45°C. Thermal waters in the area are heated by the geothermal gradient. The waters are classified as hot or very hot and as brackish waters. On the basis of International Association of Hydrogeologists Classification (IAH), waters are grouped as Ca–Na-HCO₃–CO₂-bearing thermal and mineral waters. Chemical analyses indicate a chemical composition of Ca>(Na+K)>Mg - HCO₃>SO₄>Cl. Saturation calculations reveal that the waters are oversaturated with respect to calcite, dolomite and aragonite while undersaturated with respect to gypsum, anhydrite and halite minerals. On the basis of ¹⁸O, ²H and ³H isotope data, Kolan waters are of meteoric origin, recharged from high elevations and then circulated deeply.     

Hydrogeochemical and isotopic study of groundwater in the Habor Lake Basin of the Ordos Plateau,NW China

Hydrogeochemistry and isotopes were used to understand the origin and geochemical evolution in the Habor Lake Basin, northwestern China. Groundwater samples were taken, and the isotopic compositions δD, δ¹⁸O and major ions were analyzed. The groundwater can be divided into three types: the Quaternary groundwater, the shallow Cretaceous groundwater and the deep Cretaceous groundwater. The groundwater chemistry is mainly controlled by the feldspar weathering and dolomite weathering, the dissolution of Glauber’s salt, and cation exchange. Chemistry of lake water is mainly controlled by evaporation and precipitation. The stable isotopes of oxygen and hydrogen in groundwater cluster along the local meteoric water line, indicating that groundwater is of meteoric origin. Comparing with shallow groundwater, deep groundwater is depleted in heavy isotopes indicating that deep groundwater was recharged during late Pleistocene and Holocene, during which the climate was more wetter and colder than today.     

Sources of dissolved ions revealed by chemical and isotopic tracers in the Geum River,South Korea

Water samples were collected in the main channel of the Geum River, South Korea, and measured dissolved elemental concentrations and isotopic compositions of nitrate in order to identify the factors controlling water chemistry. Elemental concentrations significantly increased location-wise after the confluence from urban areas, indicating the changes in solute sources from chemical weathering to anthropogenic inputs such as manure, fertilizers, and sewage. In particular, the effect of sewage input is manifested in the concentrations of Cl^?, SO₄ ^2?, and Na⁺, while the NO₃ ^? concentration is influenced mainly by soil inputs with minor contributions from manure and fertilizer because both δ¹⁵N–NO₃ and δ¹⁸O–NO₃ indicate NO₃ ^? mostly consists of soil-derived nitrates in the upper reaches but manure/sewage nitrates in the lower reaches. The relative proportion of three factors, Cl^?, Ca²⁺+Mg²⁺, and NO₃ ^?, indicates that water chemistry in the upstream is controlled by the soil weathering but that in the downstream by the sewage. Seasonally, water chemistry during summer is dominated by the soil weathering due to the flushing effect but that during winter by the sewage. This study suggests that the relative proportion of three factors can be used for tracing natural and anthropogenic sources in water chemistry.     

Hydrogeochemical and isotopic characteristics of the Ilica geothermal system (Erzurum,Turkey)

In this paper, the hydrochemical isotopic characteristics of samples collected from geothermal springs in the Ilica geothermal field, Eastern Anatolia of Turkey, are examined and described. Low-temperature geothermal system of Ilica (Erzurum, Turkey) located along the Eastern Anatolian fault zone was investigated for hydrogeochemical and isotopic characteristics. The study of ionic and isotopic contents shows that the thermal water of Ilica is mainly, locally fed by groundwater, which changes chemically and isotopically during its circulation within the major fault zone reaching depths. The thermal spring has a temperature of 29–39 °C, with electrical conductivity ranging from 4,000 to 7,510 µS/cm and the thermal water is of Na–HCO₃–Cl water type. The chemical geothermometers applied in the Ilica geothermal waters yielded a maximum reservoir temperature of 142 °C according to the silica geothermometers. The thermal waters are undersaturated with respect to gypsum, anhydrite and halite, and oversaturated with respect to dolomite. The dolomite mineral possibly caused scaling when obtaining the thermal waters in the study area. According to the enthalpy chloride-mixing model, cold water to the thermal water-mixing ratio is changing between 69.8 and 75 %. The δ¹⁸O–δ²H compositions obviously indicate meteoric origin of the waters. Thermal water springs derived from continental precipitation falling on to higher elevations in the study area. The δ¹³C ratio for dissolved inorganic carbonate in the waters lies between 4.63 and 6.48 ‰. In low-temperature waters carbon is considered as originating from volcanic (mantle) CO₂.     

Hydrogeochemical and isotopic characterization of the groundwater in the Chari-Baguirmi depression, Republic of Chad

The Chari Baguirmi groundwater in the Republic of Chad is undergoing a steady deterioration both qualitative and quantitative due to climatic (severe droughts) and anthropogenic (overexploitation) constraints. However, this major water resource has not been to date the object of any comprehensive scientific investigation. To fill this gap and consider a sustainable exploitation, a hydrodynamic and hydrochemical study was undertaken. This aquifer is located south of Lake Chad and displays a significant natural piezometric depression. Piezometric campaign on an area of 70,000 km², bounded by Lake Chad, the Chari River, the mountains of Guera and the dunes of Harr, was conducted to understand the hydrodynamics of the groundwater. Water samples were collected on 124 points scattered over the study area. Hydrochemical and isotopic analyses (¹⁸O and ²H) were achieved on all samples. The interpretation of hydrochemical data was done using the Piper diagram, the multivariate analysis (hierarchical ascending classification), the index of base exchanges and ratios of Na/Cl, Na/SO₄, Cl/SO₄, Br/Cl, Sr/Ca. The hydrochemical results coupled with groundwater isotopes data allowed to understand the processes that govern the mineralization and the origin of groundwater salinity. These investigations allowed on the one hand to differentiate between two poles of water mixing and second, to demonstrate that the mineralization process and origin of salinity in the center of depression are both related to the lithology of the geological formations crossed by groundwater flow and climatic events causing evaporation of water from the aquifer.     

Hydrogeochemical and isotopic evidences of the groundwater regime in Datong Basin, Northern China

Datong Basin is one of the Cenozoic faulted basins in Northern China’s Shanxi province, where groundwater is the major source of water supply. The results of hydrochemical investigation show that along the groundwater flow path, from the margins to the lower-lying central parts of the basin, groundwater generally shows increases in concentrations of TDS, HCO₃ ^?, SO₄ ^2?, Cl^?, Na⁺ and Mg²⁺ (except for Ca²⁺ content). Along the basin margin, groundwater is dominantly of Ca–HCO₃ type; however, in the central parts of the basin it becomes more saline with Na–HCO₃-dominant or mixed-ion type. The medium-deep groundwater has chemical compositions similar to those of shallow groundwater, except for the local area affected by human activity. From the mountain front to the basin area, shallow groundwater concentrations of major ions increase and are commonly higher than those in medium-deep aquifers, due to intense evapotranspiration and anthropogenic contamination. Hydrolysis of aluminosilicate and silicate minerals, cation exchange and evaporation are prevailing geochemical processes occurring in the aquifers at Datong Basin. The isotopic compositions indicate that meteoric water is the main source of groundwater recharge. Evaporation is the major way of discharge of shallow groundwater. The groundwater in medium-deep aquifers may be related to regional recharges of rainwater by infiltrating along the mountain front faults, and of groundwater permeating laterally from bedrocks of the mountain range. However, in areas of groundwater depression cones, groundwater in the deep confined aquifers may be recharged by groundwater from the upper unconfined aquifer through aquitards.     

Hydrogeochemical and isotopic constraints on the origins of dryland salinity,Murray Basin,Victoria, Australia

Combined hydrogeological and hydrogeochemical data allow flow systems and the origins of solutes in the Honeysuckle Creek area of the southeastern Murray Basin, which is an area affected by dryland salinity, to be constrained. Recharge occurs both on the uplands that are composed of fractured Violet Town Volcanic rocks and the Riverine Plain that comprises sediments of the Shepparton and Coonambidgal Formations. Groundwater from the Violet Town Volcanics has low salinity (<20 mmol/L Cl) and major ion geochemistry that is controlled largely by dissolution of silicate minerals. Low Cl/Br ratios (as low as 281 molar) suggest that this groundwater has not dissolved halite. Groundwater that recharged through the Riverine Plain sediments has higher Cl/Br ratios (up to 1146) and Cl concentrations of <20 mmol/L, consistent with it dissolving minor halite. Higher salinity (>20 mmol/L) groundwater has intermediate Cl/Br ratios (600–1000), which indicate that the high salinities do not simply result from halite dissolution. Rather, mixing of groundwater homogenises Cl/Br ratios, and evaporation as a consequence of a shallow water table is the dominant process that increases salinity. Oxygen and H isotopes also indicate that mixing and evaporation have occurred. These results indicate that land use over the whole region, not just the uplands, needs to be considered in any salinity management plans. Additionally future development of salinity is controlled by depth to the water table on the plains and the efficiency of recharge rather than by salt stores (halite or brines) in the unsaturated zone.     

渭河沉积物浸出的水文地球化学效应研究

基于渭河咸阳段（中游）和渭南段（下游）沉积物在水更新条件下的浸出实验及水文地球化学模拟,分析了浸出液中3个特征值和8个水化学组分的变化规律及5种矿物质饱和指数的变化特征.结果表明：浸出液中电导率、Eh值和pH值均随着换水量的增加呈现出波动式上升的变化趋势,电导率增加趋势中咸阳段高于渭南段,Eh值增加趋势中渭南段高于咸阳段,说明渭河下游沉积物的颗粒更细,物质还原性更强,浸出液由弱酸性逐步向弱碱性转变;浸出液的HCO₃^-、Cl^-、SO₄^2-含量均表现出随着换水量的增加呈现出先迅速增加,而后逐步减少直至趋于稳定的变化过程,且咸阳段的变化幅度明显高于渭南段,而CO₃^2-含量则呈现不断减少的趋势;Ca²⁺、Mg²⁺、Na⁺、K⁺含量均表现出随着换水量的增加呈现出先迅速增加,而后趋于稳定的变化过程,且咸阳段的起始含量和增加幅度均高于渭南段;浸出液中无水石膏、石膏的饱和指数随换水量的增加呈现相同的变化规律,且饱和指数都小于0,咸阳段饱和指数在换水量小于22.5%时溶解能力强,换水量大于22.5%后趋于饱和并开始沉淀的特征,渭南段换水量为12.5%时饱和指数最小,换水量大于或小于12.5%后饱和指数均呈缓慢增加的趋势;方解石、白云石的饱和指数随换水量的增加也呈现相同的变化规律,且饱和指数都大于0,咸阳段在换水量小于12.5%时溶解能力较强,换水量大于12.5%后处于饱和状态并开始沉淀,渭南段在换水量小于5%时溶解能力较强,换水量大于5%后处于饱和状态并开始沉淀;NaCl饱和指数在换水量小于10%时溶解能力较强,换水量大于15%后开始沉淀.咸阳段沉积物中五种矿物质的饱和指数均要大于渭南段,说明渭河中游咸阳段沉积物在水不断更新条件下矿物质溶解能力低于下游渭南段,且沉淀能力较强、沉淀量较大.     

Hydrogeochemical and isotopic evidence for trans-formational flow in a sedimentary basin: Implications for CO2 storage

Deep saline aquifers are considered as the most promising option for geologic disposal of CO₂. One of the main concerns, however, is the integrity of the caprocks between and above the storage formations. Here, a hydrogeochemical and isotopic investigation is presented, using ionic chemistry, stable isotopes (δ¹⁸O, δ²H and ⁸⁷Sr/⁸⁶Sr) and radiocarbon dating, on five saline aquifers on a regional scale, namely: Neogene Minghuazhen, Guantao, Ordivician, Cambrian and Precambrian, all found in the Bohai Bay Basin (BBB) in North China. Groundwater recharge, flow pattern, age and mixing processes in the saline aquifers show that the Neogene Guantao Formation (Ng) in the Jizhong and Huanghua Depressions on both of the west and east sides of the Cangxian Uplift is a prospective reservoir for CO₂ sequestration, with a well confined regional seal above, which is the clayey layers in the Neogene Minghuazhen Formation (Nm). However, this is not the case in the Cangxian Uplift, where the Ng is missing where structural high and fault zones are developed, creating strong hydraulic connections and trans-formational flow to the Nm aquifer. Comparing storage capacity and long-term security between the various hydrogeologic units, the depressions are better candidate sites for CO₂ sequestration in the BBB.     

Hydrogeochemical and isotopic composition of a low-temperature geothermal source in northwest Turkey: case study of Kirkgecit geothermal area

Chemical and isotopic compositions of three hot springs and one cold spring in the Kirkgecit geothermal field, located 15 km southwest of Canakkale-Biga in the northwest of Turkey, were monitored five times during 2005 and 2007. The physico-chemical characteristics of the hot springs are average discharge 3–3.5 L/s, surface temperature 45–52°C, pH 8.9–9.3, and electrical conductivity (EC) 620–698 μS/cm. The cold spring has a temperature of 12–13°C, pH 7.5–8.3, and EC 653–675 μS/cm. The hot waters are Na-SO₄ type, whereas the cold water is Ca-HCO₃ type. Chemical geothermometers suggest that the reservoir temperature is around 80–100°C. The isotopic data (oxygen-18, deuterium and tritium) indicate that the thermal waters are formed by local recharge and deep circulation of meteoric waters.     

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.     

Silicon isotopic composition of dissolved silicon and suspended particulate matter in the Yellow River, China, with implications for the global silicon cycle

The silicon isotopic composition of dissolved silicon and suspended particulate matter (SPM) were systematically investigated in water samples from the mainstem of the Yellow River and 4 major tributaries. The SPM content of the Yellow River varied from 1.4 to 38,560 mg/L, averaging 3568 mg/L, and the δ³⁰Si of suspended particulate matter (δ³⁰Si_SPM) varied from 0.3‰ to −0.4‰, averaging −0.02‰. The major factors affecting the SPM content and the δ³⁰Si_SPM values in the Yellow River were inferred to be the mineralogical, chemical and isotopic characteristics of the sediments from the Loess Plateau and a combination of the climate and the flow discharge of the river.The major ions in the Yellow River water were Na⁺, Ca²⁺, Mg²⁺, HCO₃⁻, SO₄²⁻ and Cl⁻. High salt concentration was observed in samples from the middle and lower reaches, likely reflecting the effects of evaporation and irrigation because the Na⁺, Mg²⁺, SO₄²⁻ and K⁺ concentrations were correlated with the Cl⁻ concentration. The dissolved Si concentration (D_Si) increased downstream, varying from 0.016 to 0.323 mM. The δ³⁰Si of dissolved Si (δ³⁰Si_Diss) varied from 0.4‰ to 2.5‰, averaging 1.28‰. The major processes controlling the D_Si and δ³⁰Si_Diss of the Yellow River are (a) the weathering of silicate rocks, (b) the formation of phytoliths in plants, (c) the evaporation of water from and the addition of meteoric water to the river system, which only affects concentrations, (d) the adsorption and desorption of aqueous monosilicic acid on iron oxide, and (e) the dissolution of phytoliths in soils.The D_Si and δ³⁰Si_Diss values of global rivers vary spatially and temporally in response to changes in climate, chemical weathering intensity and biological activity. The moderately positive δ³⁰Si_Diss values observed in the Yellow River may be attributed to the higher rates of chemical weathering and biological activities that have been observed in this catchment in comparison with those of other previously studied catchments, excluding the Yangtze River. Human activities may also potentially influence chemical weathering and biological activities and affect the D_Si and δ³⁰Si_Diss values of the major rivers of the world. Further river studies should be performed to gain a better understanding of the global Si isotope budget.     

Hydrogeochemical evaluation of groundwater quality and seasonal variation in East Bokaro coalfield region,Jharkhand

Groundwater samples collected from the East Bokaro coalfield of Jharkhand state, India during the dry and rainy seasons of the year 2012. Samples were analyzed for the assessment of groundwater quality in the study area. The results of the chemical analysis indicate that the pH values were found alkaline in nature during both the season. The major cations in groundwater was in the order of Na⁺>Ca²⁺>Mg²⁺>K⁺ during the dry season while Ca²⁺>Na⁺>Mg²⁺>K⁺ during the rainy season. The abundance of the major anions was of HCO₃^->SO₄^2->Cl^->NO₃^->F^- did not change on the seasonal basis. The average NO₃^-concentration was exceeded the desirable limit for drinking water as per Indian standard in the rainy season. Silicate weathering was inferred to be a dominant process, controlling the groundwater chemistry in both seasons, with lesser contributions by carbonate weathering and ion exchange. Leaching of salts from the unsaturated zone also has a major impact on groundwater quality during the rainy season. The water quality data indicate that groundwater is generally suitable for irrigation. However, higher salinity and residual sodium carbonate values at some sites may limit groundwater use and therefore an adequate drainage and water management plan for the study area is required.     

Hydrogeochemical and isotopic characterizations of an aquifer in the semi-arid region of the Mexican Highlands

This work addresses hydrogeochemical processes in shallow aquifers, represented by the Quaternary alluvial deposits, from a part of the semi-arid Mexican Highlands through the evaluations of physicochemical parameters as well as the δ¹⁸O and δ²H compositions of groundwater. Mifflin diagram separates the Na-bicarbonate, sulphate and mixed groundwater into one group showing interactions with volcanic lithology in the recharge zones and another group interacting with the evaporite rich sedimentary formation. In the Gibbs diagram, the samples with Cl^?/(Cl^? + HCO₃^?) < 0.4 showed higher influence of ion exchange and the samples with Cl^?/(Cl^? + HCO₃^?) > 0.4 showed higher effects of evaporation. All of them were oversaturated with carbonate minerals (i.e., calcite and dolomite) and unsaturated with evaporites (i.e., gypsum and halite). Evaporation (earlier stage) occurred before the water-rock interactions (later stage). Evolution occurs through three different routes such as up to 7.5‰ enrichment in δ¹⁸O caused by the infiltration with a certain delay and subsequently, the water-rock interaction became dominant. Ternary mixing models revealed dominant influence of local recharge (C₁) on the water system, contributing 70.4%. Water-rock interaction (C₃) with 18% and evaporation (C₂) with 11.6% had comparatively less influences. The presence of nitrate (2–60 mg/L) in the groundwater indicated variable degrees of anthropogenic pollution.     

An isotopic biogeochemical study of the Green River oil shale

Thirty-five different samples from three different sulfur cycles were examined in this stratigraphically oriented study of the Shell 22x-l well (U.S.G.S. C177 core) in the Piceance Basin, Colorado. Carbon isotopic compositions of constituents of Green River bitumens indicate mixing of three main components: products of primary photoautotrophs and their immediate consumers (delta approximately -30% vs PDB), products of methanotrophic bacteria (delta approximately -85%), and products of unknown bacteria (delta approximately -40%). For individual compounds synthesized by primary producers, delta-values ranged from -28 to -32%. 13C contents of individual primary products (beta-carotane, steranes, acyclic isoprenoids, tricyclic triterpenoids) were not closely correlated, suggesting diverse origins for these materials. 13C contents of numerous hopanoids were inversely related to sulfur abundance, indicating that they derived both from methanotrophs and from other bacteria, with abundances of methanotrophs depressed when sulfur was plentiful in the paleoenvironment. gamma-Cerane coeluted with 3 beta(CH3),17 alpha(H),21 beta(H)-hopane, but delta-values could be determined after deconvolution. gamma-Cerane (delta approximately -25%) probably derives from a eukaryotic heterotroph grazing on primary materials, the latter compound (delta approximately -90%) must derive from methanotrophic organisms. 13C contents of n-alkanes in bitumen differed markedly from those of paraffins generated pyrolytically. Isotopic and quantitative relationships suggest that alkanes released by pyrolysis derived from a resistant biopolymer of eukaryotic origin and that this was a dominant constituent of total organic carbon.     

Thickness and stable isotopic characteristics of modern seasonal climate-controlled sub-annual travertine laminas in a travertine-depositing stream at Baishuitai, SW China: implications for paleoclimate reconstruction

A continuous high-resolution (monthly) record of stable isotopes (δ¹³C and δ¹⁸O) in a well-laminated freshwater travertine deposited at Baishuitai, SW China from May 1998 to November 2001 was presented. The travertine exhibits clear annual bands with coupled brown/white color laminations. Throughout field investigation, it was found that the thin (1.5–2.2 mm), brown porous lamina was formed in the monsoonal rainy season from April to September, whereas the thick (5–8 mm), dense white lamina was formed in the dry season from October to March. The comparisons of lamina thickness and stable isotope signals in the travertine with the meteorological records allow us to constrain the relevant geochemical processes in the travertine formation under different climate conditions and to relate climate variables to their physicochemical proxies in the travertine record. Sympathetic variations in lamina thickness, δ¹³C and δ¹⁸O along the sampled profile reflect changes in hydrogeochemistry, showing that thin lamina and low δ¹³C and δ¹⁸O values occur in warm and rainy seasons. The decreased amount of calcite precipitation and low δ¹³C values during the warm and rainy seasons is caused by dilution of overland flow after rainfall. The low δ¹⁸O values are believed to be related to the rainfall amount effect in subtropical monsoonal regions. This process is thought to be markedly subdued whenever the amount of rainfall is lower than a given threshold. Accordingly, distinct minima in lamina thickness, δ¹³C and δ¹⁸O are interpreted to reflect events with above-average rainfall, possibly heavy floods, and vice versa. This study demonstrates the potential of freshwater travertine to provide valuable information on seasonal or even monthly rainfall variations.