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1.
Oxygen and hydrogen isotopes were used in this study to detect a hydraulic connection between a sinkhole lake and a karst spring. In karst areas, surface water that flows to a lake can drain through sinkholes in the lakebed to the underlying aquifer, and then flows in karst conduits and through aquifer matrix. At the study site located in northwest Florida, USA, Lake Miccosukee immediately drains into two sinkholes. Results from a dye tracing experiment indicate that lake water discharges at Natural Bridge Spring, a first-magnitude spring 32 km downgradient from the lake. By collecting weekly water samples from the lake, the spring, and a groundwater well 10 m away from the lake during the dry period between October 2019 and January 2020, it was found that, when rainfall effects on isotopic signature in spring water are removed, increased isotope ratios of spring water can be explained by mixing of heavy-isotope-enriched lake water into groundwater, indicating hydraulic connection between the lake and the spring. Such a detection of hydraulic connection at the scale of tens of kilometers and for a first-magnitude spring has not been previously reported in the literature. Based on the isotope ratio data, it was estimated that, during the study period, about 8.5% the spring discharge was the lake water that drained into the lake sinkholes. 相似文献
2.
Soil water stable isotopes are widely used across disciplines (e.g., hydrology, ecology, soil science, and biogeochemistry). However, the full potential of stables isotopes as a tool for characterizing the origin, flow path, transport processes and residence times of water in different eco-, hydro-, and geological compartments has not yet been exploited. This is mainly due to the large variety of different methods for pore water extraction. While recent work has shown that matric potential affects the equilibrium fractionation, little work has examined how different water retention characteristics might affect the sampled water isotopic composition. Here, we present a simple laboratory experiment with two well-studied standard soils differing in their physico-chemical properties (e.g., clayey loam and silty sand). Samples were sieved, oven-dried and spiked with water of known isotopic composition to full saturation. For investigating the effect of water retention characteristics on the extracted water isotopic composition, we used pressure extractors to sample isotopically labelled soil water along the pF curve. After pressure extraction, we further extracted the soil samples via cryogenic vacuum extraction. The null hypothesis guiding our work was that water held at different tensions shows the same isotopic composition. Our results showed that the sampled soil water differed isotopically from the introduced isotopic label over time and sequentially along the pF curve. Our and previous studies suggest caution in interpreting isotope results of extracted soil water and a need to better characterize processes that govern isotope fractionation with respect to soil water retention characteristics. In the future, knowledge about soil water retention characteristics with respect to soil water isotopic composition could be applied to predict soil water fractionation effects under natural and non-stationary conditions. In this regard, isotope retention characteristics as an analog to water retention characteristics have been proposed as a way forward since matric potential affects the equilibrium fractionation between the bound water and the water vapour. 相似文献
3.
Mass balance calculations and hydrodynamics of groundwater flow suggest that the solutes in brines of the coastal sabkha aquifer from the Emirate of Abu Dhabi are derived largely from ascending geologic brines into the sabkha from the underlying formations. Solute interpretation for the ascending brine model (ABM) was based on two independent but secondary lines of evidence (solute ratios and solute fluxes). In the current study, direct primary evidence for this ABM was provided through analyses of δ81Br, δ37Cl, and 87Sr/86Sr. Different solute histories of geologic brine and sea water provide an “isotopic fingerprint” that can uniquely distinguish between the two possible sources. Samples from the coastal sabkha aquifer of Abu Dhabi were determined to have a mean δ81Br of 1.17‰ that is statistically equal, at the 95% confidence level, to the mean of 1.11‰ observed in the underlying geologic brine and statistically different than sea water. Similarly, the δ37Cl in sabkha brine has a mean of 0.25‰ and is statistically equal to a mean of 0.21‰ in the underlying geologic brines at the 95% confidence level and statistically different from sea water. Also, dissolved strontium isotope data are consistent with the ABM and even with the complex set of processes in the sabkha, the variance in strontium isotope results is similar to the geologic brine. These observations provide primary direct evidence consistent that the major source of these solutes (and presumably others in the aquifer) is from discharging geologic brines, not from adjacent sea water. 相似文献
4.
Aquatic plants are major input sources of autochthonous organic matter in lake sediments, but investigations on fatty acid(FA) and n-alkane distributions in aquatic plants are currently limited, greatly hindering the applications of their isotope geochemistry in lacustrine environments. Here, the reported n-alkyl lipid distributions of aquatic plants in globally studied lakes,together with newly obtained aquatic plant n-alkyl lipid data in Chinese lakes(Yunnan and Inner Mongolia), are used to understand their distribution characteristics. The results show that aquatic plants have predominantly mid-chain lipids(C_(23)–C_(25) n-alkanes and C_(22)–C_(24) FAs), differing from that of terrestrial plants(dominant by long-chain lipids), but the long-chain n-alkanes(e.g., C_(27) and C_(29)) and long-chain FAs(e.g., C_(26) and C_(28)) also show high abundances in most samples. Submerged plants have high concentrations of long-chain n-alkanes(avg. 47 μg g~(-1)) and long-chain FAs(avg. 170 μg g~(-1)), close to those in terrestrial plants, indicating that submerged plants may make large contributions of long-chain n-alkyl lipids to lake sediments, while the contributions of long-chain n-alkyl lipids derived from algae to lake sediments may be small because of their low concentrations(avg. 2 μg g~(-1) for n-alkanes and 9 μg g~(-1) for FAs). We find that lipid molecular proxies(including ACL_(14-32) and ATR_(14-18)) can be reliably used to distinguish the FAs sourced from algae and other plants, and Paq′ values can be utilized to distinguish the nalkane sources between submerged plants and terrestrial plants. Aquatic plants do not have significant δD differences among different chain-length n-alkanes and FAs for each sample, suggesting that the offset between δD values of different chain-length n-alkyl lipids in lake sediments can help determine sedimentary lipid input sources and infer paleohydrological changes. 相似文献
5.
The hydrogen isotopic composition(δD) of n-alkanes in lacustrine sediments is widely used in palaeoenvironmental studies, but the heterogeneous origins and relative contributions of these lipids provide challenges for the interpretation of the increasing dataset as an environment and climatic proxy. We systematically investigated n-alkane δD values from 51 submerged plants(39 Potamogeton, 1 Myriophyllum, and 11 Ruppia), 13 algae(5 Chara, 3 Cladophora, and 5 Spirogyra) and 20 terrestrial plants(10 grasses and 10 shrubs) in and around 15 lakes on the Tibetan Plateau. Our results demonstrate that δD values of C_(29) nalkane are correlated significantly with the lake water δD values both for algae(R~2=0.85, p0.01, n=9) and submerged plants(R~2=0.90, p0.01, n=25), indicating that δD values of these algae and submerged plants reflect the δD variation of lake water. We find that apparent hydrogen isotope fractionation factors between individual n-alkanes and water(εa/w) are not constant among different algae and submerged plants, as well as in a single genus under different liminological conditions, indicating that the biosynthesis or environmental conditions(e.g. salinity) may affect their δD values. The δD values of submerged plant Ruppia in the Xiligou Lake(a closed lake) are significant enriched in D than those of terrestrial grasses around the lake(one-way ANOVA,p0.01), but the algae Chara in the Keluke Lake(an open lake) display similar δD values with grasses around the lake(one-way ANOVA, p=0.8260.05), suggesting that the n-alkane δD values of the algae and submerged plants record the signal of D enrichment in lake water relative to precipitation only in closed lakes in arid and semi-arid area. For each algae and submerged plant sample, we find uniformed δD values of different chain length n-alkanes, implying that, in combination with other proxies such as Paq and Average Chain Length, the offset between the δD values of different chain length n-alkanes can help determine the source of sedimentary n-alkanes as well as inferring the hydrological characteristics of an ancient lake basin(open vs closed lake). 相似文献
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7.
《中国科学D辑(英文版)》2008,(6)
During the 22nd Chinese Antarctic Research Expedition (CHINARE-22), the atmospheric gas samples above the oceanic surface and near the surface were collected on the track for the scientific ship "Xuelong" and on Millor Peninsula of eastern Antarctica, respectively, using the Tedlar gas bags. Every day the sampling times were 10:00 and 22:00 (local time), respectively. In the laboratory, high-precision measurement of the isotopic compositions for N2O in these gas samples was conducted using Thermo Finnigan MAT-253 Isotopic Mass Spectrometer with a fully automated interface for the pre-GC concen-tration (PreCon) of trace gases. The temporal and spatial variations of δ 15N and δ 18O in atmospheric N2O were analyzed. The mean δ 15N and δ 18O-N2O values above the oceanic surface were (7.21±0.50)‰ and (44.52±0.52)‰, respectively. From 30°N to Antarctica, the δ 15N (6.05‰―7.88‰) linearly increased with the rate of about 0.01‰ with the latitude while the δ 18O (43.05‰―48.78‰) showed a large fluctua-tion. The δ 15N negatively correlated with air temperature and N2O concentration, and slightly positively correlated with δ 18O. The summertime variations of δ 15N and δ 18O-N2O appeared the same trend on Millor Peninsula of eastern Antarctica. They significantly positively correlated with each other and negatively with N2O concentration. The δ 15N and δ 18O-N2O at different sites averaged (7.42±0.35)‰ and (44.69±0.49)‰, respectively, slightly higher than those above the oceanic surface, significantly higher than those of atmospheric N2O in the low-latitude regions of Northern Hemisphere. The predominant factors affecting the spatial variations of δ 15N and δ 18O values were also discussed. The isotopic data given in this study can help to investigate the global and regional N2O budgets. 相似文献
8.
Telogenetic epikarst carbon sourcing and transport processes and their associated hydrogeochemical responses are complex and dynamic. Carbon dioxide (CO2) transport rates in the epikarst zone are often driven by hydrogeochemical responses, which influence carbonate dissolution and conduit formation. This study examines the influence of land use on carbon sourcing and carbonate dissolution kinetics through a comparative analysis of separate, but similar, epikarst systems in south-central Kentucky. The use of high-resolution hydrogeochemical data from multiple data loggers and isotope analysis from collected water samples reflects the processes within these epikarst aquifers, which are estimated to contribute significantly to bedrock dissolution. Results indicate that, in an agricultural setting, long-term variability and dissolution is governed by seasonal production of CO2 . In a more urbanized, shallower epikarst system, land cover may affect CO2 transport between the soil and underlying bedrock. This concentration of CO2 potentially contributes to ongoing dissolution and conduit development, irrespective of seasonality. The observed responses in telogenetic epikarst systems seem to be more similar to eogenetic settings, which is suggested to be driven by CO2 transport occurring independent of high matrix porosity. The results of this study indicate site-specific responses with respect to both geochemical and δ13CDIC changes on a seasonal scale, despite regional geologic similarities. The results indicate that further comparative analyses between rural and urban landscapes in other karst settings is needed to delineate the impact of land use and seasonality on dissolution and carbon sourcing during karst formation processes. © 2019 John Wiley & Sons, Ltd. 相似文献
9.
Luigi Marini Valeria Chiappini Roberto Cioni G. Cortecci E. Dinelli Claudia Principe Giorgio Ferrara 《Bulletin of Volcanology》1998,60(3):187-194
Sulfur contents and δ34S values of Somma-Vesuvius magmas are consistent with syneruptive, open-system degassing at temperatures of 800–850°C for
Plinian pumices and 1100–1200°C for lavas. The extent of degassing appears to be greater in lavas than in pumices. The key
parameter controlling the 34S/32S ratio of Somma-Vesuvius volcanics is the average magma oxidation state, which generally varies from 0.85 to 1.20 Δ NNO units
for lavas and from 1.20 to 1.40 Δ NNO units for pumices. Consequently, S contents and δ34S values of magmas constitute a potentially valuable tool in estimating their average redox conditions. The results of this
study may help in risk mitigation when the Vesuvius magmatic system evolves toward eruptive conditions.
Received: 20 January 1998 / Accepted: 5 May 1998 相似文献
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12.
Kwadwo Ansong Asante Tetsuro Agusa Reiji Kubota Hiroko Mochizuki Shuhei Nishida Suguru Ohta Annamalai Subramanian 《Marine pollution bulletin》2010,60(9):1560-1570
Trace elements (TEs) and stable isotope ratios (δ15N and δ13C) were analyzed in fish from deep-water of the Sulu Sea, the Celebes Sea and the Philippine Sea. Concentrations of V and Pb in pelagic fish from the Sulu Sea were higher than those from the Celebes Sea, whereas the opposite trend was observed for δ13C. High concentrations of Zn, Cu and Ag were found in non-migrant fish in deep-water, while Rb level was high in fish which migrate up to the epipelagic zone, probably resulting from differences in background levels of these TEs in each water environment or function of adaptation to deep-water by migrant and non-migrant species. Arsenic level in the Sulu Sea fish was positively correlated with δ15N, indicating biomagnification of arsenic. To our knowledge, this is the first study on relationship between diel vertical migration and TE accumulation in deep-water fish. 相似文献
13.
The sorption of AuCl4
−,AuCl2
− and Au(S2O3)3- on δ-MnO2 was investigated at pH2–11.6, 0.01 mol/L and 0.1 mol/L NaNO3 solutions. At pH 4 in two electrolyte strength solutions, Au sorption densities on δ-MnO2 are 0.18–0.21 and 0.28μmoL/m2 for AuCl4
− and Au(S2O3)2
3-, respectively, and the Au surface coverage is approximate to or lower than 1%. This adsorption of the two Au complexes decreases
as the solution pH increases, which conforms to the sorption regularity of the anion on δ-MnO2. The Au sorption decreases in the sequence of Au(S2O3)2
3- >AuCl4
− >AuC12
−. The intrinsic equilibrium constants (logK
int) of the three Au complexes are 1.17–2.7, much higher than those of Cu and Cd. The hydrolysis products of AuCl4
- are preferentially adsorbed by δ-MnO2 and the inner-sphere Au-surface complexes are formed on the surface.
Project supported by the National Studying-abroad Foundation, the National Natural Science Foundation of China (Grant No.
49573200) and the Australian Mining Industry. 相似文献
14.
JIANG FuQing ZHOU XiaoJing LI AnChun & LI TieGang Key laboratory of Marine Geology Environment 《中国科学D辑(英文版)》2009,(2)
Sediment samples were collected from the lower channel of the Yangtze River and the Yellow River and the contents of rare earth elements (REEs) were measured. In addition, some historical REEs data were collected from published literatures. Based on the δEuN-ΣREEs plot, a clear boundary was found be-tween the sediments from the two rivers. The boundary can be described as an orthogonal polynomial equation by ordinary linear regression with sediments from the Yangtze River located above the curve and sedimen... 相似文献
15.
Gao Chen Jason J. Venkiteswaran Sherry L. Schiff William D. Taylor 《Aquatic Sciences - Research Across Boundaries》2014,76(3):313-329
A transient model, hereafter referred to as ROM-TM, was developed to quantify river ecosystem metabolic rates and reaeration rates from field observation of changes in dissolved O2 (DO) and the ratio of 18O to 16O in DO (δ18O-DO). ROM-TM applies an inverse modeling approach and is programmed using MATLAB. Parameters describing photosynthesis, ecosystem respiration, gas exchange, and isotopic fractionation, such as maximum photosynthetic rate (P m ), photosynthetic efficiency parameter (a), respiration rate at 20 °C (R 20 ), gas exchange coefficient (K), respiration isotopic fractionation factor (a R ), and photorespiration coefficient (β R ), can be abstracted by minimizing the sum of square errors between the fitted data and the observed field data. Then DO and δ18O-DO time series can be reconstructed using estimated parameters and input variables. Besides being capable of teasing apart metabolic processes and gas exchange to provide daily average estimates of metabolic parameters at the ecosystem scale, ROM-TM can be used to address issues related to light including light saturation phenomena at the ecosystem level, the effect of cloud cover on the metabolic balance, and photorespiration. Error and uncertainty analysis demonstrates that ROM-TM is stable and robust for the random errors of DO time series. The photosynthetic parameters P m and a are more sensitive than other parameters to lower-resolution time series data. 相似文献
16.
Pan Luo Ping'an Peng Gerd Gleixner Zhuo Zheng Zhonghe Pang Zhongli Ding 《Earth and Planetary Science Letters》2011,301(1-2):285-296
Estimating past elevation not only provides evidence for vertical movements of the Earth's lithosphere, but also increases our understanding of interactions between tectonics, relief and climate in geological history. Development of biomarker hydrogen isotope-based paleoaltimetry techniques that can be applied to a wide range of sample types is therefore of continuing importance. Here we present leaf wax-derived n-alkane δD (δDwax) values along three soil altitudinal transects, at different latitudes, in the Wuyi, Shennongjia and Tianshan Mountains in China, to investigate δDwax gradients and the apparent fractionation between leaf wax and precipitation (εwax-p).We find that soil δDwax track altitudinal variations of precipitation δD along the three transects that span variable environment conditions and vertical vegetation spectra. An empirical δDwax-altitude relation is therefore established in which the average δDwax lapse rate of ? 2.27 ± 0.38‰/100 m is suitable for predicting relative paleoelevation change (relative uplift). The application of this empirical gradient is restricted to phases in the mountain uplift stage when the atmospheric circulation had not distinctly changed and to when the climate was not arid. An empirical δDwax–latitude–altitude formula is also calculated: δDwax = 3.483LAT ? 0.0227ALT ? 261.5, which gives the preliminary spatial distribution pattern of δDwax in modern China.Mean value of εwax-p in the extreme humid Wuyi Mountains is quite negative (? 154‰), compared to the humid Shennongjia (? 129‰) and the arid (but with abundant summer precipitation) Tianshan Mountains (? 130‰), which suggests aridity or water availability in the growing season is the primary factor controlling soil/sediment εwax-p. Along the Tianshan transects, values of εwax-p are speculated to be constant with altitude; while along the Wuyi and Shennongjia transects, εwax-p are also constant at the low-mid altitudes, but become slightly more negative at high altitudes which could be attributed to overestimates of precipitation δD or the vegetation shift to grass/conifer.Additionally, a reversal of altitude effect in the vertical variation of δDwax was found in the alpine zone of the Tianshan Mountains, which might be caused by atmospheric circulation change with altitude. This implies that the paleo-circulation pattern and its changes should also be evaluated when stable isotope-based paleoaltimetry is applied. 相似文献
17.
Zhixin Ke Yehui Tan Liangmin Huang Chunyu Zhao Xin Jiang 《Marine pollution bulletin》2017,114(1):183-191
Stable isotopic signatures (δ13C and δ15N) and C/N ratios of suspended particulate organic matter (POM) were investigated from the surface water of Daya Bay during summer and winter of 2015. The relatively high δ13CPOM values suggested the input of 13C-depleted terrigenous organic matter was low in Daya Bay. There were significant correlations between δ13CPOM values and chlorophyll a concentrations both during summer and winter, suggesting the δ13CPOM values were mainly controlled by the phytoplankton biomass in the surface water. The distribution of δ15NPOM values was more complicated than that of δ13CPOM and displayed low values in the outer bay and the Dan'ao River estuary. 15N-depleted ammonia originating from industrial wastewater might have strongly influenced the water quality and stable isotopic signatures of POM near the Dan'ao River estuary. The δ13CPOM and δ15NPOM values strongly reflect the influences of anthropogenic activity and eutrophication in Daya Bay. 相似文献
18.
Alejandra Piñón-Gimate María Julia Ochoa-Izaguirre Federico Páez-Osuna 《Marine pollution bulletin》2009,58(8):1144-74
Macroalgae blooms of Gracilaria vermiculophylla, Hypnea spinella and Spyridia filamentosa have been found in coastal lagoons in the SE Gulf of California. Agriculture, livestock, shrimp and poultry farms and sewage contribute anthropogenic nitrogen to the systems. The δ15N of these sources, water column and macroalgae were studied in order to identify the N supply for macroalgae blooms. δ15N of three species of macroalgae (4.3-13.6‰) were enriched compared to the water column ( 3.7-6.8‰), probably because of fractioning from the macroalgae. δ15N of POM (1.4-10.3‰) was similar to the water column but the relationship was unclear. Depending on the site, macroalgae showed different δ15N values since some sites receive more or less influence from one given source of the associated watershed, which is reflected in the different δ15N values of the macroalgae of the same system and in the relative contributions of the sources. 相似文献
19.
XIAO YingKai LIU WeiGuo MA YunQi ZHANG YanLing HE MaoYong LUO ChongGuang LIAO QingQiang 《中国科学:地球科学(英文版)》2014,57(5):1048-1060
To be used as proxies of seawater surface temperature(SST), the δ 18Oc values and Sr/Ca and Mg/Ca ratios of scleractinian coral skeletons must be verified by coral culture experiments in the laboratory. This paper describes a coral culture experiment that was conducted at several seawater temperatures T(21–28°C) using a tandem aquarium system and the new method for depositing coral skeletons grown under controlled conditions. The δ 18Oc values and the Sr/Ca and Mg/Ca ratios of the cultured coral were measured. We concluded that the δ 18Oc values and Sr/Ca and Mg/Ca ratios of the cultured coral are clearly correlated with T. The linear regression curve is δ18Oc(‰)=δ0.1427δT(°C)δ0.1495(n=18, r=0.955, p0.0001), and the slope of δ0.1427‰/°C is at the low end of the range of published values(δ0.13–δ0.29‰/°C). The Sr/Ca ratio decreases with increasing T, whereas the Mg/Ca ratio increases with increasing T, indicating a negative correlation between Sr/Ca and Mg/Ca. Their linear regression curves are Sr/Ca(mmol/mol)=δ0.04156δT+10.59(n=15, r=0.789, p0.005) and Mg/Ca(mmol/mol)= 0.04974δT+2.339(n=17, r=0.457, p0.05), respectively, which demonstrate that when Mg/Ca and Sr/Ca are increased by one unit, T increases by 5.19°C and decreases by 15.62°C, respectively. These variations are significantly lower than published values. 相似文献
20.
《中国科学:地球科学(英文版)》2017,(9)
Stable isotope paleoaltimetry has provided unprecedented insights into the topographic histories of many of the world's highest mountain ranges. However, on the Tibetan Plateau(TP), stable isotopes from paleosols generally yield much higher paleoaltitudes than those based on fossils. It is therefore essential when attempting to interpret accurately this region's paleoaltitudes that the empirical calibrations of local stable isotopes and the relations between them are established. Additionally,it is vital that careful estimations be made when estimate how different isotopes sourced from different areas may have been influenced by different controls. We present here 29 hydrogen isotopic values for leaf wax-derived n-alkanes(i.e., δD_(wax) values,and abundance-weighted average δD values of C_(29) and C_(31)) in surface soils, as well as the δD values of soil water(δD_(sw)) samples(totaling 22) from Mount Longmen(LM), on the eastern TP(altitude ~0.8–4.0 km above sea level(asl), a region climatically affected by the East Asian Monsoon(EAM). We compared our results with published data from Mount Gongga(GG). In addition,47 river water samples, 55 spring water samples, and the daily and monthly summer precipitation records(from May to October,2015) from two precipitation observation stations were collected along the GG transect for δD analysis. LM soil δD_(wax) values showed regional differences and responded strongly to altitude, varying from.160‰ to.219‰, with an altitudinal lapse rate(ALR) of.18‰ km~(-1)(R~2=0.83; p0.0001; n=29). These δD_(wax) values appeared more enriched than those from the GG transect by ~40‰. We found that both the climate and moisture sources led to the differences observed in soil δD_(wax) values between the LM and GG transects. We found that, as a general rule, ε_(wax/rw), ε_(wax/p) and εwax/sw values(i.e., the isotopic fractionation of δD_(wax) corresponding to δD_(rw), δD_p and δD_(sw)) increased with increasing altitude along both the LM and GG transects(up to 34‰ and 50‰, respectively). Basing its research on a comparative study of δD_(wax), δD_p, δD_(rw)(δD_(springw)) and δD_(sw), this paper discusses the effects of moisture recycling, glacier-fed meltwater, relative humidity(RH), evapotranspiration(ET), vegetation cover, latitude,topography and/or other factors on ε_(wax/p) values. Clearly, if ε_(wax-p) values at higher altitudes are calculated using smaller ε_(wax-p) values from lower altitudes, the calculated paleowaterδD_p values are going to be more depleted than the actual δD values, and any paleoaltitude would therefore be overestimated. 相似文献