Isotopic and geochemical characterization of invader tilapia fishes from water bodies of West Bengal and Karnataka, India

The otoliths (N = 12) of freshwater invasive species tilapia (Tilapia mossambicus) collected from two water bodies located at Kolkata and Bangalore, India, were analyzed for stable isotopes (delta 18O, delta 14C) and major and trace elements in order to assess the suitability of using otoliths as a tracer of aquatic environmental changes. The stable isotope analysis was done using the dual inlet system of a Finnigan-MAT 253 isotope ratio mass spectrometer (Thermo-Fisher, Bremen, Germany). Concentrations of major and trace elements were determined using a Thermo X-Series II quadrupole mass spectrometer. The stable isotope composition in tilapia otolith samples from Bangalore and Kolkata water bodies are quite good agreeing with that of the respective lake/pond and rain water. Elemental composition revealed in a pattern of Ca > Fe > Na > Sr > K > Ba > Cr > Mg > As > Mn > Zn > Co > Cu > Cd > Pb. The otoliths from Kolkata pond water are more enriched in Ba, Zn, Pb, Mn, Se, Cu, Zn, Cd, and Ni whereas Cr and As were found to be higher in otolith samples from Bangalore lake. The enrichment factor (EF) values of Cr were higher for both the sampling location in comparison with other metals, although all the studied metals exhibited EF values >1. The PCA shows clustering of metals in the otolith which are related either with the metabolic and physiological attributes or waterborne source. The study demonstrated the potential of stable isotope techniques to distinguish otolith specimens from varied climatic zone, while elemental composition recorded the quality of water at both the locations. The role of climate driving the quality of water can be understood by detailed and continuous monitoring of otolith specimens in the future. Future method allows reconstruction of climate and water quality from old specimens from field exposures or museum collection.

Use of Sr isotopes as a tool to decipher the soil weathering processes in a tropical river catchment, southwestern India

River water composition (major ion and Sr-87/Sr-86 ratio) was monitored on a monthly basis over a period of three years from a mountainous river (Nethravati River) of southwestern India. The total dissolved solid (TDS) concentration is relatively low (46 mg L-1) with silica being the dominant contributor. The basin is characterised by lower dissolved Sr concentration (avg. 150 nmol L-1), with radiogenic Sr-87/Sr-86 isotopic ratios (avg. 0.72041 at outlet). The composition of Sr and Sr-87/Sr-86 and their correlation with silicate derived cations in the river basin reveal that their dominant source is from the radiogenic silicate rock minerals. Their composition in the stream is controlled by a combination of physical and chemical weathering occurring in the basin. The molar ratio of SiO2/Ca and Sr-87/Sr-86 isotopic ratio show strong seasonal variation in the river water, i.e., low SiO2/Ca ratio with radiogenic isotopes during non-monsoon and higher SiO2/Ca with less radiogenic isotopes during monsoon season. Whereas, the seasonal variation of Rb/Sr ratio in the stream water is not significant suggesting that change in the mineral phase being involved in the weathering reaction could be unlikely for the observed molar SiO2/Ca and Sr-87/Sr-86 isotope variation in river water. Therefore, the shift in the stream water chemical composition could be attributed to contribution of ground water which is in contact with the bedrock (weathering front) during non-monsoon and weathering of secondary soil minerals in the regolith layer during monsoon. The secondary soil mineral weathering leads to limited silicate cation and enhanced silica fluxes in the Nethravati river basin. (C) 2015 Elsevier Ltd. All rights reserved.

Oxygen isotopes and volatiles in martian meteorites

Oxygen isotopes were measured in mineral separates from martian meteorites using laser fluorination and were found to be remarkably uniform in both δ18O and Δ17O, suggesting that martian magmas did not assimilate aqueously altered crust regardless of any other geochemical variations.

Measurements of Cl, F, H, and S in apatite from martian meteorites were made using the SIMS and NanoSIMS. Martian apatites are typically higher in Cl than terrestrial apatites from mafic and ultramafic rocks, signifying that Mars is inherently higher in Cl than Earth. Apatites from basaltic and olivine-phyric shergottites are as high in water as any terrestrial apatite from mafic and utramafic rocks, implying the possibility that martian magmas may be more similar in water abundance to terrestrial magmas than previously thought. Apatites from lherzolitic shergottites, nakhlites, chassignites, and ALH 84001 (all of which are cumulate rocks) are all lower in water than the basaltic and olivine-phyric shergottites, indicating that the slow-cooling accumulation process allows escape of water from trapped melts where apatite later formed. Sulfur is only high in some apatites from basaltic and olivine-phyric shergottites and low in all other SNCs from this study, which could mean that cumulate SNCs are low in all volatiles and that there are other controlling factors in basaltic and olivine-phyric magmas dictating the inclusion of sulfur into apatite.

Sulfur Kα X-rays were measured in SNC apatites using the electron probe. None of the peaks in the SNC spectra reside in the same position as anhydrite (where sulfur is 100% sulfate) or pyrite (where sulfur is 100% sulfide), but instead all SNC spectra peaks lie in between these two end member peaks, which implies that SNC apatites may be substituting some sulfide, as well as sulfate, into their structure. However, further work is needed to verify this hypothesis.

Ratio of natural isotopes of nitrogen. I. Primary results: soils of Dombes [Translation from: Revue d'Ecologie et de Biologie du Sol 14, 279-287, 1977]

Utilization of the heavy isotope of nitrogen as a tracer has found numerous applications in soil biology. It allows better definition of different stages of the nitrogen cycle, in particular the immobilization-mineralization cycle. In this work, the authors report the results of calculations of natural isotope ratios of nitrogen in samples of water, soil and vegetation prevailing in Dombes and discuss the possibilities of errors and coefficients of fractionation.

Preliminary use of oxygen stable isotopes and the 1983 El Niño to assess the accuracy of aging black rockfish (Sebastes melanops)

Black rockfish (Sebastes melanops) range from California to Alaska and are found in both nearshore and shallow continental shelf waters (Love et al., 2002). Juveniles and subadults inhabit shallow water, moving deeper as they grow. Generally, adults are found at depths shallower than 55 meters and reportedly live up to 50 years. The species is currently managed by using information from an age-structured stock assessment model (Ralston and Dick, 2003).

Evolution and variation of the Tsushima warm current during the late Quaternary: Evidence from planktonic foraminifera, oxygen and carbon isotopes

The evolution and variation history of the Tsushima warm current during the late Quaternary was reconstructed based on the quantitative census data of planktonic foraminiferal fauna, together with oxygen and carbon isotope records of mixed layer dweller a ruber and thermocline dweller N. dutertrei in piston core CSH1 and core DGKS9603 collected separately from the Tsushima warm current and the Kuroshio dominated area. The result showed that the Tsushima warm current vanished in the lowstand period during 40-24 cal ka BP, while the Kuroshio still flowed across the Okinawa Trough, arousing strong upwelling in the northern Trough. Meanwhile, the influence of freshwater greatly increased in the northern Okinawa Trough, as the broad East China Sea continental shelf emerged. The freshwater reached its maximum during the last glacial maximum (LGM), when the upwelling obviously weakened for the lowest sea-level and the depression of the Kuroshio. The modern Tsushima warm current began its development since 16 cal ka BP, and the impact of the Kuroshio increased in the middle and northern Okinawa Trough synchronously during the deglaciation and gradually evolved as the main water source of the Tsushima current. The modern Tsushima current finally formed at about 8.5 cal ka BP, since then the circulation structure has been relatively stable. The water of the modern Tsushima current primarily came from the Kuroshio axis. A short-term wiggle of the current occurred at about 3 cal ka BP, probably for the influences from the enhancement of the winter monsoon and the depression of the Kuroshio. The cold water masses greatly strengthened during the wiggle.

Authigenic sulfide minerals and their sulfur isotopes in sediments of the northern continental slope of the South China Sea and their implications for methane flux and gas hydrate formation

This is a report of the study of the authigenic sulfide minerals and their sulfur isotopes in a sediment core (NH-1) collected on the northern continental slope of the South China Sea, where other geophysical and geochemical evidence seems to suggest gas hydrate formation in the sediments. The study has led to the findings: (1) the pyrite content in sediments was relatively high and its grain size relatively large compared with that in normal pelagic or hemipelagic sediments; (2) the shallowest depth of the acid volatile sulfide (AVS) content maximum was at 437.5 cm (> 2 mu mol/g), which was deeper than that of the authigenic pyrite content maximum (at 141.5-380.5 cm); (3) delta S-34 of authigenic pyrite was positive (maximum: +15 parts per thousand) at depth interval of 250-380 cm; (4) the positive delta S-34 coincided with pyrite enrichment. Compared with the results obtained from the Black Sea sediments by Jorgensen and coworkers, these observations indicated that at the NH-1 site, the depth of the sulfate-methane interface (SMI) would be or once was at about 437.5-547.5 cm and the relatively shallow SMI depth suggested high upward methane fluxes. This was in good agreement with the results obtained from pore water sulfate gradients and core head-space methane concentrations in sediment cores collected in the area. All available evidence suggested that methane gas hydrate formation may exist or may have existed in the underlying sediments.

Enrichment of stable carbon and nitrogen isotopes of plant populations and plateau pikas along altitudes

Stable carbon and nitrogen isotope ratios were measured in plant populations and plateau pikas to determine enrichment in stable isotopes of three alpine meadow ecosystems at different elevations in the Qinghai-Tibet Plateau. The results indicated that stable carbon isotope signatures of plant populations at the three locations showed significant variations, delta C-13 of plant populations showed an enrichment of 0.86 parts per thousand per 1000 in over the linear proportion of the altitudinal response, while stable nitrogen isotopes showed no apparent difference. The stable nitrogen isotopes of plateau pikas became significantly isotopically heavier along altitudinal gradients and showed an enrichment of 3.17 parts per thousand/km. Stable carbon isotopes showed no significance, however, and the enrichment of 0.448 parts per thousand/km. delta C-13 and delta N-15 in plateau pikas were not significantly correlated. There appeared to be segregation between the metabolism of stable carbon and nitrogen isotopes of plateau pikas. Variances in metabolic rate at lower water availability and temperatures are presumed to be the main cause of enrichment of stable nitrogen isotopes along altitudinal gradients. Attention should be paid to construct trophic positions and to trace food chain information based oil an isotopic enrichment model.

Impacts of shale gas wastewater disposal on water quality in western Pennsylvania.

The safe disposal of liquid wastes associated with oil and gas production in the United States is a major challenge given their large volumes and typically high levels of contaminants. In Pennsylvania, oil and gas wastewater is sometimes treated at brine treatment facilities and discharged to local streams. This study examined the water quality and isotopic compositions of discharged effluents, surface waters, and stream sediments associated with a treatment facility site in western Pennsylvania. The elevated levels of chloride and bromide, combined with the strontium, radium, oxygen, and hydrogen isotopic compositions of the effluents reflect the composition of Marcellus Shale produced waters. The discharge of the effluent from the treatment facility increased downstream concentrations of chloride and bromide above background levels. Barium and radium were substantially (>90%) reduced in the treated effluents compared to concentrations in Marcellus Shale produced waters. Nonetheless, (226)Ra levels in stream sediments (544-8759 Bq/kg) at the point of discharge were ~200 times greater than upstream and background sediments (22-44 Bq/kg) and above radioactive waste disposal threshold regulations, posing potential environmental risks of radium bioaccumulation in localized areas of shale gas wastewater disposal.

Hydrochemical and isotopic tracing of mixing dynamics and water quality evolution under pumping conditions in the mine shaft of the abandoned Frances Colliery, Scotland.

Since 1995, when pumps were withdrawn from deep mines in East Fife (Scotland), mine waters have been rebounding throughout the coalfield. Recently, it has become necessary to pump and treat these waters to prevent their uncontrolled emergence at the surface. However, even relatively shallow pumping to surface treatment lagoons of the initially chemically-stratified mine water from a shaft in the coastal Frances Colliery during two dynamic step-drawdown tests to establish the hydraulic characteristics of the system resulted in rapid breakdown of the stratification within 24 h and a poor pumped water quality with high dissolved Fe loading. Further, data are presented here of hydrochemical and isotopic sampling of the extended pump testing lasting up to several weeks. The use in particular of the environmental isotopes d18O, d2H, d34S, 3H, 13C and 14C alongside hydrochemical and hydraulic pump test data allowed characterisation of the Frances system dynamics, mixing patterns and water quality sources feeding into this mineshaft under continuously pumped conditions. The pumped water quality reflects three significant components of mixing: shallow freshwater, seawater, and leakage from the surface treatment lagoons. In spite of the early impact of recirculating lagoon waters on the hydrochemistries, the highest Fe loadings in the longer-term pumped waters are identified with a mixed freshwater–seawater component affected by pyrite oxidation/melanterite dissolution in the subsurface system.

Isotopic assessment of sources and processes affecting sulfate and nitrate in surface water and groundwater of Luxembourg

Surface water and deep and shallow groundwater samples were taken from selected parts of the Grand-Duchy of Luxembourg to determine the isotopic composition of nitrate and sulfate, in order to identify sources and/or processes affecting these solutes. Deep groundwater had sulfate concentrations between 20 and 40 mg/L, d34Ssulfate values between -3.0 and -20.0‰, and d18Osulfate values between +1.5 and +5.0‰; nitrate was characterized by concentrations varying between

Oxygen isotopes from Phorcus (Osilinus) turbinatus shells as a proxy for sea surface temperature in the central Mediterranean: a case study from Malta.

The marine topshell, Phorcus (Osilinus) turbinatus, is a common component of many archaeological sites in the Mediterranean. This species has been successfully used as a palaeoclimate proxy in Italy. To test whether d18O from P. turbinatus shells can serve as a reliable palaeoclimate archive for other regions of the Mediterranean, we collected live P. turbinatus from the northeast coast of Malta each month for a year. The d18OSHELL values of the outermost growth increments of these live-collected shells ranged between-0.4 and+2.4‰. These values correspond to growing temperatures calculated from shell edge d18O of between 15 °C and 27 °C. Calculated shell edge sea surface temperatures are highly correlated with instrumental records of sea surface temperature recorded over the period of collection. The individuals analysed for this study are smaller than P. turbinatus from populations studied elsewhere in the Mediterranean. Nonetheless, d18OSHELL provides a robust record of sea surface temperatures, suggesting that smaller/younger shells in archaeological deposits can still provide reliable palaeothermometry records. This study extends the upper growth limit P. turbinatus by 2 °C compared with the previous studies of P. turbinatus in the Mediterranean and suggests that, contrary to the previous studies, growth shutdown does not occur in all P. turbinatus when sea surface temperatures exceed 25 °C. This may reflect the higher sample resolution that can be obtained from smaller/faster growing shells, or it may reflect actual higher growth tolerances of P. turbinatus populations in Malta. By showing that P. turbinatus precipitate their shells in d18O equilibrium with surrounding sea water, this study reinforces the potential for the stable isotope chemistry of P. turbinatus shells preserved in Mediterranean archaeological sites to provide a window into the climate and seasonality regimes of the past.

Tracing coastal organic enrichment: stable isotopes and biotic indices

Neste trabalho foi efectuada uma avaliação integrada usando descritores sedimentares e biológicos ao nível da espécie e da comunidade e índices bióticos de síntese para o traçamento do enriquecimento orgânico numa região, com características dispersivas, da costa Oeste de Portugal. Na área estudada existem gradientes ambientais e biológicos relacionados com a heterogeneidade da paisagem sedimentar, a qual inclui sedimentos desde areias finas limpas a vasas. Contudo, na área próxima do emissário, esta paisagem é mais homogénea e constituída por areia fina com baixo teor em finos. Nesta região, alguns dos descritores estudados deram uma indicação coerente de alterações ambientais associadas ao enriquecimento orgânico. O potencial de oxidação - redução mostrou valores negativos até 250 m do emissário, o que indicia que a degradação da matéria orgânica que entra no sistema cria condições reduzidas no sedimento. Os isótopos estáveis de carbono e azoto no sedimento diferenciam a área mais próxima do emissário, que apresenta uma depleção de acordo com uma origem terrestre da matéria orgânica naquela parte da plataforma. Uma imagem similar foi obtida pela análise dos isótopos estáveis na macrofauna que diagnosticou a origem terrestre da matéria orgânica consumida. A composição específica e a abundância das comunidades bentónicas também são significativamente diferentes junto ao emissário, onde são dominadas por espécies oportunistas, tolerantes ao enriquecimento orgânico. No entanto, os índices bióticos em validação no âmbito da implementação da Directiva Quadro da Água, não foram eficientes a mostrar as alterações bentónicas associadas ao enriquecimento orgânico apesar de alguns índices se basearem nos limiares de tolerância/sensibilidade a este tipo de perturbação. Apesar deste caso de estudo reflectir um enriquecimento orgânico moderado, uma vez que não foram detectadas alterações sedimentares ou acumulação de matéria orgânica, nem um significativo empobrecimento das comunidades biológicas junto ao emissário, a análise ao nível dos índices bióticos de síntese pode levar à perda de informação essencial e, portanto, prejudicar a nossa capacidade de diagnóstico devendo ser usados com cuidado. A análise do conjunto de dados da composição específica forneceu uma imagem mais precisa da perturbação ambiental e descritores específicos, tais como os isótopos estáveis, permitiram uma melhor compreensão da extensão espacial do enriquecimento orgânico.

Assessing the sources and magnitude of diurnal nitrate variability in the San Joaquin River (California) with an in-situ optical nitrate sensor and dual nitrate isotopes

We investigated diurnal nitrate (NO3-) concentration variability in the San Joaquin River using an in situ optical NO3- sensor and discrete sampling during a 5-day summer period characterized by high algal productivity. Dual NO3- isotopes (delta N-15(NO3) and delta O-18(NO3)) and dissolved oxygen isotopes (delta O-18(DO)) were measured over 2 days to assess NO3- sources and biogeochemical controls over diurnal time-scales. Concerted temporal patterns of dissolved oxygen (DO) concentrations and delta O-18(DO) were consistent with photosynthesis, respiration and atmospheric O-2 exchange, providing evidence of diurnal biological processes independent of river discharge. Surface water NO3- concentrations varied by up to 22% over a single diurnal cycle and up to 31% over the 5-day study, but did not reveal concerted diurnal patterns at a frequency comparable to DO concentrations. The decoupling of delta N-15(NO3) and delta O-18(NO3) isotopes suggests that algal assimilation and denitrification are not major processes controlling diurnal NO3- variability in the San Joaquin River during the study. The lack of a clear explanation for NO3- variability likely reflects a combination of riverine biological processes and time-varying physical transport of NO3- from upstream agricultural drains to the mainstem San Joaquin River. The application of an in situ optical NO3- sensor along with discrete samples provides a view into the fine temporal structure of hydrochemical data and may allow for greater accuracy in pollution assessment.