Seasonal variation in natural abundance of δ13C and 15N in Salicornia brachiata Roxb. populations from a coastal area of India

High and fluctuating salinity is characteristic for coastal salt marshes, which strongly affect the physiology of halophytes consequently resulting in changes in stable isotope distribution. The natural abundance of stable isotopes (δ¹³C and δ¹⁵N) of the halophyte plant Salicornia brachiata and physico-chemical characteristics of soils were analysed in order to investigate the relationship of stable isotope distribution in different populations in a growing period in the coastal area of Gujarat, India. Aboveground and belowground biomass of S. brachiata was collected from six different populations at five times (September 2014, November 2014, January 2015, March 2015 and May 2015). The δ¹³C values in aboveground (?30.8 to ?23.6?‰, average: ?26.6?±?0.4?‰) and belowground biomass (?30.0 to ?23.1?‰, average: ?26.3?±?0.4?‰) were similar. The δ¹³C values were positively correlated with soil salinity and Na concentration, and negatively correlated with soil mineral nitrogen. The δ¹⁵N values of aboveground (6.7–16.1?‰, average: 9.6?±?0.4?‰) were comparatively higher than belowground biomass (5.4–13.2?‰, average: 7.8?±?0.3?‰). The δ¹⁵N values were negatively correlated with soil available P. We conclude that the variation in δ¹³C values of S. brachiata was possibly caused by soil salinity (associated Na content) and N limitation which demonstrates the potential of δ¹³C as an indicator of stress in plants.     

There is no Temperature Dependence of Net Biochemical Fractionation of Hydrogen and Oxygen Isotopes in Tree-Ring Cellulose

Abstract

The isotopic composition of tree-ring cellulose was obtained over a two-year period from small diameter, riparian zone trees along an elevational transect in Big Cottonwood Canyon, Utah, USA to test for a possible temperature dependence of net biological fractionation during cellulose synthesis. The isotope ratios of stream water varied by only 3.6‰ and 0.2‰ in δD and δ¹⁸O, respectively, over an elevation change of 810m. The similarity in stream water and macroenvironment over the short (13km) transect produced nearly constant stem and leaf water δD and δ¹⁸O values. In addition, what few seasonal variations observed in the isotopic composition of source water and atmospheric water vapor or in leaf water evaporative enrichment were experienced equally by all sites along the elevational transect. The temperature at each site along the transect spanned a range of ≥ 5°C as calculated using the adiabatic lapse rate. Since the δD and δ¹⁸O values of stem and leaf water varied little for these trees over this elevation/ temperature transect, any differences in tree-ring cellulose δD and δ¹⁸O values should have been associated with temperature effects on net biological fractionation. However, the slopes of the regressions of elevation versus the δD and δ¹⁸O values of tree-ring cellulose were not significantly different from zero indicating little or no temperature dependence of net biological fractionation. Therefore, cross-site climatic reconstruction studies using the isotope ratios of cellulose need not be concerned that temperatures during the growing season have influenced results.     

Comparison of δ13C and δ18O from cellulose,whole wood,and resin-free whole wood from an old high elevation Pinus uncinata in the Spanish central Pyrenees*

δ¹³C and δ¹⁸O values from sapwood of a single Pinus uncinata tree, from a high elevation site in the Spanish Pyrenees, were determined to evaluate the differences between whole wood and resin-free whole wood. This issue is addressed for the first time with P. uncinata over a 38-year long period. Results are also compared with published isotope values of α-cellulose samples from the same tree. The differences in δ¹³C and δ¹⁸O between whole wood and resin-free whole wood vary within the analytical uncertainty of 0.3 and 0.5?‰, respectively, indicating that resin extraction is not necessary for sapwood of P. uncinata. Mean differences between cellulose and whole wood are 0.9?‰ (δ¹³C) and 5.0?‰ (δ¹⁸O), respectively. However, further analyses of different species and other sites are needed to evaluate whether the findings reported here are coherent more generally.     

Isotopic fingerprints of the Lake Żabińskie (NE Poland) hydrological system on contemporary carbonates precipitated in the lake

An isotopic monitoring was undertaken in 2012–2014 at Lake ?abińskie (Mazurian Lakeland, NE Poland). The aim was to identify the factors and processes controlling an isotopic composition of the lake water and to explore the mechanism responsible for recording the climatic signal in stable isotope composition of deposited carbonates. δ¹⁸O and δ²H in the precipitation, lake water column, inflows and outflow, δ¹⁸O and δ¹³C in the carbonate fraction of sediments trapped in the water column were recorded with monthly resolution. A relationship between δ¹⁸O and δ²H in local precipitation was used to estimate the local meteoric water line. The dataset obtained for the water enabled to identify the modification of the water’s isotopic composition due to evaporation, connected with seasonal lake water stratification and mixing patterns. Statistically significant correlation coefficients suggest that the δ¹⁸O of the carbonate fraction in the sediment traps depends on the δ¹⁸O of rainfall water and on air temperature. The fractionation coefficient α shows that in summer months the carbonate precipitation process is closest to equilibrium. As expected for an exorheic lake, no significant correlation was observed between δ¹⁸O and δ¹³C in precipitated carbonate.     

Groundwater of the Crimean peninsula: a first systematic study using stable isotopes

ABSTRACT

Karst springs in the Main Range of the Crimean Mountains and the Crimean Piedmont show a restricted range of values (δ¹⁸O?=?–10.5 to –8.0 ‰, δ²H?=?–72 to –58 ‰), somewhat more negative than the weighted mean of meteoric precipitation. This suggests preferential recharge at higher elevations during winter months. Groundwater tapped by boreholes splits in three groups. A first group has isotopic properties similar to those of the springs. The second group shows significantly lower values (δ¹⁸O?=?–13.3 to –12.0 ‰, δ²H?=?–95 to –82 ‰), suggesting recharge during colder Pleistocene times. The third group has high isotope values (δ¹⁸O?=?–2.5 to +1.0 ‰, δ²H?=?–24 to –22 ‰); the data points are shifted to the right of the Local Meteoric Water Line, suggesting water–rock exchange processes in the aquifer. These boreholes are located in the Crimean Plains and discharge mineralized (ca. 25 g L^?1) thermal (65°C) water from a depth of 1600–1800 m. Groundwater associated with mud volcanoes on the Kerch peninsula have distinct isotope characteristics (δ¹⁸O?=?–1.6 to +9.4 ‰, δ²H?=?–30 to –18 ‰). Restricted δ²H variability along with variable and high δ¹⁸O values suggest water–rock interactions at temperatures exceeding 95 °C.     

In situ measurement of CO2 and water vapour isotopic compositions at a forest site using mid-infrared laser absorption spectroscopy

We conducted continuous, high time-resolution measurements of CO₂ and water vapour isotopologues (¹⁶O¹²C¹⁶O, ¹⁶O¹³C¹⁶O and ¹⁸O¹²C¹⁶O for CO₂, and H₂¹⁸O for water vapour) in a red pine forest at the foot of Mt. Fuji for 9 days from the end of July 2010 using in situ absorption laser spectroscopy. The δ¹⁸O values in water vapour were estimated using the δ²H–δ¹⁸O relationship. At a scale of several days, the temporal variations in δ¹⁸O-CO₂ and δ¹⁸O-H₂O are similar. The orders of the daily Keeling plots are almost identical. A possible reason for the similar behaviour of δ¹⁸O-CO₂ and δ¹⁸O-H₂O is considered to be that the air masses with different water vapour isotopic ratios moved into the forest, and changed the atmosphere of the forest. A significant correlation was observed between δ¹⁸O-CO₂ and δ¹³C-CO₂ values at nighttime (r²≈0.9) due to mixing between soil (and/or leaf) respiration and tropospheric CO₂. The ratios of the discrimination coefficients (Δ_a/Δ) for oxygen (Δ_a) and carbon (Δ) isotopes during photosynthesis were estimated in the range of 0.7–1.2 from the daytime correlations between δ¹⁸O-CO₂ and δ¹³C-CO₂ values.     

Solar Radiation Affects Modern Tree-Ring δ13C: Observations at a Cool-Temperate Forest in Japan

Abstract

Tree-ring δ¹³C of shoots in two deciduous tree species (Acer rufinerve and Clerodendrum trichotomum) at the cool-temperate forest in Japan showed similar trends with time for four years. The variation of tree-ring δ¹³C positively correlated with the total solar radiation during the growing season, although it did not always correlate with other climatic parameters. Tree-ring δ¹³C of a tree-core from 1982 to 1993 in A. rufinerve also correlated strongly with the total solar radiation. We conclude that solar radiation most probably affected the tree-ring δ¹³C in this moist cool temperate forest, because increasing solar radiation can cause Ci (intercellular CO₂ partial pressure) to decrease, consequently increasing δ¹³C.     

Isotope fractionation of sandy-soil water during evaporation – an experimental study

Soil samples containing water with known stable isotopic compositions were prepared. The soil water was recovered by using vacuum/heat distillation. The experiments were held under different conditions to control rates of water evaporation and water recovery. Recoveries, δ¹⁸O and δ²H values of the soil water were determined. Analyses of the data using a Rayleigh distillation model indicate that under the experimental conditions only loosely bound water is extractable in cases where the recovery is smaller than 100?%. Due to isotopic exchange between vapour and remaining water in the micro channels or capillaries of the soil matrix, isotopic fractionation may take place under near-equilibrium conditions. This causes the observed relationship between δ²H and δ¹⁸O of the extracted water samples to have a slope close to 8. The results of this study may indicate that, in arid zones when soil that initially contains water dries out, the slope of the relationship between δ²H and δ¹⁸O values should be close to 8. Thus, a smaller slope, as observed by some groundwater and soil water samples in arid zones, may be caused by evaporation of water before the water has entered the unsaturated zone.     

Influence of air pollution and site conditions on trends of carbon and oxygen isotope ratios in tree ring cellulose

Oxygen and carbon isotopic compositions of tree ring cellulose (δ¹³C_cell and δ¹⁸O_cell) were measured for pines growing at four sites in east Germany. Three sites differed markedly in soil water availability within a short distance and the fourth site served as a reference. The choice of the sites was guided by the desire to detect effects of air pollution on the long-term trend of isotopic compositions and to examine the influence of soil water availability on the relationship between the carbon and oxygen isotope ratios. Locations in east Germany are particularly well suited for the study of pollution effects because there was a steady increase in environmental contamination until the German Reunification in 1990, followed by a sharp decline due to the implementation of stricter environmental standards.

The long-term trend of δ¹³C_cell showed an extraordinary increase in the period 1945–1990 and a rapid decrease after 1990, whereas δ¹⁸O_cell remained nearly constant. The increase of δ¹³C_cell is explained by secondary fractionation caused by phytotoxicity of SO₂. Two effects are mainly responsible for the secondary fractionation under SO₂ exposure: increase of dark respiration, and changes in photosynthate allocation and partitioning. Both effects do not influence δ¹⁸O_cell. Furthermore, a significant positive correlation between the year-to-year variations of carbon and oxygen isotope ratios (δ¹³C_resid and δ¹⁸O_resid) has been found for all sites. The slopes of the relationship between δ¹³C_resid and δ¹⁸O_resid differ insignificantly. It is concluded that this relationship is not influenced by soil water availability but by climatic variables.     

Reliability of stable carbon and oxygen isotope compositions of pedogenic needle fibre calcite as environmental indicators: examples from Western Europe

Stable carbon and oxygen isotope analyses were conducted on pedogenic needle fibre calcite (NFC) from seven sites in areas with roughly similar temperate climates in Western Europe, including the Swiss Jura Mountains, eastern and southern France, northern Wales, and north-eastern Spain. The δ¹³C values (?12.5 to?6.8 ‰ Vienna Pee Dee Belemnite (VPDB)) record the predominant C₃ vegetation cover at the sites. A good correlation was found between mean monthly climatic parameters (air temperature, number of frost days, humidity, and precipitation) and δ¹⁸O values (?7.8 to?3.4‰ VPDB) of all the NFC. Similar seasonal variations of δ¹⁸O values for monthly NFC samples from the Swiss sites and those of mean monthly δ¹⁸O values of local precipitation and meteorological data point out precipitation and preferential growth/or recrystallisation of the pedogenic needle calcite during dry seasons. These covariations indicate the potential of stable isotope compositions of preserved NFC in fossil soil horizons as a promising tool for palaeoenvironmental reconstructions.     

Tracing the pathways of Neotropical migratory shorebirds using stable isotopes: A pilot study

We evaluated the potential use of stable isotopes to establish linkages between the wintering grounds and the breeding grounds of the Pectoral Sandpiper (Calidris melanotos), the White-rumped Sandpiper (Calidris fuscicollis), the Baird's Sandpiper (Calidris bairdii), and other Neotropical migratory shorebird species (e.g., Tringa spp.). These species molt their flight feathers on the wintering grounds and hence their flight feathers carry chemical signatures that are characteristic of their winter habitat. The objective of our pilot study was to assess the feasibility of identifying the winter origin of individual birds by: (1) collecting shorebird flight feathers from several widely separated Argentine sites and analyzing these for a suite of stable isotopes; and (2) analyzing the deuterium and ¹⁸O isotope data that were available from precipitation measurement stations in Argentina. Isotopic ratios (δ¹³C, δ¹⁵N and δ³⁴S) of flight feathers were significantly different among three widely separated sites in Argentina during January 2001. In terms of relative importance in separating the sites, δ³⁴S was most important, followed by δ¹⁵N, and then δ¹³C. In the complete discriminant analysis, the classification function correctly predicted group membership in 85% of the cases (jackknifed classification matrix). In a stepwise analysis δ¹³C was dropped from the solution, and site membership was correctly predicted in 92% of cases (jackknifed matrix). Analysis of precipitation data showed that both δD and δ¹⁸O were significantly related to both latitude and longitude on a countrywide scale (p < 0.001). Other variables, month, altitude, explained little additional variation in these isotope ratios. Several issues were identified that will likely constrain the degree of accuracy one can expect in predicting the geographic origin of birds from Argentina. There was unexplained variation in isotope ratios within and among the different wing feathers from individual birds. Such variation may indicate that birds are not faithful to a local site during their winter stay in Argentina. There was significant interannual variation in the δD and δ¹⁸O of precipitation. Hence, specific locations may not have a constant signature for some isotopes. Moreover, the fractionation that occurs in wetlands due to evaporation significantly skews local δD and δ¹⁸O values, which may undermine the strong large-scale gradients seen in the precipitation data. We are continuing the research with universities in Argentina with a focus on expanding the breadth of feather collection and attempting to resolve the identified issues.     

δ2H, δ13C and δ18O from whole wood, α-cellulose and lignin methoxyl groups in Pinus sylvestris: a multi-parameter approach

Novel tree ring parameters – δ¹³C and δ²H from methoxyl groups – have been developed to reconstruct palaeoclimate. Tests with δ¹³C and δ¹⁸O derived from whole wood and cellulose samples, however, indicated differences in the isotopic composition and climate signal, depending on the extracted wood component. We assess this signal dependency by analysing (i) δ¹³C and δ¹⁸O from whole wood and cellulose and (ii) δ¹³C and δ²H from methoxyl groups, using Pinus sylvestris L. growing near Altenkirchen (Germany). Results indicate significant correlations among the time series derived from whole wood, cellulose, and lignin methoxyl groups. Compared with the whole wood samples, δ¹³C from methoxyl groups showed a different and overall lower response to climate parameters. On the other hand, δ²H from methoxyl groups showed high correlations with temperature and was also correlated with ring width, indicating its potential as a temperature proxy. Isotope time series with the highest correlation with climatic parameter were: (i) whole wood and cellulose δ¹³C with growing season precipitation and summer temperature; (ii) methoxyl groups with spring precipitation; (iii) whole wood and cellulose δ¹⁸O correlates with annual evapotranspiration and water balance; and (iv) methoxyl group δ²H with spring temperatures. These findings reveal that multiple climate elements can be reconstructed from different wood components and that whole wood proxies perform comparably to cellulose time series.     

Stable isotopes determination in some Romanian wines

This paper presents a study concerning the isotopic fingerprint (¹⁸O and ¹³C) of some wines prepared from relevant Romanian grape varieties (e.g. Feteasca Alba (FA), Feteasca Regala (FR) and Cabernet Sauvignon (CS)) obtained in different vintage years (2002, 2003, 2004, 2007 and 2008). These wines were obtained from different vineyards having a significant role in the wine market: Cotesti, Tohani, Stefanesti, Aiud, Cotnari, Bucium, Murfatlar, Bujoru, Dragasani and Valea Calugareasca. Several observations related to the dependence of isotope ratios on geographical origin and climatic conditions were drawn. The authentic wines obtained from the FA grape variety from six different vineyards showed δ¹⁸O values in the range of+3.28 (Cotesti region – 45 °38′N/27 °04′E) to?2.60 ‰ (Aiud region – 46 °19′N/23 °45′E). The δ¹³C values were very similar for all the samples with an average of about?26 ‰. The difference between the δ¹⁸O values was due to the different climatic zones, which have an influence on the δ¹⁸O values of wine water. For the wine variety CS obtained from the Dealu Mare–Tohani vineyard, production years 2003 and 2004, a greater difference in the δ¹⁸O values of wine water ranging from 1.89 (in 2004) to 5.35 ‰ (in 2003) was noted. This difference is explained by the different mean annual temperatures in 2003 and 2004.     

Isotopic characteristics of meteoric waters in the Belgrade region

Abstract

The stable isotope composition of hydrogen (δ²H) and oxygen (δ¹⁸O) in monthly precipitation and river water (Sava River and Danube) samples in the Belgrade area gathered between 1992 and 2005 are determined. The local meteoric water line δ²H=7.8 (±0.2) δ¹⁸O+7.3(±1.6) (r ²=0.98, n=60, σ=0.52) for the whole period of observation is close to the global meteoric water line. The amount-weighted mean δ²H and δ¹⁸O values of precipitation were?65±27 ‰ and?9.4±3.4 ‰, respectively. Good correlation between δ¹⁸O values (r>rsim0.67) and ambient temperature and relative humidity was obtained. Stream-water data ranged from?94 to?60 ‰ for δ²H and from?11.0 to ～5.7 ‰ for δ¹⁸O with highly statistically significant difference (p>0.01) between the Sava River and the Danube. In addition, the isotopic compositions of local precipitation and adjacent river water at monitoring sites were compared. Obtained data will give an opportunity to improve the knowledge of mixing stream water and local groundwater, and assessment of potential groundwater risks and pressures in the Belgrade basin.     

Pleistocene age paleo-groundwater inferred from water-stable isotope values in the central part of the Baltic Artesian Basin

A new data set of δ²H and δ¹⁸O in the groundwater from the central part of the Baltic Artesian Basin is presented. The hydrogeological section is subdivided into stagnation, slow exchange and active exchange zones. Na–Ca–Cl brine found at the deepest part – the stagnation zone – is characterized by δ¹⁸O values above ?5?‰ and δ²H values approaching ?40?‰ with respect to Vienna Standard Mean Ocean Water. The slow exchange zone where waters of mostly intermediate salinity reside is characterized by δ¹⁸O values around ?11.7?‰ and δ²H values around ?85.3?‰. Mean δ¹⁸O and δ²H values of the fresh groundwater in the active water exchange zone are ?11.1 and ?79.9?‰, respectively. Characteristically, the groundwater in the active and slow exchange zone is isotopically more depleted compared with the precipitation values observed, and the depletion increases with depth down to the level where strongly enriched brines are encountered.     

Spring response to precipitation events using δ18O and δ2H in the Tanour catchment,NW Jordan

The Tanour spring is one of the several karst springs located in the northern part of Jordan. Water samples from the Tanour spring and precipitation were collected in the area of Ajloun in NW Jordan for the analysis of stable oxygen and hydrogen isotopes to evaluate the spring response to precipitation events. Rainwater and snow samples were collected from different elevations during winters of 2013–2014 and 2014–2015. In addition, spring samples were collected between December 2014 and March 2015. δ¹⁸O values in rainwater vary from ?3.26 to ?17.34?‰ (average: ?7.84?±?3.23?‰), while δ²H values range between ?4.4 and ?110.4?‰ (average: ?35.7?±?25.0?‰). Deuterium excess ranges from 17.8 to 34.1?‰ (average: 27.1?±?4.0?‰). The Local Meteoric Water Line for the study area was calculated to be δ²H?=?7.66*δ¹⁸O?+?24.43 (R²?=?0.98). Pre-event spring discharge showed variation in δ¹⁸O (range ?6.29 to ?7.17?‰; average ?6.58?±?0.19?‰) and δ²H values (range ?28.8 to ?32.7?‰; average: ?30.5?±?1.0?‰). In contrast, δ¹⁸O and δ²H rapidly changed to more negative values during rainfall and snowmelt events and persisted for several days before returning to background values. Spring water temperature, spring discharge, and turbidity followed the trend in isotopic composition during and after the precipitation events. The rapid change in the isotopic composition, spring discharge, water temperature, and turbidity in response to recharge events is related to fast water travel times and low storage capacity in the conduit system of the karst aquifer. Based on the changes in the isotopic composition of spring water after the precipitation events, the water travel time in the aquifer is in the order of 5–11 days.     

Editor change

Beaver Lake and Radok Lake, the largest known epishelf lake and the deepest freshwater lake on the Antarctic continent, respectively, were isotopically (δ²H, δ¹⁸O) and hydrogeochemically studied. Radok Lake is an isothermal and non-stratified, i.e. homogeneous water body, while Beaver Lake is stratified with respect to temperature, salinity, and isotopic composition. The results for the latter attest to freshwater (derived from snow and glacier melt) overlying seawater.     

Stable isotope composition of the meteoric precipitation in Croatia

The precipitation is the input into the water system. Its stable isotope composition has to be known for the proper use and management of water resources. Croatia is not well represented in the Global Network of Isotopes in Precipitation (GNIP) database, and the geomorphology of the country causes specific local conditions. Therefore, at the Stable Isotope Laboratory (SILab), Rijeka, we monitor the stable isotope composition (δ¹⁸O, δ²H) of precipitation. Since δ¹⁸O and δ²H are well correlated, we concentrate the discussion on the δ¹⁸O distribution. Together with GNIP, our database contains 40 stations in Croatia and in the neighbouring countries. Their different latitudes, longitudes and altitudes give information of great detail, including the influence of the topographic structure on the precipitation in the south-eastern part of Europe, as well as the complex interplay of the different climate conditions in the area. Within a few hundred kilometres, the stable isotope values display a significant change from the maritime character in the south (mean δ¹⁸O around?6 to?8%‰) to the continental behaviour in the north (mean δ¹⁸O around?8 to?11%‰). Depending on the location, the mean δ¹⁸O values vary with altitude at a rate of approximately?0.2%‰/100 m and?0.4%‰/100 m, respectively. Also the deuterium excess has been found to depend on location and altitude. The data are being used to construct a δ¹⁸O map for the entire area.     

C and O stable isotopic signatures of fast-growing dripstones on alkaline substrates: reflection of growth mechanism,carbonate sources and environmental conditions

Secondary carbonate precipitates (dripstones) formed on concrete surfaces in four different environments – Mediterranean and continental open-space and indoor environments (inside a building and in a karstic cave) – were studied. The fabric of dripstones depends upon water supply, pH of mother solution and carbonate-resulting precipitation rate. Very low δ¹³C (average?28.2‰) and δ¹⁸O (average?18.4‰) values showed a strong positive correlation, typical for carbonate precipitated by rapid dissolution of CO₂ in a highly alkaline solution and consequent disequilibrium precipitation of CaCO₃. The main source of carbon is atmospheric or biogenic CO₂ in the poorly ventilated karstic cave, which is reflected in even lower δ¹³C values. Statistical analysis of δ¹³C and δ¹⁸O values of the four groups of samples showed that the governing factor of isotope fractionation is not the temperature, but rather the precipitation rate.     

Postnatal development of urea synthesis in VLBW-infants as estimated by 15N-ammonium chloride urine test: Differences between AGA- and SGA-Infants

A prototype off-axis integrated cavity output spectrometer (OA-ICOS) utilizing two identical cavities together with a near-infrared (1.63 μm) external cavity tunable diode laser is described. The two-cavity design—one for a reference gas and one for a sample gas—takes advantage of classical double-beam infrared spectrometer characteristics in reducing uncertainties due to laser scan or power instabilities and major temperature variations by a factor of three or better compared with a single-cavity scheme. This is the first OA-ICOS instrument designed to determine ¹³C/¹²C and ¹⁸O/¹⁶O ratios from CO₂ rotation/vibration fine structure in three different combination bands. Preliminary results indicate that at 0.8 Hz a precision of 3.3 and 2.8 \permil\ is obtained for δ¹³C and δ¹⁸O, respectively, over a period of 10 h and a pure CO₂ gas sample at 26 hPa. By averaging 100 spectra over a subset of the data, we achieved a precision of 1.6 and 0.8 \permil\ for δ¹³C and δ¹⁸O, respectively.