Fundamentals of Isotope Geochemistry

“…(HDO, H2 18O) have slightly lower saturation vapour pressures than the ordinary water molecule (H2 16O); hence when changes of state occur during evaporation and condensation, a slight fractionation takes place (discussed in detail by Clark and Fritz (1997) and Kendall and Caldwell (1998)).”

“These ideal tracers are applied by precipitation and are generally distinct isotopically, which makes them reliable tracers of subsurface flow processes (Kendall and Caldwell, 1998).”

“isotopically distinguishable meteoric waters across elevational gradients and between cold and warm seasons (Craig 1961, Dansgaard 1964; Kendall and Caldwell 1998).”

“Individual components of mixed gases should plot on straight lines as a function of the inverse of concentration (Kendall and Caldwell, 1998).”

“…expressed by equation (4), emax = 1% is the standard deviation associated to deuterium measurements, and dD is the relative isotope content of a sample in comparison with the ‘‘Vienna Standard Mean Ocean Water’’ or VSMOW [e.g., Kendall and Caldwell, 1998] represented in parts per thousand (%).”

“(1)–(8), the slopes of evaporation lines will typically range from 2.5 to 5, markedly shallower than typical meteoric water lines, which usually have slopes of roughly 8 (Kendall and Caldwell, 1998).”

“Finally, stable and radioactive isotope signatures of water (deuterium, tritium, oxygen) can give insights into the timescales and transport behaviour of nitrate pollution in groundwater and surface water (e.g. Boehlke and Denver 1995; Kendall and Caldwell 1998; Wassenaar et al. 2006).”

“Changes in solute isotopic ratios generally occur in predictable and recognisable directions, hence allowing them to be reconstructed from the isotopic compositions (Kendall and Caldwell, 1998; Kendall, 1998).”

“Naturally-occurring stable water isotopes (υ18O and υD) are generally recognized as the preferred tracers for hydrograph separation studies (Kendall and Caldwell, 1998), but their widespread use may be limited by high Copyright 2007 John Wiley & Sons, Ltd. analytical costs.”

“Interpretation of stable water isotope patterns is complicated, however, in cases where water sources available to the plants are likely to experience isotopic fractionation as water evaporates from the soil profile (Craig and Gordon 1965; Clark and Fritz 1997; Kendall and Caldwell 1998).”

“Stable isotopes are generally considered to be the most accurate chemical tracers for hydrograph separation [Kendall and Caldwell, 1998].”

“Stable isotopes are conservative, naturally occurring tracers that are applied by precipitation events and are typically distinct isotopically, making them reliable tracers of subsurface flow processes (Kendall and Caldwell, 1998).”

“…of water sources, and chemical tracers (Cl, SiO2, etc.) and non-conservative isotope tracers (υ13C, υ87Sr, υ34S, etc.) as indicators of water flowpaths but only indirectly as indicators of water sources (Kennedy et al., 1986; Wels et al., 1991; Kendall et al., 1995; Kendall and Caldwell, 1998).”

“…focused on the discretization of water flow paths and water residence times in the environment using stable isotopes (Stout, 1967; Hooper and Shoemaker, 1986; Kennedy et al., 1986; Turner et al., 1987; Maulé and Stein, 1990; McDonnell et al., 1991; Cooper et al., 1993; Kendall and Caldwell, 1998).”

“composition of water (43), the soil solution becomes enriched in (18)O through evaporation.”

“The analytical precision of that instrument is typically one standard deviation for carbon and nitrogen and is in the range of 0.05–0.2‰, which is small relative to the range of values that occur in nature (Kendall and Caldwel 1998).”

“The water cycle connects evaporation of oceanic water, formation of clouds, cloud transfer by wind far from an initial source of the water vapor, precipitation, and construction of the isotopic content of the run-off back to the ocean (Gat, 1996; Kendall and Caldwell, 1998; Araguás-Araguás and others, 2000; Taylor and…”

“…lake surface evapuration in remote areas of northern Canada , Ambienr humidity is the most impon a nt control on how t> vaporation trom an open-water surface (or from a leaf SLtrlal·e or ponded water in a w atershed ) fractionates the isotopes of h yJrogen and oxygen (Kendall & Caldwell 1998).”

“…3% to .20% among these outlier lakes, suggesting that lack of synchrony did not arise from consistently greater effects of nonequilibrium kinetic fractionation of H compared to that of O (Kendall and Caldwell 1998), or technical errors in estimation of small changes in 2H content of surface waters.”

“This deviation from the GMWL is mainly due to evaporation-induced kinetic fractionation effects (Merlivat and Jouzel, 1979; Jacob and Sonntag, 1991; Zimmermann et al., 1967) and Rayleigh fractionation in the closed system (Jouzel et al., 1997; Kendall and Caldwell, 1998).”

“For example, during biological processing of these elements, organisms generally tend to favor the utilization of the lighter isotope from an energetic standpoint (Kendall and Caldwell 1998).”

“…used, thus neglecting the influence of gradual depletion of heavy isotopes with the duration of an event (cf. Kendall and Caldwell, 1998), resulting in a potential overestimation of pre-event contributions at early stages of the events and underestimation…”

“Th e H and O isotopes are only fractionated in shallow surface reservoirs by processes such as snow melting and evaporation (transpiration does not fractionate these isotopes) (Kendall and Caldwell, 1998).”

“The pursuit of d values of each component in equation (1) or (2) is described in the following : [10] The isotope compositions of the precipitating vapor (dPV) can be derived from that of the precipitation of the sampling location (dP )[ Clark and Fritz, 1997; Kendall and Caldwell, 1998 ]:”

“This shows the relative change of δ18O to δ2H in precipitation assuming equilibrium fractionation in the atmosphere, which produces a slope of 8 (see Kendall and Caldwell, 1998 for full details).”

“However, lake-water oxygen isotope ratios may also be affected by changes in isotopic composition of input water, including catchment runoff, groundwater and precipitation falling directly into the lake (Kendall and Caldwell, 1998).”

“This is mainly because of the disproportional impact that kinetic fractionation processes have on oxygen compared with hydrogen isotopes (Kendall & Caldwell, 1998).”

“4 molecule which requires less energy to break the bonds (Kendall and Caldwell, 1998).”

“End-member δ13CDIC ranges for equilibrium and kinetically controlled reactions (Kendall & Caldwell, 1998) were calculated following Jin et al. (2009) and Lehn et al. (2017).”

“The process of converting river water to groundwater enriches the heavy isotopes (δD and δO) increasing the concentrations of δD and δO (Clark and Fritz 1997; Kendall and Caldwell 1998).”

“2006; Cook 2012), d(18)O and d (2)H of water when SW and GW signatures are evidently different, provide information about fluxes and exchange dynamics (Kendall and Caldwell 1998; Négrel et al. 2003; Osenbrück et al. 2013; Mohammed et al. 2014), and may even help to distinguish the effect of anthropogenic activities (e.”

“Values of δ13C and δ15N were determined according to δ [‰]¼(Rx/Rs 1) 1000, where Rx and Rs denote the ratios of heavy to light isotopes (i.e. 13C/12C or 15N/14N) of the sample and a standard material, respectively (e.g. Kendall and Caldwell, 1998; Peterson and Fry, 1987).”

“lakes [ Kendall and Caldwell, 1998 ] into equation (3).”

“Water samples for stable oxygen isotope analysis were collected and stored in scintillation vials containing minimal air space and sealed with Parafilm to curtail evaporative loss and fractionation (Kendall & Caldwell, 1998).”

“Water samples for stable oxygen isotope analysis were collected in scintillation vials containing minimal air space and sealed with Parafilm to curtail evaporative loss and fractionation (Kendall & Caldwell, 1998).”

“Compared to conventional IRMS, the IRIS technique has the advantages of simple preparation and operation, comparative portability for application in the field, and applicability with relatively small amounts of water samples (ppb, ppt) [71–75].”

“, 2010) and preferential microbial metabolism of the lighter isotope (due to lower energy costs associated with breaking intra-molecular bonds (Kendall and Caldwell, 1998)).”

“The sources of CO2 in streamwater can be identified using stable carbon isotope analyses (Campeau et al., 2018; Kendall & Caldwell, 1998; Venkiteswaran et al., 2014). δ13C values of streamwater CO2 depend on the relative contribution of carbon from respiration, weathering, and atmospheric exchange…”

“To estimate δ18OE, we used equation (2.20) of Kendall and Caldwell (1998): CHANG ET AL.”

“7 is consistent with closed-system behavior for a kinetic fractionation process (Ding et al., 1996; Kendall and Caldwell, 1998): a finite supply of reactant (dissolved silica) and negligible back-reaction (minimal dissolution of precipitated silica) leading to progressive isotopic enrichment of…”

“Water dD was enriched in 2 Hi n floodplain ponds compared with riverine habitats due to greater opportunity for evaporative fractionation ( Kendall and Caldwell 1998 ) to be expressed in floodplain ponds as a result of their longer water residence time relative to the Colorado River.”

“Furthermore, they can be used to investigate hydrological processes such as mechanisms responsible for streamflow generation (e.g., Kendall and Caldwell, 1998), in groundwater studies (e.g., Gonfiantini et al., 1998), and rainfall–runoff studies (e.g., Genereux and Hooper, 1998).”

“This relationship is the fractionation factor a which is determined using Rayleigh equations [6].”

“The effect of surface evaporation on the dD and dO of residual soil water generally decreases with depth along a mixing gradient defined by the diffusion kinetics of the heavier isotopologues of water away from the liquid–vapor interface against the transport of water from deeper soil horizons by capillary action (Zim…”

“We present data only for spores produced in liquid media because most of the 32 different media used here were liquid media, and the presence of agar is often associated with evaporative enrichment of the water in the medium (evaporation increases the relative amounts of (2)H and (18)O in the residual water [40]) (45)…”

“This trend reflects the typical behavior for evaporation of water and is caused by the isotope fractionation during the liberation of H2O from the solution into the atmosphere [28].”

“Stable isotope ratios (δ 18O, δ 2H) and radioisotopes ( 3H) in water offer many unique advantages in these systems (Cook & Bohlke, 2000; Kendall & Caldwell, 1998).”

“This model describes that isotopically lighter CH4 is preferentially removed in a closed system where the supply of reactant (i.e. CH4) is limited, leaving residual CH4 enriched in 13C and 2H (Rayleigh, 1902; Kendall and Caldwell, 1998).”

“Once groundwater is no longer subject to evaporation, both δ18O and Cl– (mg/l) act as conservative groundwater tracers, which maintain their tracer signatures until they mix with waters of different δ18O and Cl– (mg/l) levels (Kendall and Caldwell 1998).”

“For instance, the range of dN of DIN derived from synthetic fertilizers is 0–3‰, while that derived from waste water and animal manure is 10–25‰ (Kendall and Caldwell, 1998).”

“Key words: acid mine drainage, hydrochemistry, isotope hydrology, zinc”