Fundamentals of Isotope Geochemistry

“The C and N isotope ratios are reported as 13C and 15N values, where the standard is Pee Dee Belemnite carbonate for C (Kendall and Caldwell, 1998) and atmospheric N2 for N.”

“En effet, les bactéries utilisent préférentiellement les sulfates les plus légers, c’està-dire ceux composés de l’isotope le plus léger du soufre ((32)S), par rapport aux sulfates les plus lourds contenant des isotopes plus lourds du soufre ((33)S, (34)S, (36)S) [18].”

“41 As a result, the equilibrium reaction of 7 ⇌ 8 + H 2 O 2 or 11 ⇌ 12 + H 2 O 2 lowers δ 18 O H d 2 O d 2 for category II olefins (Figure 2b).”

“18 O and 2 H values in precipitation (the ultimate water source for surface and groundwater) vary significantly with latitude and altitude [23–27].”

“The CAI values were calculated by the following formulas (meq/l): The actual 3 H value is calculated by the formula (Kendall and Caldwell 2006; Karaog˘lu et al. 2019).”

“A Rayleigh fractionation model was applied to describe the kinetic fractionation of N between NO− 3 and evolved NH+ 4 (Guy et al., 1993; Kendall & Caldwell, 1998; Maggi & Riley, 2010).”

“Kendall and Caldwell (1998) Péclet effect The general Péclet effect describes the balance between advective water flow and back-diffusion of isotopically enriched water at evaporation sites within leaves; in the context of xylem sampling, it is most relevant as the mechanism by which this enriched…”

“…conservatively during water–rock interaction, dissolution and ion exchange, and therefore retain information on re-charge origin, flow pathways and mixing processes even in chemically evolved aquifer systems (Gat 1996; Kendall and McDonnell 1998; Carrière et al. 2023; Proteau-Bédard et al. 2023).”

“K and Eric A. Caldwell (1998), provided a comprehensive overview of isotope behavior in hydrological systems, including the relationship between temperature and δ¹⁸O values [30].”

“In addition, isotopic concentrations offer a foundational framework for delineating water sources and hydrological dynamics (Kendall and Caldwell, 1998).”

“Whereas, he rest of the sample (w4, w10, and w17) appears to be below the (GMWL) 10, intercept, indicating that low-humidity conditions are, [13].”

“Moreover, the identification of nitrate pollution sources often faces other difficulties such as: heterogeneity in landscape, the spatial correlation of the study area may overlap the possible impacts in the basin, the influence of seasonality on the sources of nitrate and on the response of the aquatic system, the pr…”

“Normally, organisms preferentially use lighter isotopes of elements for inclusion in their organic and inorganic structural parts when compared to inorganic calcite (De La Rocha, 2003; Gabitov et al., 2012; Kendall & Caldwell, 1998).”

“Stable isotope ratios of water (δ2H and δ18O) can reveal much about the history of different water sources because they fractionate systematically as a result of phase changes in the hydrological cycle (e.g., condensation, melting, and evaporation; Gat 1980, Kendall and Caldwell 1998).”

“Secondly, isotope fractionation increases with decreasing temperature (Kendall and Caldwell 1998). B is either present in trigonal coordination at the B site and/or in tetragonal coordination at the T site (Fig. 1.1). In aqueous fluids and at acidic to near neutral pH, which is needed to crystalize tourmaline (Smith 1…”

“The stable isotopic ratios of water depend on the altitude, latitude, and temperature of precipitation, and on the extent of evaporation of surface water or soil water (Kendall and Caldwell, 1998).”

“Water isotopes and chemistry to trace sediment sources, adapting approaches developed in volcanic and catchment hydrology studies (Kendall and Caldwell, 1998; Carey and Quinton, 2005).”

“Environmental tracers are naturally occurring or anthropogenic chemicals or isotopes that can indicate water sources and flow processes such as recharge, flow rate, geologic subsurface interactions, residence times, and mixing be-tween sources (Kendall and Caldwell, 1998).”

“Environmental isotopes, including hydrogen, carbon, nitrogen, and oxygen, possess distinctive characteristics (Fry, 2006; Kendall & Caldwell, 1998) that make them effective tracers for understanding the cycling of water and nutrients in the environment.”

“Results are reported as per mil (‰) relative to Vienna Pee Dee Belemnite (PDB) [43].”

“This stagnant water undergoes a greater evaporation process than river water, raising the concentration of oxygen-18 (Dansgaard, 1964; Gat, 1995; 1996; Kendall and Caldwell, 1998; see next section).”

“However, areas may have different slopes and intercepts due to different rainfall evaporation conditions or source evaporation conditions in various air mass sources [2,3, 36-40].”

“the heavier isotope generally preferentially accumulates in the species or compounds with higher oxidation state while lighter isotopes accumulates in species or compounds in their reduced state [22].”

“Various processes in nature may fractionate the heavier or lighter stable isotope of carbon (Kendall & Caldwell 1998) In vegetation, the photosynthetic process preferentially uptakes the lighter isotope during carbon fixation (Schlesinger 1997; Ehleringer & Cerling 2000).”

“In equilibrium fractionation, isotopes of an element are redistributed among species that are in equilibrium (Kendall and Caldwell, 1998).”

“…isotope has a stronger molecular bond (oxygen-18 [18O] has a stronger molecular bond than oxygen-16 [16O] and deuterium [2H] has a stronger molecular bond than hydrogen-1 [1H]), the liquid phase of water generally is isotopically “heavier” than the gaseous phase (Kendall and Caldwell, 1998).”

“The extent to which evapotranspiration processes influenced groundwater and solute dynamics across the macrocosms, was indicated by the seasonal variability of the conservative hydrochemical tracers Cl- and 18O (Bibby, 1981; Kendall & Caldwell, 1998).”

“Hence, they can be used at large scales, for instance to evaluate the mixing between two components (see e.g. Sklash and Farvolden, 1979; Kendall and Caldwell, 1998; Soulsby et al., 2003; Leibundgut et al., 2011), or to estimate the reaction time in a catchment by studying how an input signal in rainfall is converted…”

“The compositions of the isotopes (2)H (D) and (18)O were analyzed to obtain δD (‰) and δ(18)O (‰), respectively, which are defined as the relative deviation of the parts per thousand ratios from that of a standard according to the following equation (Kendall and Caldwell, 1998):”

“All samples were collected in February 2001 and analyzed through standard techniques (Kendall and Caldwell, 1998; Plummer and Busenberg, 2000).”