The hydrogen isotope ratio of water cryogenically extracted from plant stem samples (δ2Hstem_CVD) is routinely used to aid isotope applications that span hydrological, ecological, and paleoclimatological research. However, an increasing number of studies have shown that a key assumption of these applications—that δ2Hstem_CVD is equal to the δ2H of plant source water (δ2Hsource)—is not necessarily met in plants from various habitats. To examine this assumption, we purposedly designed an experimental system to allow independent measurements of δ2Hstem_CVD, δ2Hsource, and δ2H of water transported in xylem conduits (δ2Hxylem) under controlled conditions. Our measurements performed on nine woody plant species from diverse habitats revealed a consistent and significant depletion in δ2Hstem_CVD compared with both δ2Hsource and δ2Hxylem. Meanwhile, no significant discrepancy was observed between δ2Hsource and δ2Hxylem in any of the plants investigated. These results cast significant doubt on the long-standing view that deuterium fractionation occurs during root water uptake and, alternatively, suggest that measurement bias inherent in the cryogenic extraction method is the root cause of δ2Hstem_CVD depletion. We used a rehydration experiment to show that the stem water cryogenic extraction error could originate from a dynamic exchange between organically bound deuterium and liquid water during water extraction. In light of our finding, we suggest caution when partitioning plant water sources and reconstructing past climates using hydrogen isotopes, and carefully propose that the paradigm-shifting phenomenon of ecohydrological separation (“two water worlds”) is underpinned by an extraction artifact.

in Wiley Online Library (wileyonlinelibrary.com).Solubilities of H 2 S in five 1-alkyl-3-methylimidazolium carboxylates ionic liquids (ILs) have been measured at temperatures from 293.15 to 333.15 K and pressures up to 350 kPa. It is shown that these ILs have significantly larger absorption capacities for H 2 S than those common ILs reported in the literature. The solubility is found to increase dramatically with the increasing alkalinity of the anions and slightly with the increasing length of the alkyl chains on the cations. It is further demonstrated that the absorption isotherms are typically nonideal. With the assumption of complex formation between H 2 S and ILs, a reaction equilibrium thermodynamic model is developed to correlate the experimental solubilities. The model favors a reaction mechanism of AB 2 type that two IL molecules interact with one H 2 S molecule. Thermodynamic parameters such as Henry's law constants, reaction equilibrium constants, and heat of complex formation are also calculated to evaluate the absorption process of H 2 S in these ILs.

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Three dual Lewis base functionalized ionic liquids (DLB‐ILs) tethered with both carboxyl and tertiary amine groups on their anions were designed for highly efficient and selective absorption of H2S. It was found that the DLB‐ILs could reversibly absorb 0.39–0.84 mol of H2S per mole of IL at 1 bar and 60 °C, which is significantly higher than that of other ILs. On the contrary, the CO2 absorption in this class of DLB‐ILs was shown to be quite limited relative to H2S owing to the coupling effect of the two Lewis base groups. It is the dual Lewis base functionalization that enables the significantly high values calculated for the ideal absorption selectivity for H2S/CO2, that is, 13–26 at 1 bar and 29–70 at 0.1 bar (60 °C). The selectivity even goes up to >100 at low pressures and high temperatures. It was further illustrated from DFT calculations and spectroscopy studies that the cooperation interaction of carboxyl⋅⋅⋅H2S⋅⋅⋅amine and the reduced binding with CO2 were the major contributions to the high H2S absorption capacity and H2S/CO2 selectivity.