Vertical Nitrate Migration And Denitrification Zones In The Regional Recharge Area (Lwowek Region, Poland)

This article presents an examination of the influence of groundwater flow pattern and denitrification on nitrate migration in the regional recharge zone. For the investigation, both multicomponent chemical tracers and isotopic methods were used. The study revealed different denitrification intensities in regions with groundwater extraction and regions with natural gradients manifested by different levels of potable water contamination by nitrate. A contaminant plume was discovered in shallow parts of the aquifer which percolated into deeper parts of the flow system in the regions with a downward gradient induced by groundwater withdrawal, where the influence of denitrification was limited. The local conditions leading to intense of denitrification, i.e., local changes in geological conditions (low-permeability silt inserts), were also documented. The presented research proves that vertical changes in groundwater chemistry should be examined for effective groundwater resource management and protection, as they are extremely important in regional recharge zones with a downward gradient.

Climate-induced reversal of tree growth patterns at a tropical treeline

Globally, cold-limited trees and forests are expected to experience growth acceleration as a direct response to warming temperatures. However, thresholds of temperature limitation may vary substantially with local environmental conditions, leading to heterogeneous responses in tree ecophysiology. We used dendroecological and isotopic methods to quantify shifting tree growth and resource use over the past 143 years across topographic aspects in a high-elevation forest of central Mexico. Trees on south-facing slopes (SFS) grew faster than those on north-facing slopes (NFS) until the mid-20th century, when this pattern reversed notably with marked growth rate declines on SFS and increases on NFS. Stable isotopes of carbon, oxygen, and carbon-to-nitrogen ratios suggest that this reversal is linked to interactions between CO2 stimulation of photosynthesis and water or nitrogen limitation. Our findings highlight the importance of incorporating landscape processes and habitat heterogeneity in predictions of tree growth responses to global environmental change.

Detection of exogenous sugars in pineapple juice using compound-specific stable hydrogen isotope analysis

An improved procedure for determining 2H/1H isotope ratios, using gas chromatography-isotope ratio mass spectrometry, has been used to detect the addition of exogenous C4-plant-derived sugars to pineapple juice. Isotopic techniques are commonly used to identify the addition of low-cost sugars to fruit juices and are difficult to subvert as it is not economically viable to change the isotopic ratios of the sugars. However, the addition of cane sugar to pineapple juice has presented a significant challenge that is only detected by site-specific 13C analysis of the methyl and methylene positions of ethanol derived from pineapple sugars, measured by nuclear magnetic resonance. This new GC-IRMS-based procedure utilises the trifluoroacetate derivative of sucrose to allow direct measurement of the carbon-bound non-exchangeable hydrogen. This provides advantages over alternative isotopic methods in terms of analysis time and sensitivity. This feasibility study has demonstrated the potential to reliably differentiate between authentic pineapple juices and those adulterated with commercial beet and cane sucrose.

Ore-Bearing Magmatic Systems with Complex Sn–Au–Ag Mineralization in the North-Eastern Verkhoyansk–Kolyma Orogenic Belt, Russia

This paper reports the results of a study of magmatic rocks with Sn–W–Au–Ag mineralization from the Kuranakh, Elikchan, and Istekh ore fields in the Northern batholith belt of the north-eastern Verkhoyansk–Kolyma orogenic belt in Eastern Russia. Using petrographic, mineralogical, geochemical, and isotopic methods, we determined the mineral compositions, petrochemistry, and geochemistry of magmatic rocks, the P–T conditions of their generation and crystallization, and their geodynamic affinity. The studied magmatic rocks have common geochemical characteristics that likely reflect the influence of fluids supplied from a long-lived, deep-seated mantle source. The ore fields are characterized by Sn–W–Au–Ag–Pb polygenetic mineralization. The magmatic and metallogenic evolution comprised five stages for the formation of magmatic rocks and ores. During the first stage (Berriasian–Barremian), arc-related magmatic rocks formed in an active continental margin setting and were associated with Au–Ag mineralization. The second, third, and fourth stages (Aptian–Campanian) took place in a crustal extension and rift setting, and were accompanied by Au–Ag and Sn–W mineralization. During the fifth (post-magmatic) stage, Sn–Ag–Sb and Pb–Ag mineralization occurred.

Stable isotope insights into dryland ecohydrology

<p>Isotopic tracing of water sources for plants is an increasingly common method that supports insight into climatic controls on water availability to plants and their use of this available water, especially in water-limited environments where isotopic endmembers are distinct. Recent advances in this field of research have enabled characterization of annual and seasonal water use by plants, whose water sources vary in contribution along a continuum between groundwater (isotopically light) to infiltrated precipitation (isotopically heavy). Xylem samples are commonly used to characterize real-time uptake of water from roots, and they can be contextualized with respect to endmember water sources via sampling of root zone water, providing these endmembers are isotopically distinct. The time integration of seasonally varying water source usage results in the annually recorded isotopic signal recorded in tree ring cellulose for temperate trees and shrubs, which reflects the dominant water source used in the season of growth. This has enabled dendro-isotopic methods that are commonly used to reconstruct past climates (isotopically light = colder/wetter; isotopically heavy = warmer/drier). However, questions have arisen about the utility of these annually integrated dendro-isotopic signatures, given the strong seasonal variations of water use that are particularly pronounced in dryland ecosystems, including notable water source switching by plants.      </p><p>In our recent work, we have been pushing isotopic methods in new directions to better understand what plants can tell us about how climate affected hydrology across dryland regions, and about the associated plant responses. Drylands pose interesting research challenges, since water is typically the key limiting factor on dryland plant growth, and it is fundamental to the health, functioning, composition, distribution, and evolution of vegetation communities. In drylands, water availability to plants may vary dramatically across space and time, creating challenges for simple analyses of annual water use signatures. To aid the understanding of climatically-controlled ecohydrology in drylands, we have developed a new tool (ISO-Tool) based on established biochemical fractionation theory, which allows for back-calculation of water sources used for growth from tree-ring isotopes. This tool generates critical knowledge for evaluating dendro-isotopic signatures within the same reference frame as sampled endmember water sources, and it can be used for both annual and seasonal analyses of plant water use. We have also been working on a set of interdisciplinary metrics we call water stress indicators (WSIs), which support corroboration of information on climatic forcing, water availability, plant water uptake, and ecological health of terrestrial vegetation.   </p><p>Using these new methods, we have been able to identify important hydroclimatic gradients in water usage for the same species that reflect the local expression of climate into plant-available water. We have also begun to understand the whole continuum from climate forcing to root-zone water availability to tree growth to canopy health. We believe this broader continuum perspective is critical for tackling key ecohydrological questions especially in drylands, where we expect large variability in water availability across space and time.         </p>

Quantification of soil C inputs from organic fertilizers in tropical long-term field experiments: potential of stable carbon isotopes

<p>Soil C stocks can be increased by spreading organic fertilizer (OF) in crop fields. OF-derived C (OF-C) is usually estimated according to the differential with and without OF inputs [1-4]. But OF applications may boost crop production or induce initial-C mineralization due to an indirect effect (e.g. priming) [5-6]. Therefore, crop derived C and native-C (before plot testing) may change during the experiment link to OF additions. Thus, the differential method might not be the suitable one for quantifying OF-C. In this study, we used stable <sup>13</sup>C isotopes to avoid such OF-C estimation biases and compared two isotopic methods to the differential method. Both isotopic methods were set up with synchronous controls (e.g. soil δ<sup>13</sup>C signature compared to plot with and without OF inputs) and diachronous control (e.g. soil δ<sup>13</sup>C signature compared to the soil at the beginning of the experiment). In order to assess the all three methods, this study was implemented on an Arenosol and an Andosol with a 13-year history of compost or slurry amendment. The differential and synchronic isotopic methods gave similar OF-C estimations for the Arenosol, while for the Andosol both isotopic methods estimated twofold higher OF-C levels compared to the differential method. Changes in crop-C production or priming as a result of OF applications might explain this gap. Moreover, the control isotopic signature (without OF) slightly changed due to crop-C integrated during the experiment. Which is why the isotopic synchronic method was the most suitable compared to diachronic isotopic method. According to this method, OF-C retention was OF-nature dependent (21% for compost, 8% for slurry), and soil type and climate dependent (42% compost retention in the Andosol and 21% in the Arenosol), highlighting the recent carbon input retention capacity of Andosols. This method is also relevant to quantify the priming effect in field trials, in our case it was not possible due to the δ<sup>13</sup>C evolution of the soil without OF input.</p><p>[1] Y. Lou et al., CATENA, vol. 87, no 3, p. 386‑390, déc. 2011, doi: 10.1016/j.catena.2011.07.006.</p><p>[2] L. Paetsch et al., Agriculture, Ecosystems & Environment, vol. 223, p. 211‑222, mai 2016, doi:10.1016/j.agee.2016.03.008.</p><p>[3] H. Liu et al., Agriculture, Ecosystems & Environment, vol. 265, p. 320‑330, oct. 2018, doi: 10.1016/j.agee.2018.06.032.</p><p>[4] F. Liang et al., Geoderma, vol. 337, p. 853‑862, mars 2019, doi: 10.1016/j.geoderma.2018.10.033.</p><p>5] Y. Kuzyakov et al., Soil Biology and Biochemistry, vol. 32, no 11, p. 1485‑1498, oct. 2000, doi:10.1016/S0038-0717(00)00084-5.</p><p>[6] S. Fontaine et al., Soil Biology and Biochemistry, vol. 35, no 6, p. 837‑843, juin 2003, doi: 10.1016/S0038-0717(03)00123-8.</p>

Comparison of methodologies used to define the protein quality of human foods and support regulatory claims

Protein quality (PQ) is the capacity of a protein to meet the amino acid (AA) requirements of an individual. There are several methodologies for determining the PQ of foods. The protein efficiency ratio is an animal growth bioassay. The protein-digestibility-corrected AA score considers the AA requirements of a reference population, and the true nitrogen digestibility coefficient for each ingredient. The digestible indispensable AA score is based on true ileal AA digestibility and better represents bioavailability of AAs. In vitro techniques for assessment of PQ are available but require validation against a greater range of protein sources. Isotopic methods, such as the indicator AA oxidation and dual tracer techniques measure AA relative bioavailability and digestibility, respectively, but require sophisticated equipment, and may not be cost nor time effective for the industry to adopt. The present review discusses advantages and disadvantages of methodologies for determining PQ of food for humans focused on methods that are or could be adopted by regulatory agencies. Understanding the framework and resources available for PQ determination will help in the selection of appropriate methods depending on the application. Novelty Understanding the framework and resources available for PQ determination will help in the selection of appropriate methods depending on the application.

How Can Technical Aspects Help Improving K-Ar Isotopic Data of Illite-Rich Clay Materials into Meaningful Ages? The Case of the Dominique Peter Uranium Deposit (Saskatchewan, Canada)

Previously published K-Ar dating results of <2 μm illite separates from uranium-hosting and associated barren rocks from Dominique Peter district of the Carswell circular structure in the Athabasca Basin (Canada) were considered to trace four distinct tectonic-thermal events at 1447 ± 45, 1282 ± 40 and 1184 ± 15 (all errors at ± 2 Ma, with a younger, less constrained episode at ~900 Ma. Recent analyses of K-Ar ages of additional <0.2 μm illite fractions from a few initial samples demonstrate that the intermediate ages at ~1280 and ~1185 Ma result, in fact, from mixing of two generations of illite that precipitated at ~1450 and ~900 Ma. They have, therefore, no stratigraphic value, while the two tectonic-thermal episodes at 1448 ± 48 and 937 ± 39 Ma appear to be historically sound. In fact, the analytical procedure of isotopic dating clay materials is of more importance than is often stated. For instance, a safe way to evaluate and constrain best numerical isotopic data of clay separates into ages is combining data of two size splits from several samples. If such age data, especially from size fractions of indurated host rocks, are scattered and point towards the higher data of the coarser fractions, they are potentially enriched in earlier crystallized K-rich components, and should consequently be discarded. The occurrence of detrital or early-crystallized components in clay-rich separates becomes a serious concern when comparing ages generated by various isotopic methods on mineral separates of various whole rocks. It is especially verified in very old, metal-rich deposits such as the uranium-rich deposits of the Saskatchewan Basin. These deposits and their host rocks were studied extensively by a large spectrum of isotopic methods on many types of rocks in a widely dispersed area, and for which the numerical statistics became, sometimes, more central in the interpretation than the specificity of the successive events in the host rocks.

Supplemental Material: Volcanic record of the arc-to-rift transition onshore of the Guaymas basin in the Santa Rosalía area, Gulf of California, Baja California

Item S1: Analytical methods, including XRF and ICP-MS whole-rock geochemical analysis, ⁴⁰Ar-³⁹Ar geochronological analytical methods, and zircon isotopic methods. Item S2: Excel spreadsheet of whole-rock geochemical data, including XRF and LA-ICPMS data. Item S3: ⁴⁰Ar-³⁹Ar geochronological data: Summary table, and data tables and plots for each sample. Item S4: U-Pb zircon data. Item S5. Hf-isotope zircon data. Item S6: Outcrop photos. Item 7: Photomicrographs, including examples of all samples dated by ⁴⁰Ar-³⁹Ar. Item S8: Summary of published definitions of adakites and high magnesium andesites. Item S9: KMZ files for geologic maps.