Determination of contamination sources and geochemical reactions in groundwater of a mine area using Cu, Zn, and S-O isotopes.

To determine contamination sources and pathways, the use of multiple isotopes, including metal isotopes, can increase the reliability of environmental forensic techniques. This study differentiated contamination sources in groundwater of a mine area and elucidated geochemical processes using Cu, Zn, S-O, and O-H isotopes. Sulfate reduction and sulfide precipitation were elucidated using concentrations of dissolved sulfides, δ34SSO4, δ18OSO4, and δ66Zn. The overlying contaminated soil was possibly responsible for the contamination of groundwater at <5 mbgl, which was suggested by low δ65Cu values (0.419-1.120‰) reflecting those of soil (0.279-1.115‰). The existence of dissolved Cu as Cu(I) may prevent the increase in δ65Cu during leaching of contaminated soil in the sulfate-reducing environment. In contrast, the groundwater at >5 mbgl seemed to be highly affected by the contamination plume from the adit water, which was suggested by high SO42- concentrations (407-447 mg L-1) and δ65Cu (0.252-2.275‰) and δ66Zn (-0.105‰-0.362‰) values at a multilevel sampler approaching those of the adit seepages. Additionally, the O-H isotopic ratios were distinguished between <5 mbgl and >5 mbgl. Using δ65Cu and δ66Zn to support the determination of groundwater contamination sources may be encouraged, particularly where the isotopic signatures are distinct for each source.

Dietary and homeostatic controls of Zn isotopes in rats: a controlled feeding experiment and modeling approach.

The stable isotope composition of zinc (δ66Zn), which is an essential trace metal for many biological processes in vertebrates, is increasingly used in ecological, archeological, and paleontological studies to assess diet and trophic level discrimination among vertebrates. However, the limited understanding of dietary controls and isotopic fractionation processes on Zn isotope variability in animal tissues and biofluids limits precise dietary reconstructions. The current study systematically investigates the dietary effects on Zn isotope composition in consumers using a combined controlled feeding experiment and box-modeling approach. For this purpose, 21 rats were fed one of seven distinct animal- and plant-based diets and a total of 148 samples including soft and hard tissue, biofluid, and excreta samples of these individuals were measured for δ66Zn. Relatively constant Zn isotope fractionation is observed across the different dietary groups for each tissue type, implying that diet is the main factor controlling consumer tissue δ66Zn values, independent of diet composition. Furthermore, a systematic δ66Zn diet-enamel fractionation is reported for the first time, enabling diet reconstruction based on δ66Zn values from tooth enamel. In addition, we investigated the dynamics of Zn isotope variability in the body using a box-modeling approach, providing a model of Zn isotope homeostasis and inferring residence times, while also further supporting the hypothesis that δ66Zn values of vertebrate tissues are primarily determined by that of the diet. Altogether this provides a solid foundation for refined (paleo)dietary reconstruction using Zn isotopes of vertebrate tissues.

67Zn and 111Cd labelled green manure to determine the fate and dynamics of zinc and cadmium in soil-fertilizer-crop systems.

Isotope source tracing enables to accurately determine the fate of nutrients that are applied with fertilizers to soils. While this approach is well established for major nutrients such as nitrogen, it is not yet established for trace metals. Here, we aimed to determine the fate of the micronutrient zinc (Zn) and the contaminant cadmium (Cd) that were applied with an organic fertilizer to a soil-wheat system. A pot study was conducted in which wheat was grown on an alkaline soil. The soils received green manure and/or soluble Zn fertilizer and were compared with non-fertilized control treatments (n = 4 experimental replicates). The green manure was labelled with the stable isotopes 67Zn and 111Cd. For an efficient sample throughput, a method was provided and validated to determine enriched stable isotope ratios (67Zn:66Zn and 111Cd:110Cd) and the Zn and Cd concentrations in one analytical run. To this end, single collector ICP-MS analyses and stable isotope mass balances calculations were combined. Applying this method revealed that the addition of green manure increased neither Zn nor Cd concentrations in wheat grains due to biomass dilution effects. Isotope source tracing showed that the largest fraction of these metals in the wheat shoots derived from the soil in all treatments (Zn 87-99 %, Cd 94-98 %). Moreover, the addition of green manure increased the transfer of Zn and Cd from soil to wheat by a factor 1.9 for both elements. This increased transfer was likely related to a nitrogen fertilization effect that increased root and shoot biomass and thereby the soil exploration of the wheat. This study demonstrated how the fate and dynamics of multiple trace metals can be efficiently determined in soil-fertilizer-crop systems using isotope source tracing.

Seasonal and multi-decadal zinc isotope variations in blue mussels from two sites with contrasting zinc contamination levels.

Zinc (Zn) isotope compositions in soft mussel tissues help identify internal biological processes and track coastal Zn sources in coastal environments, thus aiding in managing marine metal pollution. This study investigated the seasonal and multi-decadal Zn isotope compositions of blue mussels (genus Mytilus) from two French coastal sites with contrasting Zn environmental contamination. Concurrently, we characterized the isotope ratios of sediments and plankton samples at each site to understand the associations between organisms and abiotic compartments. Our primary objective was to determine whether these isotope compositions trace long-term anthropogenic emission patterns or if they reflect short-term biological processes. The multi-decadal isotope profiles of mussels in the Loire Estuary and Toulon Bay showed no isotope variations, implying the enduring stability of the relative contributions of natural and anthropogenic Zn sources over time. At seasonal scales, Zn isotope ratios were also constant; hence, isotope effects related to spawning and body growth were not discernible. The multi-compartmental analysis between the sites revealed that Toulon Bay exhibits a remarkably lower Zn isotope ratio across all studied matrices, suggesting the upward transfer of anthropogenic Zn in the food web. In contrast, the Zn isotope variability observed for sediments and organisms from the Loire Estuary fell within the natural baseline of this element. In both sites, adsorptive geogenic material carrying significant amounts of Zn masks the biological isotope signature of plankton, making it difficult to determine whether the Zn isotope ratio in mussels solely reflects the planktonic diet or if it is further modified by biological homeostasis. In summary, Zn isotope ratios in mussels offer promising avenues for delineating source-specific isotope signatures, contingent upon a comprehensive understanding of the isotope fractionation processes associated with the trophic transfer of this element through the plankton.

Discrimination of metal contaminant sources in river sediments influenced by mining and smelting activities using stable Pb and Zn isotopes.

To determine the sources and pathways of lead (Pb) and zinc (Zn) in river sediments contaminated with metals from mining and smelting activities, metal concentrations and Pb and Zn isotope ratios were measured in river water and sediment, and potential metal contaminant samples (imported Zn concentrates, smelting wastes, soils around the smelter, mine ores, and riverside tailings). Zn and cadmium (Cd) concentrations in river water and sediment samples were 30- and 11-25-fold higher, respectively, near the smelter than upstream, while a 6-fold increase in sediment Pb concentrations was detected over the same region. Sediment samples near the smelter (207Pb/206Pb = 0.8638 and 208Pb/206Pb = 2.0960) were observed to have a different Pb isotopic composition from upstream of the smelter (207Pb/206Pb = 0.8322 and 208Pb/206Pb = 2.0502), with δ66Zn values increasing from -0.01 to 0.82‰. Analysis of Pb and Zn isotopes and concentrations revealed that dust-contaminated soils were a major Pb source, and baseline sediments were found to be contaminated by regional mining tailings. For Zn in sediments, the main Zn sources were groundwater-derived Zn (δ66Zn = 1.02 ± 0.43‰, n = 4), dust-contaminated soils (δ66Zn = -0.18 ± 0.08‰, n = 3), and tailings-contaminated sediments (δ66Zn = 0.01 ± 0.07‰, n = 10). Endmember mixing model results showed that dust-contaminated soils contributed 78% and 64% of sediment Pb and Zn, respectively, within 2 km of the Zn smelter, decreasing to negligible levels after 47.1 km downstream. Downstream of the smelter, groundwater-derived Zn contributed 54% of sediment Zn, whereas tailings contaminated sediments contributed 70% and 25% of Pb and Zn, respectively.

Copper and zinc isotope systematics in different bivalve mollusk species from the French coastline: Implications for biomonitoring.

Zinc (Zn) and copper (Cu) stable isotopic compositions have been analyzed in various species of bivalve mollusks worldwide, but no comprehensive systematic interspecies comparison exists. Thus, we assessed isotope differences between species harvested in emblematic French coastal ecosystems to unveil biologically driven Cu and Zn isotope fractionation patterns. Inter-species isotopic variability of Cu is larger than Zn, with organisms that regulate internal concentrations displaying preferential bioaccumulation of heavy isotopes. The degree of internal isotope fractionation decreases from mussels > clams > oysters, affecting Cu more than Zn. The less pronounced Zn inter-specie variability helps preserve source information more reliably. Spatial analysis of a single oyster species denotes thus an important isotope variability of environmental Zn sources, including natural, anthropogenic and dietary components. Overall, results highlight the importance of considering systematic offset in Cu and Zn isotope values when comparing data from different bivalve species.

Adsorption of Zn(II) from aqueous solution and separation of zinc isotopes by displacement chromatography using chelating adsorbent.

The removal of zinc ions (Zn(II)) in water and the separation of zinc isotopes were fully investigated in this study. Imidodiacetic acid (IDA) type adsorbent (named PSGI) based on polystyrene spheres (PS) was synthesized by simultaneous irradiation grafting. By adsorption method, the removal of Zn(II) from water by the chelating adsorbent was studied in batch experiments. Under optimized condition, PSGI showed the removal efficiency of more than 98 % for Zn(II) and the adsorption capacity of 70.1 mg/g. Langmuir isothermal and pseudo-second-order kinetic model fitted the experimental results better, indicating that the adsorption is dominated by chemical adsorption. The spent adsorbent (PSGI-Zn) was used for further zinc isotope separation by displacement chromatography using EDTA-NH4 solution as eluent. Due to the mass effect of isotopes, 70Zn was found to preferentially fractionated into the front-end effluents with the highest front enrichment values of 70Zn/64Zn. By extending the migration distance to 20 m, we obtained the best isotope enrichment with the front maximum enrichment values as 1.0949, 1.0739 and separation coefficient values as 1.977 × 10-3, 8.33 × 10-3 corresponding to the isotope pairs 66Zn/64Zn, 68Zn/64Zn.

Zinc Supply Affects Cadmium Uptake and Translocation in the Hyperaccumulator Sedum Plumbizincicola as Evidenced by Isotope Fractionation.

This study employs stable isotope analysis to investigate the mechanisms of cadmium (Cd) and zinc (Zn) interaction in the metal hyperaccumulating plant species Sedum plumbizincicola. To this end, the Cd and Zn isotope compositions of root, stem, leaf, and xylem sap samples were determined during metal uptake and translocation at different Cd and Zn concentrations. The enrichment of light isotopes of both elements in plants during uptake was less pronounced at low metal supply levels, likely reflecting the switch from a low-affinity to a high-affinity transport system at lower levels of external metal supply. The lower δ114/110Cd values of xylem sap when treated with a metabolic inhibitor decreasing the active Cd uptake further supports the preference of heavier Cd isotopes during high-affinity transport. The Δ66Znplant-initial solution or Δ66Znplant-final solution values were similar at different Cd concentrations, indicating negligible interaction of Cd in the Zn uptake process. However, decreasing Zn supply levels significantly increased the enrichment of light Cd isotopes in plants (Δ114/110Cd = -0.08‰) in low-Cd treatments but reduced the enrichment of light Cd isotopes in plants (Δ114/110Cd = 0.08‰) under high Cd conditions. A systematic enrichment of heavy Cd and light Zn isotopes was found in root-to-shoot translocation of the metals. The Cd concentrations of the growth solutions thereby had no significant impact on Zn isotope fractionation during root-to-shoot translocation. However, the Δ114/110Cdtranslocation values hint at possible competition between Cd and Zn for transporters during root-to-shoot transfer and this may impact the transport pathway of Cd. The stable isotope data demonstrate that the interactions between the two metals influenced the uptake and transport mechanisms of Cd in S. plumbizincicola but had little effect on those of Zn.

A Neandertal dietary conundrum: Insights provided by tooth enamel Zn isotopes from Gabasa, Spain.

The characterization of Neandertals' diets has mostly relied on nitrogen isotope analyses of bone and tooth collagen. However, few nitrogen isotope data have been recovered from bones or teeth from Iberia due to poor collagen preservation at Paleolithic sites in the region. Zinc isotopes have been shown to be a reliable method for reconstructing trophic levels in the absence of organic matter preservation. Here, we present the results of zinc (Zn), strontium (Sr), carbon (C), and oxygen (O) isotope and trace element ratio analysis measured in dental enamel on a Pleistocene food web in Gabasa, Spain, to characterize the diet and ecology of a Middle Paleolithic Neandertal individual. Based on the extremely low δ66Zn value observed in the Neandertal's tooth enamel, our results support the interpretation of Neandertals as carnivores as already suggested by δ15N isotope values of specimens from other regions. Further work could help identify if such isotopic peculiarities (lowest δ66Zn and highest δ15N of the food web) are due to a metabolic and/or dietary specificity of the Neandertals.

Zn isotope fractionation in laterites from Yunnan province, southwest China: Implications for the Zn cycles and its environmental impacts in (sub-) tropics.

The weathering and development of laterites can influence trace element cycling in (sub-) tropics. Zinc (Zn) is a ubiquitous trace metal that involves both abiotic and biotic processes in soils. To explore Zn behavior in laterites, Zn cycling in (sub-) tropics, and the environmental impacts, Zn isotope systematics were presented for two laterite profiles from Yunnan province, southwest China. The laterite samples exhibit the δ66Zn of 0.02 ‰-0.56 ‰, indicating a light shift of Zn isotope ratios (Δ66Znlaterite-parent rock = -0.47 ‰-0.07 ‰) relative to bulk parent granite. This observation is attributed to the preferential preservation of light Zn isotopes on the surface of secondary Fe oxides. As a result, laterites are likely to control the instantaneous riverine δ66Zn in (sub-) tropical regions heavier than unweathered rocks. The isotopic signature of different vegetation covered soils show that shrub-covered soils are stronger leached (average τZn = -0.61) and have a smaller Δ66Znlaterite-parent rock (=-0.15 ‰), relative to forest-covered soils (=-0.20 ‰). Due to the strong loss of Zn (average τZn = -0.61 to -0.12) and large amounts of low-bioavailable Zn preserved in oxides, the micronutrient supplies for plant growth are difficult to maintain and need more fertilization. This study is helpful for a better understanding of global Zn cycling and the management of micronutrients in (sub-) tropical soil-plant systems.

Zinc in soil reflecting the intensive coal mining activities: Evidence from stable zinc isotopes analysis.

In the mining area affected by coal mining activities for a long time, heavy metal Zn pollution poses a serious threat to soil quality and human health, and direct evidence showing the relationship between Zn accumulation mechanism in soils and mining activities is lacking. In this study, the Zn content and isotopes composition (δ66Zn) from soil and environmental samples around mining area were determined and analyzed to clarify the Zn characteristics in soil. Moreover, the distribution and source of Zn content in soil of mining area were analyzed by mathematical statistics, correlation analysis and isotope mass mixing model. The results showed that: (1) the Zn content in soil ranged from 95 to 327 mg·kg-1 (mean: 233 mg·kg-1), exceeding the control point and the soil background value of Anhui Province; (2) the results of Zn isotope analysis showed that Zn in soil mainly derived from the wind dispersion input of fine particles in gangue and fly ash, followed by the natural weathering of parent material; (3) isotopic mass mixing model can be used to distinguish the contribution of anthropogenic and natural Zn sources. Mining input was the main contribution source of Zn in soil (mean: 67%), followed by natural background (mean: 33%). The employment of Zn isotopes can effectively evaluate the impact of anthropogenic and natural long-term processes on Zn in the soil of the mining area, and provide important information for the formulation of soil metal pollution control measures.

Trophic ecology of a Late Pleistocene early modern human from tropical Southeast Asia inferred from zinc isotopes.

Tam Pà Ling, a cave site in northeastern Laos, has yielded the earliest skeletal evidence of Homo sapiens in mainland Southeast Asia. The reliance of Pleistocene humans in rainforest settings on plant or animal resources is still largely unstudied, mainly due to poor collagen preservation in fossils from tropical environments precluding stable nitrogen isotope analysis, the classical trophic level proxy. However, isotopic ratios of zinc (Zn) in bioapatite constitute a promising proxy to infer trophic and dietary information from fossil vertebrates, even under adverse tropical taphonomic conditions. Here, we analyzed the zinc isotope composition (66Zn/64Zn expressed as δ66Zn value) in the enamel of two teeth of the Late Pleistocene (63-46 ka) H. sapiens individual (TPL1) from Tam Pà Ling, as well as 76 mammal teeth from the same site and the nearby Nam Lot cave. The human individual exhibits relatively low enamel δ66Zn values (+0.24‰) consistent with an omnivorous diet, suggesting a dietary reliance on both plant and animal matter. These findings offer direct evidence of the broad utilization of resources from tropical rainforests by one of the earliest known anatomically modern humans in Southeast Asia.

Zinc isotopes from archaeological bones provide reliable tropic level information for marine mammals.

In marine ecology, dietary interpretations of faunal assemblages often rely on nitrogen isotopes as the main or only applicable trophic level tracer. We investigate the geographic variability and trophic level isotopic discrimination factors of bone zinc 66Zn/64Zn ratios (δ66Zn value) and compared it to collagen nitrogen and carbon stable isotope (δ15N and δ13C) values. Focusing on ringed seals (Pusa hispida) and polar bears (Ursus maritimus) from multiple Arctic archaeological sites, we investigate trophic interactions between predator and prey over a broad geographic area. All proxies show variability among sites, influenced by the regional food web baselines. However, δ66Zn shows a significantly higher homogeneity among different sites. We observe a clear trophic spacing for δ15N and δ66Zn values in all locations, yet δ66Zn analysis allows a more direct dietary comparability between spatially and temporally distinct locations than what is possible by δ15N and δ13C analysis alone. When combining all three proxies, a more detailed and refined dietary analysis is possible.

Zinc stable isotope analysis reveals Zn dyshomeostasis in benign tumours, breast cancer, and adjacent histologically normal tissue.

The disruption of Zn homeostasis has been linked with breast cancer development and progression. To enhance our understanding of changes in Zn homeostasis both inside and around the tumour microenvironment, Zn concentrations and isotopic compositions (δ66Zn) were determined in benign (BT) and malignant (MT) tumours, healthy tissue from reduction mammoplasty (HT), and histologically normal tissue adjacent to benign (NAT(BT)) and malignant tumours (NAT(MT)). Mean Zn concentrations in NAT(BT) are 5.5 µg g-1 greater than in NAT(MT) (p = 0.00056) and 5.1 µg g-1 greater than in HT (p = 0.0026). Zinc concentrations in MT are 12.9 µg g-1 greater than in HT (p = 0.00012) and 13.3 µg g-1 greater than in NAT(MT) (p < 0.0001), whereas δ66Zn is 0.17‰ lower in MT than HT (p = 0.017). Benign tumour Zn concentrations are also elevated compared to HT (p = 0.00013), but are not significantly elevated compared to NAT(BT) (p = 0.32). The δ66Zn of BT is 0.15‰ lower than in NAT(BT) (p = 0.045). The similar light δ66Zn of BT and MT compared to HT and NAT may be related to the isotopic compensation of increased metallothionein (64Zn-rich) expression by activated matrix metalloproteinase (66Zn-rich) in MT, and indicates a resultant 66Zn-rich reservoir may exist in patients with breast tumours. Zinc isotopic compositions thus show promise as a potential diagnostic tool for the detection of breast tumours. The revealed differences of Zn accumulation in healthy and tumour-adjacent tissues require additional investigation.

Evaluation of production cross-sections for theranostic 67Cu radionuclide via proton-induced nuclear reaction on 68Zn target.

Copper-67 (T1/2 = 61.83 h, Eß-mean=141 keV, Iß-total=100%; Eγ = 184.577 keV, Iγ = 48.7%) is a promising radionuclide for theranostic applications especially in radio immunotherapy. However, one of the main drawbacks for its application is related to its limited availability. Various nuclear reaction routes investigated in the last years can result in 67Cu production, although the use of proton beams is the method of choice taken into account in this work. The goal of this work is a revision of the cross-sections aimed at 67Cu yield, which were evaluated for the 68Zn(p,2p)67Cu reaction route up to 80 MeV proton energy. A well-defined statistical procedure, i.e., the Simultaneous Evaluation on KALMAN (SOK), combined with the least-squares concept, was used to obtain the evaluated data together with the covariance matrix. The obtained evaluated data were also compared to predictions provided by the nuclear reaction model codes TALYS and EMPIRE, and a partial agreement among them has been found. These data may be useful for both existing and potential applications in nuclear medicine, to achieve an improvement and validation of the various nuclear reaction models, and may also find applications in other fields (e.g., activation analysis and thin layer activation).

Zinc isotope variations in archeological human teeth (Lapa do Santo, Brazil) reveal dietary transitions in childhood and no contamination from gloves.

Zinc (Zn) isotope ratios of dental enamel are a promising tracer for dietary reconstruction in archeology, but its use is still in its infancy. A recent study demonstrated a high risk of Zn contamination from nitrile, and latex gloves used during chemical sample preparation. Here we assess the potential impact of the use of such gloves during enamel sampling on the Zn isotope composition of teeth from a population of early Holocene hunter gatherers from Lapa do Santo, Lagoa Santa, Minas Gerais, Brazil. We first examined the amount of Zn and its isotopic composition released from the gloves used in this study by soaking them in weak nitric acid and water. We compared Zn isotope ratios obtained from teeth that were sampled wearing nitrile, latex or no gloves. Finally, we performed a linear mixed model (LMM) to investigate post hoc the relationship between the gloves used for sampling and the Zn isotope variability in dental enamel. We found that the gloves used in this study released a similar amount of Zn compared to previous work, but only in acidic solution. Zn isotope ratios of teeth and the LMM identified no sign of significant Zn coming from the gloves when teeth were handled for enamel sampling. We hypothesize that Zn in gloves is mostly released by contact with acids. We found that the main source of Zn isotope variability in the Lapa do Santo population was related to the developmental stage of the tooth tissues sampled. We report identical results for two individuals coming from a different archeological context. Tooth enamel formed in utero and/or during the two first years of life showed higher Zn isotope ratios than enamel formed after weaning. More work is required to systematically investigate if Zn isotopes can be used as a breastfeeding tracer.

Zinc isotopes in Late Pleistocene fossil teeth from a Southeast Asian cave setting preserve paleodietary information.

Stable carbon and nitrogen isotope ratios of collagen from bone and dentin have frequently been used for dietary reconstruction, but this method is limited by protein preservation. Isotopes of the trace element zinc (Zn) in bioapatite constitute a promising proxy to infer dietary information from extant and extinct vertebrates. The 66Zn/64Zn ratio (expressed as δ66Zn value) shows an enrichment of the heavy isotope in mammals along each trophic step. However, preservation of diet-related δ66Zn values in fossil teeth has not been assessed yet. Here, we analyzed enamel of fossil teeth from the Late Pleistocene (38.4-13.5 ka) mammalian assemblage of the Tam Hay Marklot (THM) cave in northeastern Laos, to reconstruct the food web and assess the preservation of original δ66Zn values. Distinct enamel δ66Zn values of the fossil taxa (δ66Zncarnivore < δ66Znomnivore < δ66Znherbivore) according to their expected feeding habits were observed, with a trophic carnivore-herbivore spacing of +0.60‰ and omnivores having intermediate values. Zn and trace element concentration profiles similar to those of modern teeth also indicate minimal impact of diagenesis on the enamel. While further work is needed to explore preservation for settings with different taphonomic conditions, the diet-related δ66Zn values in fossil enamel from THM cave suggest an excellent long-term preservation potential, even under tropical conditions that are well known to be adverse for collagen preservation. Zinc isotopes could thus provide a new tool to assess the diet of fossil hominins and associated fauna, as well as trophic relationships in past food webs.

Assessment of the metal contamination evolution in the Loire estuary using Cu and Zn stable isotopes and geochemical data in sediments.

In this work, a multi-elemental approach combining Cu and Zn stable isotopes is used to assess the metal contamination evolution in the Loire estuary bulk sediments. Elemental geochemical data indicate an increase of metal concentrations from the beginning of the industrial period peaking in the 1990s, followed by an attenuation of metal contamination inputs to the estuary. Zinc isotope compositions suggest a binary mixing process between Zn derived from terrigenous material and multi-urban anthropogenic sources. Copper isotope systematics indicate a single natural dominant source represented by weathered silicate particles from soils and rocks. This work demonstrates the applicability of Zn isotopes to identify anthropogenic Zn sources in coastal systems, even under a low to moderate degree of contamination. Further studies are required to constrain Cu sources and to elucidate possible effects of grain-size and mineralogy in the Cu isotope composition of sediment in the Loire estuary.

Zinc Absorption From Agronomically Biofortified Wheat Is Similar to Post-Harvest Fortified Wheat and Is a Substantial Source of Bioavailable Zinc in Humans.

BACKGROUND: Limited data exist on human zinc absorption from wheat biofortified via foliar (FBW) or root (hydroponically fortified wheat, HBW) zinc application. Stable isotope labels added at point of consumption (extrinsic labeling) might not reflect absorption from native zinc obtained by intrinsic labeling. OBJECTIVES: We measured fractional and total zinc absorption (FAZ, TAZ) in FBW and HBW wheat, compared with control wheat (CW) and fortified wheat (FW). The effect of labeling method was assessed in HBW (study 1), and the effect of milling extraction rate (EXR, 80% and 100%) in FBW (studies 2 and 3). METHODS: Generally healthy adults (n = 71, age: 18-45 y, body mass index: 18.5-25 kg/m2) were allocated to 1 of the studies, in which they served as their own controls. In study 1, men and women consumed wheat porridges colabeled intrinsically and extrinsically with 67Zn and 70Zn. In studies 2 and 3, women consumed wheat flatbreads (chapatis) labeled extrinsically. Zinc absorption was measured with the oral to intravenous tracer ratio method with a 4-wk wash-out period between meals. Data were analyzed with linear mixed models. RESULTS: In study 1 there were no differences in zinc absorption from extrinsic versus intrinsic labels in either FW or HBW. Similarly, FAZ and TAZ from FW and HBW did not differ. TAZ was 70-76% higher in FW and HBW compared with CW (P < 0.01). In studies 2 and 3, TAZ from FW and FBW did not differ but was 20-48% higher compared with CW (P < 0.001). Extraction rate had no effect on TAZ. CONCLUSIONS: Colabeling demonstrates that extrinsic zinc isotopic labels can be used to accurately quantify zinc absorption from wheat in humans. Biofortification through foliar zinc application, root zinc application, or fortification provides higher TAZ compared with unfortified wheat. In biofortified wheat, extraction rate (100-80%) has a limited impact on total zinc absorption. These studies were registered on clinicaltrials.gov (NCT01775319).

Dynamic homeostasis modeling of Zn isotope ratios in the human body.

Recent research performed on volunteers and patients suggested that diet, health, and basal metabolic rates (BMR) are factors controlling the bodily Zn isotope compositions (isotopic homeostasis). However, our poor understanding of the variability of Zn distribution among the different organs and fluids of the human body, and the ensuing isotope fractionation, limits the use of this isotopic system as a typical diagnostic tool for cancers and for past hominin diet reconstructions. Using box model calculations, we investigated the dynamics of Zn isotope variability in blood and other body tissues as well as the consistency of the hypothesis of heavy Zn isotope accumulation through time in the human body. We compare the results of the model with data obtained from control feeding experiments and from archeological samples. Model simulations indicate that the absence of an aging drift in non-circumpolar populations cannot be explained by their lower BMR. We argue that the drift observed in the blood of a circumpolar population results from a differential diet between young and older individuals in this population. When applied to the δ66Zn measured in blood, bones, or teeth, the present box model also offers insight into the isotope composition of the human diet, and therefore into its nature. Applying the model to isotopic observations on the remains of past hominins is a promising tool for diet reconstruction.