Isotope Approach Research Articles

Identifying groundwater characteristics and controlling factors in Jiaozhou Bay’s northern coastal region, China: a combined approach of multivariate statistics, isotope analysis, and field empirical investigations

Explicit identification of hydrochemical processes and their controlling factors within groundwater systems is critical for the sustainable utilization of water resources in coastal urban areas. This study was undertaken in the North Coastal Region of Jiaozhou Bay (NCRJB), located in the eastern part of Shandong Province, China, an area grappling with significant issues of groundwater quality degradation and water scarcity. A total of 105 groundwater samples and 34 surface water samples, collected from 2020 to 2024, were analyzed and studied using various hydrogeological tools, multivariate statistical analyses, and water quality assessment methods. These include the Piper diagram, hydrochemical facies evolution diagram (HFE-D), Principal Components Analysis (PCA), correlation analysis, stable isotope analysis, Water Quality Index (WQI), and USSL diagrams. The results indicated that all surface water and pore groundwater samples were categorized as Na-Cl type, exhibiting high Total Dissolved Solids (TDS) and Electrical Conductivity (EC) values, characteristics that render them poor to unsuitable for drinking and irrigation purposes. The fracture groundwater is predominantly of the Ca-Na-Cl mixed type, with average suitability for irrigation and a limited proportion (22.5%) deemed suitable for drinking. Seawater intrusion, primarily through the surface water system, and the impact of human activities were identified as the predominant controlling factors con-tributing to the degradation of the local groundwater environment. Field empirical investigations further validated the results derived from hydrogeological assessments, multivariate statistical analyses, and isotopic approaches. The long-term shifts in hydrochemical properties, along with the latent threat of seawater intrusion, exhibit an upward trend during the dry season and show a certain degree of mitigation during the wet season. This study highlights that field investigations, in conjunction with hydrochemical tools, multivariate statistical analyses, and stable isotope analysis, can successfully furnish reliable insights into the predominant mechanisms governing regional groundwater evolution within the context of long-term and intricate envi-ronmental settings.

Hydrochemical Characteristics and Formation Mechanism of Geothermal Fluids in Zuogong County, Southeastern Tibet

Zuogong County is located in the southeast of Tibet, which is rich in hot spring geothermal resources, but its development and utilization degree are low, and the genetic mechanism of the geothermal system is not clear. Hydrogeochemical characteristics of geothermal water are of great significance in elucidating the genesis and evolution of geothermal systems, as well as the sustainable development and utilization of geothermal resources. The hydrogeochemical characteristics and genesis of the geothermal water in Zuogong County were investigated using hydrogeochemical analysis, a stable isotope (δD, δ18O) approach, and an inverse simulation model for water–rock reactions using the PHREEQC. The results indicated that the Zuogong geothermal system is a deep circulation heating type without a magmatic heat source. The chemical types present in the geothermal water from the Zuogong area are HCO3 and HCO3·SO4, and the main cations are Na+ and Ca2+. The groundwater is replenished by atmospheric precipitation and glacier meltwater. The salt content of geothermal water mainly comes from the interaction between water and surrounding rocks during the deep circulation process. The reservoir temperature of geothermal water in Zuogong is 120–176 °C before mixing with non-geothermal water and drops to 62–98 °C after mixing with 58 to 79% of non-geothermal water. According to the proposed conceptual model, geothermal water mainly produces water–rock interaction with aluminosilicate minerals in the deep formation, while in shallow areas it interacts mainly with sulfate minerals. These findings contribute to a better understanding of the geothermal system in Zuogong County, Tibet.

Detangling past and modern zinc anthropogenic source contributions in an urbanized coastal river by combining elemental, isotope and speciation approaches

The accumulation of trace metals in the environmental compartments of coastal rivers is a global and complex environmental issue, requiring multiple tools to constrain the various anthropogenic sources and biogeochemical processes affecting the water quality of these environments. The Valao fluvio-estuarine system (Rio de Janeiro, Brazil) presents a challenging case of a coastal river contaminated by both modern and historical anthropogenic metal sources, located in the land and in the intra-estuary, continuously mixed by tidal cycles. This study employed a combination of spatial distribution analysis of trace metals including gadolinium (Gd), zinc (Zn) isotopic analyses, and X-ray absorption spectroscopy (XAS) to distinguish between these sources. The concentrations of metals in both dissolved (water samples) and surficial sediment compartments (Suspended Particulate Matter and sediment samples) display an overall enrichment trend from upstream to downstream. Multivariate statistical analysis allows to discriminate geogenic elements derived from watershed geology (Ti, K, and Mg) vs anthropogenic contaminants from urban runoff and domestic sewage discharges (Cu, Cr, Pb, Zn, and Gd); and legacy metal contaminants (Zn and Cd) remobilized from ancient metallurgical wastes and transported upstream in the estuary during tidal cycles. The anthropogenic Gd concentration in the dissolved compartment increases along the watercourse, highlighting continuous ongoing sewage discharge. Zinc solid speciation also indicates that Zn contribution from legacy metallurgy waste is primarily associated with sulfide-Zn and Zn-phyllosilicate in the outlet estuary, while in upstream sediments of fluvio-estuarine system, Zn is found bound to organic matter. Zinc isotope systematically reveals a progressive downstream shift to heavier isotope compositions. Upstream, the relatively pristine site and the urbanized section of the river exhibit a relatively uniform δ66/64Zn value (+0.20 ± 0.07 ‰) in suspended particulate matter (SPM) and surficial sediments. These results indicate that domestic sewage discharges contribute to Zn enrichment in sediments of the Valao fluvio-estuarine system but without modifying its isotope signature in sediments. The sediment of the downstream estuarine section shows a heavier δ66/64Zn value (+0.48 ± 0.08 ‰), indicating the strong influence of the intra-estuarine source identified as the historical metallurgic contamination. An integrated view of the geochemical tracers allows thus inferring that the untreated sewage and legacy metallurgical contamination are the primary sources of anthropogenic Zn contamination. It highlights the progressive mixing along the estuarine gradient under tidal dynamics. The influence of the former source continuously expands from the headland towards the estuary.

Extreme precipitation reduces the recent photosynthetic carbon isotope signal detected in ecosystem respiration in an old-growth temperate forest.

The successful utilization of stable carbon isotope approaches in investigating forest carbon dynamics has relied on the assumption that the carbon isotope compositions (δ13C) therein have detectable temporal variations. However, interpreting the δ13C signal transfer can be challenging, given the complexities involved in disentangling the effect of a single environmental factor, the isotopic dilution effect from background CO2 and the lack of high-resolution δ13C measurements. In this study, we conducted continuous in situ monitoring of atmospheric CO2 (δ13Ca) across a canopy profile in an old-growth temperate forest in northeast China during the normal year 2020 and the wet year 2021. Both years exhibited similar temperature conditions in terms of both seasonal variations and annual averages. We tracked the natural carbon isotope composition from δ13Ca to photosynthate (δ13Cp) and to ecosystem respiration (δ13CReco). We observed significant differences in δ13Ca between the two years. Contrary to in 2020, in 2021 there was a δ13Ca valley in the middle of the growing season, attributed to surges in soil CO2 efflux induced by precipitation, while in 2020 values peaked during that period. Despite substantial and similar seasonal variations in canopy photosynthetic discrimination (Δ13Ccanopy) in the two years, the variability of δ13Cp in 2021 was significantly lower than in 2020, due to corresponding differences in δ13Ca. Furthermore, unlike in 2020, we found almost no changes in δ13CReco in 2021, which we ascribed to the imprint of the δ13Cp signal on above-ground respiration and, more importantly, to the contribution of stable δ13C signals from soil heterotrophic respired CO2. Our findings suggest that extreme precipitation can impede the detectability of recent photosynthetic δ13C signals in ecosystem respiration in forests, thus complicating the interpretation of above- and below-ground carbon linkage using δ13CReco. This study provides new insights for unravelling precipitation-related variations in forest carbon dynamics using stable isotope techniques.

Kinetic Modeling of In Vivo K+ Distribution and Fluxes with Stable K+ Isotopes: Effects of Dietary K+ Restriction.

Maintaining extracellular potassium (K+) within narrow limits, critical for membrane potential and excitability, is accomplished through the internal redistribution of K+ between extracellular fluid (ECF) and intracellular fluid (ICF) in concert with the regulation of renal K+ output to balance K+ intake. Here we present evidence from high-precision analyses of stable K+ isotopes in rats maintained on a control diet that the tissues and organs involved in the internal redistribution of K+ differ in their speed of K+ exchange with ECF and can be grouped into those that exchange K+ with ECF either rapidly or more slowly ("fast" and "slow" pools). After 10 days of K+ restriction, a compartmental analysis indicates that the sizes of the ICF K+ pools decreased but that this decrease in ICF K+ pools was not homogeneous, rather occurring only in the slow pool (15% decrease, p < 0.01), representing skeletal muscles, not in the fast pool. Furthermore, we find that the dietary K+ restriction is associated with a decline in the rate constants for K+ effluxes from both the "fast" and "slow" ICF pools (p < 0.05 for both). These results suggest that changes in unidentified transport pathways responsible for K+ efflux from ICF to ECF play an important role in buffering the internal redistribution of K+ between ICF and ECF during K+ restriction. Thus, the present study introduces novel stable isotope approaches to separately characterize heterogenous ICF K+ pools in vivo and assess K+ uptake by individual tissues, methods that provide key new tools to elucidate K+ homeostatic mechanisms in vivo.

Slow recovery in trophic structure of restored wetlands in Northeast China

Restoration measures have been widely implemented in wetland ecosystems globally to bend the curve of biodiversity loss and restore associated ecological functions. However, assessments of the effectiveness of wetland restoration have predominantly focused on the recovery of taxonomic composition, while few studies have assessed the effectiveness of these efforts from a food web perspective. Here, we incorporated stable isotope approach to investigate trophic structure in natural and restored wetlands in Northeast China. The investigated consumers, including zooplankton, macroinvertebrates, and fish, exhibited lower δ15N and higher δ13C values in restored wetlands than in natural wetlands. Natural wetlands exhibited higher trophic positions and a wider range of trophic levels compared to restored wetlands. Primary consumers in natural wetlands relied more on particulate organic matter (POM, 42.9 % ± 24.1 %), while those in restored wetlands were more dependent on substrate organic matter (SOM, 42.3 % ± 23.9 %). Compared to natural wetlands, isotopic richness was significantly lower in restored wetlands, with smaller isotopic variation (SEAs) in basal resources, aquatic invertebrates, and fish. Our findings reveal that the recovery of trophic structures in restored wetlands lags behind that of taxonomic composition. Future restoration efforts should prioritize enhancing habitat heterogeneity and resource availability to support a diverse range of trophic levels. Monitoring trophic dynamics is essential for assessing the progress of wetland restoration and should be integrated into monitoring schemes.

A multi-analytical approach for the identification of pollutant sources on black crust samples: Stable isotope ratio of carbon, sulphur, and oxygen

This study is focused on the identification of pollutant sources on black crust (BC) samples from the Monumental Cemetery of Milan (Italy), through a multi-analytical approach based on the determination of stable isotope ratios of carbon, sulphur, and oxygen. Six black crust samples, mainly developed on marble sculptures over a time span of 100–150 years, were analysed.For the first time, δ13C was measured for BC samples: δ13C values of the pulverized samples (from −1.2 to +1.3 ‰) are very close to the values obtained from the carbonate matrix, whereas after the removal of the matrix through acidification, δ13C values of BC samples from Milan range from −27.2 to −22.1 ‰, with no significant variation between samples with different ratios of organic carbon to elemental carbon. In sum, the δ13C values obtained for all BC samples fall within the range of anthropogenic emissions such as vehicle traffic, coal combustion and industrial emissions.δ34S and δ18O values of sulphate from BC samples range from −6.3 to +7.0 ‰ and from +7.6 to +10.5 ‰, respectively. Coupling the analysis of the oxygen isotope ratio with that of sulphur enables a more precise identification of the origin of sulphates: the observed isotopic composition falls in the range typical for anthropogenic emission of sulphur dioxide.Overall, in this study, C, S and O isotopes were combined for the first time to assess pollutant sources on black crust samples: this multi-stable isotope approach allowed to show that the BC formation on monuments from the Monumental Cemetery of Milan mostly results from anthropogenic emissions from fossil fuels combustion by road vehicles and factories, as well as domestic heating.

Evaluating Source Complexity in Blended Milk Cheese: Integrated Strontium Isotope and Multi-Elemental Approach to PDO Graviera Naxos.

Graviera Naxos, a renowned cheese with Protected Designation of Origin status, is crafted from a blend of cow, goat, and sheep milk. This study focused on assessing the Sr isotopic and multi-elemental composition of both the processed cheese and its ingredients, as well as the environmental context of Naxos Island, including samples of milk, water, soil, and feed. The objective was to delineate the geochemical signature of Graviera Naxos cheese and to explore the utility of Sr isotopes as indicators of geographic origin. The 87Sr/86Sr values for Graviera Naxos samples ranged from 0.70891 to 0.70952, indicating a relatively narrow range. However, the Sr isotopic signature of milk, heavily influenced by the feed, which originates from geologically distinct areas, does not always accurately reflect the local breeding environment. Multi-elemental analysis revealed variations in milk composition based on type and season; yet, no notable differences were found between raw and pasteurized milk. A mixing model evaluating the contributions of milk, sea salt, and rennet to the cheese's Sr isotopic signature suggested a significant average contribution of 73.1% from sea salt. This study highlights the complexities of linking dairy products with their geographical origins and emphasizes the need for sophisticated geochemical authentication methods.

Drought effects in Mediterranean forests are not alleviated by diversity‐driven water source partitioning

Abstract Tree species diversity in forest ecosystems could reduce their vulnerability to extreme droughts through improved microclimate and below‐ground water source partitioning driven by contrasting species‐specific water use patterns. However, little is known about the seasonal dynamics of belowground water uptake that determine whether diversity positively or negatively impacts tree carbon assimilation and water exchange. Using a network of 30 permanent plots in Mediterranean forests with increasing tree species diversity (from monospecific to four‐species mixtures), we examined the seasonal patterns of in‐situ aboveground carbon and water relations and belowground water sources on 265 trees from four pine and oak species over 2 years using hydraulic and stable isotope approaches. We found that increasing species diversity in broadleaf and conifer mixtures induced strong soil water source partitioning between oak and pine species. As conditions became drier during the summer in mixed stands, oak species took up water from deeper soil sources, while pines were systematically limited to shallow ones. Despite significant belowground moisture partitioning, stronger drought‐induced reductions in photosynthesis, stomatal conductance, and leaf water potential were still observed in diverse compared with monospecific stands for pines but with some benefits for oaks. Synthesis: Our findings reveal that tree species diversity promoted belowground water source partitioning in mixed oak and pine stands, potentially reducing competition for water in more diverse ecosystems. Yet, our results show that it is insufficient to buffer the adverse impacts of severe droughts on aboveground tree carbon and water use, leading to higher water stress, especially for pines.

To Eat or Not to Eat: Novel Stable Isotope Models Reveal a Shift in Carnivory with Nutrient Availability for Aquatic Utricularia spp.

Freshwater nitrogen inputs are increasing globally, altering the structure and function of wetland ecosystems adapted to low nutrient conditions. Carnivorous wetland plants, Utricularia spp., are hypothesised to reduce their reliance on carnivory and increase their assimilation of environmental nutrients when the supply of ambient nutrients increases. Despite success in using stable isotope approaches to quantify carnivory of terrestrial carnivorous plants, quantifying carnivory of aquatic Utricularia requires improvement. We developed stable isotope mixing models to quantify aquatic plant carnivory and used these models to measure dietary changes of three Utricularia species: Utricularia australis, U. gibba, and U. uliginosa in 11 wetlands across a 794 km gradient in eastern Australia. Diet was assessed using multiple models that compared variations in the natural abundance nitrogen isotope composition (δ15N) of Utricularia spp. with that of non-carnivorous plants, and environmental and carnivorous nitrogen sources. Carnivory supplied 40 - 100 % of plant nitrogen. The lowest carnivory rates coincided with the highest availability of ammonium and dissolved organic carbon. Our findings suggest that Utricularia populations may adapt to high nutrient environments by shifting away from energetically costly carnivory. This has implications for species conservation as anthropogenic impacts continue to affect global wetland ecosystems.

Evaporation from dams governing the water cycle dynamics of a regulated river basin from the Western Ghats: Sharavati, India

Study regionSharavati River, Karnataka, India. Study focusA small mountainous river system, Sharavati, was selected to study the impact of river damming on the hydrological cycle. Sharavati river flow is regulated by two dams, Linganamakki and Gersoppa. Despite the Western Ghats' global significance in controlling local and regional climates, the effects of damming on its hydrological cycles have received limited attention. A stable water isotopic approach was employed in the study. New hydrological insights for the regionThe line-conditioned excess (lc-excess) was primarily negative across all seasons. Notably, the pre-monsoon season exhibited comparatively higher evaporation with high negative lc-excess, while the postmonsoon lc-excess values approached zero, indicating minimal evaporation. The sampling points from the dams exhibited very high evaporation signals, the evaporative loss during the pre-monsoon season from the Linganamakki reservoir was estimated as 10 %, and from the Gersoppa dam was 6 %. Consequently, groundwater sampled near the dams, plotted along the local evaporation line indicating recharge from the evaporated reservoir water. Damming has affected the hydrological cycle of the heavily regulated Sharavati River, transforming the entire catchment into a connected, narrow lake-like structure, especially during the pre-monsoon season. Since the Western Ghat river systems are regulated by many large and small dams, it is pertinent to study the impact of damming on the hydrological cycles of the entire system.

Erosion of fish trophic position: an indirect effect of fishing on food webs elucidated by stable isotopes.

Fishing has significant trophodynamic impacts on marine communities, including reductions in the mean trophic position (TP) of the ecosystem resulting from a decrease in the abundance and size of species and individuals with high TPs. This study demonstrates the erosion of fish TP, an additional process that results in lower TP of individuals of a given size, which may exacerbate the effects of fishing on the food web. A stable isotope approach based on the tRophicPosition Bayesian method was used to quantify the TP of 12 target marine species at a given length, and compare their TP between fishery-restricted areas and trawled areas. The results show a difference in the TP of six benthic and apical nekto-benthic predators, which feed in the median at about 0.5 TP lower in trawled areas. It appears that current 'fishing down marine food webs' analyses may underestimate the trophic effects of fishing. Accounting for changes in trophodynamics of individuals at a given size is important to detect indirect effects through food web interactions. The application of a trawling ban may lead to the restoration of lost trophic structure; however, trophic changes may occur more slowly than changes in biomass. This article is part of the theme issue 'Connected interactions: enriching food web research by spatial and social interactions'.

Unexpected contributions by carbonates and organic matter in a silicate-dominated tropical catchment: An isotope approach

The understanding of global carbon has rarely extended to small-scale tropical river basins. To address these uncertainties, this study aims to investigate the importance of rock weathering and organic matter turnover in the carbon cycle in a terrain dominated by crystalline silicate rocks. The geochemical composition of the dissolved and particulate carbon phases (DIC, DOC and POC) and their stable carbon isotopes were studied in the Deduru Oya River in Sri Lanka. Dissolved inorganic carbon (DIC) was the most dominant carbon phase and its contribution to the total carbon pool varied between 67 and 89 %. Furthermore, the δ13CDIC values in the river varied between −1.1 and −16.5 ‰. The lithological characteristics and molar ratios between Ca2+, Mg2+ and HCO3− indicated rock weathering mainly by CO2 and carbonic acid. The δ13CDIC values for groundwater input were −15.9 ‰, while for carbonate weathering, mainly due to fertiliser input, they reached a value of −12.7 ‰. This input was fed into an isotope mass balance to determine the relative contributions. However, the isotope mass balance was only plausible after correcting for the effects on δ13CDIC caused by degassing and photosynthesis. Our study demonstrated that carbonate weathering and organic matter turnover are essential components of the river carbon cycle even in a silicate dominated catchment. They can represent up to 60 % of the DIC pool. Combined with the higher organic matter turnover and high pCO2 in the river water, it can be suggested that the Deduru Oya River acts as a net source of CO2 in the atmosphere. Our study shows that CO2 degassing and in-stream photosynthesis in tropical river systems need to be considered along with chemical weathering to account for carbon transport and turnover in tropical rivers.

Comparison with carbonate rocks hosted iron skarn in the eastern Sakarya Zone (Gümüşhane, NE Turkey): a geomorphologic, geochemical and stable isotopic approach

Comparison with carbonate rocks hosted iron skarn in the eastern Sakarya Zone (Gümüşhane, NE Turkey): a geomorphologic, geochemical and stable isotopic approach

Mercury sources, transport, and transformation in rainfall-runoff processes: Mercury isotope approach

Mercury (Hg) in runoff water poses significant ecological risks to aquatic ecosystems that can affect organisms. However, accurately identifying the sources and transformation processes of Hg in runoff water is challenging due to complex natural conditions. This study provides a comprehensive investigation of Hg dynamics in water from rainfall to runoff. The Hg isotope fractionation in water was characterized, which allows accurate quantification of Hg sources, transport, and transformations in rainfall-runoff processes. Δ200Hg and corrected Δ199Hg values can serve as reliable tracers for identifying Hg sources in the runoff water and the variation of δ202Hg can be explained by Hg transformation processes. During runoff migration processes, Hg from rainfall is rapidly absorbed on the land surface, while terrestrial Hg entering the water by the dissolution process becomes the primary component of dissolved mercury (DHg). Besides the dissolution and adsorption, microbial Hg(II) reduction and demethylation of MeHg were dominant processes for DHg in the runoff water that flows through the rice paddies, while photochemical Hg(II) reduction was the dominant process for DHg in the runoff water with low water exchange rates. Particulate Hg (PHg) in runoff water is dominantly originated by the terrestrial material and derived from the dissolution and adsorption process. Tracking sources and transformations of Hg in runoff water during the rainfall-runoff process provides a basis for studying Hg pollution in larger water bodies under complex environmental factors.

Food web collapse and regime shift following goldfish introduction in permanent ponds.

In a global context of invasive alien species (IAS), native predators are often eradicated by functionally different IAS, which may induce complex cascading consequences on ecosystem functioning because of the key role predators play in structuring communities and stabilizing food webs. In permanent ponds, the most abundant freshwater systems on Earth, global human-mediated introductions of alien omnivores such as the pet trade goldfish are driving broad-scale patterns of native predators' exclusion, but cascading consequences on food web structure and functioning are critically understudied. We compared food webs of naturally fishless ponds versus ponds where dominant native predators (newts) had been extirpated by invasive goldfish within the last decade. Integrating community-wide isotopic, taxonomic and functional traits approaches, our study reveals that pond food webs collapsed in both vertical and horizontal dimensions following goldfish introduction and the associated exclusion of native predators. Consumer taxonomic diversity was drastically reduced, essentially deprived of amphibians as well as predatory and mobile macroinvertebrates to the profit of burrowing, lower trophic level consumers (detritivores). Changes in community structure and function underlined a regime shift from a macrophyte-dominated system mainly characterized by benthic primary production (periphyton), to a macrophyte-depleted state of ponds hosting communities mainly associated with phytoplankton primary production and detritus accumulation, with higher tolerance to eutrophication and low dissolved oxygen concentration. Results underline major impacts of widely introduced omnivores such as the goldfish on the functioning of pond ecosystems with potentially dramatic consequences on the key ecosystem services they deliver, such as global biodiversity support or water quality improvement. They also shed light on the key role of submerged aquatic vegetation in supporting diverse communities and complex food webs in shallow lentic systems and call for urgent consideration of threats posed by IAS on ponds' ecosystems by managers and policymakers.

Stable isotope hydrology of a polymictic lake: Capturing transience of groundwater interactions

Although there have been many studies of groundwater inflow to small lakes, no systematic attention has been paid to the role of the time interval in the reliability of transient flow analysis. We addressed this issue in a two-year study of the isotope hydrology and water budget of a small lake in eastern Washington State (USA) that has been subject to limited management over several decades. The weighted local meteoric water line is δ2H = 7.14 δ18O – 5.22, reflecting the impact of convective recycling in this semi-arid region of inland northwestern North America. Groundwater inflow to the lake was quantified over two years using a short-interval isotopic transient mass balance approach. Calculated inflow was less than a fifth of the lake’s total water budget. Unrealistic temporal fluctuation of the calculated inflow was apparently correlated with fluctuation of the observed isotopic ratio of lake water (δL). We obtained realistic lake fluctuation and groundwater–lake exchange estimates by experimenting with the time interval of the isotope mass balance. It is crucial to acknowledge that each lake possesses unique characteristics that influence hydrologic and isotopic variations. Therefore, the optimal time interval for sampling and calculating mass balance may vary among different small lakes. Our findings have implications for long-term studies with frequent interval sampling.

Quantification of PFAS in rice and maize: Validation of a UHPLC-HRMS/MS isotopic dilution approach in support to food safety

In the present work, an analytical method for the quantification of per and poly fluoroalkyl substances (PFAS) in rice and maize has been developed and then validated with a metrological approach. PFAS are a group of human-made chemicals used in a variety of industries and consumer products for their water- and grease-resistant properties. Studies have shown that PFAS can contaminate soil and water, and there is concern about their bioaccumulation in edible plants, fruits, and cereals. The presence of PFAS has been identified in rice and other food products, including maize, as indicated by studies and scientific literature. This is particularly alarming since some PFAS have been associated with adverse health effects and rice and maize account for over 20% of the annual food intake worldwide. Despite this evidence, the regulation currently in place is not covering cereal matrices and limits of quantification for matrices encompassed by the current legislation are defined for a small group of PFAS. In this study an UHPLC-HRMS/MS based method was validated, obtaining a LOQ (Limit Of Quantification) ranging between 2 ng/kg and 32 ng/kg and robustness in line with EU guidelines and recommendation for PFAS in food. Additionally, a metrological approach was employed to estimate the uncertainty budget, utilizing modeling and experimental methods, and comparing the outcomes, aiming to characterize with high accuracy PFAS in rice and maize and support control bodies to assess contamination in suspected areas. A comparison of uncertainty of different approaches was conducted after applying the method to 30 real samples.

Testing the TTG–Metabasite Connection in the Southern Superior Province: an Integrated Geochemical, Isotopic, and Petrogenetic Modelling Approach

Abstract Archean cratons are dominated by tonalite–trondhjemite–granodiorite (TTG) suites, the products of crustal differentiation that formed early continental crust. These rocks may have been primarily generated by partial melting of hydrated basaltic crust in a variety of settings including subduction zones or the deep lithosphere. Sources are mainly inferred from examination of TTGs alone, as potential source rocks are rarely exposed. In the southern Superior Province, Canada, the Kapuskasing Uplift exposes an important crustal cross-section with upper- to middle-crustal TTGs and lower-crustal metabasites, which show evidence of having produced trondhjemitic anatectic melt. Here, we test the hypothesis that these metabasites were the source of the Mesoarchean to Neoarchean TTGs in the Kapuskasing Uplift by combining phase equilibrium and melt trace element modelling with whole-rock and zircon Lu–Hf isotope analysis and geochronology (garnet Lu–Hf and zircon U–Pb) of metabasic samples. By comparison of the results with existing data from TTGs in the Kapuskasing Uplift, we determined that the metabasites are plausible source rocks for the TTGs. The Lu–Hf systematics of the metabasites and TTGs are the most robust evidence of a genetic connection. Modelling results support an increase in TTG source depth over time. New geochronological data constrain partial melting of metabasite and crystallization of anatectic melt between ca. 2685 Ma and ca. 2600 Ma, coeval with crystallization of only the youngest TTGs. Overall, these results indicate a complex history of intracrustal differentiation in the Kapuskasing Uplift, with partial melting of two isotopically distinct lower-crustal metabasic sources at different times and depths.

Different Dynamics Drive Indian Ocean Moisture to the Southern Slope of Central Himalayas: An Isotopic Approach

AbstractThis study uses precipitation oxygen isotopes (δ18Op) to examine key dynamics that deliver moisture to the southern slope of central Himalayas over different seasons. Results show that the majority of pre‐monsoon δ18Op values are relatively high and controlled by the westerlies and local moisture. However, some abnormally low δ18Op values coincide with higher precipitation amounts during the pre‐monsoon season due to moisture driven northwards from the Bay of Bengal and Arabian Sea to central Himalayas by anomalous circulations (quasi‐anticyclone, anticyclone, or/and westerlies trough). The size and location of the quasi‐anticyclone also influences the magnitude of the δ18Op decrease. In comparison, the monsoon δ18Op values are lower due to the combined effects of the Indian summer monsoon and convection. Our findings indicate that researchers need to consider the signals of abnormally low δ18Op values during the pre‐monsoon season when attempting to interpret ice core and tree‐ring records from central Himalayas.