Compound-Specific Isotope Analysis Provides Direct Evidence for Identifying the Source of Residual Pesticides Diazinon and Procymidone in the Soil-Plant System.

Compound-specific isotope analysis stands as a promising tool for unveiling the behavior of pesticides in agricultural environments. Using the commercial formulations of persistent fungicide procymidone (PRO) and less persistent insecticide diazinon (DIA), respectively, we analyzed the concentration and carbon isotope composition (δ13C) of the residual pesticides through soil incubation experiments in a greenhouse (for 150 days) and lab conditions (for 50-70 days). Our results showed that the magnitude of δ13C variation depends on pesticide specificity, in which PRO in the soil exhibited little variation in δ13C values over the entire incubation times, while DIA demonstrated an increased δ13C value, with the extent of δ13C variability affected by different spiking concentrations, plant presence, and light conditions. Moreover, the pesticides extracted from soils were isotopically overlapped with those from crop lettuce. Ultimately, the isotope composition of pesticides could infer the degradation and translocation processes and might contribute to identifying the source(s) of pesticide formulation in agricultural fields.

Enhanced dietary reconstruction of Korean prehistoric populations by combining δ13C and δ15N amino acids of bone collagen.

Compound specific stable isotope analysis of amino acids (CSIA-AA) is a powerful tool for determining dietary behaviors in complex environments and improving dietary reconstructions. Here, we conducted CSIA-AA on human (n = 32) and animal (n = 13) remains from two prehistoric archaeological sites (Mumun, Imdang) to assess in more detail the dietary sources consumed by prehistoric Korean populations. Results of estimated trophic position (TP) using Δ15NGlx-Phe show that the Imdang individuals consumed aquatic resources, as well as terrestrial resources. Principal component analysis (PCA) using δ13C and δ15N essential amino acid (EAA) values show that the Imdang humans closely cluster with game birds and terrestrial herbivores, whilst the Mumun humans closely cluster with C4 plants. Quantitative estimation by a Bayesian mixing model (MixSIAR) indicates that the Imdang humans derived a large proportion of their proteins from terrestrial animals and marine fish, whereas the main protein sources for the Mumun humans were C4 plants and terrestrial animals. Additionally, the comparison between the EAA and bulk isotope models shows that there is a tendency to overestimate the consumption of plant proteins when using bulk isotopic data. Our CSIA-AA approach reveals that in prehistoric Korea there were clear differences in human diets through time. This study adds to a growing body of literature that demonstrates the potential of CSIA-AA to provide more accurate estimations of protein consumption in mixed diets than previous bulk isotopic studies.

Stable Isotope Analysis of Residual Pesticides via High Performance Liquid Chromatography and Elemental Analyzer-Isotope Ratio Mass Spectrometry.

To broaden the range of measurable pesticides for stable isotope analysis (SIA), we tested whether SIA of the anthranilic diamides cyantraniliprole (CYN) and chlorantraniliprole (CHL) can be achieved under elemental analyzer/isotope ratio mass spectrometry with compound purification in high-performance liquid chromatography (HPLC). Using this method, carbon isotope compositions were measured in pesticide residues extracted from plants (lettuce) grown indoors in potting soil that were treated with 500 mg/kg CHL and 250 mg/kg CYN and were followed up for 45 days. Our results show that the CYN and CHL standard materials did not have significant isotope differences before and after clean-up processing in HPLC. Further, when applied to the CYN product and CHL product in soil, stable isotope differences between the soil and plant were observed at <1.0‱ throughout the incubation period. There was a slight increase in the variability of pesticide isotope ratio detected with longer-term incubation (CHL, on average 1.5‱). Overall, we measured the carbon isotope ratio of target pesticides from HPLC fraction as the purification and pre-concentration step for environmental and biological samples. Such negligible isotopic differences in pesticide residues in soils and plants 45 days after application confirmed the potential of CSIA to quantify pesticide behavior in environments.

Amino acid nitrogen and carbon isotope data: Potential and implications for ecological studies.

Explaining food web dynamics, stability, and functioning depend substantially on understanding of feeding relations within a community. Bulk stable isotope ratios (SIRs) in natural abundance are well-established tools to express direct and indirect feeding relations as continuous variables across time and space. Along with bulk SIRs, the SIRs of individual amino acids (AAs) are now emerging as a promising and complementary method to characterize the flow and transformation of resources across a diversity of organisms, from microbial domains to macroscopic consumers. This significant AA-SIR capacity is based on empirical evidence that a consumer's SIR, specific to an individual AA, reflects its diet SIR coupled with a certain degree of isotopic differences between the consumer and its diet. However, many empirical ecologists are still unfamiliar with the scope of applicability and the interpretative power of AA-SIR. To fill these knowledge gaps, we here describe a comprehensive approach to both carbon and nitrogen AA-SIR assessment focusing on two key topics: pattern in AA-isotope composition across spatial and temporal scales, and a certain variability of AA-specific isotope differences between the diet and the consumer. On this basis we review the versatile applicability of AA-SIR to improve our understanding of physiological processes as well as food web functioning, allowing us to reconstruct dominant basal dietary sources and trace their trophic transfers at the specimen and community levels. Given the insightful and opportunities of AA-SIR, we suggest future applications for the dual use of carbon and nitrogen AA-SIR to study more realistic food web structures and robust consumer niches, which are often very difficult to explain in nature.

Isotopic investigation of skeletal remains at the Imdang tombs reveals high consumption of game birds and social stratification in ancient Korea.

Understanding the development of early states on the Korean Peninsula is an important topic in Korean archaeology. However, it is not clear how social structure was organized by these early states and what natural resources were utilized from their surrounding environments. To investigate dietary adaptation and social status in ancient Korea, stable isotope ratios and radiocarbon dates were measured from humans and animals from the Imdang cemetery, Gyeongsan city, South Korea. The results indicate that the Imdang diet was mainly based on C3 plants and terrestrial animals. Animal remains in the graves were directly consumed as daily food items as well as for ritual offerings. MixSIAR modeling results revealed that the dietary sources for the humans were: game birds > C3 plants > terrestrial herbivores > marine fish > C4 plants. The finding that the game birds represented the highest contribution to the whole diet, indicates that game birds must have been intensively hunted. Furthermore, elites consumed more game birds than their retainers and they also consumed seafood as a privileged dietary item in the Imdang society. This study demonstrates that the Apdok was a stratified society having high variations in the consumption of food items available to an individual and provides new insights about the subsistence and social status of the early ancient Apdok state on the Korean Peninsula.

Application of Compound-Specific Isotope Analysis in Environmental Forensic and Strategic Management Avenue for Pesticide Residues.

Unintended pesticide pollution in soil, crops, and adjacent environments has caused several issues for both pesticide users and consumers. For users, pesticides utilized should provide higher yield and lower persistence while considering both the environment and agricultural products. Most people are concerned that agricultural products expose humans to pesticides accumulating in vegetation. Thus, many countries have guidelines for assessing and managing pesticide pollution, for farming in diverse environments, as all life forms in soil are untargeted to these pesticides. The stable isotope approach has been a useful technique to find the source of organic matter in studies relating to aquatic ecology and environmental sciences since the 1980s. In this study, we discuss commonly used analytical methods using liquid and gas chromatography coupled with isotopic ratio mass spectrometry, as well as the advanced compound-specific isotope analysis (CSIA). CSIA applications are discussed for tracing organic pollutants and understanding chemical reactions (mechanisms) in natural environments. It shows great applicability for the issues on unintended pesticide pollution in several environments with the progress history of isotope application in agricultural and environmental studies. We also suggest future study directions based on the forensic applications of stable isotope analysis to trace pesticides in the environment and crops.

The carbon isotope ratios of nonessential amino acids identify sugar-sweetened beverage (SSB) consumers in a 12-wk inpatient feeding study of 32 men with varying SSB and meat exposures.

BACKGROUND: The carbon isotope ratios (CIRs) of individual amino acids (AAs) may provide more sensitive and specific biomarkers of sugar-sweetened beverages (SSBs) than total tissue CIR. Because CIRs turn over slowly, long-term controlled-feeding studies are needed in their evaluation. OBJECTIVE: We assessed the responses of plasma and RBC CIRAA's to SSB and meat intake in a 12-wk inpatient feeding study. METHODS: Thirty-two men (aged 46.2 ± 10.5 y) completed the feeding study at the National Institute of Diabetes and Digestive and Kidney Diseases in Phoenix, Arizona. The effects of SSB, meat, and fish intake on plasma and RBC CIRAA's were evaluated in a balanced factorial design with each dietary variable either present or absent in a common weight-maintaining, macronutrient-balanced diet. Fasting blood samples were collected biweekly from baseline. Dietary effects on the postfeeding CIR of 5 nonessential AAs (CIRNEAA's) and 4 essential AAs (CIREAA's) were analyzed using multivariable regression. RESULTS: In plasma, 4 of 5 CIRNEAA's increased with SSB intake. Of these, the CIRAla was the most sensitive (ß = 2.81, SE = 0.38) to SSB intake and was not affected by meat or fish intake. In RBCs, all 5 CIRNEAA's increased with SSBs but had smaller effect sizes than in plasma. All plasma CIREAA's increased with meat intake (but not SSB or fish intake), and the CIRLeu was the most sensitive (ß = 1.26, SE = 0.23). CIRs of leucine and valine also increased with meat intake in RBCs. Estimates of turnover suggest that CIRAA's in plasma, but not RBCs, were in equilibrium with the diets by the end of the study. CONCLUSIONS: The results of this study in men support CIRNEAA's as potential biomarkers of SSB intake and suggest CIREAA's as potential biomarkers of meat intake in US diets. This trial was registered at clinicaltrials.gov/ct2/show/NCT01237093 as NCT01237093.

The Carbon Isotope Ratios of Serum Amino Acids in Combination with Participant Characteristics can be Used to Estimate Added Sugar Intake in a Controlled Feeding Study of US Postmenopausal Women.

BACKGROUND: The carbon isotope ratio (CIR) is a proposed biomarker for added sugar (AS) intake in the United States; however, because the CIR is also associated with meat intake in most populations the need for specificity remains. The CIR of amino acids (AAs) has the potential to differentiate sugars from meat intakes, because essential AAs must derive from dietary protein whereas certain nonessential AAs can be synthesized from sugars. OBJECTIVES: We tested whether serum CIR-AAs in combination with participant characteristics could meet a prespecified biomarker criterion for AS intake in the Nutrition and Physical Activity Assessment Study Feeding Study (NPAAS-FS) of the Women's Health Initiative, a population in which the whole-serum CIR was not associated with AS intake. METHODS: Postmenopausal women (n = 145) from Seattle, WA, were provided with individualized diets that approximated their habitual food intakes for 2 wk. Dietary intakes from consumed foods were characterized over the feeding period using the Nutrition Data System for Research. The CIR of 7 AAs-Ala, Gly, Val, Leu, Ile, Pro, and Phe-were measured in fasting serum collected at the end of the 2-wk feeding period, using gas chromatography-combustion isotope ratio mass spectrometry. Biomarker models were evaluated using regression R2 ≥ 0.36 as a major biomarker criterion, based on the benchmark R2 values of well-established recovery biomarkers in the NPAAS-FS. RESULTS: AS intake was associated with CIR-Ala (ρ = 0.32; P < 0.0001). A model of AS intake based on CIR-Ala, CIR-Gly, CIR-Ile, smoking, leisure physical activity, and body weight met the biomarker criterion (R2 = 0.37). Biomarker-estimated AS intake was not associated with meat or animal protein intake. CONCLUSIONS: Results support serum CIR-AAs in combination with participant characteristics as potential biomarkers of AS intake in US populations, including those with low AS intake.The Women's Health Initiative is registered at clinicaltrials.gov (NCT00000611).

Evaluation of the quantity and the carbon isotopic composition of amino acids by using diverse sample residues after lipid extraction.

Compound-specific stable isotope analysis (CSIA) becomes a critical tool in the fields of ecology and biogeochemistry to trace basal carbon sources such as amino acids (AAs) and fatty acids (FAs) in natural environments. However, in many studies, either AAs or FAs have been analyzed due to restricted sample amounts. The aim of this study is to report a single-sample preparation method by identifying AAs using lipid-free residues derived from a typical FA analytic procedure. The capability of the lipid-free residues was evaluated by determining AA quantities and carbon isotopic compositions (δ13C) across diverse sample matrices, including soil, suspended particulate organic matter (SPM), fish tissue, and cultured cyanobacteria (N = 3). Our result showed that the use of lipid-free residues after a typical lipid extraction procedure in most samples did not significantly reduce the AA quantities, relative to the conventional AA method (done by using whole samples), except in case of samples of soil. Moreover, δ13C compositions of the most AAs (from essential to nonessential AAs) in all samples were not significantly different, with an average isotope difference of < 2.1‰ between the two methods. Overall results indicate that the residual parts after extracting lipid fraction are useful for reliable AA quantification and individual isotopic information. Ultimately, one sample preparation for determining FA and AA data enables us to characterize one (or multiple) basal carbon source(s) within rare samples despite their limited abundance. Graphical abstract.

Complementary approach for accurate determination of carbon isotopic compositions in γ-hydroxybutyric acid using gas chromatography/combustion-isotope ratio mass spectrometry.

RATIONALE: γ-Hydroxybutyric acid (GHB) is a naturally endogenous neurotransmitter that is popular as a recreational drug due to its sedative, hypnotic, and euphoric effects. GHB derived from endogenous production or exogenous ingestion has been effectively discriminated by carbon isotopic compositions (δ13 C values) through gas chromatography/combustion-isotope ratio mass spectrometry (GC/C-IRMS). However, an unintended uncertainty of isotopic signatures caused by a wide range of GHB quantities remains unsolved when using only single-isotope corrections of the di-TMS derivative. METHODS: The δ13 C values of the original GHB standard were first determined by elemental analyzer/isotope ratio mass spectrometry (EA/IRMS). The δ13 C values of silylated GHB in concentrations from 10 to 500 ppm were determined by GC/C-IRMS. With respect to the silylated reaction products, the correction of δ13 C values for the introduced carbons was calculated from a stoichiometric mass balance equation. RESULTS: The results showed a significant quantity-dependent trend in δ13 C values of introduced carbon (δ13 Cdi-TMS values) with increased GHB standard concentrations (r2 = 0.70, p <0.05). We applied a logarithmic equation to determine isotopic data in low-GHB urine specimens from five healthy female volunteers. The δ13 CGHB values in urine samples corrected with quantity-dependent δ13 Cdi-TMS values were different by an average of 2.7‰ from those corrected with single δ13 Cdi-TMS values (p <0.05). CONCLUSIONS: Our results suggest that the overall residual amount-dependent isotope fractionation should be mathematically corrected by the logarithmic function and this may improve the reliability of isotopic analysis to evaluate the origin of GHB before applying the approach to routine toxicological and forensic studies.

Serum Nitrogen and Carbon Stable Isotope Ratios Meet Biomarker Criteria for Fish and Animal Protein Intake in a Controlled Feeding Study of a Women's Health Initiative Cohort.

Background: Natural abundance stable isotope ratios are candidate biomarkers of dietary intake that have not been evaluated in a controlled feeding study in a US population. Objectives: Our goals were to evaluate dietary associations with serum carbon (CIR), nitrogen (NIR), and sulfur (SIR) isotope ratios in postmenopausal women, and to evaluate whether statistical models of dietary intake that include multiple isotopes and participant characteristics meet criteria for biomarker evaluation. Methods: Postmenopausal women from the Women's Health Initiative (n = 153) were provided a 2-wk controlled diet that approximated each individual's habitual food intake. Dietary intakes of animal protein, fish/seafood, red meat, poultry, egg, dairy, total sugars, added sugars, sugar-sweetened beverages (SSBs), and corn products were characterized during the feeding period with the use of the Nutrition Data System for Research (NDS-R). The CIR, NIR, and SIR were measured in sera collected from fasting women at the beginning and the end of the feeding period. Linear models based on stable isotope ratios and participant characteristics predicted dietary intake. The criterion used for biomarker evaluation was R2 ≥ 0.36, based on the study's power to detect true associations with R2 ≥ 0.50. Results: The NIR was associated with fish/seafood intake and met the criterion for biomarker evaluation (R2 = 0.40). The CIR was moderately associated with intakes of red meat and eggs, but not to the criterion for biomarker evaluation, and was not associated with intake of sugars (total, added, or SSB). A model of animal protein intake based on the NIR, CIR, and participant characteristics met the criterion for biomarker evaluation (R2 = 0.40). Otherwise, multiple isotopes did not improve models of intake, and improvements from including participant characteristics were modest. Conclusion: Serum stable isotope ratios can, with participant characteristics, meet biomarker criteria as measures of fish/seafood and animal protein intake in a sample of postmenopausal women. This trial was registered at clinicaltrials.gov as NCT00000611.

Water-borne cues of a non-indigenous seaweed mediate grazer-deterrent responses in native seaweeds, but not vice versa.

Plants optimise their resistance to herbivores by regulating deterrent responses on demand. Induction of anti-herbivory defences can occur directly in grazed plants or from emission of risk cues to the environment, which modifies interactions of adjacent plants with, for instance, their consumers. This study confirmed the induction of anti-herbivory responses by water-borne risk cues between adjoining con-specific seaweeds and firstly examined whether plant-plant signalling also exists among adjacent hetero-specific seaweeds. Furthermore, differential abilities and geographic variation in plant-plant signalling by a non-indigenous seaweed as well as native seaweeds were assessed. Twelve-day induction experiments using the non-indigenous seaweed Sargassum muticum were conducted in the laboratory in Portugal and Germany with one local con-familiar (Portugal: Cystoseira humilis, Germany: Halidrys siliquosa) and hetero-familiar native species (Portugal: Fucus spiralis, Germany: F. vesiculosus). All seaweeds were grazed by a local isopod species (Portugal: Stenosoma nadejda, Germany: Idotea baltica) and were positioned upstream of con- and hetero-specific seaweeds. Grazing-induced modification in seaweed traits were tested in three-day feeding assays between cue-exposed and cue-free ( = control) pieces of both fresh and reconstituted seaweeds. Both Fucus species reduced their palatability when positioned downstream of isopod-grazed con-specifics. Yet, the palatability of non-indigenous S. muticum remained constant in the presence of upstream grazed con-specifics and native hetero-specifics. In contrast, both con-familiar (but neither hetero-familiar) native species reduced palatability when located downstream of grazed S. muticum. Similar patterns of grazer-deterrent responses to water-borne cues were observed on both European shores, and were almost identical between assays using fresh and reconstituted seaweeds. Hence, seaweeds may use plant-plant signalling to optimise chemical resistance to consumers, though this ability appeared to be species-specific. Furthermore, this study suggests that native species may benefit more than a non-indigenous species from water-borne cue mediated reduction in consumption as only natives responded to signals emitted by hetero-specifics.