Geographical verification of Pleuropterus multiflorus thunb. by functional compounds, stable isotope ratios, and multielement combined with machine learning methods

The dry roots of Pleuropterus multiflorus Thunb. (PM) have been traditionally utilized as functional foods and medicines China and various Asian countries. They are extensively cultivated in multiple provinces in China, with variations in prices and qualities. This study aims to investigate the regional characteristics of PM by 4 stable isotope ratios, 40 multielement and 16 functional compounds contents, using a total of 357 samples from 8 different geographical origins. Machine learning methods were developed to authenticating the geographical origins of PM, yielding the accuracy range from 94.44 % to 100 % in the test set. Notably, the protected designation of origin, Deqing PM, exhibited a high accuracy of 100 % in most models, A total of 30 significant prediction variables, encompassing 16 functional compounds, δ2H, 12 rare earth elements, and Cu, were identified. Additionally, the study identified altitude, high temperature, and dry or moisture index as the primary influenced environmental factors.

Distributions and potential sources of traditional and emerging polycyclic aromatic hydrocarbons in sediments from the lower reach of the Yangtze River, China

This study investigated the current contamination status and potential sources of traditional and emerging polycyclic aromatic hydrocarbons (t-PAHs and e-PAHs) in the sediments across a wide area of the Yangtze River, spanning nine cities. Fifty-seven sediment samples were collected in 2019, from which 15 t-PAHs and 11 e-PAHs were analyzed using GC-MSD. In addition, organic carbon (OC), total nitrogen (TN), and carbon and nitrogen stable isotope ratios (δ¹³C and δ¹⁵N) in sediments were measured to evaluate associations with PAHs contamination. OC, TN, and their stable isotope ratios showed a wide range of site-specific contents and values, indicating high variation in contamination and sources. Concentrations of t-PAHs and e-PAHs in sediments ranged from 0.6 to 200,000 ng g^-1 dry weight (dw) and 1.1 to 20,000 ng g^-1 dw, respectively. Hotspot sites located in Nanjing (PuKou), Taizhou (JingJiang), and Suzhou (ZhangJiaGang). PAHs contamination reflected land use type and human activity in the surrounding area. Positive matrix factorization (PMF) modeling showed that, on average (n = 57), vehicle emissions were the most dominant contribution (57%), followed by petroleum (28%) and fossil fuel combustion (15%). Sites with high PAHs contamination in sediments were of severe ecological risk. Contributions to the potential risks of PAHs were most significant in the order of dibenz[a,h]anthracene, benzo[b]fluoranthene, and benzo[a]pyrene. The primary origin of these compounds appeared to be fossil fuel combustion. The results of this study are expected to provide useful baseline data on the current contamination status and potential sources of traditional and emerging pollutants in the sediments of the Yangtze River, China.

Changes in the characteristics of organic matter associated with hydrodynamics and phytoplankton size structure in the central-eastern Yellow Sea

The central-eastern Yellow Sea is an important region for transporting organic matter (OM) to the Pacific Ocean, however, there is limited information available regarding the characteristics and sources of OM in this area. The present study investigated the concentrations and stable isotopic compositions of carbon (δ¹³C) and nitrogen (δ¹⁵N) for particulate matter and sediment in the central-eastern Yellow Sea during April 2019. The physicochemical properties (i.e., salinity, temperature, fluorescence, and nutrients), size-fractionated phytoplankton biomass (Chl-a), and concentration and fluorescence characteristics of dissolved organic matter (DOM) were also determined. The satellite SST and Chl-a data indicated that mixing cold and warm water masses were observed. Phytoplankton blooms occurred a few days before our sampling campaign. Considering the high concentration of suspended solids in the bottom layer, resuspended sediment caused by tidal currents could be a major source of OM in coastal areas. The δ¹³C values of particulate organic matter (POM) in the coastal area were higher (-23 to -22‰) than those of OM from terrestrial sources (approximately -28 to -27‰). Instead, the lowest δ¹³C values were observed in the central part of our study area, where the relative abundance of picophytoplankton was high. These results indicated that phytoplankton-derived OM after phytoplankton spring blooms in the coastal area could be the primary source of OM rather than terrestrial origins. In addition, the source of OM that presented low δ¹³C values could be picophytoplankton-derived OM. The characteristics of DOM were related to biological processes (mediated by phytoplankton and bacteria) and resuspension of sedimentary organic matter. We did not detect an influx of large amounts of terrestrial OM in coastal sediments. Overall, the source and characteristics of OM appeared to be influenced by the hydrodynamics and the distribution properties of lower trophic-level organisms in the central-eastern Yellow Sea during the spring season.

Assessment of heavy metal accumulation in freshwater fish of Dongting Lake, China: Effects of feeding habits, habitat preferences and body size

We measured the concentrations of Cr, Fe, Ni, Cu, Zn, Cd, Pb and Hg, and the stable isotope ratios (δ¹³C and δ¹⁵N) in 87 fish samples within 12 economic fish species collected from the Dongting Lake, the second largest freshwater lake in China. With few exceptions in concentration of Cr, most of fish species showed lower concentrations of the 8 metals than legislation thresholds. Piscivorous fishes had significantly higher values of δ¹⁵N (possessing higher trophic level) and metal concentrations than planktivorous and herbivorous fishes. Moreover, demersal fishes showed higher concentrations of Cu, Zn, Cd and Pb than pelagic and benthopelagic fishes. We found positive correlations between concentrations of Fe, Pb and Hg and δ¹⁵N ratio, confirming the biomagnification of the three metals through trophic transfer. In contrast, fishes showed clear growth dilution effect for Ni, Zn, Cu, Pb and Hg, indicated by the negative correlations between their concentrations and fish weight or length. Multiple regression analysis demonstrated that growth dilution and biomagnification effects simultaneously governed the metal concentrations in fish muscle, and the two effects' importance varied among different metals. The human health risk assessment indicated that all 8 metals gave target hazard quotient (THQ) values < 1.0, i.e., the estimated daily intake (EDI) of metals did not exceed the oral reference dose (RfD), indicating a safe consumption of these fish species for consumer. Our study provides comprehensive approaches to better understand the determining processes and potential risk of heavy metals in freshwater lake fishes.

Potential application of light element stable isotope ratio in crude fiber for geographical origin verification of raw and cooked kabocha pumpkin (Cucurbita maxima)

In this study, we investigated the possibility of the geographical origin discrimination between Japanese and Mexican kabocha pumpkin using δ¹³C and δ¹⁸O in lyophilized raw flesh. Kabocha harvested in Hokkaido, the major kabocha production area in Japan, could be discriminated against not only that grown in Mexico but also that in New Zealand. However, seasoning after cooking or processing affected the δ¹³C and the δ¹⁸O values. Crude fiber extraction eliminated the effect of seasonings and enabled the adoption of the δ¹³C and δ¹⁸O values in crude fiber for the geographical origin verification of kabocha even after cooking and processing. The usage of δ¹³C and the δ¹⁸O in crude fiber would extend the application possibilities of stable isotope analysis in the geographical origin determination of various cooked and processed vegetables and fruits as well as raw materials.

Temporal and spatial variations in hydrophobicity dependence of field-derived metrics to assess the biomagnification potential of hydrophobic organochlorine compounds

The bioaccumulation potential ("B") of compounds is one of the major considerations in assessing chemical hazards. A variety of metrics, including hydrophobicity (K_OW), bioconcentration factor (BCF), bioaccumulation factor (BAF), and to an increasing degree biomagnification factor (BMF) and trophic magnification factor (TMF), are widely used to characterize "B". In the present study, the variation and hydrophobicity-dependence of each of these metrics for recalcitrant hydrophobic organochlorine compounds (HOCs) was determined from four food webs collected in two different seasons at two different sites of the Han River, Korea. Measured environmental parameters and stable isotopic ratios exhibited distinct seasonal and spatial shifts in the ecological condition of the river. The observed values of individual metrics were positively and linearly related with their log K_OW values, but linearized slopes differed significantly among the four food webs, with the largest variation being exhibited by TMF and log fugacity ratio (log F) followed by log BMF > log BAF. When based on field-derived mean linear equations, different log K_OW values were obtained for a critical point for the identification of biomagnification of HOCs. Consequently, the biomagnification potential of HOCs and its relationship with K_OW can vary, being seriously affected by not only on the metrics used for its assessment but also on spatial and temporal variations in ecological conditions. Our results indicate that TMF for "B" might be more robust than the other metrics but the development of new methodologies to reduce uncertainty and to enhance the accuracy of TMFs by correcting for ecological variation, together with addition efforts to harmonize individual metrics for "B".

Potential geo-discriminative tools to trace the origins of the dried slices of shiitake (Lentinula edodes) using stable isotope ratios and OPLS-DA

The Lentinus edodes species, known as shiitake, has a history of extensive use in many cuisines in several East Asian countries owing to its unique and pleasant flavor and texture. As international food trade increases, reliable discrimination of geographical origin is becoming increasingly crucial in Korea to identify cheaper imported Chinese shiitake. Herein, stable isotope ratios (i.e., δ¹³C, δ¹⁵N, δ¹⁸O, and δ³⁴S) were measured with a stable isotope ratio mass spectrometer, and a geographical discrimination method using orthogonal projection to latent structure-discriminant analysis was developed. The externally validated discrimination method showed excellent predictability (Q²_cum = 0.881) and illustrated that δ¹⁸O and δ¹⁵N were important isotope markers for the geographical discrimination of dried shiitake slices. This study extends the knowledge of geographical differences between China and Korea evidenced by the shiitake isotope signatures, thereby contributing to potential geographical authentication with broader applications for international shiitake markets.

Differentiating the geographical origin of Ethiopian coffee using XRF- and ICP-based multi-element and stable isotope profiling

To test the potential of different analytical tools to determine the geographical origin of Ethiopian coffee, 103 green arabica coffee samples from four coffee regions in Ethiopia were subjected to multi-elements and δ¹³C, δ¹⁵N and δ¹⁸O determinations. Multi-elements were determined by using inductively coupled plasma (ICP)- and X-ray fluorescence spectrometry (XRF)-based techniques, and δ¹³C, δ¹⁵N and δ¹⁸O were determined by using elemental analyzer-isotope ratio mass spectrometry. Using linear discriminant analysis, XRF-based multi-elements with and without δ¹³C appeared to be most effective in discriminating the geographical origin of coffee, giving higher classification accuracy (89 and 86%, respectively) than ICP-based multi-elements with and without stable isotopes (80%, each). These results demonstrate the potential of XRF-based multi-element profiling as a relatively fast and low-cost tool to trace the geographical origin of Ethiopian coffee. All together this study offers the proof of concept for a promising method that, upon standardization, could be used for coffee provenance authentication and fraud detection.

Discrimination of organic milk by stable isotope ratio, vitamin E, and fatty acid profiling combined with multivariate analysis: A case study of monthly and seasonal variation in Korea for 2016-2017

This study examined the monthly and seasonal variations of δ¹³C, δ¹⁵N, fatty acids (FAs), and vitamin E in organic milk (OM) and conventional milk (CM) collected in Korea during 2016-2017, discriminating OM authenticity with chemometric approaches. Compared to CM, the mean δ¹³C and δ¹⁵N values were lower in OM, whereas the mean α-tocopherol and nutritionally desirable FA contents were higher in OM. Furthermore, δ¹³C, δ¹⁵N, and FA contents vary significantly with the season in OM, whereas α-tocopherol does not show a specific seasonal trend in either OM or CM. Chemometric approaches provided reliable chemical markers, notably C18:3n-3, C18:2n-6, and δ¹³C_bulk-milk, for accurate OM discrimination according to sampling season. Our findings elucidate milk nutritional quality issues and also provide valuable insight into the control of fraudulent OM labeling in Korea, with potential application in other countries.

Lithium, magnesium and sulfur purification from seawater using an ion chromatograph with a fraction collector system for stable isotope measurements

We describe the mass descrimination and validation of an offline method for purification of Li, Mg and S with an ion chromatograph coupled to an automated fraction collector for use prior to stable isotope measurements. Significant sub-fraction mass fractionation was observed for both the Li and the Mg stable isotope ratios. The lighter Li and heavier Mg isotopes were preferentially retained by the column, resulting in ⁷Li/⁶Li and ²⁶Mg/²⁴Mg biases up to 85.8‰ and 0.95‰, respectively. The isotopic compositions of Li, Mg, and S separated from seawater were δ⁷Li_L-SVEC = +30.9‰, δ²⁶Mg_DSM3 = -0.83 ± 0.10‰, and δ³⁴S_VCDT = +19.4 ± 0.6‰; each chromatographic peak was completely recovered, and the results were in good agreement with the published values regardless of whether or not chemical suppressor was used. The purification method enables multi-isotope analysis of a sample using various mass spectrometry techniques, such as multiple-collector inductively coupled plasma and thermal ionization mass spectrometry.

Identification of sources and seasonal variability of organic matter in Lake Sihwa and surrounding inland creeks, South Korea

Coastal areas are subjected to significant allochthonous organic matter deposits from surrounding areas; however, limited information is available on the source and delivery of this organic matter. In this study, to assess seasonal changes in the sources of organic matter in Lake Sihwa (Korea), biodegradability, fluorescence property, and stable isotopic compositions (carbon, nitrogen, and sulfur) of the organic matter were determined. Water samples were collected from the inner lake (n = 9) and inland creeks (n = 10) in five separate events, from November 2012 to October 2013. Organic matter originating from rural, urban, and industrial areas was examined as the potential sources. The organic matter contents and biodegradability in the industrial area were the highest, whereas low concentrations and poor biodegradability of organic matter were found in the rural area, and moderate properties were observed in the urban area. In Lake Sihwa, a large concentration of total organic matter and enhanced biodegradability were observed during March and August. However, main source of organic matter differed between the sampling events. The largest contribution of organic matter, deriving from marine phytoplankton, was found in March. On the other hand, in August, the organic matter originating from the industrial area, which is characterized by high levels of heavy metals and persistent organic pollutants, was significantly increased. Our results could be useful to enhance the management of water bodies aimed at reducing the organic matter concentrations and improving the water quality of Lake Sihwa, and even that of the Yellow Sea.

Occurrence and trophic magnification of polybrominated diphenyl ethers (PBDEs) and their methoxylated derivatives in freshwater fish from Dianshan Lake, Shanghai, China

In this study, polybrominated diphenyl ethers (PBDEs) and methoxylated polybrominated diphenyl ethers (MeO-PBDEs) were analyzed in eleven freshwater fish species from Dianshan Lake, Shanghai, China. The highest concentrations of PBDEs and MeO-PBDEs were found in snakehead, with mean values of 38 ng g^-1 lw and 4.2 ng g^-1 lw, respectively. BDE-47 was the predominant congener of PBDEs, followed by BDE-154. Congener pattern variation of PBDEs was observed among different fish species, implying differences in biotransformation potential among fish. Yellow catfish showed highest concentrations of BDE-99, -153 and -183, suggesting that it is more resistant to debromination than any other fish analyzed in the present study. Trophic magnification factors were in the range of 1.35-1.81 for all the PBDE congeners, but not for 2'-MeO-BDE-68. Negative relationship was observed between PBDEs concentration and sample size (length and weight), indicating fish size dilution effect.

The association between carbon and nitrogen stable isotope ratios of human hair and metabolic syndrome

BACKGROUND

It has been reported that stable isotope ratios can be used as biomarkers for animal protein intake. Meat consumption and high protein intake could be risk factors for metabolic disorders. We investigated whether the stable isotope ratios of carbon and nitrogen are associated with metabolic syndrome.

METHODS

We conducted a cross-sectional study of 399 subjects (233 men and 166 women). Hair samples from 399 subjects were measured for stable isotope ratios of carbon (δ(13)C) and nitrogen (δ(15)N).

RESULTS

The δ(15)N values progressively increased with the number of components of the metabolic syndrome present in study subjects (P for trend 0.047). In multivariable models, δ(15)N values were positively associated with the presence of metabolic syndrome (odds ratio, 1.53; 95% confidence interval, 1.09-2.14), whereas δ(13)C values were not (odds ratio, 0.97; 95% confidence interval, 0.72-1.30). The odds ratio (95% confidence interval) for metabolic syndrome comparing the highest to the lowest quartiles of δ(15)N values was 2.64 (1.17-5.92).

CONCLUSIONS

The nitrogen, but not carbon, stable isotopic ratio of hair is independently associated with the presence of metabolic syndrome. The hair δ(15)N value might be a surrogate marker for clustering of risk factors in metabolic syndrome.

Modeling the dynamics of stable isotope tissue-diet enrichment

Reconstructions of dietary composition and trophic level from stable isotope measurements of animal tissue rely on predictable offsets of stable isotope ratios from diet to tissue. Physiological processes associated with metabolism shape tissue stable isotope ratios, and as such the spacing between stable isotope ratios of diet and tissue may be influenced by processes such as growth, nutritional stress, and disease. Here, we develop a model of incorporation stable isotopes in diet to tissues by coupling stable isotope dynamics to a model of macronutrient energy metabolism. We use the model to explore the effect of changes in dietary intake, both composition and amount, and in energy expenditure, on body mass and carbon and nitrogen stable isotope ratios of tissue.

Characterization and source identification of organic matter in view of land uses and heavy rainfall in the Lake Shihwa, Korea

The characteristics and sources of organic matter in water of the Lake Shihwa, which receives inputs from rural, urban, and industrial areas, were evaluated by examining the biodegradable organic carbon concentration, fluorescence spectra, and carbon and nitrogen isotope ratios, especially during rainy season and dry season. The organic matter transported from rural areas was of refractory nature, while that of industrial origin decomposed rapidly. As compared to the dry season, the organic matter in the rainy season was characterized by a reduced labile fraction. During the dry season, the autochthonous organic matter dominated in the lake, however, the contributions of allochthonous organic sources by industrial and rural areas significantly increased at rainy season. This investigation revealed that the transport of organic matter of anthropogenic origin to the Lake Shihwa was mainly influenced by heavy rainfall. Moreover, each anthropogenic source could differently influence the occurrence of organic matter in water of the Lake Shihwa.

Monosoonal precipitation responses of shrubs in a cold desert community on the Colorado Plateau

South-eastern Utah forms a northern border for the region currently influenced by the Arizona monosoonal system, which feeds moisture and summer precipitation into western North America. One major consequence predicted by global climate change scenarios is an intensification of monosoonal (summer) precipitation in the aridland areas of the western United States. We examined the capacity of dominant perennial shrubs in a Colorado Plateau cold desert ecosystem of southern Utah, United States, to use summer moisture inputs. We simulated increases of 25 and 50 mm summer rain events on Atriplex canescens, Artemisia filifolia, Chrysothamnus nauseosus, Coleogyne ramosissima, and Vanclevea stylosa, in July and September with an isotopically enriched water (enriched in deuterium but not ¹⁸O). The uptake of this artificial water source was estimated by analyzing hydrogen and oxygen isotope ratios of stem water. The predawn and midday xylem water potentials and foliar carbon isotope discrimination were measured to estimate changes in water status and water-use efficiency. At. canescens and Ch. nauseosus showed little if any uptake of summer rains in either July or September. The predawn and midday xylem water potentials for control and treatment plants of these two species were not significantly different from each other. For A. filifolia and V. stylosa, up to 50% of xylem water was from the simulated summer rain, but the predawn and midday xylem water potentials were not significantly affected by the additional summer moisture input. In contrast, C. ramosissima showed significant uptake of the simulated summer rain (>50% of xylem water was from the artificial summer rain) and an increase in both predawn and midday water potentials. The percent uptake of simulated summer rain was greater when those rains were applied in September than in July, implying that high soil temperature in midsummer may in some way inhibit water uptake. Foliar carbon isotope discrimination increased significantly in the three shrubs taking up simulated summer rain, but pre-treatment differences in the absolute discrimination values were maintained among species. The ecological implications of our results are discussed in terms of the dynamics of this desert community in response to changes in the frequency and dependability of summer rains that might be associated with a northward shift in the Arizona monsoon boundary.

Variations in stream water uptake by Eucalyptus camaldulensis with differing access to stream water

The stable isotopes ²H and ¹⁸O were used to determine the water sources of Eucalyptus camaldulensis at three sites with varying exposure to stream water, all underlain by moderately saline groundwater. Water uptake patterns were a function of the long-term availability of surface water. Trees with permanent access to a stream used some stream water at all times. However, water from soils or the water table commonly made up 50% of these trees' water. Trees beside an ephemeral stream had access to the stream 40-50% of the time (depending on the level of the stream). No more than 30% of the water they used was stream water when it was available. However, stream water use did not vary greatly whether the trees had access to the stream for 2 weeks or 10 months prior to sampling. Trees at the third site only had access to surface water during a flood. These trees did not change their uptake patterns during 2 months inundation compared with dry times, so were not utilising the low-salinity flood water. Pre-dawn leaf water potentials and leaf ¹³C measurements showed that the trees with permanent access to the stream experienced lower water stress and had lower water use efficiencies than trees at the least frequently flooded site. The trees beside the ephemeral stream appeared to change their water use efficiency in response to the availability of surface water; it was similar to the perennial-stream trees when stream water was available and higher at other times. Despite causing water stress, uptake of soil water and groundwater would be advantageous to E. camaldulensis in this semi-arid area, as it would provide the trees with a supply of nutrients and a reliable source of water. E. camaldulensis at the study site may not be as vulnerable to changes in stream flow and water quality as previously thought.

Water utilization of tropical hardwood hammocks of the Lower Florida Keys

Predawn water potential of representative plant species, together with stable isotope composition of stem water and potential water sources were investigated in four low-elevation tropical hardwood hammocks in the Lower Florida Keys, during a one year period. Hammock species had the lowest water potentials when soil water content was low and/or soil salinity was high, but differences in groundwater salinity had no effect on the water potential. Comparison of D/H ratio of plant stem water with soil and ground water corroborates the conclusion that they are primarily utilizing soil water and not groundwater. Thus, tropical hardwood hammocks are buffered from saline groundwater, and are able to thrive in areas where groundwater salinity is as high as 25‰. The effect of sea level rise on these forests may depend more on changes in the frequency of tidal inundation of the soil surface than on changes in groundwater salinity.