National-scale investigation of dual nitrate isotopes and chloride ion in South Korea: Nitrate source apportionment for stream water.

Nitrate sources in surface water have been identified using dual-isotope compositions of nitrate with various tools to efficiently manage the water quality at the local scale. Correlation between Cl and NO3 has also been used to identify NO3. In this study, we assess the reliability of the dual-isotope approach and Cl in terms of nitrate source apportionment. To this end, we collected stream water samples throughout South Korea to estimate nitrate sources in streams and determine whether the land-use pattern was closely related to nitrate sources. The δ15N-NO3 ranging from -1.3 to 14.8‰ showed a spatial distribution that was lower in mountain ranges (<7‰) than plain areas (>8‰). The Cl concentration in this national-scale distribution was also assessed. The relationship between the proportion of Cl and δ15N-NO3 classifies nitrate sources into areas characterized by three land-use patterns: (1) agricultural and business areas, (2) forests in highlands, and (3) lowland forests, of which (1) had proportions of Cl >50%, while (2) and (3) were <50%. The samples in (3) showed δ15N-NO3 values > 6‰, similar to those of (1). Deuterium excess of samples was negatively correlated (R2 = 0.53) with δ15N-NO3, accounting for the fact that δ15N-NO3 reflected land-use patterns. Samples were dominantly affected by agriculture-derived sources and domestic sewage showed NO3/Cl of <0.4 and δ15N-NO3 of >6‰. These results suggest that nitrate source apportionment should be comprehensively evaluated considering the dual-isotope approach, land-use patterns, and Cl proportions.

Association between Nitrogen Stable Isotope Ratios in Human Hair and Serum Levels of Leptin.

Stable isotope ratios have been reported to be potential biomarkers of dietary intake and nutritional status. High serum levels of leptin, a hormone which regulates energy metabolism and food intake, are associated with insulin resistance and metabolic syndrome. However, little is known about the association between stable isotope ratios and the metabolic risk in humans. We investigated whether the carbon and nitrogen stable isotope ratios in hair are associated with serum leptin levels. Hair samples were collected from 399 healthy adults (233 men and 166 women) aged 40 to 70 years of a community-based cohort in Korea and the bulk stable isotope ratios of carbon (δ13C) and nitrogen (δ15N) were measured for all hair samples. Serum leptin levels were analyzed by radioimmunoassay. δ15N showed positive correlations with serum leptin levels. In multivariate models, increasing δ15N were associated with elevated serum leptin levels (defined as ≥ the median values), whereas δ13C were not significantly associated with serum leptin levels. The odds ratio (95% confidence interval) per 1‰ increase in δ15N for an elevated serum leptin level was 1.58 (1.11-2.26). In participants with high body mass index, δ15N showed positive associations with serum leptin levels, whereas these associations were not seen in participants with low body mass index. The nitrogen stable isotopic ratio in hair is positively associated with serum leptin levels. The hair δ15N could be used as a clinical marker to estimate metabolic risk.

Early-stage changes in natural (13)C and (15)N abundance and nutrient dynamics during different litter decomposition.

Decomposition, nutrient, and isotopic (δ(13)C and δ(15)N) dynamics during 1 year were studied for leaf and twig litters of Pinus densiflora, Castanea crenata, Erigeron annuus, and Miscanthus sinensis growing on a highly weathered soil with constrained nutrient supply using litterbags in a cool temperate region of South Korea. Decay constant (k/year) ranged from 0.58 to 1.29/year, and mass loss ranged from 22.36 to 58.43 % among litter types. The results demonstrate that mass loss and nutrient dynamics of decomposing litter were influenced by the seasonality of mineralization and immobilization processes. In general, most nutrients exhibited alternate phases of rapid mineralization followed by gradual immobilization, except K, which was released throughout the field incubation. At the end of study, among all the nutrients only N and P showed net immobilization. Mobility of different nutrients from decomposing litter as the percentage of initial litter nutrient concentration was in the order of K > Mg > Ca > N ≈ P. The δ(13)C (0.32-6.70 ‰) and δ(15)N (0.74-3.90 ‰) values of residual litters showed nonlinear increase and decrease, respectively compared to initial isotopic values during decomposition. Litter of different functional types and chemical quality converged toward a conservative nutrient use strategy through mechanisms of slow decomposition and slow nutrient mobilization. Our results indicate that litter quality and season, are the most important regulators of litter decomposition in these forests. The results revealed significant relationships between litter decomposition rates and N, C:N ratio and P, and seasonality (temperature). These results and the convergence of different litters towards conservative nutrient use in these nutrient constrained ecosystems imply optimization of litter management because litter removal can have cascading effects on litter decomposition and nutrient availability in these systems.

Contribution of carbonate-derived dissolved inorganic carbon into autochthonous particulate organic carbon in two small temperate Korean rivers (Geum and Seomjin).

In this study, we estimated the contributions of carbonate mineral weathering to dissolved inorganic carbon (DIC) and carbonate-derived DIC to autochthonous particulate organic carbon (POC) in two temperate Korean rivers. We combined stoichiometric and stable carbon isotopic approaches to calculate the contribution of autochthonous POC, considering diverse riverine DIC sources. We collected surface water samples from May 2016 to May 2018 and analyzed the major ion composition of rivers along with the concentrations and stable carbon isotopes of DIC. Our estimates showed that the relative abundances of carbonate mineral weathering (0.41 ± 0.11 in the Geum River and 0.43 ± 0.07 in the Seomjin River) were only slightly lower than those of silicate mineral weathering (0.59 ± 0.1 in the Geum River and 0.57 ± 0.07 in the Seomjin River). The resulting percentage contributions of DIC derived from the carbonate mineral weathering to riverine autochthonous POC, if we consider the additional DIC sources of atmospheric and soil-derived CO2, were 10 ± 3 % in the Geum River and 2 ± 1 % in the Seomjin River. The calculated annual fluxes of carbonate-derived DIC for 2016-2018 were 23.2 ± 0.3 Gg C yr-1 in the Geum River and 1.1 ± 0.4 Gg C yr-1 in the Seomjin River. Moreover, the calculated annual fluxes of carbonate-derived POC were 3.6 ± 0.5 Gg C yr-1 in the Geum River and 0.1 ± 0.7 Gg C yr-1 in the Seomjin River. Accordingly, our study provides the first insight into the contribution of carbonate-derived DIC to riverine autochthonous POC in small temperate Korean river systems, dominated by silicate rocks.

Mineral extraction from asbestos-containing waste (ACW) and changes in its morphology during treatment with ammonium salts.

Asbestos is a known carcinogen and a banned hazardous material. However, the generation of asbestos-containing waste (ACW) is increasing because of the demolition of old constructions, buildings, and structures. Therefore, asbestos-containing wastes need to be effectively treated to render them harmless. This study aimed to stabilize asbestos wastes by using for the first time three different ammonium salts at low reaction temperatures. The treatment was performed with ammonium sulfate (AS), ammonium nitrate (AN), and ammonium chloride (AC) at concentrations of 0.1, 0.5, 1.0, and 2.0 M and reaction times of 10, 30, 60, 120, and 360 min intervals at 60 °C. Asbestos waste samples were treated in both plate and powder form during the experiment. The results demonstrated that the selected ammonium salts could extract the mineral ions from asbestos materials at a relatively low temperature. Concentrations of the minerals extracted from powdered samples were higher than those extracted from plate samples. AS treatment demonstrated better extractability compared to that of AN and AC, based on the concentrations of magnesium and silicon ions in the extract. The results implied that among the three ammonium salts, AS had better potential to stabilize the asbestos waste. This study demonstrated the potential of ammonium salts for treating and stabilizing asbestos waste at low temperatures by extracting the mineral ions from the asbestos fibers.Implications: This study aims to establish an effective treatment to stabilize the hazardous asbestos waste to harmless forms. We have attempted treatment of asbestos with three ammonium salts (ammonium sulfate, ammonium nitrate, ammonium chloride) at relatively lower temperature. The selected ammonium salts could extract the mineral ions from asbestos materials at a relatively low temperature. These results suppose that asbestos containing materials could change the harmless state by using simple method. Among the ammonium salts, especially, AS has better potential to stabilize the asbestos waste.

Acid mine drainage and smelter-derived sources affecting water geochemistry in the upper Nakdong River, South Korea.

Both the smelter and acid mine drainage (AMD) in uppermost streams impact water geochemistry and deteriorate water quality. Efficient water quality management requires identifying the contribution of each source to stream water geochemistry. In this study, we aimed to determine the natural and anthropogenic sources (AMD and smelting) affecting water geochemistry by considering seasonality. Water samples were collected, from May 2020 to April 2021, in a main channel (Nakdong River) and tributaries in a small watershed including mines and smelters. The watershed is characterized by a carbonate-rich area in the upper-middle reaches and silicate-rich area in the middle-lower reaches. On the plots of Ca/Na vs. Mg/Na and 2(Ca + Mg) vs. HCO3 + 2SO4, the water geochemistry was predominantly explained by the carbonate and silicate weathering associated with sulfuric and carbonic acids. According to typical δ15N values for sources, nitrate contribution from soil-N mainly impacted water geochemistry, regardless of seasonality; the contribution from agricultural activity and sewage was negligible. Water geochemistry in the main channel samples was discriminated before and after passing through the smelter. The effects of the smelter were evident in elevated SO4, Zn, and Tl concentrations and in δ66Zn values; this was further supported by the relationships between Cl/HCO3 and SO4/HCO3 and between δ66Zn and Zn. These results were pronounced during winter, when the flush-out effect was absent. Our results suggest that multi-isotopes and chemical composition analyses can trace multiple sources influencing the water geochemistry in watersheds containing AMD and smelters.

Using stable isotope analysis to discriminate gasoline on the basis of its origin.

RATIONALE: Leakage of gasoline and diesel from underground tanks has led to a severe environmental problem in many countries. Tracing the production origin of gasoline and diesel is required to enable the development of dispute resolution and appropriate remediation strategies for the oil-contaminated sites. METHODS: We investigated the bulk and compound-specific isotopic compositions of gasoline produced by four oil companies in South Korea: S-Oil, SK, GS and Hyundai. The relative abundance of several compounds in gasoline was determined by the peak height of the major ion (m/z 44). RESULTS: The δ(13)C(Bulk) and δD(Bulk) values of gasoline produced by S-Oil were significantly different from those of SK, GS and Hyundai. In particular, the compound-specific isotopic value (δ(13)C(CSIA)) of methyl tert-butyl ether (MTBE) in S-Oil gasoline was significantly lower than that of gasoline produced by other oil companies. The abundance of several compounds in gasoline, such as n-pentane, MTBE, n-hexane, toluene, ethylbenzene and o-xylene, differed widely among gasoline from different oil companies. CONCLUSIONS: This study shows that gasoline can be forensically discriminated according to the oil company responsible for its manufacture using stable isotope analysis combined with multivariate statistical analysis.

Chemical and isotopic compositions of bottled waters sold in Korea: chemical enrichment and isotopic fractionation by desalination.

A total of 54 Korean bottled waters were investigated to characterize their origins and types using elemental and isotopic composition, as well as to identify elemental and isotopic changes in desalinated marine water that arise due to desalination. The different types of bottled water displayed a wide pH range (3.42 to 7.21). The elemental compositions of still and sparkling waters were quite similar, whereas desalinated marine water was clearly distinguished by its high concentrations of Ca, Mg, B, and Cl. In addition, desalinated marine water had much higher isotope ratios of oxygen and hydrogen (-0.5 and -2‰, respectively) than still and sparkling waters (-8.4 and -57‰). The elemental composition of desalinated marine water was adjusted through post-treatment procedures; in particular, boron was greatly enriched during desalination processes. The carbon isotope compositions of dissolved inorganic carbon (δ(13)C(DIC) values) varied widely according to the origins of the bottled waters (-25.6 to -13.6‰ for still water, -31.2 to -26.7‰ for sparkling water, and -24.1 to -6.3‰ for desalinated marine water). This indicates that carbon isotopes in dissolved inorganic carbon are significantly fractionated by desalination processes and re-modified through post-treatment procedures. The results suggest that combined elemental and stable isotopic tracers are useful for identifying the origin of bottled water, verifying elemental and isotopic modifications during desalination processes, and characterizing various water types of bottled waters.

Geographic origins of Korean and Chinese kimchi determined by multiple elements.

An elemental analysis was performed on 30 Korean and Chinese kimchi samples in combination with strontium (Sr) isotope ratio measurements to develop a method for tracing the geographic origins of Korean and Chinese kimchi. We found a distinct difference between Korean and Chinese kimchi in such specific elements as K, Na, Ca, Ba, Sr, Zn, Li, and Sc, but no significant difference in the Sr isotope ratio. A comparative analysis was performed with washed kimchi (containing no submaterial) and unwashed kimchi to evaluate the effect of submaterials on the determination of geographic origin. A linear discriminant analysis provided a clear distinction between Korean and Chinese kimchi. The results indicate that combining multi-elemental and statistical analyses has the potential to determine the geographic origins of such processed food as kimchi.

Determination of the geographical origin of kimchi by (1)H NMR-based metabolite profiling.

Kimchi is a well-known traditional Korean food. Its geographical origins can be determined by its biochemical composition. This study identified the biochemical compositions of kimchi extracts from Korea and China by (1)H nuclear magnetic resonance (NMR) spectroscopy followed by multivariate data analysis. Principal component analyses (PCA) clearly discriminated between extracts prepared in the two countries. The identified metabolites, including amino acids, organic acids, sugars, and ethanol, contributed to discriminating the geographical origin of kimchi extracts. Furthermore, differences in composition by origin were predicted with high accuracy in external validation models. These results establish biochemical profiles for kimchi extracts, and indicate that metabolomics can be used in the discrimination of food origins.

Dietary homogenization and spatial distributions of carbon, nitrogen, and sulfur isotope ratios in human hair in South Korea.

Dietary homogenization has progressed worldwide due to westernization and the globalization of food production systems. We investigated dietary heterogeneity in South Korea by examining the spatial distribution of carbon (C), nitrogen (N), and sulfur (S) isotope ratios using 264 human hair samples. Overall, variation in isotope values was small, indicating low dietary heterogeneity. We detected differences in δ13C, δ15N, and δ34S values between administrative provinces and metropolitan cities; inter-regional differences were typically < 1 ‰. Values of δ34S were significantly lower in hair samples from inland regions relative to those from coastal locations, and a similar pattern was observed in δ15N values. Understanding geographic variation in δ34S and δ15N values in human hair is useful for provenancing humans in South Korea.

Tracing the geographical origin of beefs being circulated in Korean markets based on stable isotopes.

We have examined the carbon, nitrogen and oxygen isotopic compositions of American, Mexican, Australian, New Zealand and Korean beefs, which are currently being circulated in Korean markets, to check whether stable isotope ratios can identify their country of origin. Each beef exhibited statistically distinct isotopic compositions, especially in oxygen and carbon, because of the different isotopic compositions of their water and cattle feeds. Nevertheless, their isotopic compositions still showed some overlap, especially among USA, Australian, and Korean beefs, which sometimes resulted in significant misidentification when a single isotope was considered. However, the discrimination was generally successful when both the carbon and the oxygen isotopes were used.

Characteristics of Carbonate Formation from Concentrated Seawater Using CO2 Chemical Absorption Methodology.

Carbon capture and storage is a popular CO2-reduction technology, and carbon capture and utilization (CCU) technology has been reported frequently over the years. However, CCU has certain disadvantages, including the requirement of high energy consumption processes such as mineral carbonation. In addition, stable metal sources are required to fix CO2. This study used concentrated seawater to supply metal ions. In addition, the selected 5 wt % amine solution changed CO2 into aqueous CO2 to reduce the additional energy required to form the metal carbonate under moderate conditions. As a result, precipitates were formed because of the reaction of carbonate radicals with metal ions in the seawater. These precipitates were analyzed by X-ray diffraction and field-emission scanning electron microscopy, and they were found to mostly consist of CaCO3 and NaCl. Furthermore, it was verified that the conversion solution maintained its CO2-loading capacity even after the solids and liquid were filtered twice. Therefore, the proposed method permits a substantial reuse of CO2 and waste seawater when sufficient metal ions are supplied. Therefore, methods to improve their purity will be developed in future studies.

Seasonal contrast of particulate organic carbon (POC) characteristics in the Geum and Seomjin estuary systems (South Korea) revealed by carbon isotope (δ13C and Δ14C) analyses.

In this study, we newly investigated surface water samples collected in two contrasting Korean estuary systems (i.e., closed Geum and open Seomjin estuaries) along a salinity gradient in winter (December) in 2016. The main objectives were to determine the source of particulate organic carbon (POC) in winter and to assess the environmental factors inducing seasonal differences in POC characteristics. Concentrations and dual carbon isotopes (δ13C and Δ14C) of POC were analyzed together with concentrations and stable carbon isotopes (δ13C) of dissolved inorganic carbon (DIC) and compared with those obtained in summer (August) in 2016. Our study provided a new insight that for both estuarine systems, the seasonal contrast in POC characteristics was associated with stronger wind-induced estuarine sediment resuspensions in winter than in summer providing a greater contribution of aged POC to the total POC pool in winter.

Datasets for spatial variation of O and H isotopes in waters and hair across South Korea.

The data presented here include the results of oxygen (δ18O) and hydrogen (δ2H) isotope analyses of water and human scalp hair samples collected from throughout the South Korea. The purpose of data collection was to generate isoscapes of oxygen and hydrogen isotopes for South Korea. To achieve the objective, we collected human scalp hair and three different types of water samples: groundwater, stream water and tap water. The data presented in the article are raw isotope data of water and hair samples in tabulated manner and interpolated isoscapes generated using those data. Further information related to the datasets and discussion about them can be found in the related research article entitled "Spatial variations in oxygen and hydrogen isotopes in waters and human hair across South Korea" [1].

Spatial variations in oxygen and hydrogen isotopes in waters and human hair across South Korea.

The spatial distribution of isotopic signatures in the form of isoscape is a valuable tool to map their spatial heterogeneity in various environmental settings. However, only limited information about δ18O and δ2H in water across South Korea is available and to our knowledge no study so far has tried to examine the isotopic heterogeneity of tap water and human scalp hair in South Korea. Here, we present the first national scale analyses of stream water, groundwater, tap water, and human scalp hair isoscapes for South Korea. Stream water, groundwater, tap water, and human scalp hair samples were collected from across South Korea. These samples were analyzed for δ18O and δ2H, and the isotopic data were then used to generate interpolated δ18O and δ2H isoscapes for South Korea. The results of linear regression analyses showed strong and significant relationships between δ18Ohair and δ18Owater (R2 = 0.83, P < 0.002) and between δ2Hhair and δ2Hwater (R2 = 0.74, P < 0.006), primarily reflecting a close co-relationship between water and hair. The slopes of linear regressions for δ18O (Δδ18Ohair/Δδ18Owater) and δ2H (Δδ2Hhair/Δδ2Hwater) suggested that approximately 27% of hydrogen and 36% of oxygen in hair keratin were derived from the local drinking water. Interpolated δ18O and δ2H isotope maps of stream water, groundwater, and tap water samples collected from across South Korea showed similar spatial patterns of isotope variability. These samples showed a clear latitudinal gradient with high isotopic values in the south which progressively decrease toward the north. The same trends were observed in hair isoscapes as well, and had gradients matching the isotopic pattern of water samples. The strong relationship between water and human hair, and the consistent spatial pattern between them suggest that hair isotope signatures in South Korea can be used in provenance- and forensic-related activities.

Tracing the sources of nitrate in the Han River watershed in Korea, using delta15N-NO3- and delta18O-NO3- values.

The dissolved nitrate concentrations and their nitrogen and oxygen isotopic ratios were analyzed in seasonal samples from Korea's Han River to ascertain the seasonal and spatial variations of dissolved nitrate and its possible sources. Nitrate concentrations in the South Han River (SHR) were much higher than those in the North Han River (NHR), probably because of the more extensive distribution of agricultural fields, residential areas and animal farms in the SHR drainage basin. The nitrogen isotopic composition of dissolved nitrate indicates that nitrate-nitrogen (NO(3)(-)-N) is derived mainly from atmospheric deposition and/or soil organic matter in the NHR but comes principally from manure or sewage, with only a minor contribution from atmospheric deposition or soil organic matter, in the SHR. The oxygen isotopic compositions of dissolved nitrate suggest that most atmospheric nitrate undergoes microbial nitrification before entering the river.

A fast, simple calibration method for organic carbon isotope analysis using continuous-flow elemental analyzer interfaced with an isotope ratio mass spectrometer.

Continuous flow analysis using an elemental analyzer interfaced with an isotope ratio mass spectrometer (EA-IRMS) is faster and requires much less material than conventional analytical methods. Although using an EA-IRMS is simple and fast, accurate calibration strongly depends on matching sample and reference peak heights by adjusting the sample weight. This paper describes a new modification for calibration using only the major ion beam intensity (nA) without weighing each sample or increasing the number of reference materials.

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.

An integrated analysis for determining the geographical origin of medicinal herbs using ICP-AES/ICP-MS and (1)H NMR analysis.

ICP-MS and (1)H NMR are commonly used to determine the geographical origin of food and crops. In this study, data from multielemental analysis performed by ICP-AES/ICP-MS and metabolomic data obtained from (1)H NMR were integrated to improve the reliability of determining the geographical origin of medicinal herbs. Astragalus membranaceus and Paeonia albiflora with different origins in Korea and China were analysed by (1)H NMR and ICP-AES/ICP-MS, and an integrated multivariate analysis was performed to characterise the differences between their origins. Four classification methods were applied: linear discriminant analysis (LDA), k-nearest neighbour classification (KNN), support vector machines (SVM), and partial least squares-discriminant analysis (PLS-DA). Results were compared using leave-one-out cross-validation and external validation. The integration of multielemental and metabolomic data was more suitable for determining geographical origin than the use of each individual data set alone. The integration of the two analytical techniques allowed diverse environmental factors such as climate and geology, to be considered. Our study suggests that an appropriate integration of different types of analytical data is useful for determining the geographical origin of food and crops with a high degree of reliability.