Jong-Sik Ryu

Characterizing the origins of bottled water on the South Korean market using chemical and isotopic compositions

We analyzed the major elements and stable isotopes of oxygen, hydrogen, and carbon (dissolved inorganic carbon: DIC) in various types of bottled water (domestic and foreign) commercially available in South Korea to classify the water types and to identify their origins. Only marine waters and some sparkling waters could be discriminated by their physicochemical compositions. Oxygen and hydrogen isotopes made marine waters more distinguishable from other water types. The determination of the carbon isotope composition of DIC was clearly useful for distinguishing between naturally and artificially sparkling waters. In addition, statistical analysis also appeared to aid in the discrimination of bottled water types. Our results indicate that a method that combines chemical and stable isotope composition analysis with statistical analysis is the most useful for discriminating water types and characterizing the origins of bottled water.

Comparison of pH and counter-ion effect in surfactant-assisted remediation

In order to determine whether pH or counter-ion is more effective in modifying surfactant effectiveness, column experiments were performed. Ottawa sand was selected for model soil and toluene was used as a model contaminant. DOSL (anionic surfactant) was used for this study. The greatest recovery of toluene in column tests was 92%, which was obtained with a surfactant + NaOH. The effect of NaCl in changing effectiveness was less than that of NaOH. Much greater effectiveness was observed using surfactant solutions containing NaOH. The effect of NaOH in changing effectiveness was not due to Na+ effects, but to the OH− as shown by these experimental results. The effect of counter-ion (Na+) was small, and was much less than that of pH in surfactantassisted remediation.

Determination of the Source of Bioavailable Sr Using 87Sr/86Sr Tracers: A Case Study of Hot Pepper and Rice

The geographical origin of agricultural products has been intensively studied, but links between agricultural products and the environments are poorly established. Soils, water (streamwater and groundwater), and plants (hot pepper, Capsicum annuum; and rice, Oryza sativa) were collected from all regions of South Korea and measured Sr isotope ratios ((87)Sr/(86)Sr). Sequential leaching of soil showed that Sr in the exchangeable and carbonate fractions (bioavailable) had a lower (87)Sr/(86)Sr ratio than that in the silicate fraction, consistent with a low (87)Sr/(86)Sr ratio in the plant. Although the bedrock-soil-water-plant system is closely linked, statistical analysis indicated that (87)Sr/(86)Sr ratios of the plant showed the greatest agreement with those of water and the exchangeable fraction of soil. This study is the first report of (87)Sr/(86)Sr isoscapes in South Korea and first demonstrates that the agricultural product is strongly linked with the exchangeable fraction of soil and water.

Precise determination of the lithium isotope ratio in geological samples using MC-ICP-MS with cool plasma

Lithium has two naturally occurring isotopes, 6Li and 7Li, with approximate relative abundances of 7.5% and 92.5%, respectively. Due to large Li isotope variations in nature, lithium isotopes have the potential to reveal important information relevant to nuclear technology, biomedicine, astrophysics, and geochemistry. With the advent of multi-collector inductively coupled mass spectrometry (MC-ICP-MS), studies of Li isotopes have largely focused on the analysis of geological materials, with varying degrees of accuracy. However, this technique has often been affected by either baseline interferences or isobaric interferences on mass 6 and 7 during ionization in Ar plasma, which is mainly due to the Li compound with hydrogen gas, and double-charged nitrogen and carbon ions at higher levels of RF power. In this study, we reduced baseline interferences in Ar plasma using a cool plasma (∼800 W) technique with a X-type cone. Lithium was separated using a cation exchange column (BioRad AG50W-X8, 200–400 mesh) with a mixture of 6 N HNO3 and 80% methanol at <0.2 mL min−1 elution speed. The short-term reproducibility of δ7Li values of the NASS-5 seawater standard was 30.55 ± 0.45‰ (2σ, n = 15). Measured δ7Li values of rock and seawater standards ranged from 2.48 to 30.55‰, in good agreements with reported values.

A revisited method for Mg purification and isotope analysis using cool-plasma MC-ICP-MS

Magnesium is an important element in both the lithosphere and biosphere. Many previous studies have focused on directly tracing Mg cycles using Mg isotopes, and various methods for Mg purification and isotopic measurement have been previously elucidated. Here, we present a newly developed Mg separation method, along with a verification of the method by measuring the Mg isotope composition (expressed as δ26Mg relative to DSM-3) of various standard materials. All matrix cations causing significant mass bias were effectively removed through this Mg purification methodology, resulting in an Mg yield of ∼100% when the matrix concentration did not exceed 5% of the Mg concentration. Following this, Mg isotope ratios were measured using a Neptune MC-ICP-MS equipped with an X-cone under cool plasma conditions, reducing interferences while optimizing instrumental sensitivity. The long-term reproducibilities of the δ26MgDSM-3 values of CAM-1 and SRM980 were −2.65 ± 0.08 (2σ, n = 14) and −4.34 ± 0.08‰ (2σ, n = 10), respectively. The Mg isotopic compositions in a variety of international rock and seawater standards were between −0.17 and −0.86‰, in good agreement with the reported values. These results indicate that the Mg purification method presented here, followed by isotope analysis using cool plasma, is an efficient high-precision method for determining Mg isotope compositions.

Comparison of the oxygen and hydrogen isotopes in the juices of fast-growing vegetables and slow-growing fruits.

We have analyzed the oxygen and hydrogen isotopic composition of juices from fruits and vegetables collected from a small orchard in order to investigate the differences in isotopic enrichment and evaporation intensity between fast-growing vegetables and slow-growing fruits grown under the same climatic conditions. The oxygen and hydrogen isotope levels were much higher in the juices of the fruits and vegetables than in the source waters in which they grew because of evaporation effects. According to our data, fast-growing vegetables are subject to greater evaporation than slow-growing fruits. An evaporation experiment using the source water showed that the oxygen and hydrogen isotopic composition of the 60-80% residual fraction was similar to that of the isotopically enriched grape juice, whereas those of the plume and tomato juices were very close to that of the 80-90% residual fraction, thus proving the effect of evaporation.

Effects of bedrock on the chemical and Sr isotopic compositions of plants

AbstractThis study was conducted to investigate the relationship between the chemical and isotopic compositions of plants and the lithology of their growth location. This relationship is one of the principles underlying the geographical discrimination used for agricultural, forestry, and food products. Locations in South Korea with solely basaltic (Jeju), granitic (Gongju), and carbonate (Yeongwol) rocks were selected as test sites, and bedrocks, soils, and plants in each location were sampled. The multi-element compositions and Sr isotope ratios (87Sr/86Sr) were analyzed for all samples, including various soil fractions (exchangeable, carbonates, silicates) and plant parts (tree leaves, vegetable leaves, and fruits). Based on a preliminary statistical analysis (ANOVA), Ca, Mg, K, Al, Sr concentrations, and 87Sr/86Sr ratios were selected as key variables with greater variability with location. Using these variables, a multivariate statistical analysis was conducted, and three soil fractions and plant parts were successfully discriminated according to their geographical origin (i.e., bedrock type) with statistical significance. The results indicated that Sr isotope ratios of bedrocks can be preserved in soils (except in silicate fractions) and plants throughout weathering and plant physiological processes, and are the most critical variable in the tracing of bedrock characteristics.

Hydrochemistry and isotope geochemistry of Song Stream, a headwater tributary of the South Han River, South Korea

To investigate the geochemical and isotopic characteristics of a headwater tributary of the South Han River, we analyzed major elements, stable isotopes of oxygen, hydrogen, carbon, and sulfur, and strontium (Sr) isotopes of stream and groundwater samples collected from the Song Stream watershed in summer 2003. The stream water samples of the study area were divided into three water types, among which dissolved ion concentrations differed considerably. Our results strongly indicate that the chemical composition of Song Stream is controlled by silicate and carbonate weathering, as well as anthropogenic contamination, and variations in major dissolved ions and Sr isotopic ratios are mainly correlated to lithological variations in the watershed. The dissolved loads of the main channel of Song Stream are largely controlled by carbonate dissolution. Thus, the water chemistry of the main channel is probably dominated by the chemical weathering of carbonates, even where carbonates comprise only a minor proportion of the bedrock geology. The Sr isotopes and Mg/Ca molar ratios indicate that a dolomite end-member may exist in the study area, which would be compatible with the cationic characteristics of Song Stream. All groundwater samples from the study area, except for one, had significantly high nitrate concentrations (0.75–2.42 mmol/L) that exceeded the drinking-water standard and possibly resulted from both sewage and agricultural inputs.

Seasonal and spatial variations in water chemistry and nitrate sources in six major Korean rivers

Seasonal and spatial variations in water chemistry and contaminant sources were investigated in six major rivers in South Korea that vary widely in drainage area and length. The dissolved-load content of the rivers varied seasonally, and some dissolved ions such as Cl− and NO3− showed large spatial differences in all of the rivers. The water type changed from Ca–HCO3 in the upper reaches to Na–Cl–NO3 in the lower reaches, indicating anthropogenic contamination in the lower reaches. Compared with two relatively pristine rivers (the Sumjin and Mankyung rivers), the other four rivers, which flow through agricultural and urban areas, registered much higher Cl− and NO3− concentrations. Statistical analysis showed that seasonal and spatial variations in water chemistry occurred in all the rivers. The nitrogen and oxygen isotopes of dissolved nitrate indicated that the rivers flowing through urban and agricultural areas were significantly affected by manure, sewage, or both.

Natural and anthropogenic sources and processes affecting water chemistry in two South Korean streams.

Acid mine drainage (AMD) in a watershed provides potential sources of pollutants for surface and subsurface waters that can deteriorate water quality. Between March and early August 2011, water samples were collected from two streams in South Korea, one dominantly draining a watershed with carbonate bedrock affected by coal mines and another draining a watershed with silicate bedrock and a relatively undisturbed catchment area. The objective of the study was to identify the sources and processes controlling water chemistry, which was dependent on bedrock and land use. In the Odae stream (OS), the stream in the silicate-dominated catchment, Ca, Na, and HCO3 were the dominant ions and total dissolved solids (TDS) was low (26.1-165 mg/L). In the Jijang stream (JS), in the carbonate-dominated watershed, TDS (224-434 mg/L) and ion concentrations were typically higher, and Ca and SO4 were the dominant ions due to carbonate weathering and oxidation of pyrite exposed at coal mines. Dual isotopic compositions of sulfate (δ(34)SSO4 and δ(18)OSO4) verified that the SO4 in JS is derived mainly from sulfide mineral oxidation in coal mines. Cl in JS was highest upstream and decreased progressively downstream, which implies that pollutants from recreational facilities in the uppermost part of the catchment are the major source governing Cl concentrations within the discharge basin. Dual isotopic compositions of nitrate (δ(15)NNO3 and δ(18)ONO3) indicated that NO3 in JS is attributable to nitrification of soil organic matter but that NO3 in OS is derived mostly from manure. Additionally, the contributions of potential anthropogenic sources to the two streams were estimated in more detail by using a plot of δ(34)SSO4 and δ(15)NNO3. This study suggests that the dual isotope approach for sulfate and nitrate is an excellent additional tool for elucidating the sources and processes controlling the water chemistry of streams draining watersheds having different lithologies and land-use patterns.