Uncovering the characteristics of plastic-associated biofilm from the inland river system of Mongolia.

The occurrence and characteristics of plastic debris in aquatic and terrestrial environments have been extensively studied. However, limited information exists on the properties and dynamic behavior of plastic-associated biofilms in the environment. In this study, we collected plastic samples from an inland river system in Mongolia and extracted biofilms to uncover their characteristics using spectroscopic, isotopic, and thermogravimetric techniques. Mixtures of organic and mineral particles were detected in the extracted biofilms, revealing plastic as a carrier for exogenous substances, including contaminants, in the river ecosystem. Thermogravimetric analysis (TGA) indicated the predominant contribution of minerals primarily comprising aluminosilicate and calcite, representing approximately 80 wt% of the biofilms. Differential thermal analysis (DTA) coupled with Fourier transform infrared (FTIR) spectrometry operated at 25°C-600 °C enabled the detection of gaseous decomposition products, such as CO2, H2O, CO, and functional groups (O-H, C-H, C-O, CO, CC, and C-C), released from biopolymers in the extracted biofilms. Dehydration, dehydroxylation, and decarboxylation reactions explain the thermal properties of biofilms. The stable carbon (δ13C) and nitrogen (δ15N) isotope ratios of the biofilms demonstrated variable signatures ranging from -24.1‰ to -27.0‰ and 3.1‰-12.3‰, respectively. A significant difference in the δ13C value (p < 0.05) among the upstream, middle, and downstream research sites could be characterized by available organic carbon sources in the river environment, depending on the research sites. This study provides insights into the characteristics and environmental behavior of biofilms which are useful to elucidate the impact of plastic-associated biofilms on organic matter and material cycling in aquatic ecosystems.

Quantitative imaging of trace elements in solid samples by online isotope dilution laser ablation-inductively coupled plasma-mass spectrometry.

For quantitative visualization of trace elements, an online isotope dilution (ID) laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) method capable of accurately correcting the detection amount of targets is presented. Two aerosols from an ablated sample and a nebulized isotopically enriched spike solution were mixed online using a dual-port spray chamber. In this paper, transmission efficiency (TE) of each of the two gas streams to the ICP-MS detector is revealed, and the quantification values were corrected by including the ratio of TEs in the calculation of the online ID method. To verify the developed method, Fe and Sr as model elements in five certified reference materials (CRMs, glass: SRM 610, 612, 614, alloy: SS-356, -383) were quantified without the use of matrix-matched CRMs. The resultant values agreed with the certified values of CRMs in the range of 92.7-104.7% and 92.8-109.0% for Fe and Sr, respectively. The LODs (3σ) were 0.54 and 0.17 µg g-1 for Fe and Sr, respectively. In addition, the applicability of this method to quantitative imaging of unknown solid samples was demonstrated for actual biological hard tissues (a mouse incisor, human primary tooth, and fish otolith) using the result of shot-analysis. The results were consistent with the reported concentration range obtained by wet chemical analysis.

Tracking the behavior and characteristics of microplastics using a multi-analytical approach: a case study in two contrasting coastal areas of Japan.

The global survey for the presence of microplastics (MPs) in aquatic environments has attracted widespread scientific attention over the past decade. However, evaluating the composition and characteristics of these anthropogenic debris using highly sensitive techniques is still under consideration. This study demonstrates a multidimensional analytical approach, including isotopic and thermogravimetric analyses to evaluate characteristics and behavior of MPs in the environment. The MP samples were collected in two contrasting coastal areas of Japan. The stable carbon isotope (δ13C) ratios of field-collected polyethylene (PE), polypropylene (PP), and polystyrene (PS) MPs ranged from -25.6‰ to -31.4‰, -23.4‰ to -30.9‰, and -27.3‰ to -28.6‰, respectively. The detected isotope signatures were similar to those of commercial products. In addition, the differences in δ13C signature were determined between MPs with different colors. Through thermal analysis, the single-step endothermic process was observed for environmental PE and PS-MPs. Patterns in the thermograms revealed dissimilarities in degradability among the PE-MPs with different colors. The results reveal that degradation (aging) may play a significant role in the behavior and characteristics of MP debris in the aquatic environment. The present study provides fundamental data of environmental MPs from the isotopic and thermogravimetric aspects and highlights the usefulness of the approach for advances in MP research.

Mass-spectrometric determination of iodine-129 using O2-CO2 mixed-gas reaction in inductively coupled plasma tandem quadrupole mass spectrometry.

This paper presents a mass-spectrometric method for determining the radionuclide iodine-129 (129I) from the significant amount of interference in inductively coupled plasma tandem quadrupole mass spectrometry (ICP-MS/MS) using a dynamic reaction cell passing a mixture gas of O2 and CO2. Thus far, mass spectrometry analysis of trace amounts of 129I has been hampered by the presence of xenon-129 (129Xe) and the formation of polyatomic ions from excess amounts of stable isotope 127I. In this study, flowing a mixture gas of O2 and CO2 into the dynamic reaction cell (Q2) successfully removed both 129Xe interference and polyatomic interference (127IH2) in the analysis of 129I in ICP-MS/MS. The resulting ratio of (background noise of m/z 129)/127I was 4.6 × 10-10 ± 3.3 × 10-10, which enables the analysis of 10 mBq/L of 129I in the presence of 100 mg/L of stable 127I without chemical separation. The detection limit of this method was 0.73 mBq/L (= 0.11 ng/L) with an APEX-Q sample inlet desolvation device. For demonstration purposes, spike and recovery analysis of rainwater was performed, and good agreement between the spiked and recovered amounts was achieved.

PERFORMANCE EVALUATION OF COMMERCIAL SCINTILLATION COCKTAILS FOR LOW-LEVEL TRITIUM COUNTING BY HIGH-CAPACITY LIQUID SCINTILLATION COUNTER.

Low-background liquid scintillation counter is one of the popular measuring instruments used to investigate tritium radioactivity in environmental media. These instruments require the liquid sample and organic solvent to be mixed for tritium measurement. In the European Union, the registration, evaluation, authorization and restriction of chemicals regulation was established to control the use of chemical substances of very high concern. It is important to find continuously available alternative reagents. In this paper, a performance evaluation was conducted using four scintillation cocktails according to Japanese conventional procedure; although one of them, Gold Star LT2, contains nonylphenol ethoxylate, it will continue to be available for research and development. From the evaluation results it was confirmed that Gold Star LT2 would be a satisfactory alternative scintillator, which is similar performance of Ultima Gold LLT.

Sensitivity enhancement in inductively coupled plasma mass spectrometry using nebulization methods via nitrogen mixed gas effect.

We demonstrate the sensitivity enhancement in inductively coupled plasma mass spectrometry (ICP-MS) by combining ultrasonic nebulization via the nitrogen mixed gas effect. We showed the effect of nitrogen gas concentration (0-5%) in the nebulizer gas on the signal sensitivity for 63 elements using commercially available (concentric and ultrasonic) nebulizers. In addition, the limit of detection (ng L-1) was calculated in each case. Finally, we compared the sensitivity (i.e., the slope of the calibration curve), background noise intensity, and three-dimensional intensity distribution in the plasma to elucidate the effects of the concurrent use of mixed gas plasmas and nebulization methods.

Online solid-phase extraction-inductively coupled plasma-quadrupole mass spectrometric quantification of 90Sr using 88Sr/86Sr isotope dilution method.

Due to the lack of a correlation with the natural Strontium (Sr) isotopes, it is difficult to apply the isotope dilution (ID) method to an artificial radioactive mononuclide Strontium-90 (90Sr), in inductively coupled plasma-quadrupole mass spectrometry (ICP-QMS). Meanwhile, online solid-phase extraction (SPE)-ICP-QMS (SPE-ICP-QMS) serves as an automatic sequential analytical technique for measuring the ultra-trace amounts of radionuclides; however, apparent assay values obtained using this method are often negatively affected by differences in the sample matrix composition between standard and actual samples. In this study, the pg L-1 level of 90Sr was successfully measured by combining online SPE-ICP-QMS and the ID method with 88Sr/86Sr ratios in one sample injection, without the radioactive standard. Although naturally occurring abundant isobaric 90Zr significantly influences 90Sr quantification during mass spectrometry, consecutive separations between automated SPE and dynamic reaction cell (DRC) oxidation enable 90Sr quantification, even in the presence of isobaric 90Zr (acceptable down to 5.7 × 10-9 of 90Sr/Zr in sample solution), using this method. Through this method, both radioactive 90Sr and naturally occurring Sr were simultaneously quantified using 88Sr-to-86Sr and 88Sr-to-90Sr ratios without radioactive 90Sr standard solutions. This simultaneous quantification of stable Sr and 90Sr was achieved within 15 min with good recovery rates. The limit of detection of 90Sr was 1.1 pg L-1 (equivalent to radioactivity 5.6 Bq L-1) for a 10 mL injection. Finally, water collected from an actual contaminated water storage tank at the Fukushima Daiichi Nuclear Power Plant (Fukushima, Japan) was analyzed using the proposed method, and the obtained results agreed well with those obtained using conventional analytical methods.

Online Solid-Phase Extraction-Inductively Coupled Plasma-Quadrupole Mass Spectrometry with Oxygen Dynamic Reaction for Quantification of Technetium-99.

Quantification of pg/L levels (i.e., 0.6 mBq/L) of radioactive technetium-99 (99Tc) was achieved within 15 min in the presence of isobaric and polyatomic interference sources such as ruthenium-99 (99Ru) and molybdenum hydride (98Mo1H) at 3-11 orders of magnitude higher concentrations. Online solid-phase extraction-inductively coupled plasma-quadrupole mass spectrometry (ICP-QMS) with oxygen (O2) dynamic reaction cell (online SPE-ICP-MS-DRC) was shown to be a thorough automatic analytical system, circumventing the need for human handling. At three stepwise separations (SPE-DRC-Q mass filters), we showed that interference materials allowed the coexistence of abundance ratios of 1.5 × 10-13 and 1.1 × 10-5 for 99Tc/Mo and 99Tc/Ru, respectively. A classical mathematical correction using the natural isotope ratio of 99Ru/102Ru was used to calculate the residues of 99Ru. Using this optimized system, a detection limit (DL; 3σ) of 99Tc was 9.3 pg/L (= 5.9 mBq/L) for a 50 mL injection and sequential measurements were undertaken at a cycle of 24 min/sample. For the measurement of a lower concentration of 99Tc, an AG1-X8 anion-exchange column was used to study 20 L of seawater. Its DL was approximately 1000 times greater than that of previous methods (70.0 fg/L). Thus, this method withstands coexistences of 5.8 × 10-18 and 3.5 × 10-9 for 99Tc/Mo and 99Tc/Ru, respectively. Spike and recovery tests were conducted for environmental samples; the resulting values showed good agreement with the spike applied.

Development of Online Dilution System for Quantification of 90Sr Using Automatic Solid-phase Extraction Inductively Coupled Plasma Mass Spectrometry.

In this paper, we propose an online dilution system for the rapid quantification of radioactive strontium-90 (90Sr) with inductively coupled plasma mass spectrometry coupled solid-phase extraction and O2 dynamic reaction (cascade ICP-MS). The proposed system automatically provides a higher dilution ratio, which is at most 3.3 ± 0.2-times the ratio obtained by the previous method, without increasing the analysis time (<15 min). A detection limit of 2.7 Bq/kg wet (0.54 pg/kg wet) was achieved. The recovery test results were consistent with two different spiked values.

Ultrasonic Mist Generation Assist Argon-Nitrogen Mix Gas Effect on Radioactive Strontium Quantification by Online Solid-Phase Extraction with Inductively Coupled Plasma Mass Spectrometry.

The Ar-N2 mix gas effect can easily improve the sensitivity of ICPMS; however, this effect discriminates against Sr. In this study, it was found that Ar-N2 mixed gases introduced into nebulizing gas enhanced the sensitivity of online solid-phase extraction (SPE) with inductively coupled plasma mass spectrometry (ICPMS) for radioactive strontium quantification. An ultrasonic nebulizer (USN) improved the Ar-N2 mixture gases effect of Sr and the mix gases (with USN) enhanced 3.7-times the signal intensity of Sr in normal pure Ar gas (with USN) in an online SPE-ICPMS. By adapting the gas-loading means from a nebulizing gas unit via USN, no careful tuning was necessary for the plasma turning. With this signal enhancement, a 0.06 pg/L detection limit (0.3 Bq/L) was achieved for radioactive strontium (90Sr) in online SPE-ICPMS within 30 min. In addition, environmental paddle water in the Fukushima Nuclear Power Plant was measured and the valued correspond to that obtained by radiometry.