Spectral pretreatments, such as background removal from Raman big data, are crucial to have a smooth link to advanced spectral analysis. Recently, we developed an automated background removal method, where we considered the shortest length of a spectrum by changing the scaling factor of the background spectrum. Here, we propose a practical way to correct the systematic error caused by noise from measurements. This correction has been realized to be more effective and accurate for automatic background removal.
A facile colorimetric method was developed for detecting 6-mercaptopurine (6-MP) using silver nanoparticles (AgNPs). The addition of 6-MP to AgNPs led to the aggregation of AgNPs with a color change from yellow to brown. The ratio between the absorbance at 394 and 530 nm (A394/A530) was used for a quantitative analysis of 6-MP. A linear range of 0 – 0.5 μM was obtained with a detection limit of 10 nM. The developed method is cost-effective and simple.
Groundwater contamination by stray gas (mainly methane) in areas of shale-gas development has captured publics, political and scientific attention. However, the sources and potential mechanisms of groundwater contamination are still debated. Noble gases can provide useful information on fluid migration for discerning the scale, conditions, and physical mechanisms. In this study, details about analytical technology and theoretical approach of noble gases in tracing groundwater contaminations are presented. In addition, applications of noble-gases isotopes for determining contamination sources and potential pathways are explored and reviewed. Recent developments are discussed and highlighted with focusing on new utilities of noble-gas isotope parameters in evaluating groundwater contamination. Some usages of indicators (4He/20Ne, CH4/36Ar, 4He/CH4, etc.) are discussed through specific research articles. And it is a new trend to make comprehensive use of multiple geochemical parameters to determine the occurrence, source, and process of methane pollution in groundwater.
We monitored the relationship between the cadmium (Cd) concentration uptake of rice and the oxidation-reduction potential (ORP) at the soil surface with the supplementation of fermented botanical waste-based amendment (FBWA), an organic fertilizer prepared from woody and food wastes. This study was carried out for 3 years in the western part of Jiangsu Province, China. It was found that the Cd concentration taken up by rice was correlated to a decreased the ORP of the cultivated soil. The yield of rice was ∼1.20 times higher than that of the control plot. The effects of reducing the Cd content in rice and increasing the rice yield remained for 2 years after FBWA application. Finally, Cd was immobilized in the soil with adsorption to FBWA or the decomposed products. The ORP measurement during rice cultivation might be a key index to predict the suppression effect of Cd uptake into the rice or limitation of the sustainable effect by the FBWA.
An analyte molecule was ionized using a femtosecond laser as the ionization source and was measured by a twin-type time-of-flight mass spectrometer with long (42 cm) and short (6.4 cm) flight tubes. The signal was measured using an analog signal digitizer and a time-correlated single ion counting system, and performance was evaluated by comparing data obtained from both instruments. The short mass spectrometer had a mass resolution of 450 and was used in the trace analysis of allergenic substances in a fragrance.
The characteristic changes in steelmaking slag and humic acids (HAs) derived from a slag-compost fertilizer and their relation to the elution of Fe were evaluated in tank tests in Mashike, Hokkaido and Tsushima, Nagasaki. Analyses of iron, nitrogen and phosphate in the eluate, changes in the chemical states on the surface of the steelmaking slag, and the macro-structural features of the isolated HAs were investigated during the test. Temporal changes in Fe concentrations in the tanks were consistent with data collected in previous studies. Analyses of the surface by 57Fe Mössbauer spectroscopy showed that the concentration of Fe2+ in the fertilizer decreased and the ratio of Fe3+ increased, indicating that Fe2+ was preferentially eluted from the slag surface. The yields of HAs were significantly decreased during the test when steelmaking slag was mixed with compost. Changes in the UV-vis absorptivities indicated that de-aromatization had occurred. These results indicate that microorganisms that were present under these experimental conditions became activated by the mixing of compost with steelmaking slag, and are closely related to the continuous elution of Fe. The residual Fe in the fertilizer after the tests was investigated by analyzing seawater and the levels of extractable Fe. The trends for extractable Fe concentrations were consistent with the results obtained by 57Fe Mössbauer spectroscopy and UV-vis spectra.
Microspheres of aluminosilicate glass from volcanic sediment, whose surfaces were modified with functional groups, Shirasu-balloons (SB), were investigated as an adsorbent to remove cadmium ions from contaminated soil. The introduction of thiol groups (–SH) on the surface of SB enabled it to adsorb cadmium ions. Meanwhile, the introduction of an alkyl group (–ODS) made the surface of SB hydrophobic, and consequently increased the mechanical strength of SB. Those adsorbents could float up on the water surface after the adsorption process. The prepared adsorbent was characterized by FTIR spectrophotometry, elemental analysis and optical microscopy for making photographic images. The adsorption of cadmium ions on the adsorbent was investigated by comparing the results by a plain SB with those by thiol-functionalized SB. The adsorption maximum for cadmium ions was 3.75 mg/g for SH-SB and 2.62 mg/g for SH-ODS-SB, respectively. The adsorption of cadmium ions on functionalized SH-SB and SH-ODS-SB fitted well to the Langmuir isotherm equation. After a shaking time of 24 h, the recovering ratios of the absorbents from soil were 73 wt% for SH-SB and 98 wt% for SH-ODS-SB absorbents. In addition, the kinetic and adsorption-desorption properties of the adsorbent were also considered.
A certified reference material, NIMD-01, was developed for the analysis of mercury speciation in human hair. We collected the hair of Vietnamese males from a barbershop in Hanoi in 2016 and prepared 1200 bottles containing 3 g of sieved and blended hair powder. The certified value was given on a dry-mass basis, with the moisture content obtained by drying at 85°C for 4 h. Certified values with the expanded uncertainties (coverage factor, k = 2) were as follows: methylmercury, 0.634 ± 0.071 mg kg−1 as mercury; total mercury, 0.794 ± 0.050 mg kg−1; copper, 12.8 ± 1.4 mg kg−1; zinc, 234 ± 29 mg kg−1; selenium, 1.52 ± 0.29 mg kg−1. An indicative arsenic concentration of 0.17 ± 0.03 mg kg−1 was measured. Extended uncertainties were estimated by sample homogeneity, long- and short-term stabilities, and a characterization from measurements made by collaborating laboratories.
Beach sand samples were collected along a coastal area 32 km south of the Fukushima Daiichi Nuclear Power Plant (FDNPP) in Fukushima Prefecture, Japan, 5 years after the FDNPP accident. Desorption experiments were performed on the sand samples using seawater in a batch experimental system to understand the forms of existence of radiocesium in sand and their desorption behavior in a coastal environment. The percentage of radiocesium desorption decreased exponentially with an increase in the number of desorption experiments for the four sand samples, with 137Cs radioactivity from 16 to 1077 Bq kg−1 at surface and deeper layers from three sites. Total desorption percentage ranged from 19 to 58% in 12 desorption experiments. The results indicate that the weak adsorption varies with the sampling sites and their depth layer. To understand the desorption behavior of radiocesium in the sand samples, the desorption experiments were performed for a sand sample by using natural and artificial seawater, and NaCl solution in the presence and absence of KCl. The 137Cs desorption from the sand collected at a depth of 100 – 105 cm from the ground surface (137Cs radioactivity 1052 ± 25 Bq kg−1) was 0.1% by ultrapure water, 3.7% by 1/4 seawater and 7.1% by 1/2 seawater, 2.2% by 470 mM NaCl solution (corresponding to a similar concentration of seawater) and 10 – 12% by seawater, artificial seawater and 470 mM NaCl + 8 mM KCl solution. These results indicate that about 10% of radiocesium adsorbed on the sand is mainly desorbed by ion exchange of potassium ion in seawater, though the concentration of major cation, or sodium ion, in seawater makes a small contribution on 137Cs desorption from the sand samples.
This work presents a novel, simple, rapid, and cost effective method for semi-quantitative analysis of arsenic(III) in water sample. The method was based on the digital image colorimetry (DIC) of difluoroboron-curcumin doped starch film (BF2-cur-film) and arsenic ion in water. A red BF2-cur-film (9.4 μm) was fabricated by entrapped difluoroboron-curcumin (BF2-curcumin, particle size of 60 – 113 nm) in tapioca starch film. When the standard solution of arsenic (1 mL) was added into small plastic tube containing BF2-cur-film on its inner lid, blue solution (λmax at 610 nm) was observed instead of orange color in blank solution (λmax at 495 nm). When BF2-cur-film was used in conjunction with DIC, a wide linear range of 0 – 10 mg L−1 with good linearity (R2 > 0.99) was obtained from green channel with low detection limit of 0.04 mg L−1. Moreover, good precision (0.9 – 1.2%RSD, n = 4 days) and accuracy (0.03% relative error) were also achieved.
New chelating resins immobilizing carboxymethylated polyallylamine (CM-PAA) were prepared by immobilizing PAAs with some molecular weights on methacrylate resins and then carboxymethylating a part of amino groups in the PAAs using various amounts of sodium monochloroacetate. The molecular weight of PAA barely affected both the amount of PAA immobilized on the resin and the relationship between the carboxymethylation (CM) rate and the ratio of the amount of monochloroacetate used in the CM step. The selectivity of CM-PAA resin for solid-phase extraction of trace elements was almost the same as that of a resin immobilizing carboxylymethylated polyethyleneimine; 10 elements, namely Cd, Co, Cu, Fe, Mo, Ni, Pb, Ti, V, and Zn, could be quantitatively recovered over a wide pH range and alkali and alkaline earth elements were scarcely extracted under acidic and neutral conditions. The CM-PAA resin was applicable to the separation and preconcentration of the elements in a certified reference material (Waste Water, EU-L-1) and a real environmental water sample (ground water).
The removal efficiency of Cs from contaminated soil depends on its chemical species bound with the soil components. Therefore, in this study, we observed the elution behavior of Cs based on speciation analysis in a Cs removal experiment conducted on contaminated soils. The treatment method was optimized using simulated contaminated soil and applied to actual contaminated soil on a large scale as well. The elution rate of Cs was approximately 50% or more in both actual and simulated contaminated soil using the optimized treatment method. From the obtained results, a robust treatment method using an eluting reagent and a magnetic adsorbent with low energy costs is proposed. Additionally, the usefulness of speciation analysis in decontamination studies was confirmed.
We developed an ion-associate phase (IAP)-extraction/acid back-extraction system for the preconcentration and atomic spectrometric determination of lithium trace amounts in water. The chelating reagent for lithium also works as a constituent of the extraction phase. The lithium in a 10 mL sample solution was converted through a chelate complex reaction with 2,2,6,6-tetramethyl-3,5-heptanedione (HDPM). The addition of a benzyldimethyltetradecylammonium ion caused the formation of IAP suspension in the solution. Centrifugation of the solution led to the isolation of a liquid organic phase and the lithium complex was extracted as the upper phase from the centrifuge tube. After the aqueous phase was removed, lithium was back-extracted with a 400 μL nitric acid solution from the IAP. The acid phase was measured using liquid-electrode-plasma atomic-emission-spectrometry (LEP-AES) or graphite-furnace atomic-absorption spectroscopy (GF-AAS). The detection limits were 0.02 mg/L for LEP-AES and 0.02 μg/L for GF-AAS. This system was applied to the determination of environmental water. The HDPM in the organic phase was reusable.
Wildfires that expose the soil organic layer to high heat levels can alter soil organic matter (SOM), which includes water-soluble organic matter (WSOM) components. Various evaluation methods were used to characterize and quantify the effects of high heat levels on SOM and WSOM, including ion chromatography, thermogravimetry–differential thermal analysis (TG-DTA), colorimetry, elemental analysis, pyrolysis–gas chromatography–mass spectrometry using tetramethylammonium hydroxide (TMAH-py-GC/MS), total organic carbon (TOC) analysis, three-dimensional excitation-emission matrix (3DEEM) spectroscopy, and high-performance size-exclusion chromatography. In this study, we applied each of these evaluation methods using soil samples that were collected from broadleaf, coniferous, and bamboo forests and peatland in Japan and exposed to different initial high heat levels. Based on the TG-DTA results, the remaining mass in select soil samples markedly decreased when reheated to approximately 200°C. Comparatively, the TMAH-py-GC/MS results indicated a drastic change in SOM composition and the production of low molecular organic components (<C10) at this temperature. The TOC analysis results also indicated a significant increase in the proportion of WSOM. Colorimetry and elemental analysis results indicated that the soil color was dependent upon the initial heating temperature and was related to the H/C and O/C atomic ratios. The results of this study can form the basis for future similar studies for accurately characterizing and quantifying the heat effects on soil, and the effects of increasing wildfires due to climate change.
Recovery of copper was attempted from municipal waste incineration ashes using acid extraction and electrodeposition by a flow-through type electrolysis cell (FE). Efficient extraction of copper from the incineration ash was obtained using 0.5 mol L−1 sulfuric acid, i.e., copper extraction rate: 78% from bottom ash and 88% from fly ash. The copper in the 10-fold diluted extractant injected into the FE was quantitatively adsorbed by applying –0.4 V and was quantitatively desorbed by eluting with nitric acid.
Electrodialytic separation of Cr(VI) and Cr(III) followed by graphite furnace atomic absorption spectrometry for monitoring of soil extraction was studied. The sensitivity was improved by in-line purification of the solutions and bi-polar pulse cleaning. The detection limit for both Cr(VI) and Cr(III) was 0.01 μg L−1. The system was successfully used to monitor the concentration change during soil extraction with dual solution line filtration. The results demonstrate the difference in concentration changes with the different sources of Cr(VI).
An automatic pH adjustment instrument was developed for the preparation of analytical samples prior to solid phase extraction, which is widely used as a pretreatment technique for the separation of sample matrixes and preconcentration of elements for analysis. Real-time monitoring of the sample pH condition was performed by observing the light signal intensity of the pH-sensitive wavelength of the pH indicating reagent. A light of pH-insensitive wavelength was selected as the reference light to cancel the signal intensity variation of the pH-sensitive light due to the difference of pH indicating reagent concentration, possible difference in transparency of sample vessels, and minute fluctuation of the light source. The pH condition was elevated by automatic addition of ammonia solution using a nebulizer in the flow line of which an electromagnetic valve was equipped. Open and close operation of the electromagnetic valve was controlled based on the difference between the real-time pH condition and the target pH condition. The effectiveness of the instrument was confirmed by using various pH indicating reagents and by analyzing trace elements in a seawater certified reference material.
The environmentally friendly electrokinetic process was investigated using model contaminated soil with Pb and humic acid. Although humic acid has a negative charge, it moved toward the cathode side by electroosmotic flow. The removal efficiency of Pb from model contaminated soil was 48.0% under 1 V/cm of the potential gradient after 72 h of operation, while it improved to 72.6% with humic acid. These results indicated that humic acid has high potential for application in the environmentally friendly remediation of soil.
Environmental contaminations of 129I were continuously monitored in various sample preparation rooms for accelerator mass spectrometry at the University of Tsukuba. Monitoring of 129I was performed in the rooms used for the treatment of samples in the past, in order to compare with the results obtained in the sample preparation rooms. Ambient levels of atmospheric 129I in each room were estimated from the measured concentrations in the alkali trap solutions. This article reports the results of one year of monitoring the temporal changes of stable iodine (127I) and 129I contamination rates in the alkali trap solutions. It was found that 129I contamination rates were lower than approximately 104 atoms cm−2 day−1 in the rooms where ether no samples or only samples with environmental background levels of 129I were handled. Values from 104 to 105 atoms cm−2 day−1 were recorded in another room where environmental samples, such as the samples derived from nuclear power plant accidents, were treated. Higher levels of 129I, ranging from 106 to 107 atoms cm−2 day−1, were recorded in rooms used for treating neutron-activated iodine. The experimental results show that the 129I level depended on the 129I sample-preparation histories for the respective rooms. It is possible to estimate the 129I contamination risk from the atmosphere to the samples by knowing the 129I level in the preparation room.
A simple digestion method for a mixed cellulose membrane filter in order to analyze trace elements in aerosols was examined. The determination of Cu, Fe and Ni in the certified reference materials of China loess (CJ-1) could be conducted using the digestion method. Trace elements in aerosols smaller than 10 μm size collected at Tokushima City and near mountain areas for each season were determined as a water-soluble fraction and all components by the digestion method. Back trajectory analysis implied that the contribution from the Asian continent was larger in the winter and spring than the summer. Systematic changes in the trace element compositions for each season were not observed, except for Fe, Th and U. Water-soluble components in aerosols at Tokushima City showed higher concentrations of all trace elements than those of the mountain areas. For aerosols in Tokushima City and near to the mountain areas, As, Bi, Cd, Cu and Pb were mainly derived from anthropogenic sources, whereas Ba, Co, Cs, Ga, Mn, Rb, Sr, Th, U and V were derived from natural crustal sources. The origin of Pb and Cd was considered based on the Pb/Cd ratio.