Biodegradation and Structural Modification of Humic Acids in a Compost Induced by Fertilization with Steelmaking Slag under Coastal Seawater, as Detected by TMAH-py-GC/MS, EEM and HPSEC Analyses.

The compost's humic acid (HA) content decreased when it was fertilized in coastal seawater with steelmaking slag, as confirmed. This study clarified the cause for this change by a detailed analysis of the structural changes in HAs based on the TMAH-py-GC/MS, HPSEC, and 3D-EEM spectra. An increase in the levels of pyrolysates of tannic acid with a low polymerization degree was attributed to the biodegradation of a high polymerized aromatic structure. Moreover, analyses of 3D-EEM, supported by HPSEC, indicated that approximately 20 kDa of the fluorescent matter was generated at the protein-like peaks (Ex/Em = 220/340 and 275/350 nm) in HAs derived from a mixture of compost with steelmaking slag. It would be caused due to the formation of HAs from the bacterial by-product by a catalytic reaction of the steelmaking slag. From these findings reported herein, we conclude that bio-degradation was a major reason for the decreased HA content, and the formation of HA from a part of the degradation products. This would be a reason for the structural modification of HA under the seawater condition.

Landside tritium leakage over through years from Fukushima Dai-ichi nuclear plant and relationship between countermeasures and contaminated water.

There has been tritium groundwater leakage to the land side of Fukushima Dai-ichi nuclear power plants since 2013. Groundwater was continuously collected from the end of 2013 to 2019, with an average tritium concentration of approximately 20 Bq/L. Based on tritium data published by Tokyo Electric Power Company Holdings (TEPCO) (17,000 points), the postulated source of the leakage was (1) leaks from a contaminated water tank that occurred from 2013 to 2014, or (2) a leak of tritium that had spread widely over an impermeable layer under the site. Based on our results, sea side and land side tritium leakage monitoring systems should be strengthened.

Mechanism of the Elution of Iron from a Slag-Compost Fertilizer for Restoring Seaweed Beds in Coastal Areas-Characteristic Changes of Steelmaking Slag and Humic Acids Derived from the Fertilizer during the Elution Process.

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.

Oxidation of antimony (III) in soil by manganese (IV) oxide using X-ray absorption fine structure.

The oxidation of antimony (III) in soils was studied using X-ray absorption fine structure (XAFS) spectra. An andosol soil sample and artificial soil samples (SiO2 blended with iron (III) hydroxide and manganese (IV) oxide) were used herein. After adding antimony (III) oxide to all soil samples, the oxidation process was observed by recording the XAFS spectra of Sb K-edge, Fe K-edge, and Mn K-edge. The results indicated that manganese (IV) oxide played an important role in the oxidation of Sb(III); however iron (III) hydroxide was not directly related to the reaction. During a 2-hr continuous Sb K-edge X-ray absorption near edge structure (XANES) measurement with an interval of 1min of one of the artificial soil samples (SiO2+MnO2+Sb2O3), a pseudo-first-order reaction was determined with an average estimated rate of 0.52±0.04hr-1. Compared to the lower oxidation rate of andosol, it is suggested that because of the low concentration of Mn(IV) in natural soils, the oxidation process of Sb(III) might be relatively slow and require more time to convert Sb(III) to Sb(V).

Reduction process of Cr(VI) by Fe(II) and humic acid analyzed using high time resolution XAFS analysis.

The initial reduction behavior of Cr(VI) to Cr(III) has not been clearly understood due to its rapid reduction reaction. In order to study the reduction process of Cr(VI) in detail, we applied quick X-ray absorption fine structure (QXAFS) analysis to observe how Cr(VI) was reduced to Cr(III) by Fe(II) and humic acid (HA) with time. The Cr(VI) concentration was analyzed every 60s, and the plots of ln(Cr(VI)/Cr(VI)0) versus time were used to evaluate the reduction process based on their linearity. Reduction by Fe(II) showed a linear relation, whereas reduction by HA showed a nonlinear relation. With combined Fe(II) and HA, the linearity was unlike those of Fe(II) and HA individually. The reduction rate was not constant. The structure of Fe(II) produced by HA during the Cr(VI) reduction was investigated by using Mössbauer spectroscopy, which showed that Fe(II) produced by HA reduction of Fe(III) had the same structure as the initial Fe(II). HA can reduce Fe(III) back to Fe(II), and reproduced Fe(II) reduces Cr(VI). For Cr(VI) reduction by combined Fe(II) and HA, each reductant contribute differently: Fe(II) directly contributes to the Cr(VI) reaction, whereas HA reduces both Cr(VI) and Fe(III).

Deposition of fission and activation products after the Fukushima Dai-ichi nuclear power plant accident.

The Great Eastern Japan Earthquake on March 11, 2011, damaged reactor cooling systems at Fukushima Dai-ichi nuclear power plant. The subsequent venting operation and hydrogen explosion resulted in a large radioactive nuclide emission from reactor containers into the environment. Here, we collected environmental samples such as soil, plant species, and water on April 10, 2011, in front of the power plant main gate as well as 35 km away in Iitate village, and observed gamma-rays with a Ge(Li) semiconductor detector. We observed activation products ((239)Np and (59)Fe) and fission products ((131)I, (134)Cs ((133)Cs), (137)Cs, (110m)Ag ((109)Ag), (132)Te, (132)I, (140)Ba, (140)La, (91)Sr, (91)Y, (95)Zr, and (95)Nb). (239)Np is the parent nuclide of (239)Pu; (59)Fe are presumably activation products of (58)Fe obtained by corrosion of cooling pipes. The results show that these activation and fission products, diffused within a month of the accident.

Chlorine isotope fractionation associated with volcanic activity at the Kusatsu-Bandaiko hot spring in Japan.

Stable chlorine isotope compositions (delta(37)Cl, per-mil: per thousand, vs. a standard sample of sea water) of Kusatsu-bandaiko hot water samples, taken regularly in the years between 1974 and 1995 in the Kusatsu-Shirane volcanic region, Japan, were measured mass-spectrometrically. The results show that the delta(37)Cl values of the waters taken before 1984 were at around-0.12 per thousand, whereas those after 1984 were at around+0.18 per thousand. The delta(37)Cl values are thus distinct across 1984, which is consistent with the classification by the Cl to S molar ratio (Cl/S): the higher the Cl/S ratio, the larger the delta(37)Cl value. The delta(37)Cl value increased as much as 0.30 per thousand during 5 years between 1980 and 1984. This isotopic enrichment is likely correlated with increasing Cl/S ratios, suggesting that the heavier isotope ((37)Cl) may have preferentially increased in the original Cl source of the hot spring across 1984 when volcanic activity likely increased at Mt Kusatsu-Shirane.

Column chromatographic boron isotope separation at 5 and 17 MPa with diluted boric acid solution.

Boron isotopic fractionation factor (S) between boron taken up in strongly basic anion exchange resin and boron in aqueous solution was determined by breakthrough column chromatography at 5 and 17 MPa at 25 degrees C, using 0.1 mM boric acid solution as feed solution. The S values obtained were 1.018 and 1.012, respectively, which were smaller than the value reported by using the same chromatographic method at the atmospheric pressure at 25 degrees C with the boron concentration of 10mM, but were larger than the values under the same condition with much higher concentration of 100 and 501 mM. Calculations based on the theory of isotope distribution between two phases estimated that 21% (5 MPa) and 47% (17 MPa) of boron taken up in the resin phase was in the three-coordinated B(OH)(3)-form, instead of in the four-coordinated B(OH)(4)-form, at high pressures even with a very diluted boric acid solution. We discussed the present results by introducing (1) hydration and (2) a partial molar volume difference between isotopic molecules. Borate may have been partially dehydrated upon transfer from the solution phase to the resin phase at high pressures, which resulted in smaller S values compared with those at the atmospheric pressure. Instead, it may be possible that the difference in the isotopic partial molar volume difference between B(OH)(3) and B(OH)(4)(-) caused the S value to decrease with increasing pressure.

Anion-exchange chromatographic study of the chlorine isotope effect accompanying hydration.

The single-stage separation factor for chlorine isotopes ((35)Cl and (37)Cl) was determined to be 1.00034 by anion exchange chromatography on a 4.5-m column operated in reverse breakthrough manner at 25 degrees C. This value is in good agreement with those obtained in our previous works. It was confirmed that the lighter isotope ((35)Cl) was preferentially fractionated into the resin phase, whereas the heavier isotope ((37)Cl) partitioned into the aqueous phase. This observation, however, contradicts the experimental results for Cl isotope fractionation during NaCl precipitation and the recent theoretical results on Cl isotope fractionation: the (37)Cl isotope selectively enriched into the solid phase and not into the aqueous phase. This discrepancy is discussed based on the theory of isotope distribution between two phases. It is suggested that the chromatographic results reflect an isotope effect accompanying hydration rather than an isotope effect due to a phase change, whereas the reverse is the case for the results in the NaCl precipitation study.

An anion-exchange chromatographic study on boron isotopic fractionation at 2 MPa at 293 K.

To study boron isotopic fractionation at high pressure, column chromatography operated in the breakthrough manner was performed at 2.0 MPa at 25.0 degrees C. The fractionation factor (S) between boron adsorbed onto strongly basic anion-exchange resin and boron in solution was obtained as 1.013, which was smaller than the values at 0.1 MPa (atmospheric pressure) found in literature. The pressure dependence of S was discussed based on the polymerization of boron in the solution and resin phases and on the occurrence of the pressure dependent isotope effect relating to the molar volume changes of boron species upon isotope substitution.