Uptake and distribution of 90Sr and stable Sr in rice plants

The stable Sr content in the aboveground parts of rice plants at various growth stages, and the distributions of 90Sr and stable Sr in rice plant components, such as polished rice, rice bran, hull, straw and root, at harvest time, were determined. The total Sr content in the aboveground rice plants was dependent on the growth stage and followed the sigmoidal shape of the growth curve. The concentration of 90Sr among the different components of rice plants varied within two orders of magnitude, whereas the 90Sr/Sr concentration ratio had a constant value. Therefore, the translocation rate of 90Sr in rice plants had similar values to that of stable Sr. However, the 90Sr/Sr concentration ratio for the rice plants was different for each study site. Only 0.6% of the total Sr was found in polished rice, while more than 99% was found in the non-edible components, of which 87% was present in the straw. These findings suggest that 90Sr in the non-edible parts could have been transferred to humans through the soil-plant system and/or feed-livestock pathway. The soil-to-plant transfer factor of 90Sr in polished rice was 0.0021 +/- 0.00007, which was two orders of magnitude lower than that in the straw. The percentage of 90Sr removed from the upper soil layer to the aboveground biomass of rice plants at harvest time was calculated as 0.094%. It is possible that approximately 0.1% of the total 90Sr content in the surface soil layer is removed from the soil-plant system by human activities every year.     

Effect of Chlorella pyrenoidosa on fecal excretion and liver accumulation of polychlorinated dibenzo-p-dioxin in mice

The effect of Chlorella pyrenoidosa on fecal excretion and liver accumulation of polychlorinated dibenzo-p-dioxin in C57BL/6N mice administered dioxin was examined. Mice were administered 2.2 microg of 1,2,3,4,7,8-hexachlorodibenzo-p-dioxin (H6CDD) dissolved in corn oil once after a period of acclimatization, after which they were fed either a basal diet, a 10% C. pyrenoidosa diet, or a 10% Spinach diet, for five weeks. Among mice fed the 10% C. pyrenoidosa diet, cumulative fecal excretion of H6CDD over the first week following administration was significantly greater (9.2-fold) than that observed among mice fed the basal diet. Moreover, excretion during the fifth week following administration of H6CDD was still significantly greater (3.1-fold) among mice fed the 10% C. pyrenoidosa diet than among mice fed the basal diet. Five weeks after administration of H6CDD, liver accumulation of H6CDD in mice fed the 10% C. pyrenoidosa diet was significantly less than that observed among mice fed either the basal diet and the Spinach diet (by 27.9% and 34.8%, respectively). These findings suggest that C. pyrenoidosa may be useful in inhibiting the absorption of dioxins via food and the reabsorption of dioxins stored already in the body in the intestinal tract, thus preventing accumulation of dioxins within the body.     

Concentration and specific activity of fallout 137Cs in extracted and particle-size fractions of cultivated soils

Fallout (137)Cs and stable Cs in soils were separated with two extractants (1M CH(3)COONH(4) solution and 0.8M CH(3)COONH(4) in 5% HNO(3) solution after H(2)O(2) oxidization). The residue remaining after removal of the oxidizable organic-bound fraction was separated into the particle-size fractions including clay, silt, fine sand and coarse sand with a sieving and sedimentation method. Then, the concentrations of (137)Cs and stable Cs in the extracted fractions and the particle-size fractions were determined. The (137)Cs contents in the exchangeable and organic-bound fractions in the soil were approximately 10 and 20%, respectively. The (137)Cs content in the strongly bound fraction was about 70%, and the concentration of (137)Cs in the clay was the richest among the particle-size fractions. The specific activity of (137)Cs (concentration ratio of fallout (137)Cs/stable Cs) decreased in the order exchangeable, organic-bound and strongly bound fractions. The data suggest that equilibrium between (137)Cs and stable Cs was not reached among those fractions, even though most of the (137)Cs that had been deposited on the soil was derived from fallout weapons tests that occurred several decades ago. The concentration of (137)Cs among the particle-size fractions in each soil was different, whereas the specific activity of (137)Cs in the particle-size fractions had a relatively similar value.     

Hydroxylation of bisphenol A by hyper lignin-degrading fungus Phanerochaete sordida YK-624 under non-ligninolytic condition

Bisphenol A (BPA) is one of the representative compounds of the endocrine disrupting compounds group and the highest volume chemicals produced worldwide. As a result, BPA is often detected in many soil and water environments. In this study, we demonstrated the transformation of BPA from liquid cultures inoculated with hyper lignin-degrading fungus Phanerochaete sordida YK-624. Under non-ligninolytic condition, approximately 80% of BPA was eliminated after 7 d of incubation. High-resolution electrospray ionization mass spectra and nuclear magnetic resonance analyses of a metabolite isolated from the culture supernatant suggested that BPA was metabolized to hydroxy-BPA, 4-(2-(4-hydroxyphenyl)propan-2-yl)benzene-1,2-diol, which has a much lower estrogenic activity than BPA. In addition, we investigated the effect of the cytochrome P450 inhibitor piperonyl butoxide (PB) on the hydroxylation of BPA, markedly lower transformation activity of BPA was observed in cultures containing PB. These results suggest that cytochrome P450 plays an important role in the hydroxylation of BPA by P. sordida YK-624 under non-ligninolytic condition.     

Design optimization and standardization of an environmental availability test under both acidic and alkaline conditions

The objective of this study was to design a procedure for an environmental availability test under both acidic and alkaline conditions for solid wastes and recycled materials and products. The procedure was designed on the basis of the Dutch availability test NEN 7371. Bottom ash from a municipal solid waste incinerator and copper slag were used as test materials. The influences of the type and intensity of liquid stirring apparatus and the open area ratio of the top of the leaching vessel were investigated experimentally, and partial least-squares modeling was applied as multivariate data analysis for the simultaneous evaluation of the three leaching conditions. Interlaboratory validation was then carried out with the participation of seven laboratories in accordance with JIS Z 8402-2/ISO 5725-2. Both repeatability and reproducibility were found to be acceptable, but precise calibration of the pH electrode is required. The proposed procedure will provide sufficient accuracy as a standard test method.     

Effect of the counter anion of cesium on foliar uptake and translocation

Direct deposition of radioactive material onto crops is one important pathway for safety assessment of radionuclides released from nuclear facilities. Foliar uptake of Cs by radish (Raphanus sativus L. cv. Redchim) was studied by applying droplets of Cs solution (CsCl or CsNO₃) on an upper leaf surface. The uptake of Cs was strongly affected by counter anions of Cs in the applied solution. Approximately 80% of Cs was absorbed for CsCl solution, while only 20% was absorbed for CsNO₃. The partition of absorbed Cs between leaf and root tuber was quite similar for both Cs compounds, which indicated that behavior of the absorbed Cs in radish was the same for both.     

Economic analysis of gradual “social exhaustion” of waste management capacity

This article proposes to analyze the quantitative effects of a gradual physical and “social” exhaustion of a landfill site on an equilibrium waste management service. A gradual social exhaustion of a landfill is defined here as an upward shift of a “subjective factor” associated with the amount of waste, based on the plausible hypothesis that an individual will not accept excessive presence of landfilled waste. Physical exhaustion occurs when the absolute capacity of a landfill site decreases. The paper shows some numerical examples using specific functions and parameters, and proposes appropriate directions for three policy objectives: to decrease the equilibrium waste disposal, to increase the economic surplus of the individual and/or the waste management firm, and to lower the equilibrium collection fee.     

Alkaline solution neutralization capacity of soil

Alkaline eluate from municipal solid waste (MSW) incineration residue deposited in landfill alkalizes waste and soil layers. From the viewpoint of accelerating stability and preventing heavy metal elution, pH of the landfill layer (waste and daily cover soil) should be controlled. On the other hand, pH of leachate from existing MSW landfill sites is usually approximately neutral. One of the reasons is that daily cover soil can neutralize alkaline solution containing Ca²⁺ as cation. However, in landfill layer where various types of wastes and reactions should be taken into consideration, the ability to neutralize alkaline solutions other than Ca(OH)₂ by soil should be evaluated. In this study, the neutralization capacities of various types of soils were measured using Ca(OH)₂ and NaOH solutions. Each soil used in this study showed approximately the same capacity to neutralize both alkaline solutions of Ca(OH)₂ and NaOH. The cation exchange capacity was less than 30% of the maximum alkali neutralization capacity obtained by the titration test. The mechanism of neutralization by the pH-dependent charge can explain the same neutralization capacities of the soils. Although further investigation on the neutralization capacity of the soils for alkaline substances other than NaOH is required, daily cover soil could serve as a buffer zone for alkaline leachates containing Ca(OH)₂ or other alkaline substances.     

Effect of exposure test conditions on leaching behavior of inorganic contaminants from recycled materials for roadbeds

Throughout the utilization of recycled materials, weathering factors such as humidity, gas composition and temperature have the potential to change the material properties and enhance the release of inorganic contaminants. In this research, the effects of weathering factors on recycled gravel materials for roadbeds were evaluated by applying three kinds of accelerating exposure tests: freezing–melting cycle test, carbonation test, and dry–humid cycle test. The effects of exposure tests were determined by X-ray diffraction (XRD) analysis and serial batch leaching test, making it possible to identify the change in release mechanisms. Sixteen elements, mainly metals, were investigated. Tested samples were molten slag from municipal solid waste, molten slag from automobile shredded residue, and crushed natural stone.After the exposure tests, the increase of cumulative release in the leaching test was generally less than 2.0 times that of the samples without the exposure test. Among the three test conditions, freezing–melting showed a slightly higher effect of enhancing the release of constituents. XRD analysis showed no change in chemical species. From these results, it was determined that the stony samples were stable enough so that their properties were not significantly changed by the exposure tests.