Removal of technetium from solution by algal flagellate Euglena gracilis

Based on limited data for the removal of radioactive (99)Tc by freshwater phytoplankton, it has been thought that phytoplankton are unsuitable for remediation of (99)Tc-contaminated waters. This work sought to verify the validity of this assumption by studying the removal of (99)TcO(4)(-) by freshwater and brackish water phytoplankton. The phytoplankton used were Euglena gracilis, Chlamydomonas pulsatilla, Chlorella vulgaris, and Spirulina platensis. Each of them was incubated for 63 d, and the removal of (99)Tc from solution was periodically determined. Significant removal of (99)Tc was observed only for E. gracilis, and the maximum removal was 70% of the total (99)Tc added. The killed cells of E. gracilis, however, removed hardly any (99)Tc. When E. gracilis cells were washed with fresh culture medium, only 13% of the total (99)Tc was desorbed. These results suggested that intracellular uptake of (99)Tc by E. gracilis occurred. These results are the first documented example of significant removal of (99)Tc by planktonic microalgae.     

Uptake and distribution of iodine in rice plants

Rice (Oryza sativa L.) plants were cultivated in an experimental field and separated at harvest into different components, including polished rice, rice bran, hull, straw, and root. The contents of iodine in these components and the soil were determined by inductively coupled plasma-mass spectrometry and radiochemical neutron activation analysis, respectively. Iodine content varied by more than three orders of magnitude among the plant components. Mean concentration of iodine in the entire plants was 20 mg kg(-1) dry weight, and the concentration of iodine in the surface soil (0-20 cm depth) was 48 mg kg(-1). The highest concentration of iodine (53 mg kg(-1) dry weight) was measured in root and the lowest concentration (0.034 mg kg(-1) dry weight) in polished rice. While the edible component (polished rice) accounted for 32% of the total dry weight, it contained only 0.055% of iodine found in the entire rice plants. Atmospheric gaseous iodine (5.9 ng m(-3)) was estimated to contribute <0.2% of the total iodine content in the biomass of rice plants; therefore nearly all of the iodine in the rice plants was a result of the uptake of iodine from the soil. The content of iodine in the aboveground part of rice plants was 16 mg kg(-1) dry weight and the percentage of iodine transferred per cropping from the soil into the aboveground biomass corresponded to 0.27% (20 mg m(-2)) of the upper soil layer content.     

Polychlorinated dibenzo-p-dioxins,polychlorinated dibenzofurans and non-ortho,mono-ortho chlorine substituted biphenyls in Japanese human liver and adipose tissue

We measured PCDDs/DFs levels in Japanese human livers and adipose tissues in 1999, and TEQ were calculated with WHO TEF. The mean total levels of PCDDs/DFs in livers and adipose tissues were 57 pg TEQ/g on a lipid basis and 49 pg TEQ/g on a lipid basis, respectively. 1,2,3,6,7,8-HxCDD, 1,2,3,4,6,7,8-HpCDD, OCDD, 2,3,4,7,8-PeCDF, 1,2,3,4,7,8-HxCDF, 1,2,3,6,7,8-HxCDF, 2,3,4,6,7,8-HxCDF, 1,2,3,7,8,9-HxCDF and 1,2,3,4,6,7,8-HpCDF concentrations in livers considerably differed from those in 1989 (p < 0.05). The mean non-ortho-chlorine substituted biphenyls levels showed 20 pg TEQ/g on a lipid basis and 17 pg TEQ/g on a lipid basis in livers and adipose tissues, respectively. In livers, the mean of 3,3',4,4'-TCB concentrations was 131 pg/g on a lipid basis, and 7.7-fold higher than that in 1989. The mean total mono-ortho-chlorine substituted biphenyls level was 13.0 pg TEQ/g on a lipid basis in livers and 21.6 pg TEQ/g on a lipid basis in adipose tissues. 3,3',4,4',5-PeCB and 3,3',4,4',5,5'-HxCB levels decreased in adipose tissues, and 3,3',4,4',5-PeCB level only decreased in livers. PCDDs, PCDFs, and mono- and non-ortho-chlorine substituted biphenyls levels may have decreased in livers and adipose tissues because of a governmental policy on dioxins discharge for the decade. Then, we estimated the correlations of PCDDs, PCDFs and the related compound levels between livers and adipose tissues. The correlative PCDDs congeners may have had a similar behavior to that between liver and adipose tissue. On the contrary, most PCDFs isomers may have different behavior between liver and adipose tissue, while 2',3,4,4',5-PeCB (IUPAC No. 123) may also have a different behavior between liver and adipose tissue.     

Deposition processes of ionic constituents to snow cover

Atmospheric deposition is an important removal process of aerosol particles and gases from the atmosphere. To elucidate the relative contributions of wet and dry processes and in-cloud and below-cloud scavenging based on deposition amounts in winter at Mt. Tateyama, central Japan, we obtained daily samples (December, 2006–March, 2007) of size-segregated aerosol particles and precipitation at Senjyugahara (SJ; 475 m a.s.l.) and vertical samples of spring snow cover at Murododaira (MR, 2450 m a.s.l., 13 km distance from SJ) on the western flank of Mt. Tateyama. The NH₄⁺ and nssSO₄^2? in aerosols were mostly found in the fine fraction (<2 μm), although Na⁺, NO₃^?, and nssCa²⁺ were mainly detected in the coarse fraction (>2 μm). Average ionic concentrations (μg g^?1) in precipitation at SJ were higher about 3.8 for Na⁺ and nssCa²⁺, 3.4 for NO₃^?, 3.7 for NH₄⁺, 2.5 for nssSO₄^2? than those at MR, whereas cumulative precipitation amounts at SJ and MR were, respectively, 84 and 175 cm of water equivalent. Wet and dry deposition amounts during the study period were estimated for sites using size-segregated aerosol data, winter averages of HNO₃, NH₃, and SO₂ concentrations, and dry deposition velocities. Particle-dry deposition comprised about 3% (Na⁺) to 11% (NH₄⁺) of the total deposition at MR. The maximum amounts of gas dry deposition were estimated, respectively, as 4, 13, and 3% of the total deposition at MR for NH₄⁺, NO₃^?, and nssSO₄^2?. The relative contributions of below-cloud scavenging (BCS) between MR and SJ were estimated as considering the wet only deposition amount at MR. Higher contributions of BCS were obtained for Na⁺ (56%) and nssCa²⁺ (45%), whereas BCSs for NH₄⁺, NO₃^?, and nssSO₄^2? were lower than 28%. Ionic constituents existing predominantly in the coarse fraction showed a large contribution of BCS.     

Polychlorinated dibenzo-p-dioxins and related compounds: The blood levels of young Japanese women

We investigated PCDDs and related compounds in the blood of young Japanese women, approximately 20 years of age, who had not yet had children, and discussed how the TEQ level of PCDDs and related compounds in their blood may affect the next generation. Means of total TEQ levels were 0.063 pg/g for whole blood basis and 21 pg/g for lipid basis. TEQ of PCDDs, PCDFs and coplanar PCBs accounted for about 43, 34 and 23% of the total TEQ in the whole blood basis, respectively. In the lipid basis, their values were about 44, 34 and 22%, respectively. Previously, we investigated PCDDs and related compounds levels in mother's breast milk, lymphocyte subpopulation and thyroid function of their children, and found negative correlations between the TEQ level of PCDDs and related compounds and CD4+/CD8+, and/or the TEQ level of PCDDs and related compounds and the T₄ level in 36 mothers and children. Of these cases, the average age was approximately 28 years. PCDDs and related compounds may be related to immunopathy, such as atopic dermatitis. The effects of PCDDs and related compounds on babies of young Japanese women are important and must be further evaluated.     

The influence of paddy soil drying on Tc insolubilization by bacteria

Tc insolubilization in four soils samples was compared by pre-incubating them in both dry and wet states, then measuring Tc concentrations in solution when the samples were saturated with an excess of water spiked with 99Tc. Soils pre-incubated in a dry state showed higher Tc insolubilization than soils incubated in a wet state. To clarify the difference in Tc insolubilization, Eh, bacterial abundances, and bacterial species compositions in the dry and wet ponding water samples were determined. For the wet ponding water samples, Eh values were forced to decrease, but no increase in Tc insolubilization was observed. The dry and wet ponding water samples had similar numbers of bacteria. However, denaturing gradient gel electrophoresis analysis revealed that they had different bacterial species compositions. These results suggested the difference in bacterial species compositions would account for the difference in Tc insolubilization.     

Concentrations and their ratio of (222)Rn decay products in rainwater measured by gamma-ray spectrometry using a low-background Ge detector

The concentrations and the concentration ratios of individual short-lived (222)Rn decay products ((214)Pb and (214)Bi) in rainwater were measured at Kumatori village (34.39 degrees N, 135.35 degrees E, approximately 70 m above sea level) in Osaka, Japan, by gamma-ray spectrometry using a low-background Ge detector. The dependence of the time variations of the concentrations and their ratios on rainfall rate was investigated. It was observed that the concentrations were negatively correlated with the rainfall rate in some rainfall events, and that there was no clear correlation in other rainfall events. The changes in the dependence of the concentration on the rainfall rate occurred after the passage of a cold front during a single rainfall event. The concentration ratios showed a weak negative correlation with the rainfall rate for most of the observed rainfall events. A scavenging model was designed in this study in order to explain the observation results. Based on the relationship between the concentrations of (214)Pb and (214)Bi in the rainwater and the rainfall rate for an individual rainfall event, the increase in the environmental gamma-ray dose rate from (214)Pb and (214)Bi deposited on the ground was calculated, and the calculated increase agreed well with that observed by the in situ measurement on flat ground.     

Effects of donor age and contamination level of dioxins and related chemicals on frequency of sister chromatid exchanges in human lymphocytes cultured in vitro

Frequencies of sister chromatid exchanges (SCEs) of human lymphocytes in control (DMSO treated) and 7,8-benzoflavone (ANF) treated cultures were measured in 39 healthy Japanese people and examined in connection with donor age. Both the control (baseline) and ANF induced SCE rates were significantly enhanced with age and highly positive correlation was observed between them. Therefore, in vivo aging seemed to have some effects on the frequencies of SCEs in human lymphocytes cultured in vitro. Concentrations of PCDDs, PCDFs and Co-PCBs in the blood and sebum of face were determined in the same Japanese subjects. Significantly positive correlation was observed between the blood and sebum in their total TEQ levels. Hence, PCDDs, PCDFs and Co-PCBs, which have been contaminating human bodies, are considered proportionally excreted from the sebum of face or body. Their total TEQ concentrations were also meaningfully increased with donor age in the sebum of face as well as in the blood. Either the baseline or ANF induced SCE frequencies was not enhanced with the total TEQ levels in the blood. Therefore, background levels of their contamination seem not to affect the SCE rates of the lymphocytes in the control and ANF treated cultures.     

Radiocarbon and stable carbon isotope compositions of chemically fractionated soil organic matter in a temperate-zone forest

To better understand the role of soil organic matter in terrestrial carbon cycle, carbon isotope compositions in soil samples from a temperate-zone forest were measured for bulk, acid-insoluble and base-insoluble organic matter fractions separated by a chemical fractionation method. The measurements also made it possible to estimate indirectly radiocarbon ((14)C) abundances of acid- and base-soluble organic matter fractions, through a mass balance of carbon among the fractions. The depth profiles of (14)C abundances showed that (1) bomb-derived (14)C has penetrated the first 16cm mineral soil at least; (2) Delta(14)C values of acid-soluble organic matter fraction are considerably higher than those of other fractions; and (3) a significant amount of the bomb-derived (14)C has been preserved as the base-soluble organic matter around litter-mineral soil boundary. In contrast, no or little bomb-derived (14)C was observed for the base-insoluble fraction in all sampling depths, indicating that this recalcitrant fraction, accounting for approximately 15% of total carbon in this temperate-zone forest soil, plays a role as a long-term sink in the carbon cycle. These results suggest that bulk soil organic matter cannot provide a representative indicator as a source or a sink of carbon in soil, particularly on annual to decadal timescales.     

Sorption behavior of selenium on humic acid under increasing selenium concentration or increasing solid/liquid ratio

The sorption of selenium (Se) on humic acid (HA) was investigated in order to better understand the fate of stable and radioactive Se in soils and sediments. An ultrafiltration technique was used to determine size distributions of HA-sorbed-Se when increasing Se concentration and solid/liquid ratio. The results showed that the Se sorption onto HA followed the Freundlich isotherm. No solid/liquid ratio-dependence was observed especially when <3 kDa molecular size fraction was used from solid/liquid separation. The Freundlich isotherm parameters K(F) and n obtained using the <3 kDa molecular size fraction for solid/liquid separation were 3.7 x 10(2) and 0.82, respectively. In addition, since dissolved HA increased with decreased ionic strength in the HA suspension, ionic strength could promote aggregation of HA. The conformational change of HA could affect the sorption behavior of Se on HA.