Investigating Pu and U isotopic compositions in sediments: a case study in Lake Obuchi, Rokkasho Village, Japan using sector-field ICP-MS and ICP-QMS

The objectives of the present work were to study isotope ratios and the inventory of plutonium and uranium isotope compositions in sediments from Lake Obuchi, which is in the vicinity of several nuclear fuel facilities in Rokkasho, Japan. Pu and its isotopes were determined using sector-field ICP-MS and U and its isotopes were determined with ICP-QMS after separation and purification with a combination of ion-exchange and extraction chromatography. The observed (240)Pu/(239)Pu atom ratio (0.186 +/- 0.016) was similar to that of global fallout, indicating that the possible early tropospheric fallout Pu did not deliver Pu from the Pacific Proving Ground to areas above 40 degrees N. The previously reported higher Pu inventory in the deep water area of Lake Obuchi could be attributed to the lateral transportation of Pu deposited in the shallow area which resulted from the migration of deposited global fallout Pu from the land into the lake by river runoff and from the Pacific Ocean by tide movement and sea water scavenging, as well as from direct soil input by winds. The (235)U/(238)U atom ratios ranged from 0.00723 to 0.00732, indicating the natural origin of U in the sediments. The average (234)U/(238)U activity ratio of 1.11 in a sediment core indicated a significant sea water U contribution. No evidence was found for the release of U containing wastes from the nearby nuclear facilities. These results will serve as a reference baseline on the levels of Pu and U in the studied site so that any further contamination from the spent nuclear fuel reprocessing plants, the radioactive waste disposal and storage facilities, and the uranium enrichment plant can be identified, and the impact of future release can be rapidly assessed.     

Comparison of PCDD/F and coplanar PCB concentrations in Japanese human adipose tissue collected in 1970-1971, 1994-1996 and 2000

Concentrations of polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs) and coplanar biphenyls (Co-PCBs) were determined in Japanese human adipose tissues. Temporal trends were assessed by comparing data collected during 1970-1971, 1994-1996 and 2000. Mean TEQ levels of PCDD/Fs in human adipose tissue showed a significant decrease from 31.6 +/- 9.2 pg-TEQ/g fat wt in 1970-1971 to 11.9 +/- 7.4 pg-TEQ/g fat wt in 2000, and coplanar PCBs decreased from 35.4 +/- 21.9 pg-TEQ/g fat wt in 1970-1971 to 15.3 +/- 8.2 pg-TEQ/g fat wt in 2000. However, some PCB congener concentrations did not change during this time. A comparison of data using the latest PCB-TEQ showed no significant changes. Therefore, research on source characterization and monitoring of short-term temporal trends on these compounds should be carried out continuously.     

Environmental fate of pesticides used in Australian viticulture V. Behaviour of atrazine in the soils of the south Australian Riverland

The transport of the s‐triazine herbicide, atrazine, through the red, calcareous earth soils of the South Australian Riverland was investigated. Small, undisturbed soil cores were extracted from the inter‐row topsoil of a vineyard adjacent to the River Murray, approximately 10 km south‐west of Overland Corner, South Australia. The vines were grown in a deep (1–4 m) reddish brown, strongly alkaline, sandy loam with a low organic carbon content (<2%). Atrazine concentrations in the leachate were dependent on application rate and soil type. High application rates on subsoil gave high rates of leaching for a longer time compared to the same application rate on topsoil and/or lower application rates on either topsoil or subsoil. Overall, 37–65% of the applied atrazine was detected in the leachate from subsoil cores, 14–25% in topsoil core leachates. Small amounts of atrazine (< 10% of applied dose) were found only in the top 2 cm of the core profiles. The results suggest that this herbicide is somewhat mobile in such strongly alkaline, sandy loam soils and that the irrigated soils of this region are likely to be prone to leaching of atrazine, and therefore that groundwater supplies in this area may be at risk of contamination through use of triazine herbicides.     

Vertical distributions of (99)Tc and the (99)Tc/(137)Cs activity ratio in the coastal water off Aomori, Japan

Using a sector-field ICP-MS the vertical distributions of the ⁹⁹Tc concentration and ⁹⁹Tc/¹³⁷Cs activity ratio were measured in the coastal waters off Aomori Prefecture, Japan, where a spent-nuclear-fuel reprocessing plant has begun test operation. The ⁹⁹Tc concentrations in surface water ranged from 1.8 to 2.4 mBq/m³, no greater than the estimated background level. Relatively high ⁹⁹Tc/¹³⁷Cs activity ratios (10-12 × 10⁻⁴) would be caused by the inflow of the high-⁹⁹Tc/¹³⁷Cs water mass from the Japan Sea. There is no observable contamination from the reprocessing plant in the investigated area. The ⁹⁹Tc concentration and the ⁹⁹Tc/¹³⁷Cs activity ratio in water column showed gradual decreases with depth. Our results implied that ⁹⁹Tc behaves in a more conservative manner than ¹³⁷Cs in marine environments.     

Spider silk has an ice nucleation activity

Several ice nucleating substances have been identified, which exist in vivo or can be extracted from biological materials. Spider silk, which has a strong ability for water condensation, has also been found to possess an ice nucleation activity. The freezing temperature of water droplets was higher in the presence than in the absence of spider silk. Moreover, by means of environmental scanning electron microscopy, it was observed that the activity is not due to foreign matter attached to the silk but to the silk fibroin itself.     

Effects of red-yellow soil acidification on seed germination of Chinese pine

Acid treatments significantly change the physical and chemical properties of red-yellos soil by lowering its pH value and leaching out aluminum(Al) ions that are harmful to the growth of plants.The structure of soil will be damaged,resulting in higher viscosity,higher water retention rate and lower air permeability of the soil.The germination rate of Chinese pine(Pinus tabulacformic Carr.)seeds sowed in soil treated with sulphuric acid(H2SO4) decreased compared to that for untreated soil.The direct cause was the large amount of Al ions leached out because of low pH values(≥3.5).The added acid decreased the soil aggregation and increased the number of micro-aggregates(under 250 μmin diameter).Such changes increased the soil‘s viscosity,which tied the pine needles to the soil after the seeds had germinated and prevented the seedlings from fully developing.     

Verification of lipofuscin-based crustacean ageing: seasonality of lipofuscin accumulation in the stomatopod Oratosquilla oratoria in relation to water temperature

To verify the lipofuscin-based age estimation of crustaceans of unknown age from wild populations, we conducted a modal analysis of lipofuscin-concentration histograms in the stomatopod Oratosquilla oratoria seasonally collected from Tokyo Bay, Japan. Confocal microscopy and subsequent image analysis were used to quantify lipofuscin concentrations in the protocerebral bridge cell mass in the brain. Conventional body length frequency analysis failed to detect modes corresponding to ≥1 year old. In contrast, four or five distinct modes were found in the lipofuscin-concentration histograms, in which modes could be readily traced across months, suggesting that each mode represented an independent age group. The lipofuscin accumulation rate fluctuated seasonally: it was high in summer (June–July) and low in winter (December–January). Cross-correlation analysis showed that the highest instantaneous lipofuscin accumulation rate was achieved in early summer before maximum bottom temperatures were reached and when the temperature was increasing most rapidly. Our findings support the usefulness of lipofuscin concentration analysis in age estimation in wild crustacean populations.     

Levels of 3,3′,4,4′-tetrachloroazobenzene in herbicides and bulk reagents

The contamination levels of different commercial herbicides and bulk reagents with the carcinogen 3,3′,4,4′-tetrachloroazobenzene (TCAB) were determined by high resolution mass spectrometry. The concentrations vary from 0.00071 to 2.8 ug/g (ppm) for the herbicides and from 0.085 to 14 ug/g for the bulk reagents. They are thus lower than those of other reports.     

Electrochemical reduction of organohalogen compound by noble metal sintered electrode

1,2,3-Trichlorobenzene (1,2,3-TCB) was used as a model sample of persistent organic pollutants (POPs) which was dechlorinated by a closed electrochemical reduction system under an inert gas atmosphere. The effect of the electrode material was examined in the reaction. Dechlorination yields in different type of cathode electrodes using sintered RuO2 (major)/Pt/PdO, sintered Pt(major)/IrO2/RuO2, sintered RuO2, sintered PdO, sintered Pt, sintered PdO/Pt, sintered Pd/Pt and plain Pd plate were 91%, 81%, 59%, 96%, 53%, 97%, 82% and 70% respectively, at reaction times of 60 or 120 min. The reaction was exothermic after initially starting at room temperature. This electrochemical reduction system was friendly technology for environment using cation exchange membrane, supplying sodium ions from sodium hydroxide solution as anolyte. Trace amounts of dichlorobenzene, as products of stepwise dechlorination, were observed with different pathways, depending on the electrode material. Electrodes with Ru and Pd were selective mainly for meta-position dechlorination, while those with Pt groups selective mainly for ortho-position (o-position) dechlorination. A PdO sintered electrode had an especially high selectivity for meta-position (m-position) dechlorination. The results suggest that dechlorination is an electrocatalytic reduction in this cation supply system.