Identification and temporal decrease of 137Cs and 134Cs in groundwater in Minami-Soma City following the accident at the Fukushima Dai-ichi nuclear power plant.

The Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident on March 11, 2011, caused severe radioactive contamination in Fukushima Prefecture. In order to clarify the safety of drinking water, we have conducted radiocesium monitoring of public tap water and groundwater in Minami-Soma City, which is 10-40 km north of the nuclear power plant. The source of tap water for Minami-Soma City is groundwater, which is treated by rapid filtration before distribution in two of the three treatment plants. The tap water was collected from six stations during 2012-2016 and groundwater was collected from 11 stations with wells between 5 and 100 m deep during 2014-2016. Radiocesium contamination of groundwater has been considered unlikely in Japan because of the small vertical migration velocity of radiocesium in Japanese soil. However, radiocesium was detected in public tap water after 2012, and the maximum 137Cs concentration of 292 mBq L-1 was observed in 2013. In all the well water, radiocesium was detected between 2014 and 2015, at concentrations similar to those observed in tap water in the same period. In tap water and groundwater, radiocesium was decreased to below the detection limit in 2016 except for four stations. Radiocesium concentration in shallow water reached a maximum between 2013 and 2015, 2-4 years after the FDNPP accident, and then decreased. The results are interpreted that dissolved 137Cs migrated in the soil and reached aquifers of various depth.

Isotope ratios of (235)U/(238)U and (137)Cs/(235)U in black rain streaks on plaster wall caused by fallout of the Hiroshima atomic bomb.

Radiological investigations of fallout from the atomic bomb detonated over Hiroshima city on 6 August 1945 are important to estimate doses for inhabitants. The authors have analyzed the concentrations of (137)Cs, (235)U, and (238)U in streaks of black rain caused by the atomic bomb using gamma-ray spectroscopy and the ICP-QMS method. The black rain streaks were deposited on a plaster wall of a house located 3.7 km west of the hypocenter that has been kept in the same condition as after the rainfall. Cesium-137 ((137)Cs) was detected from black streak samples. Concentration of (137)Cs in the black rain streaks is twice as high as fallout deposition on the ground in this area. A (235)U/(238)U atom ratio of 0.00887 was found, which is higher than the natural ratio, reflecting the fact that the atomic bomb "Little Boy" used enriched uranium as fuel. The ratio (137)Cs/(235)U was determined to be 0.0091, which is about eight times higher than the estimated ratio of 0.00113 based on the fission yield.

The effects of soil and Trifolium repens (white clover) on the fate of estrogen.

In this study, we investigated the behavior of estrogens in the rhizosphere of white clover (Trifolium repens, clover hereafter) with two different pot tests, using soil and agar as growth media. In a pot test using agar spiked with estrogen, the estrogen concentration in the agar with clover decreased to non-detectable levels within one month, while in the agar without clover, 60% of initially added estrogen remained after one month. The half-lives of estrone (E1) and 17beta -estradiol (E2) in the agar with clover were 2.4-3.8 and 13.2 d, respectively. The dissipation of E1 followed first-order rate law, while that of E2 fitted a zero-order reaction, indicating that they had different mechanisms of dissipation from agar. In the soil pot test, the behavior of E1 and E2 was not influenced by clover. An initial rapid decrease in the amount of estrogen extracted by methanol/acetic acid was followed by persistence for 1-3 months, regardless of presence of clover. Moreover, in three weeks E1 and E2 were only partly degraded by microbes extracted from the soil used in the pot test. In this study, abiotic degradation of estrogens and sorption of estrogen to soil, rather than the effects of soil microbes and clover, contributed to the initial rapid dissipation of estrogens in the soil. However, the results of the agar pot test suggested that vegetation such as clover may significantly contribute to removal of estrogens when estrogens in aqueous phase are discharged with surface runoff and preferential flow after heavy rain in agricultural fields, or when present in soils with low estrogen sorptivity.

Development of a rapid infiltration system for wastewater and river water treatment in Japan using granulated materials.

A rapid infiltration (RI) system using granulated materials was developed for wastewater and river water treatment. Granules were processed by optimized procedures from soil and waste materials with high sorption of recalcitrant dissolved organic matter (DOM) and phosphorus. Granule performance was examined by laboratory column and pilot-scale tests. During the first year of the pilot test, removal of phosphorus was removed from livestock-farm effluent at the hydraulic loading rate of 2 m/day was 50-70% and that of refractory DOM was 10-30%.

[Rapid analysis of mercury in sediments by laser ablation inductively coupled plasma mass spectrometry].

Laser ablation inductively coupled plasma mass spectrometry was used for the rapid analysis of mercury in sediment samples. The ground samples were simply briquetted prior to laser ablation. The effects of internal standardization, particle size and elemental speciation on the analytical performance were investigated. Direct analysis of sediment samples without internal standardization could yield satisfactory results. Elemental speciation and particle size within the studied range did not significantly affect the measurements. The calibration curve was obtained simply by analyzing one soil and two sediment reference materials. With the proposed LA-ICP-MS system, a detection limit of 0.02 mg x kg(-1) was achieved with a sample through put of 10 h(-1). Analytical results of sediment samples using the current system were in good agreement with those by isotope dilution hydride-generation ICP-MS.

Anomalous 235U/238U ratios and metal elements detected in the black rain from the Hiroshima A-bomb.

Contents of black rain from the A-bomb are important to clarify the health and environmental hazard caused by nuclear warfare. We analyzed the only existing physical remains of the black rain from Hiroshima A-bomb (Little Boy), a plastered wall with black streaks. Excess 137Cs and anomalous 235U/238U ratios detected in the black residues on the wall confirmed that the black streaks on the wall originated from Little Boy. The results also showed that excess 235U could be used as a fingerprint to clarify the distribution of materials discharged from Little Boy into the environment. High concentrations of lead and zinc, which may have caused a degree of heavy metal pollution in the area where the rain fell, were also detected in the black rain sample.