Siltation and radiocesium pollution of small lakes in different catchment types far from the Fukushima Daiichi nuclear power plant accident site

The Fukushima Daiichi nuclear power plant accident caused radioactive pollution in northeastern Honshu Island,Japan.This study examined the influence of snowmelt and rainfall on soil erosion pro-cesses and siltation of small lakes in Miyagi Prefecture(150 km northwest of the power plant).Two sets of slopes and lakes,respectively in pasture and forest catchments,were examined.Snowpack thickness,soil infiltration,surface runoff volume,soil and sediment physicochemical properties,Cs concentration of precipitation,meltwater,and rainwater,and lake siltation rates were determined.The total radioactive Cs content in precipitation was 0.7-7.4 Bq·L^-1 and was below the Japanese standard(10 Bq·L^-1).Total radioactive Cs was at the allowable level in water flowing down the pasture catchment slope(0.1-9.2 Bq·L^-1)during snowmelt and rainfall,as well as in pasture(0.9-8.8 Bq·L^-1)and forest(0.7-5.2 Bq·L^-1)catchment lake water.There was no soil erosion(surface runoff)in the forest catchment.Soil losses in the pasture catchment were 23 due to rainfall and 9 kg ha^-1 yr^-1 following spring snowmelt.After snow-melt,a 0.5 and 0.2 mm thick layer of silt was deposited in pasture and forest catchment lakes,respec-tively,and 1.4 and 0.6 mm were deposited during the rainfall period.Average siltation rates were 1.9 and 0.8 mm·yr^-1 for pasture and forest catchment lakes,respectively.The upper layer of lake bottom sedi-ments is represented mainly by silt fractions(2-50μm),with high organic matter(4.0-5.7%)and radiocesium(1100-1600 kg·ha^-1)contents.

Development of beta ray scanner for imaging foliar uptake of radiocesium

Large quantities of radionuclides were released from the Fukushima Daiichi Nuclear Power Plant(FDNPP)into the atmosphere,which then contaminated the soil and vegetation surrounding the FDNPP.The research on radiocesium contamination of agricultural products and wild plants is important.Therefore,we developed a simple beta ray scanner to obtain radiographs of the transport and foliar uptake of radiocesium.This simple beta ray scanner comprised a beta ray detector,a motorized sample stage,a shielding box,and a personal computer.Beta rays released from radiocesium were detected effectively using a plastic scintillator plate coupled to multipixel photon counter devices.The spatial resolving power was approximately 6 mm×4 mm(FWHM).In a preliminary experiment,a drop of radiocesium solution was placed on the upper surface of a radish leaf.Time-lapse images of radiocesium in the leaf were obtained by the beta ray scanner.Images of isotope transport in the leaf were successfully obtained with the beta ray scanner.The beta ray scanner will be used in our future research on the mechanism of the foliar uptake of radiocesium.

环境中放射性铯的迁移进展研究

介绍了环境中放射性铯的污染来源及危害;对放射性铯在环境中的迁移研究现状和进展进行了三个方面的分析总结:切尔诺贝利及福岛核事故释放的核素铯在环境中的迁移研究现状;核素铯在土壤环境中的迁移,研究发现释放到环境中的放射性铯主要分布在表层土壤中等结论;核素铯在岩石、矿物及水等环境介质中的迁移研究现状。通过综述核素铯在核事故和土壤、岩石及水等环境介质中的迁移进展,以期为评估放射性铯对环境和人体健康的影响提供理论资料。

普鲁士蓝对体内放射性铯的促排效果及其毒性研究

普鲁士蓝(PB)对^(134)Cs和^(137)Cs不仅有早期促排作用而且有晚期促排作用。大鼠口服50mg/kgPB,72h后^(134)Cs总排出率是53.9％;每天口服500mg/kg,连服6天后,第 7天^(134)Cs总排出率为94.3％。PB毒性低,当大、小鼠和犬的口服剂量分别达4.9、40、2g/kg时,均无急性及近期毒性反应;人体口服12g/3d无不良反应。

放射性锶和铯在石灰性土壤上的吸着和解吸

用^（８５，８９）Ｓｒ和^（１３４）Ｃｓ作放射性示踪剂，采用静态平衡法和选择性提取法研究了痕量锶和铯在石灰性土壤及其固相组分碳酸钙、有机质上的吸着和解吸，讨论了石灰性土壤中碳酸钙和有机质对整个土壤吸着的贡献，以及吸着－解吸滞后作用。

普鲁士蓝加速人体内铯排出效果的观察

本文介绍6例在苏联切尔诺贝利核电站事故期间受到放射性铯内污染的我国驻外人员,在本实验室接受活体测量和服用普鲁士蓝促排的观察结果。6例内污染者分两组分别于受污染后的第114天和第272天开始用药,在大约一个月期间,每人共服药54g(给药方式:每次服1g,每日3次,6天为一个疗程,间隔6天,共用药3个疗程)。观测结果表明,在促排期间,6例内污染者体内铯的生物半排期均明显缩短,^(131)Cs 的生物半排期由对照期(用药前)的54—123d 缩短到28—65d,^(134)Cs 由对照期的42—117d 缩短到23—69d;6例体内放射性铯的累积活度相对于同期未用药条件下的累积活度减少2—21%。

核应急中去除放射性铯的研究进展

核事故会造成大量的放射性铯泄漏，威胁环境与人类健康安全。因此，对进入环境及人体内的放射性铯离子的去除具有十分重要的意义。本文对核应急中放射性铯离子去除的研究进展进行了综述。目前针对环境土壤中放射性铯离子的污染主要采用直接移除表层部分，并对土壤进行净化处理，涉及的方法包括土壤淋洗法、电动力学修复法以及土壤固载法。对环境水体中放射性铯离子的去除主要采用吸附法，所用吸附剂主要有冠醚、杯芳烃、磷钼酸铵以及普鲁士蓝等。而人体中放射性铯离子的去除主要依靠普鲁士蓝口服促排药物，需要及时多次给药且见效慢，同时仍存在一些严重的不良反应，如易引起低钾血症和消化道不适。因此研究新型的核应急放射性铯离子去除药物，仍具有重要的战略意义。