Evaluation of the readsorption of plutonium and americium in dynamic fractionations of environmental solid samples

A dynamic extraction system exploiting sequential injection (SI) for sequential extractions incorporating a specially designed extraction column is developed to fractionate radionuclides in environmental solid samples such as soils and sediments. The extraction column can contain up to 5 g of a soil sample, and under optimal operational conditions it does not give rise to creation of back pressure. Attention has been placed on studies of the readsorption problems during sequential extraction using a modified Standards, Measurements and Testing (SM&T) scheme with four-step sequential extractions. The degree of readsorption in dynamic and conventional batch extraction systems is compared and evaluated by using a double-spiking technique. A high degree of readsorption of plutonium and americium (>75%) was observed in both systems, and they also exhibited similar distribution patterns of the two radionuclides. However, the dynamic system is fully automated, eliminates manual separations, significantly reduces the operational time required, and offers detailed kinetic information.     

对瑞典酸化生态系统恢复的模拟

动态模型可以弥补已有的观测的时间序列资料的不足,以及用拟森林及湖泊生态系统过去和未来化学变化的静态临界负荷计算的缺陷.     

Evidence for the presence of arsenobetaine and another organoarsenical in shrimps

Hot base digestion of fish meal and shrimps in combination with sodium borohydride reduction produces only trimethylarsine (TMA). This treatment produces TMA in different amounts relative to the total arsenic content which is mainly of organic structure. These materials of marine origin yielded 94% and 69% resp. of the calculated amount of TMA. Arsenobetaine and arsenocholine were degraded under identical conditions and were found to produce only TMA (95% and 8% resp.). Furthermore, studies using thin-layer chromatography, electrophoresis and ion-exchange chromatography have confirmed the existence of one organoarsenic compound in fish meal and two organoarsenicals in shrimps. The major organoarsenic compound in fish meal was identified as arsenobetaine by masspectroscopy. In shrimps about $\text{2}\text{3}$ of the organoarsenic compounds was shown to be arsenobetaine and there is a strong indication for the presence of arsenocholine.     

The suitability of gastropods as biomarkers

The measurement and induction of mixed function oxyigenases (MFOs) of limnetic gastropods were investigated to estimate their suitability as biomarkers. A determination of MFO activities was performed through the measurement of ethoxyresorufin-O-dealkylase (EROD), pentoxy-(PROD) and benzoxyresorufin-O-dealkylase-activity (BROD). Optimal measuring conditions of these activities were investigated in preparations of the digestive gland of 4 species of limnetic gastropods. Results indicate that MFO-activity inhibiting substances are accumulating in the microsomal pellet, the fraction commonly used for the measurement of MFO-activities. Therefore, the fraction used for induction studies was the postmitochondrial supernatant (PMS). EROD, PROD, and BROD activity ofPlanorbis planorbis andPlanorbis carinatus were measured after a treatment with Aroclor 1254 for 1–17 days. Maximal induction of EROD and PROD were 6 and 10 times the value in the control group ofP. carinatus, respectively induction inP. planorbis was lower. BROD-activity could not been measured inP. planorbis. InP. carinatus, BROD-activity increased to a maximum of 2 times after traetment with Aroclor 1254. The level of induction of EROD-activity is comparable to results described in analog studies with fish.     

Schadstoffbelastung von Stra?enkehricht und Sedimenten der Regenwasserkanalisation durch den Stra\enverkehr am Beispiel von G?ttingen

Ohne Zusammenfassung     

Critical Loads of Acidity for Forest Soils and Relationship to Forest Decline in the Northern Czech Republic

Critical load calculations in the Czech part of 'the Black Triangle' show exceedance of critical load in 75% of the forest area. A comparison with forest damage data shows an insignificant tendency toward more forest damage in areas with high exceedance. We conclude that high exceedance of critical load is a probable contributing factor to forest damage in the area.