Deterioration of Polyamideamine–Epichlorohydrin (PAE) in Aqueous Solutions During Storage: Structural Changes of PAE

Structural changes of polyamideamine–epichlorohydrin (PAE) in solution during storage at 4 °C and pH 4.2–4.5 for up to 8.9 years were studied by ¹H- and ¹³C-NMR analyses, colloidal titration and others. NMR signals due to 3-hydroxy-azetidinium groups of PAE decreased during storage, and correspondingly 2, 3-dihydroxypropyl groups were formed by the ring opening. The content of 3-hydroxy-azetidinium groups in PAE determined by ¹H-NMR were similar to that determined by the colloidal titration, although the former was higher than the latter. About 50% of the 3-hydroxy-azetidinium groups present in the fresh PAE were lost during storage for 8.9 years. Furthermore, ¹³C-NMR analysis revealed that significant depolymerization of polyamideamine chains occurred by hydrolysis of the amide linkages during storage. Rough evaluation of number average degree of polymerization (DPn) of the amideamine repeating unit showed that the DPn decreased from 12 to 2 during storage for 8.9 years.     

Oxygen Permeability and Biodegradability of Polyuronic Acids Prepared from Polysaccharides by TEMPO-Mediated Oxidation

Polyuronic acids, i.e., amylouronic acid, cellouronic acid and chitouronic acid, were prepared from starch, cellulose and chitin, respectively, by the 2,2,6,6-tetramethylpiperidine-1-oxy radical (TEMPO)-mediated oxidation, and their gas-barrier properties and biodegradability were studied in consideration to use the polyuronic acids as flexible packaging films or coating materials. Cellouronic acid and amylouronic acid had excellent oxygen-barrier properties similar to that of poly(vinyl alcohol) (PVA), while chitouronic acid did not. The regular chemical structures of the former two polyuronic acids with no bulky substituents or adducts may have brought about such high oxygen-barrier levels. An oxidized product prepared form fine microcrystalline cellulose by the TEMPO-mediated oxidation was not completely dissolved in water, but became a paste. However, this paste also formed sufficiently smooth films by coating, and had good gas-barrier property. All polyuronic acids prepared were biodegradable; cellouronic acid and chitouronic acid had high degrees of biodegradability, while amylouronic acid had quite low value. These various characteristics are significant for end use of these new polyuronic acids as gas-barrier materials for biodegradable packaging.     

Radon concentration in indoor occupational environments in Aomori Prefecture,Japan

The (222)Rn concentrations in indoor workplaces were measured in Aomori Prefecture, Japan, and the results are reported here. This survey was part of a program to measure background natural radiation dose rate in the prefecture where the first Japanese nuclear fuel cycling facilities are now under construction.The survey of the (222)Rn concentrations in indoor workplaces was carried out at 107 locations from 1996 to 1998. The (222)Rn concentrations were measured for approximately one year at each site with passive Rn detectors, which used a polycarbonate film for counting alpha-rays and could separate concentrations of (222)Rn from (220)Rn. Weeklong measurements of (222)Rn concentration and working level were carried out with active detectors to get the ratio of (222)Rn concentration during working hours to non-working hours as well as equilibrium factors in selected locations.Diurnal variation of (222)Rn concentration depended on building structure, air-conditioning, time of day and day of the week (week days or weekend). The (222)Rn concentration during working hours was generally lower than that in non-working hours. Although the annual average (222)Rn concentration in indoor occupational environments was higher than that in dwellings, radiation dose for Aomori Prefecture residents from Rn in the former was 14% of the total indoor dose by Rn because of the lower concentration in working hours and lower occupancy factor.     

Deposition of 137Cs in Rokkasho, Japan and its relation to Asian dust

Biweekly atmospheric depositions of (137)Cs were measured in Rokkasho, Aomori, Japan from March 2000 to March 2006 to study recent (137)Cs deposition. Although the deposition level was generally lower than the detectable limit, deposition samples collected in spring occasionally had measurable levels of (137)Cs. The annual (137)Cs deposition from 2001 to 2005 was 0.04-0.69 Bq m(-2) with a mean value of 0.27 Bq m(-2). Depositions of insoluble Al, Fe and Ti were strongly correlated with the (137)Cs deposition, suggesting that suspension of soil particles was the main source of the recent (137)Cs deposition. Asian dust events were coincident with some of the significant (137)Cs depositions in spring. It was found that the ratios of (137)Cs/Al and Fe/Al could be used as indices for discriminating Asian dust from suspension of the local surface soil. Backward trajectory analysis suggested southern Mongolian and northeastern China regions as sources of the significant (137)Cs depositions.     

Development of a Model for Predicting the Volatilization Flux from Unsaturated Soil Contaminated by Volatile Chemical Substances

Environmental Modeling & Assessment - This work developed a model for predicting the volatilization flux from the unsaturated soil contaminated by volatile chemical substances (VCSs) such as...