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This work applied the radiotracer technique to evaluate the chromium (Cr) sorption by sediments of a mangrove degraded area under reforestation phase. The radiotracer 51 Cr(III) was used to assess the removal kinetics of this metal from tidal water by underlying sediments in two different environments from the mangrove area of the reserve Parque Natural Municipal Barão de Mauá (Rio de Janeiro, SE Brazil). The results indicated a faster Cr(III) removal by sediments from the area with initial mangrove reforestation (t1/2 = 12.1 ± 0.1 h) than estimated for the area with older mangrove reforestation (t1/2 = 18.0 ± 0.2 h). However, this difference was explained by a stronger sediment bioturbation in the area that presented faster Cr removal (the initial mangrove reforestation zone). These results evidence the importance of the influence of biological activity in the capacity of the mangrove sediment to remove Cr(III) from tidal waters.

On average 80% of the radiopharmaceuticals used in Nuclear Medicine are labeled with 99m Tc due to its physical properties and easy attainment through of 99 Mo/ 99m Tc generators. The Directory of Radiopharmacy (DIRF) of IPEN-CNEN/SP developed a gel type chromatographic generator of MoZr with 99 Mo produced by 98 Mo(n,γ) 99 Mo reaction that occurs at the IEA-R1 Nuclear Reactor. The gel is composed of zirconium molibdate with elution volume of 12 mL with an activity of 11100 MBq (300 mCi) producing a radioactive concentration of 925 MBq (25 mCi)/mL. The fission generator gives a higher radioactive concentration around 1850 MBq (50 mCi)/mL. The aim of this work is to study a system of post-elution concentration of 99m Tc for the attainment of a high enough radioactive concentration to meet the demands of the market, with a proved quality. Two types of systems of post-elution concentration were developed: the single and the tandem. The most appropriate system for the gel generator of 99 Mo/ 99m Tc, being at the same time sterile and vacuum automated, was the tandem system using Dionex 2.5 cc/QMA cartridges. The gel generator is eluted with 10 mL of solution of 0.1% NaCl and the pertechnetate anion is retained in the QMA cartridge and further eluted with 4 mL of saline. The process takes no more than 30 minutes. The elution efficiency of the system of concentration was 90 %. At the beginning of 2009 a global crisis in the supply of 99 Mo took place making it necessary the development of alternative technologies for the production of 99 Mo/ 99m Tc generators using fission produced 99 Mo and the development of an appropriate method to extend the useful life of this generator. The results of this study showed that the same system developed for the post-concentration of the gel generator can be employed for the fission generator, using the tandem system, giving a concentration factor of 3 for the elution of 99m Tc. LISTA DE FIGURAS FIGURA 1 Curva de decaimento e crescimento do gerador de 99 Mo/ 99m Tc

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The biological activity influence on the mangrove sediment capacity to remove 65 Zn and 109 Cd from tidal water was evaluated in a site chronically polluted. Benthic Activity Indexes (BAI), corresponding to relative estimates of biological impact on radiotracer accumulation, were higher for 109 Cd (* 38%) than for 65 Zn (* 10%) in the top centimetre of sediment. However, BAI exceeded 96% for deeper sediment layers. This apparent decrease in radiotracer diffusion into deep sediments through biological activity inhibition is stronger than reported for much less polluted mangrove nearby, suggesting that benthic organisms tolerant of chronic metal pollution may affect metal sorption mechanisms.