In order to determine the physical location of contaminants in soil, two solidified soil "thin" sections, which preserve the undisturbed structural characteristics of the original soil, containing weapons-grade plutonium from the Rocky Flats Environmental Test Site were prepared. Two autoradiographic methods were used in radionuclide mapping: contact autoradiography using CR-39�� plastic alpha track detectors and neutron-induced autoradiography that produced fission fragment tracks in Lexan�� plastic detectors. The combination of the two autoradiographic methods distinguished alpha-emitting particles of natural U, from ������������������Pu and non-fissile alpha-emitters. The locations of 990 alpha "stars" caused by plutonium "hot particles" in two soil sections were recorded, particles were sized, their size-frequency and depth distributions were analyzed. Several large colloidal conglomerates of "hot particles" were found in soil profiles. One such conglomerate with a geometric size of about 500 ��m contained over 94% of the total recorded contaminant alpha activity in the sample. It was found that the upper 6.5 cm of soil contained 20% of all recorded particles (mean equivalent size 0.35 ��m). The deeper portion of the surface 6.5 cm soil layer contained 80% of the particles (with mean equivalent size 0.25 ��m). The average specific activity (SA) for 989 hot particles (with the conglomerate of the particles excluded) with equivalent diameters over 80 nm was found to be greater than 23.9 Bq g����� (about 90% of the overall average SA). For dissolved and defragmented (below 80 nm of equivalent diameter) actinide particles, SA was found smaller than 2.9 Bq g�����. Over 99% of the total actinide contaminant activity in the analyzed soil sample (with the conglomerate of the particles included) was found in particles with equivalent diameters over 0.08 ��m. it suggests that larger particles of plutonium oxide moved down more slowly than smaller ones and no significant breakup of plutonium oxide particles occurred since the original plutonium soil deposition. Both profiles of the depth contaminant activity and number of actinide particles have distinctive peaks at the same depth, about 10 cm. Independent from nuclear track analysis, this pattern of the actinides depth distribution was observed in the measured gamma activity depth profile of �������Am (daughter product of �������Pu beta decay) in solidified soil blocks. / Graduation date: 2001

Several methods for evaluating the permittivity of soil samples using measurements in the time domain were studied. A number of algorithms for inverting the measured data to obtain epsilon were investigated and three different types of sampling devices were examined. The investigation examined the positive and negative aspects of three different types of sample holders to determine a method of obtaining dielectric information from in-situ time domain measurements. A scheme using a twin lead balun driven ground probe was proposed and analysed with regard to accuracy and sensitivity to measurement error. / Ph. D.

CNPq / Esta dissertação de mestrado apresenta um estudo da concentração do 222Rn nas águas subterrâneas de Curitiba e Região Metropolitana, além de medições realizadas no solo e as concentrações do 226Ra na água. A pesquisa mostra os passos para aquisição das amostras de águas nos poços convencionais e artesianos de Curitiba e Região Metropolitana, a determinação da concentração do 222Rn com a câmara de ionização AlphaGUARD®, a construção de uma sonda e uma broca especial para coletar o 222Rn no solo, a metodologia para a coleta do gás no solo e a determinação da concentração do 226Ra através de equações com base nos valores de concentrações do 222Rn. Foram coletadas amostras de 47 locais. Nas concentrações de 222Rn na água houve uma maior freqüência de amostras com valor de concentração entre 20,1 Bq/L a 50 Bq/L. Nas concentrações de 226Ra a maior freqüência de incidência se encontra entre 1,1 Bq/L e 2,0 Bq/L. No solo foram feitos medições em 4 regiões, onde a maior concentração encontrada foi 38523 Bq/m3. A região Sul de Curitiba foi o local onde foram encontradas as concentrações de 222Rn e 226Ra mais altas. / This present study describes the concentration of 222Rn in groundwater in Curitiba and urban region, and measurement made in soil, and concentrations of 226Ra in water. The research shows the steps for acquisition of water samples in conventional wells and boreholes in Curitiba and urban region, the determining the concentration of 222Rn with the ionization chamber AlphaGUARD®, the construction of a probe and a special drill to collect the 222Rn soil, the methodology for collecting the gas in the soil, and determining the concentration of 226Ra using equations based on the values of concentrations of 222Rn. Samples were collected from 47 locations. There was a higher frequency of samples with concentration of 222Rn between 20.1 Bq/L to 50 Bq/L, and concentration 226Ra between 1.1 Bq/L to 2.0 Bq/L. In the ground were made measurements in four regions, where the highest concentration found was 38,523 Bq/m³. The southern region of Curitiba was the place where there were higher concentrations of 222Rn and 226Ra.