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Submitted by Jorge Silva (jorgelmsilva@ufrrj.br) on 2017-08-22T19:26:53Z No. of bitstreams: 1 2016 - Sidinei Julio Beutler.pdf: 3474278 bytes, checksum: 1adaf2ecd1077cf6ca3fa70c64954a43 (MD5) / Made available in DSpace on 2017-08-22T19:26:53Z (GMT). No. of bitstreams: 1 2016 - Sidinei Julio Beutler.pdf: 3474278 bytes, checksum: 1adaf2ecd1077cf6ca3fa70c64954a43 (MD5) Previous issue date: 2016-02-25 / CAPES / The Histosols are a major source of carbon storage in terrestrial environments and have high susceptibility to carbon losses when disturbed. The objective of this study was to generate pedotransfer functions (FPT) to assess the accuracy of previously published equations, applying them to predict soil bulk density (Bd) in organic soils from Brazil; to evaluate subsidence rate, and the variation of Bd and carbon of humic substances in Histosols over a period of one year; and to estimate stock and potential loss of carbon in Histosols from Rio de Janeiro State. For the first part of the study, there were used organic horizons, i.e., soil materials with total organic carbon (TOC) equal to or greater than 80 g kg-1 soil, totaling 280 horizons from different regions of Brazil. It was used the multiple linear regression technique and the equations were validated on independent data. There were tested 9 equations already published in the literature. The equations with better performance were the Hollis and FPT2, with R2 validation parameters of 0.48 and 0.49. When the clay fraction data is availlable, it is recommended to use the FPT1 equation; if there is no data on clay it is recommended the FPT2 and Hollis equations, which have only the TOC as a predictor variable. For the second part, a greenhouse experiment was carried out. For that, undisturbed samples were collected using PVC pipes, of two profiles of Organossolos Tiom?rficos, one in the neighborhood of Santa Cruz (SC Profile), city of Rio de Janeiro, and one in Mag? (Profile MG) municipality. There were evaluated 3 drainage levels, at 30, 60, and 100 cm deep, with 5 measuremts over time, being 0, 90, 180, 270, and 360 days (4 replicates). The MG profile presented the highest rates of subsidence, reaching 1.30 cm year-1 for the 100 cm drainage. Bd increased over time for both profiles, and the deeper drainage increased values in the SC profile. The deeper drainage favored the reduction of pH for both profiles. The TOC showed a decreasing trend over time. The values of carbon in the fulvic acid fraction (FAF), humic acid fraction (HAF), and humin fraction (HUM) showed no differences according to drainage levels. However, over time they showed high sensitivity to temperature changes, showing high levels of FAF and HAF at the end period and a consequent reduction in humin fraction. For the third and final section, there were used 43 soil profiles, where 18 of them did not have bulk density data, which were estimated by the FPTs. Comparisons between measured and estimated data groups was performed using the Wilcoxon test. The spatial distribution of the variables was performed using the IDW interpolation method. The average values of TOC was 228.0 g kg-1, Bd was 0.48 Mg m-3, the thickness of the profiles was 86 cm, the depth was 90 cm and the average stock TOC was 73.51 kg m-2. The spatialization showed qualitative differences for the variables in the different profile locations. The estimated TOC stock for the profiles form RJ State was 27,178,631.8 Mg. The estimated rates of loss were 10.87 kg m-2 for Histosols more recently drained and high TOC; of 7.16 kg m-2 for intermediate drained Histosols; and 1.46 kg m-2 for Histosols with longer time after drainage and low TOC. Soils with high TOC levels are more likely to have high losses TOC when disturbed. / Os Organossolos s?o uma importante fonte de estoque de carbono nos ambientes terrestres e possuem alta suscetibilidade ?s perdas de carbono quando perturbados. O objetivo do presente trabalho foi gerar equa??es, avaliar a acur?cia de equa??es j? publicadas, aplicando-as para a predi??o da densidade do solo (Ds) em solos org?nicos do Brasil; avaliar a taxa de subsid?ncia, a varia??o da Ds, e o carbono das subst?ncias h?micas em Organossolos ao longo do per?odo de um ano; e estimar o estoque e as potenciais perdas de carbono nos Organossolos do Estado do Rio de Janeiro. Para a primeira parte, trabalhou-se com horizontes org?nicos, i.e., materais de solo com teores de carbono org?nico total (COT) iguais ou maiores que 80 g kg-1 de solo, totalizando 280 horizontes em diferentes regi?es do Brasil. Foi empregada a t?cnica de regress?o linear m?ltipla e as equa??es foram validadas sobre dados independentes. Foram testadas 9 equa??es j? publicadas na literatura. As equa??es com melhor desempenho foram FPT2 e Hollis, com par?metros de valida??o R2 de 0,48 e 0,49. Em casos onde os teores de argila estejam quantificados, recomenda-se a equa??o FPT1, e na sua aus?ncia recomenda-se as equa??es FPT2 e Hollis, que possuem somente o COT como vari?vel preditora. Para a segunda parte, realizou-se um experimento em casa de vegeta??o. Foram coletadas amostras indeformadas em tubos de PVC, de dois perfis de Organossolo Tiom?rfico, sendo um no bairro Santa Cruz (Perfil SC), munic?pio de Rio de Janeiro, e outro no munic?pio de Mag? (Perfil MG). Foram avaliados 3 n?veis de drenagem, sendo de 30, 60, e 100 cm de profundidade, 5 avalia??es ao longo do tempo, sendo de 0, 90, 180, 270, e 360 dias (com 4 repeti??es). O perfil MG apresentou as maiores taxas de subsid?ncia, chegando a 1,30 cm ano-1 para a drenagem de 100 cm. A Ds aumentou ao longo do tempo para os dois perfis, e a drenagem mais profunda aumentou os valores no perfil SC. A drenagem mais profunda favoreceu a redu??o do pH para os dois perfis. Os teores de COT apresentaram tend?ncia de redu??o ao longo do tempo. Os valores de carbono da fra??o ?cido f?lvico (FAF), fra??o ?cido h?mico (FAH), e fra??o humina (HUM), n?o mostraram diferen?as de acordo com os n?veis de drenagem. No entanto, ao longo do tempo, apresentaram alta sensibilidade ?s varia??es de temperatura, mostrando elevados teores de FAF e FAH no per?odo final, e a consequente redu??o dos teores de HUM. Para a terceira e ?ltima parte do estudo, foram usados 43 perfis de Organossolos, sendo que 18 deles n?o apresentavam os dados de densidade do solo (Ds), os quais foram estimados por meio de FPTs. As compara??es entre os grupos de dados medidos e estimados foi feita pelo teste de Wilcoxon. A espacializa??o das vari?veis foi realizado atrav?s do m?todo de interpola??o IDW. Os valores m?dios de COT foi de 228,0 g kg-1, a Ds foi de 0,48 Mg m-3, a espessura dos perfis foi de 86 cm, a profundidade foi de 90 cm, e o estoque m?dio de COT foi de 73,51 kg m-2. A espacializa??o mostrou diferen?as qualitativas para as vari?veis nos diferentes locais. Foi estimado um estoque de COT de 27.178.631,8 Mg para os Organossolos do Estado do RJ. As taxas estimadas de perdas foram de 10,87 kg m-2 para Organossolos com drenagem mais recente e altos teores de COT; de 7,16 kg m-2 para Organossolos intermedi?rios; e 1,46 kg m-2 para Organossolos com menores teores de COT e longo tempo de drenagem. Solos com altos teores de COT est?o mais propensos a terem altas perdas de COT quando perturbados.

One of the largest environmental threats believed to be facing us today is global warming due to the accumulation of green house gases (GHG). The concentrations of GHG in the atmosphere are a result of the net strength of different sinks and sources. Forests, in this context, are of particular interest because of their dual role as both sinks and sources. Most forests are net sinks for CO2 but others, such as drained forests, may be significant sources of both CO2 and N20. Consequently, it is essential to understand the fluxes of GHG between drained forests and the atmosphere in order to obtain accurate estimates of national GHG budgets. The findings reported in this thesis and the accompanying papers are based on dark chamber flux measurements of soil GHG fluxes and modelled annual net primary productions in five drained forest sites and two undrained sites situated on organic soil. Temporal variations in forest floor CO2, release could be explained, to a large extent, by differencies in temperature and groundwater level. The within-site spatial variation in soil GHG fluxes could only be explained to a very small extent by distance to tree stems. Much of the among-site variations in soil CO2 and CH4 release could be caused by differences in the mean annual groundwater table, while N20 emissions were strongly correlated to the carbon-to-nitrogen ratio of soil organic matter. Most poorly drained forested areas are probably net sinks for GHG as the CO2 uptake by trees more than compensates for the soil GHG emissions. However, the total drained forested area in Sweden was estimated to be a net source of GHG. The CO2 release from decomposition of soil organic matter stored before drainage was estimated to be substantial. Corresponding to 15% of the CO2 release from the consumption of fossil fuels. / <p>On the day of the public defence of the doctoral thesis the status of the articles I and II was: Conditionally accepted; article III was: Submitted and articles IV and V was: Manuscript. The title of article III was on the day of the public defence "Can the distribution of trees explain the spatial variation in N2O emissions from boreal forest soils?".</p>

Submitted by Jorge Silva (jorgelmsilva@ufrrj.br) on 2017-02-21T17:24:10Z No. of bitstreams: 1 2015 - Paula Fernanda Chaves Soares.pdf: 3452589 bytes, checksum: a609eacd7f5462af0a01edb94f3837f5 (MD5) / Made available in DSpace on 2017-02-21T17:24:10Z (GMT). No. of bitstreams: 1 2015 - Paula Fernanda Chaves Soares.pdf: 3452589 bytes, checksum: a609eacd7f5462af0a01edb94f3837f5 (MD5) Previous issue date: 2015-02-25 / CAPES / According to the Brazilian Soil Classification System the Organossolos (Histosols) are characterized by horizons with high organic matter content and a given thickness. The carbon content is related to pedogenesis processes; however for the carbon addition and maintenance in the soil in such amount and thickness to meet the criteria of the classification system there are several factors working in conjunction, culminating in the soil genesis process. These soils can be formed by paludization or litter accumulation. The overall objective of the study was to characterize and classify Organossolos and to verify the influence of their genesis in the soil attributes, evaluating physical and chemical properties; in addition, the application of isotopic methods for analyzing natural abundance of carbon and nitrogen isotopes, relating the data with changes in vegetation and in soil evolution. The soils are under Atlantic Forest in the state of Rio de Janeiro. There were selected four profiles in different environments, one in the municipality of Mag? in the plains neighboring the Guanabara Bay, the second in Campos dos Goytacazes municipality, near Lagoa Feia, both in hot and humid climate and lowland plain relief. Two other soil profiles were located in Itatiaia municipality, in the highland section of the Itatiaia National Park, under cold weather and humid and mountainous vegetation environment. A series of analytical procedures were made: description and morphological characterization, analysis of chemical and physical properties, determination of carbon and nitrogen, chemical fractionation of humic substances, mineral material (MM), density of organic matter (DOM), minimum residue (MR), solubility in sodium pyrophosphate (SSP), determination of fibers and Von Post decomposition scale; plus the quantification of natural abundance of carbon isotopes (12C and13C) and nitrogen (14N and 15N), and carbon dating by the method of C. The RJ-01 profile was classified as ORGANOSSOLO Tiom?rfico S?prico t?pico, the RJ-02 as ORGANOSSOLO H?plico S?prico t?pico, the RJ-03 as ORGANOSSOLO H?plico H?mico t?pico and RJ-04 as ORGANOSSOLO F?lico S?prico cambiss?lico, equivalent to Sulfosaprists (RJ-01) Haplosaprists (RJ-02), Haplohemists (RJ-03) and Udifolists (RJ-04), in the Soil Taxonomy (USDA-NRCS). The RJ- 01 was significantly thicker and higher in carbon content in the subsurface. The RJ-02 profile was shallower, but had a higher organic matter deposition. The RJ-03 profile had the organic matter (OM) with the oldest C dating, in the range of 3351-3699 years at 40-50 cm. However, the RJ-04 profile stood out from the others because it had better soil drainage, higher degree of OM humification. Also, this profile had a variation of ?6 of 13C, indicating a change in local floristic composition with an increase of vegetation with C3 photosynthetic cycle, which is a hint of climate change. / De acordo com o Sistema Brasileiro de Classifica??o de Solo os Organossolos s?o caracterizados por horizontes com elevado teor de material org?nico e uma espessura m?nima. O teor de carbono esta ligado ao processo pedogen?tico, por?m para que ocorra a adi??o e manuten??o de carbono em quantidade e espessura de forma a atender os crit?rios do sistema de classifica??o uma s?rie de fatores atua em conjunto, culminando com o processo de g?nese do solo. Esses solos podem ser formados atrav?s de um desses processos: paludiza??o ou acumula??o de liteira. O objetivo geral do trabalho foi caracterizar e classificar Organossolos e verificar a influ?ncia da sua g?nese sobre os atributos ed?ficos, analisando as propriedades f?sicas e qu?micas; ainda a aplica??o de m?todos de an?lise da abund?ncia natural de is?topos de carbono e nitrog?nio, relacionando-as as altera??es na vegeta??o e na evolu??o do solo, em dois ambientes de Floresta Atl?ntica, no Estado do Rio de Janeiro. Para tanto foram selecionados quatro perfis em locais distintos, um em Mag? ao fundo da Ba?a de Guanabara, o segundo em Campos dos Goytacazes pr?ximo a Lagoa Feia, ambos em ambientes de clima quente e ?mido e relevo plano de v?rzea. Outros dois perfis localizam-se em Itatiaia, na parte alta do Parque Nacional de Itatiaia (PNI), em ambiente de clima frio e ?mido e vegeta??o altomontana. Realizou-se uma s?rie de procedimentos anal?ticos: descri??o e caracteriza??o morfol?gica, an?lises de atributos qu?micos e f?sicos, determina??o de carbono e nitrog?nio, fracionamento qu?mico das subst?ncias h?micas, material mineral (MM), densidade da mat?ria org?nica (DMO), res?duo m?nimo (RM), solubilidade em pirofosfato de s?dio (IP), determina??o de fibras (FE e FN) e escala de decomposi??o de Von Post, abundancia natural de is?topos do carbono (12C e 13C) e nitrog?nio (14N e 15N) e data??o da mat?ria org?nica do solo atrav?s do m?todo de C. O perfil RJ-01 foi classificado como ORGANOSSOLO Tiom?rfico S?prico t?pico, o RJ-02 como ORGANOSSOLO H?plico S?prico t?pico, o RJ-03 como ORGANOSSOLO H?plico H?mico t?pico e o RJ-04 como ORGANOSSOLO F?lico S?prico cambiss?lico. O perfil RJ-01 apresentou maior espessura e teores de carbono mais elevados em subsuperf?cie. O perfil RJ-02 foi o de menor profundidade, por?m possui maior deposi??o atual de mat?ria org?nica (MO). O perfil RJ- 03 possui a MO mais antiga, datando na faixa de 3351-3699 anos a 40-50 cm. No entanto, o perfil RJ-04 destacou-se dos demais por apresentar melhor drenagem e maior grau de humifica??o da MO. Al?m disso, esse perfil mostrou varia??o do valor de C de ?6, indicando altera??o na composi??o flor?stica local, com o aumento de vegeta??o do ciclo fotossint?tico C3, o que ? apontado como ind?cio de altera??es clim?ticas.

This study presents different aspects on the use of deterministic methods including Artificial Neural Networks (ANNs), and linear and nonlinear regression, as well as probabilistic methods including Bayesian inference and Monte Carlo methods to develop reliable solutions for challenging problems in geotechnics. This study addresses the theoretical and computational advantages and limitations of these methods in application to: 1) prediction of the stiffness and strength of stabilized organic soils, 2) determination of unknown foundations for bridges vulnerable to scour, and 3) uncertainty quantification for one-dimensional diffusion processes. ANNs were successfully implemented in this study to develop nonlinear models for the mechanical properties of stabilized organic soils. ANN models were able to learn from the training examples and then generalize the trend to make predictions for the stiffness and strength of stabilized organic soils. A stepwise parameter selection and a sensitivity analysis method were implemented to identify the most relevant factors for the prediction of the stiffness and strength. Also, the variations of the stiffness and strength with respect to each factor were investigated. A deterministic and a probabilistic approach were proposed to evaluate the characteristics of unknown foundations of bridges subjected to scour. The proposed methods were successfully implemented and validated by collecting data for bridges in the Bryan District. ANN models were developed and trained using the database of bridges to predict the foundation type and embedment depth. The probabilistic Bayesian approach generated probability distributions for the foundation and soil characteristics and was able to capture the uncertainty in the predictions. The parametric and numerical uncertainties in the one-dimensional diffusion process were evaluated under varying observation conditions. The inverse problem was solved using Bayesian inference formulated by both the analytical and numerical solutions of the ordinary differential equation of diffusion. The numerical uncertainty was evaluated by comparing the mean and standard deviation of the posterior realizations of the process corresponding to the analytical and numerical solutions of the forward problem. It was shown that higher correlation in the structure of the observations increased both parametric and numerical uncertainties, whereas increasing the number of data dramatically decreased the uncertainties in the diffusion process.

Submitted by Leticia Schettini (leticia@ufrrj.br) on 2016-10-03T15:58:13Z No. of bitstreams: 1 2011 - Paula Fernanda Chaves Soares.pdf: 2114719 bytes, checksum: 6297f456308144b9c0a8b946d61316f4 (MD5) / Made available in DSpace on 2016-10-03T15:58:13Z (GMT). No. of bitstreams: 1 2011 - Paula Fernanda Chaves Soares.pdf: 2114719 bytes, checksum: 6297f456308144b9c0a8b946d61316f4 (MD5) Previous issue date: 2011-02-15 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico - CNPQ / The Histosols are characterized by high organic content, distinguishing this class from others in the Brazilian System of Soil Clasification. Because of this characteristic they are more fragile in face of agricultural use and management than mineral soils. The agricultural drainage is the most important practice that changes soil properties and it is the cause of subsidence, which impacts on other attributes. On the other hand, Histosols are an important natural reservoir of carbon in the soil. However, there are few studies on the dynamics of carbon and nitrogen and potential contribution of greenhouse gases as a result of agricultural usage. The study aims to identify changes in edaphic attributes and dynamics of carbon and nitrogen of Histosols in a floodplain environment in State of Rio de Janeiro, according to types of land use and agricultural management. Three areas with different managements were selected. Two areas are located in Macae municipality, under pasture and annual crop rotation, and the third in Santa Cruz, in Rio de Janeiro city, cultivated with cassava (Manihot esculenta). They were evaluated: chemical and physical attributes, including aggregate stability and specific attributes of Histosols; content soil organic matter (SOM), carbon in the fractions - humin (HUM-C), humic acid (HAF-C) and fulvic acid (C-FAF); stocks of C and N; and flux of gases CO2 and N2O from soil to atmosphere. In general, the area cultivated with cassava had the highest values for the exchangeable cations at all depths; in the first sampling the H value varied from 32.1 to 33.2 cmolc kg-1, and Ca from 20.4 to 15.7 cmolc kg-1. In the second sampling K and P (5.16 to 4.36 cmol c kg-1, and 4 mg kg-1, respectively) were highest in the cassava crop area. The levels of (SOM) were highest in the pasture for the two sampling periods, with values ranging from 306.3 to 249.0 g kg-1 (WB method) and 297.8 to 278,5 g kg-1 (oven method) for the first sampling, and from 303.2 to 153.9 g kg-1 (WB) and 322.9 to 176.1 g kg-1 (oven) in the second period, indicating that this usage is less aggressive to the soil. The physical properties of Histosols may be used to indicate degree of subsidence. Thus, the high values of particle density and bulk density (1.9 and 0.8 Mg m-3); the total volume of pores that ranged from 54 to 60% with the lowest values in the two samplings; and minimum residue and mineral material highest than other usages (0.49 to 0.44 cm and 85.1 cm-1 to 80.7%, respectively) in the cassava area point to the high subsidence ot these soil. As for SOM chemical fractionation, the C_HUM indicated that this fraction had highest expression in all areas. In the second sampling the cassava area showed the lowest values of C-HUM (79.05 to 76.27 g kg-1), followed by C_FAH (44.56 to 40.05 g kg-1) and C_FAF (20.37 to 14.36 g kg-1). The stocks of C and N were highest in the pasture area, indicating better preservation of SOM, with values from 72.93 to 117.12 mg kg-1 for C and from 8.35 to 2,67 mg kg-1 for N. The values of CO2-C flux were within the range of variation proposed by the IPCC, where the highest emission value corresponded to 0.09 Mg CO2 ha-1 day-1 in the pasture area. The values of N2O-N flux were lower than the emission rate proposed by the IPCC, with the highest value around 270 g N2O-N m-2 day-1 in the area with beans. In general, the area with pasture management stood up as management that caused the least damage to the Histosols properties, among the land use evaluated. / Os Organossolos caracterizam-se pelo alto teor de material org?nico, que distingue essa classe das demais no Sistema Brasileiro de Classifica??o de Solo. Ainda, por essa caracter?stica s?o solos mais fr?geis diante do uso e manejo agr?cola que solos com dom?nio de minerais. Dentre as pr?ticas que mais alteram as propriedades ed?ficas, a drenagem ? a mais importante e ? respons?vel pelo processo de subsid?ncia com impactos em v?rios atributos. Por outro lado, os Organossolos s?o importante reservat?rio natural de carbono no solo. Ainda assim s?o poucos os estudos sobre a din?mica de carbono e nitrog?nio e o potencial de contribui??o com gases de efeito estufa diante do manejo agr?cola. O estudo visa identificar altera??es nos atributos ed?ficos e na din?mica de carbono e nitrog?nio de Organossolos em ambiente de v?rzea no Estado do Rio de Janeiro, em fun??o de tipos de uso e manejo agr?cola. Foram selecionadas tr?s ?reas com manejos distintos. Duas ?reas localizam-se em Maca?, com pastagem e rota??o de culturas anuais, e a terceira em Santa Cruz, no Rio de Janeiro, com mandioca (Manihot esculenta). Foram avaliados: atributos qu?micos e f?sicos, incluindo estabilidade de agregados e atributos espec?ficos de Organossolos; teores de mat?ria org?nica do solo (MOS) e o teor de C nas fra??es humina (C-HUM), ?cido h?mico (C-FAH) e ?cido f?lvico (C-FAF); estoques de C e N; e fluxos dos gases CO2 e N2O do solo para a atmosfera. Em geral, a ?rea com mandioca apresentou os maiores valores para o complexo sortivo em todas as profundidades; na primeira coleta o H variou de 32,1 a 33,2 cmolc kg-1, e o Ca entre 20,4 e 15,7 cmolc kg-1. Na segunda coleta destacam-se os valores de K e P (5,16 e 4,36 cmolc kg-1 e 4 mg kg-1, respectivamente) tamb?m maiores na ?rea com mandioca. A MOS mostrou maior teor na ?rea de pastagem para as duas coletas, com valores variando entre 306,3 a 249,0 g kg-1 (m?todo WB) e 297,8 a 278,5 g kg-1 (m?todo da mufla) na primeira coleta, e para a segunda coleta de 303,2 a 153,9 g kg-1 (WB) e 322,9 a 176,1 g kg-1 (mufla), o que indica que esse manejo ? menos agressivo ao solo. As propriedades f?sicas dos Organossolos podem indicar o seu grau de subsid?ncia. Assim, os valores altos de densidade da part?cula e densidade do solo (em torno de 1,9 e 0,8 Mg m-3) mais o volume total de poros, que variou de 54 a 60% sendo os menores nas duas coletas, e o res?duo m?nimo e material mineral com valores maiores (0,49 a 0,44 cm cm-1 e 85,1 a 80,7%, respectivamente) indicam para a ?rea de mandioca maior grau de subsid?ncia. No fracionamento qu?mico da MOS o C_HUM indicou que essa fra??o teve maior express?o em todos as ?reas. Na segunda coleta a ?rea de mandioca apresentou os menores valores de CHUM (79,05 a 76,27 g kg-1) seguidos de C_FAH (44,56 a 40,05 g kg-1) e C_FAF (20,37 a 14,36 g kg-1). Os estoques de carbono e nitrog?nio foram mais altos no solo sob pastagem, indicando melhor conserva??o da MOS, com valores entre 117,12 e 72,93 Mg kg-1 para C e 8,35 e 2,67 Mg kg-1 para N. Os valores de fluxo de C-CO2 estiveram dentro da faixa de varia??o proposta pelo IPCC, em que o maior valor de emiss?o correspondeu a 0,09 Mg CO2 ha-1 dia-1 na ?rea de pastagem. Os valores de N-N2O foram menores que a taxa de emiss?o proposta pelo IPCC, com o valor mais elevado em torno de 270 ?g N-N2O m-2 dia-1 e na ?rea com feij?o. Em geral, a pastagem se destacou como o manejo que causou menor altera??o nas propriedades dos Organossolos, dentre as formas de uso da terra avaliadas.

Microbially induced calcite precipitation (MICP) has been used for a number of years as a technique for the improvement of various geological materials. MICP has been used in a limited capacity in organic rich soils with varying degrees of success. Investigators hypothesized that microbially-induced cementation could be improved in organic soils by using a surfactant. Varying amounts of Sodium Dodecyl Sulfate (SDS) were added to soils of varying organic content and a mixing procedure was used to treat these soils via MICP. Treated specimens were tested for unconfined compressive strength (UCS). Results appeared to show direct relationships between SDS content and treated specimen strength although significant variability was present in the data. In addition, results also indicated that while addition of SDS during MICP treatment strengthens soil, the strengthening is likely from the formation of a calcium dodecyl sulfate (CDS) complex in which the CDS surrounds the soil in a matrix, and formation of MICP-induced calcite has very little to do with overall soil performance. As such, a new method for stabilizing loose soils dubbed ‘Surfactant-induced soil stabilization’ (SISS) was further explored by treating additional soil specimens. Samples treated using this technique showed increases in strength when compared to untreated specimens. In addition, preliminary data indicated that SISS treated specimens were insoluble. The SISS technique presents a number of advantages when compared to traditional soil stabilization techniques. In particular it should be relatively low-cost and simple to administer since its only components are SDS and calcium chloride. Additionally, these constituents are relatively more sustainable than chemicals associated with more-traditional loose soil stabilization techniques.