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Impactos da mudança do uso e cobertura do solo na emissão de óxido nitroso e abundância de bactérias desnitrificantes no solo
(Universidade Federal de São Carlos, 2018-05-03) Nishisaka, Caroline Sayuri; Carmo, Janaina Braga do; https://lattes.cnpq.br/8627099224335903; Navarrete, Acacio Aparecido; https://lattes.cnpq.br/2264331242602494; https://lattes.cnpq.br/2979508513390472
Agriculture is responsible for 80% of nitrous oxide emissions on earth's atmosphere, the most potential greenhouse gas among the three main gases (CO2, CH4 and N2O). Citriculture and silviculture play an important role on Brazilian economics due to the high demand of orange and wood products for exportation. Thus, in order to get a better understand about the role of those cultures on N2O emission, this research aims to evaluate N2O emissions from Citrus sinensis and Eucalyptus spp. crops, adjacent forests of each agriculture field were used as control. Citrus and eucalyptus sites are located in Sorocaba and Salto de Pirapora municipality, both in the state of Sao Paulo, Brazil. In each agriculture field and adjacent forest, eight static chambers were randomly installed, and gas sample were collected during dry and wet region season. Soil samples were collected in each field of study from five random sampling points, for further physicochemical, molecular analysis and microcosm incubation. Gas samples were collected from microcosm after moisture adjustment in 70% of field capacity. All gas samples were analyzed by gas chromatography technique. The number of copies of genes related to denitrifying process (nirK, nirS e nosZ) was determined by quantitative real time PCR. Seasonality had significant (P<0.05) influence on N2O emission in field, and N2O fluxes in incubated soil. It was observed positive correlation among dissolved organic carbon (DOC) concentration on soil, soil and plant residue total carbon and nitrogen content and N2O emissions. High nirK, nirS and nosZ gene abundance was found on soil collected during wet season, comparing to those collected on dry season, in both field and microcosm, which was correlated with DOC content and soil moisture. However, there were not significant differences on genes abundance comparisons between cultivated soils and adjacent forests. In conclusion, the seasonality has influence in both N2O emission and denitrifying bacteria abundance present in citrus- and eucalyptus-cultivated soils, mainly through the effects on soil and plant residue physicochemical characteristics, especially those related to COD and soil moisture.
O uso de resíduo de construção civil como substituto de agregados naturais em concretos: avaliação de alguns parâmetros de durabilidade
(Universidade Federal de São Carlos, 2018-05-03) Nanya, Carolina Shimomura; Capuzzo, Valdirene Maria Silva; https://lattes.cnpq.br/9977729587548984; Ferreira, Fernanda Giannotti da Silva; https://lattes.cnpq.br/0329487394818763; https://lattes.cnpq.br/6108203227140594
The concern about the environmental impacts generated by the construction industry, which traditionally requires large quantities of raw materials and usually generate a large amount of waste, motivated the development of the Solid Waste National Policy that regulates and seek for sustainable solutions that can mitigate these effects. Additionally to this is the increased inspection of waste disposal and the interest of construction companies in reducing their costs, so the use of the recycled aggregate in the production of conventional concrete, appears as an alternative source of raw material. The research was developed with the objective of studying the influence of the use of recycled aggregates of construction and demolition waste in concrete submitted to different aggressive agents. The study presents the granulometric and physical characteristics of fine and coarse aggregates, being the recycled coarse aggregates were obtained from the process of recycling waste from the construction industry and collected at the provider Sand Beautiful View, located in Sobradinho, northern region of Brasília. After the characterization of the materials, the concrete test specimens were dosed by mass, with the substitution of the recycled aggregates in volume, in five replacement contents of the coarse recycled aggregate (0%, 30%, 50%, 70% e 100%). The water cement ratio considered was 0,55 and it was considered an additional amount of water obtained from tests of absorption with the recycled aggregate. In order to maintain the workability it was used superplasticizer additive. It was analyzed the following properties: compressive strength, diametric compression tensile strength, modulus of elasticity, absorption of water by capillarity, water absorption, voids index and specific mass, depth of ions chloride, carbonation and electrical resistivity. The results showed the feasibility of the use of the recycled coarse aggregate in the concrete production, considering the mechanical properties of the concretes, since it complies with the requirements specified in NBR 12655: 2015, and also the durability, since the results indicate low (CEB 192) and moderate (COST 509) risk of corrosion, and the depth of penetration of chloride ions as well as the carbonation did not exceed the concrete cover thickness. The substitution content of 30% of recycled aggregate presented better results from a mechanical and durability point of view and present to be the ideal replacement contend for the construction and demolition waste.