Amazonia as a carbon source linked to deforestation and climate change

Amazonia hosts the Earth's largest tropical forests and has been shown to be an important carbon sink over recent decades1-3. This carbon sink seems to be in decline, however, as a result of factors such as deforestation and climate change1-3. Here we investigate Amazonia's carbon budget and the main drivers responsible for its change into a carbon source. We performed 590 aircraft vertical profiling measurements of lower-tropospheric concentrations of carbon dioxide and carbon monoxide at four sites in Amazonia from 2010 to 20184. We find that total carbon emissions are greater in eastern Amazonia than in the western part, mostly as a result of spatial differences in carbon-monoxide-derived fire emissions. Southeastern Amazonia, in particular, acts as a net carbon source (total carbon flux minus fire emissions) to the atmosphere. Over the past 40 years, eastern Amazonia has been subjected to more deforestation, warming and moisture stress than the western part, especially during the dry season, with the southeast experiencing the strongest trends5-9. We explore the effect of climate change and deforestation trends on carbon emissions at our study sites, and find that the intensification of the dry season and an increase in deforestation seem to promote ecosystem stress, increase in fire occurrence, and higher carbon emissions in the eastern Amazon. This is in line with recent studies that indicate an increase in tree mortality and a reduction in photosynthesis as a result of climatic changes across Amazonia1,10.</p

Amazonia as a carbon source linked to deforestation and climate change

Amazonia hosts the Earth’s largest tropical forests and has been shown to be an important carbon sink over recent decades1,2,3. This carbon sink seems to be in decline, however, as a result of factors such as deforestation and climate change1,2,3. Here we investigate Amazonia’s carbon budget and the main drivers responsible for its change into a carbon source. We performed 590 aircraft vertical profiling measurements of lower-tropospheric concentrations of carbon dioxide and carbon monoxide at four sites in Amazonia from 2010 to 20184. We find that total carbon emissions are greater in eastern Amazonia than in the western part, mostly as a result of spatial differences in carbon-monoxide-derived fire emissions. Southeastern Amazonia, in particular, acts as a net carbon source (total carbon flux minus fire emissions) to the atmosphere. Over the past 40 years, eastern Amazonia has been subjected to more deforestation, warming and moisture stress than the western part, especially during the dry season, with the southeast experiencing the strongest trends5,6,7,8,9. We explore the effect of climate change and deforestation trends on carbon emissions at our study sites, and find that the intensification of the dry season and an increase in deforestation seem to promote ecosystem stress, increase in fire occurrence, and higher carbon emissions in the eastern Amazon. This is in line with recent studies that indicate an increase in tree mortality and a reduction in photosynthesis as a result of climatic changes across Amazonia1,10

Comparative Study of Commercial Oxide Electrodes Performance in Electrochemical Degradation of Organics in Aqueous Solutions

In this paper the potentiality of two types of DSAâ commercial electrodes, for electrochemical treatment of effluents, is investigated. Oxide anodes, with nominal composition of 70TiO2/30RuO2 and 45IrO2/55Ta2O5, were used in a flow-cell reactor for the electrooxidation of phenol. Comparative results were presented as phenol concentration decay as a function of electrolysis time, as well as COD and TOC concentration reduction. The cell reactor was operated at current densities, ranging from 15 to 150 mA cm-2 and solution linear velocity was 0.24 m s-1. Results reported in this paper showed that phenol and quinones were degraded to a very low concentration, besides only a small portion of the organic carbon is reduced. Starting from 100 mg L-1, after five hours of electrolysis at 100 mA cm-2, concentrations reached 0.4 mg L-1 of phenol, 1 mg L-1 of hydroquinone, 7 mg L-1 of benzoquinone and TOC was reduced by 35%.Neste trabalho foi realizado um estudo visando a potencial aplicação de dois eletrodos comerciais tipo DSAâ no tratamento eletroquímico de efluentes aquosos. Anodos com composição superficial 70TiO2/30RuO2 e 45IrO2/55Ta2O5 foram usados num reator de fluxo com densidades de corrente de 15 a 150 mA.cm-2 e velocidade da solução de 0,24 m.s-1. Os resultados mostram que fenol e as quinonas são degradados até concentrações muito baixas, embora apenas uma pequena fração seja mineralizada. A partir de uma solução com 100 mg.L-1 de fenol, a 100 mA.cm-2, após cinco horas de eletrólise foram encontrados 0,4 mg.L-1 de fenol, 1 mg.L-1 de hidroquinona e 7 mg.L-1 de benzoquinona. TOC foi reduzido em 35%.606

A presença dos moinhos hidráulicos no Brasil

O presente artigo pretende recolocar a importância do estudo da história da técnica para o entendimento das estruturas agrárias e das paisagens culturais brasileiras. Investigando a história dos moinhos hidráulicos no país, procura-se apontar o potencial existente no estudo da cultura material a eles associada e em uma abordagem histórica da terminologia. Desse modo três grandes questões são abordadas: o papel dos moinhos nas estruturas agrárias do interior do país, as raízes mediterrânicas das técnicas envolvidas na construção desses maquinismos e a importância das mós remanescentes