Can land use changes alter carbon, nitrogen and major ion transport in subtropical brazilian streams?

Diversos estudos têm sido desenvolvidos em bacias de drenagem tropicais no intuito de avaliar o impacto da urbanização e das práticas agrícolas na qualidade dos corpos d'água. No Brasil, as savanas (conhecidas regionalmente como Cerrado) representam 23% do território brasileiro, sendo uma região importante no crescimento nacional, especialmente devido às intensas atividades agrícolas. A finalidade deste trabalho é apresentar uma avaliação dos fluxos de carbono, nitrogênio e principais íons em córregos com diferentes usos do solo (vegetação, cana de açúcar e eucalipto) em uma região de Cerrado, SE Brasil. A cana de açúcar e o eucalipto alteram o transporte dos elementos investigados nessas pequenas bacias de drenagem. As concentrações mais elevadas de todos os parâmetros analisados (parâmetros abióticos, íons, carbono orgânico dissolvido e carbono inorgânico dissolvido) foram encontradas na bacia de cana de açúcar (SCW). As concentrações observadas para os cátions na bacia do eucalipto (EW) (Mg, Ca, K, Na), assim como Carbono Inorgânico Dissolvido (CID) e Carbono Orgânico Dissolvido (COD), apresentaram valores intermediários entre as bacias do Cerrado e da cana de açúcar, sugerindo um impacto moderado dessa plantação aos corpos d'água. Mesma tendência foi observada para os fluxos de íons e nutrientes, sendo, novamente, os maiores valores encontrados na bacia de cana-de-açúcar. Os autores sugerem que o cultivo da cana de açúcar representa um importante fator na modificação da química de pequenas bacias de drenagem.Several studies in tropical watersheds have evaluated the impact of urbanization and agricultural practices on water quality. In Brazil, savannas (known regionally as Cerrados) represent 23% of the country's surface, representing an important share to the national primary growth product, especially due to intense agriculture. The purpose of this study is to present a comprehensive evaluation, on a yearly basis, of carbon, nitrogen and major ion fluxes in streams crossing areas under different land use (natural vegetation, sugar cane and eucalyptus) in a savanna region of SE Brazil. Eucalyptus and sugar cane alter the transport of the investigated elements in small watersheds. The highest concentration of all parameters (abiotic parameters, ions, dissolved organic carbon DOC - and dissolved inorganic carbon - DIC) were found in Sugar Cane Watersheds (SCW). The observed concentrations of major cations in Eucalyptus Watersheds (EW) (Mg, Ca, K, Na), as well as DIN and DOC, were found frequently to be intermediate values between those of Savanna Watersheds (SW) and SCW, suggesting a moderate impact of eucalyptus plantations on the streamwater. Same trends were found in relation to ion and nutrient fluxes, where the higher values corresponded to SCW. It is suggested that sugar cane plantations might be playing an important role in altering the chemistry of water bodies

Cycling process and emission of effect gases greenhouse in hydroelectric reservoir of the center-West of Brazil (Cerrado)

Foi apresentado um sistema automatizado para monitorar fluxos de metano (CH4) e do dióxido de carbono (CO2) na relação da água/ar de ecossistemas aquáticos. Consiste em uma série de câmaras flutuantes dinâmicas acopladas a um analisador photo acústico infravermelho de gás. Associado os outros sensores atmosféricos e de qualidade da água, foi possível identificar os fatores atmosféricos, hidrológico e biológico que afetam emissões de CH4 e de CO2 no reservatório de Corumbá (estado de Goiás), uma terra inundada antropogenica de savana. O estudo realizado em novembro 2004 e em março/agosto 2005 permitiu uma inter-correlação desobstruídos de estabelecimento da câmara, embora relações ligadas da profundidade-fluxo. Os fluxos de CH4 borbulhando médios em novembro 2004, em março e em agosto 2005 eram respectivamente 0.05 ± 2.19, 4 ± 45 e 505 o ± 1192 mg/m2/d. Para os mesmos meses, as emissões de CH4 difusivo médias foram 17 o ± 6, 37 ± 9 e 69 o ± 28 mg/m2/d, visto que os fluxos difusivo do CO2 foram respectivamente 59 o ± 398, 385 ± 629 e o ± 1466 1223 mg/m2/d. Um aspecto interessante de bolhas de CH4 é a liberação repentina e grande em locais rasos e liberação do escoamento em locais profundos. Em uma base diária, a freqüência e o valor de bolhas de CH4 são condicionados à oxidação durante períodos da flutuação do lago, e às mudanças totais da pressão exercidas no sedimento. Em escalas de tempo sazonal, a intensidade de bolhas de CH4 é condicionada principalmente pela disponibilidade da carcaça ao metanogeneses. As frentes frias são responsáveis pela a ruptura da estratificação (misturar), favorecendo emissões do CO2 depois da oxidação CH4. As emissões do CO2 puderam também ser acopladas ao diel metanotrófico. Nossos resultados sugerem que as emissões de gás do efeito estufa de Corumbá estão controladas pela maior parte pelo nível de água e pela luz solar.It was present an automated system for monitoring methane (CH4) and carbon dioxide (CO2) fluxes at the water/air interface of aquatic ecosystems. It consists of a series of floating dynamic chambers coupled to an infrared photo acoustic gas analyzer. Associated to other atmospheric and water quality sensors, it was possible to identify atmospheric, hydrologic and biological factors affecting CH4 and CO2 emissions at Corumbá reservoir (State of Goiás), a savanna anthropogenic flooded land. The study carried out in November 2004 and March/August 2005 allowed establishing clear chamber inter-correlations, although intricate depth-flux relations. Mean CH4 bubbling fluxes in November 2004, March and August 2005 were respectively 0.05 ± 2.19, 4 ± 45 and 505 ± 1192 mg/m2/d. For the same months, mean CH4 diffusive emissions were 17 ± 6, 37 ± 9 and 69 ± 28 mg/m2/d, whereas CO2 diffusive fluxes were respectively 59 ± 398, 385 ± 629 and 1466 ± 1223 mg/m2/d. An interesting aspect of CH4 bubbling is the sudden and large release at shallow sites and seepage release at deep sites. On a daily basis, the frequency and magnitude of CH4 bubbling is conditioned to oxidation during overturn periods, and to the total pressure changes exerted on the sediment. At seasonal time scales, CH4 bubbling intensity is mainly conditioned by substrate availability to methanogenesis. Cold fronts are responsible for stratification rupture (mixing), favoring CO2 emissions following CH4 oxidation. CO2 emissions might also be coupled to diel methanotrophy. Our results suggest that greenhouse gas emissions from Corumbá are largely controlled by water level and sunlight

Methane stocks in tropical hydropower reservoirs as a potential energy source

Several studies over the last decade have shown that tropical reservoirs may constitute an appreciable source of methane (CH4) to the atmosphere. Here, we show that the use of low-cost, innovative mitigation and recovery strategies is able not only to reduce these emissions, but also to transform existing biogenic methane stocks into a renewable energy source. Recovered gas may be pumped to large consuming centers or stored locally and burned by gas turbines to generate electricity during high-demand periods, or even purified for transport applications. Our analysis shows that the use of biogenic methane may increase considerably the energy supply in countries, like Brazil, which possess large tropical reservoirs. © 2009 Springer Science+Business Media B.V

Runoff, soil loss, and sources of particulate organic carbon delivered to streams by sugarcane and riparian areas: An isotopic approach

© 2019 Elsevier B.V. Soil erosion leads to land degradation and translocation of soil particles together with associated particulate organic carbon (POC)and nutrients, thereby influencing the global carbon cycle. In the present study, we estimated the contribution of POC delivered to a first-order stream from upslope sugarcane fields and a riparian forest in southeast Brazil. The results show that the amount of surface runoff and soil erosion generated in the riparian forest is significantly lower than in the upslope sugarcane field. However, the contribution of the forest to the total stream bed POC was above 70%, even though most sediments delivered to the stream originated from the upland sugarcane fields. The discrepancy between sediment and POC delivery from both land uses is a consequence of the presence of preferential runoff pathways from the agricultural fields, through the buffer strips, to the stream. This disconnection between the main sources of sediment and POC to the first-order stream is a potentially important mechanism influencing the transfer of POC from upslope areas to waterways. This mechanism should be considered in order to more reliably assess fluxes of OC from upslope areas to first-order streams in landscapes where arable land is separated from streams by a semi-natural buffer zone with permanent vegetation.status: publishe

Biogeochemical diversity, O2-supersaturation and hot moments of GHG emissions from shallow alkaline lakes in the Pantanal of Nhecolândia, Brazil

International audienceNhecolândia is a vast sub-region of the Pantanal wetland in Brazil with great diversity in surface water chemistry evolving in a sodic alkaline pathway under the influence of evaporation. In this region, more than 15,000 shallow lakes are likely to contribute an enormous quantity of greenhouse gas to the atmosphere, but the diversity of the biogeochemical scenarios and their variability in time and space is a major challenge to estimate the regional contribution. From 4 selected alkaline lakes, we compiled measurements of the physico-chemical characteristics of water and sediments, gas fluxes in floating chambers, and sedimentation rates to illustrate this diversity. Although these lakes have a similar chemical composition, the results confirm a difference between the black-water and green-water alkaline lakes, corresponding to distinct biogeochemical functioning. This difference does not appear to affect lake sedimentation rates, but is reflected in gas emissions. Black-water lakes are CO2 and CH4 sources, with fairly constant emissions throughout the seasons. Annual carbon dioxide and methane emissions approach 0.86 mol m-2 y-1 and 0.07 mol m-2 y-1 , respectively, and no clear trend towards N2O capture or emission was observed. By contrast, green-water lakes are CO2 and N2O sinks but important CH4 sources with fluxes varying significantly throughout the seasons, depending on the magnitude of the phytoplankton bloom. The results highlight important daily and seasonal variations in gas fluxes, and in particular a hot moments for methane emissions, when the O2-supersaturation is reached during the afternoon under extreme bloom and sunny weather conditions, provoking an abrupt O2 purging of the lakes. Taking into account the seasonal variability, annual methane emissions are around 10.2 mol m-2 y-1 , i.e., much higher than reported in previous studies for alkaline lakes in Nhecolândia. Carbon dioxide and nitrous oxide consumption is estimated about 1.9 mol m-2 y-1 and 0.73 mmol m-2 y-1 , respectively. However, these balances must be better constrained with systematic and targeted measurements throughout the seasons

Carbon and Nitrogen Isotope Ratios of Food and Beverage in Brazil

Several previous studies on targeted food items using carbon and nitrogen stable isotope ratios in Brazil have revealed that many of the items investigated are adulterated; mislabeled or even fraud. Here, we present the first Brazilian isotopic baseline assessment that can be used not only in future forensic cases involving food authenticity, but also in human forensic anthropology studies. The δ13C and δ15N were determined in 1245 food items and 374 beverages; most of them made in Brazil. The average δ13C and δ15N of C3 plants were −26.7 ± 1.5‰, and 3.9 ± 3.9‰, respectively, while the average δ13C and δ15N of C4 plants were −11.5 ± 0.8‰ and 4.6 ± 2.6‰, respectively. The δ13C and δ15N of plant-based processed foods were −21.8 ± 4.8‰ and 3.9 ± 2.7‰, respectively. The average δ13C and δ15N of meat, including beef, poultry, pork and lamb were -16.6 ± 4.7‰, and 5.2 ± 2.6‰, respectively, while the δ13C and δ15N of animal-based processed foods were −17.9 ± 3.3‰ and 3.3 ± 3.5‰, respectively. The average δ13C of beverages, including beer and wine was −22.5 ± 3.1‰. We verified that C-C4 constitutes a large proportion of fresh meat, dairy products, as well as animal and plant-based processed foods. The reasons behind this high proportion will be addressed in this study

Can land use changes alter carbon, nitrogen and major ion transport in subtropical brazilian streams? Modificações no uso da terra podem alterar o transporte fluvial de carbono, nitrogênio e íons maiores?

Several studies in tropical watersheds have evaluated the impact of urbanization and agricultural practices on water quality. In Brazil, savannas (known regionally as Cerrados) represent 23% of the country's surface, representing an important share to the national primary growth product, especially due to intense agriculture. The purpose of this study is to present a comprehensive evaluation, on a yearly basis, of carbon, nitrogen and major ion fluxes in streams crossing areas under different land use (natural vegetation, sugar cane and eucalyptus) in a savanna region of SE Brazil. Eucalyptus and sugar cane alter the transport of the investigated elements in small watersheds. The highest concentration of all parameters (abiotic parameters, ions, dissolved organic carbon DOC - and dissolved inorganic carbon - DIC) were found in Sugar Cane Watersheds (SCW). The observed concentrations of major cations in Eucalyptus Watersheds (EW) (Mg, Ca, K, Na), as well as DIN and DOC, were found frequently to be intermediate values between those of Savanna Watersheds (SW) and SCW, suggesting a moderate impact of eucalyptus plantations on the streamwater. Same trends were found in relation to ion and nutrient fluxes, where the higher values corresponded to SCW. It is suggested that sugar cane plantations might be playing an important role in altering the chemistry of water bodies.<br>Diversos estudos têm sido desenvolvidos em bacias de drenagem tropicais no intuito de avaliar o impacto da urbanização e das práticas agrícolas na qualidade dos corpos d'água. No Brasil, as savanas (conhecidas regionalmente como Cerrado) representam 23% do território brasileiro, sendo uma região importante no crescimento nacional, especialmente devido às intensas atividades agrícolas. A finalidade deste trabalho é apresentar uma avaliação dos fluxos de carbono, nitrogênio e principais íons em córregos com diferentes usos do solo (vegetação, cana de açúcar e eucalipto) em uma região de Cerrado, SE Brasil. A cana de açúcar e o eucalipto alteram o transporte dos elementos investigados nessas pequenas bacias de drenagem. As concentrações mais elevadas de todos os parâmetros analisados (parâmetros abióticos, íons, carbono orgânico dissolvido e carbono inorgânico dissolvido) foram encontradas na bacia de cana de açúcar (SCW). As concentrações observadas para os cátions na bacia do eucalipto (EW) (Mg, Ca, K, Na), assim como Carbono Inorgânico Dissolvido (CID) e Carbono Orgânico Dissolvido (COD), apresentaram valores intermediários entre as bacias do Cerrado e da cana de açúcar, sugerindo um impacto moderado dessa plantação aos corpos d'água. Mesma tendência foi observada para os fluxos de íons e nutrientes, sendo, novamente, os maiores valores encontrados na bacia de cana-de-açúcar. Os autores sugerem que o cultivo da cana de açúcar representa um importante fator na modificação da química de pequenas bacias de drenagem