47 research outputs found
Can land use changes alter carbon, nitrogen and major ion transport in subtropical brazilian streams?
Diversos estudos tĂȘm sido desenvolvidos em bacias de drenagem tropicais no intuito de avaliar o impacto da urbanização e das prĂĄticas agrĂcolas na qualidade dos corpos d'ĂĄgua. No Brasil, as savanas (conhecidas regionalmente como Cerrado) representam 23% do territĂłrio brasileiro, sendo uma regiĂŁo importante no crescimento nacional, especialmente devido Ă s intensas atividades agrĂcolas. A finalidade deste trabalho Ă© apresentar uma avaliação dos fluxos de carbono, nitrogĂȘnio e principais Ăons em cĂłrregos com diferentes usos do solo (vegetação, cana de açĂșcar e eucalipto) em uma regiĂŁo de Cerrado, SE Brasil. A cana de açĂșcar e o eucalipto alteram o transporte dos elementos investigados nessas pequenas bacias de drenagem. As concentraçÔes mais elevadas de todos os parĂąmetros analisados (parĂąmetros abiĂłticos, Ăons, carbono orgĂąnico dissolvido e carbono inorgĂąnico dissolvido) foram encontradas na bacia de cana de açĂșcar (SCW). As concentraçÔes observadas para os cĂĄtions na bacia do eucalipto (EW) (Mg, Ca, K, Na), assim como Carbono InorgĂąnico Dissolvido (CID) e Carbono OrgĂąnico Dissolvido (COD), apresentaram valores intermediĂĄrios entre as bacias do Cerrado e da cana de açĂșcar, sugerindo um impacto moderado dessa plantação aos corpos d'ĂĄgua. Mesma tendĂȘncia foi observada para os fluxos de Ăons e nutrientes, sendo, novamente, os maiores valores encontrados na bacia de cana-de-açĂșcar. Os autores sugerem que o cultivo da cana de açĂșcar representa um importante fator na modificação da quĂmica 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
Pervasive gaps in Amazonian ecological research
Biodiversity loss is one of the main challenges of our time,1,2 and attempts to address it require a clear un derstanding of how ecological communities respond to environmental change across time and space.3,4
While the increasing availability of global databases on ecological communities has advanced our knowledge
of biodiversity sensitivity to environmental changes,5â7 vast areas of the tropics remain understudied.8â11 In
the American tropics, Amazonia stands out as the worldâs most diverse rainforest and the primary source of
Neotropical biodiversity,12 but it remains among the least known forests in America and is often underrepre sented in biodiversity databases.13â15 To worsen this situation, human-induced modifications16,17 may elim inate pieces of the Amazonâs biodiversity puzzle before we can use them to understand how ecological com munities are responding. To increase generalization and applicability of biodiversity knowledge,18,19 it is thus
crucial to reduce biases in ecological research, particularly in regions projected to face the most pronounced
environmental changes. We integrate ecological community metadata of 7,694 sampling sites for multiple or ganism groups in a machine learning model framework to map the research probability across the Brazilian
Amazonia, while identifying the regionâs vulnerability to environmental change. 15%â18% of the most ne glected areas in ecological research are expected to experience severe climate or land use changes by
2050. This means that unless we take immediate action, we will not be able to establish their current status,
much less monitor how it is changing and what is being lostinfo:eu-repo/semantics/publishedVersio
Pervasive gaps in Amazonian ecological research
Biodiversity loss is one of the main challenges of our time,1,2 and attempts to address it require a clear understanding of how ecological communities respond to environmental change across time and space.3,4 While the increasing availability of global databases on ecological communities has advanced our knowledge of biodiversity sensitivity to environmental changes,5,6,7 vast areas of the tropics remain understudied.8,9,10,11 In the American tropics, Amazonia stands out as the world's most diverse rainforest and the primary source of Neotropical biodiversity,12 but it remains among the least known forests in America and is often underrepresented in biodiversity databases.13,14,15 To worsen this situation, human-induced modifications16,17 may eliminate pieces of the Amazon's biodiversity puzzle before we can use them to understand how ecological communities are responding. To increase generalization and applicability of biodiversity knowledge,18,19 it is thus crucial to reduce biases in ecological research, particularly in regions projected to face the most pronounced environmental changes. We integrate ecological community metadata of 7,694 sampling sites for multiple organism groups in a machine learning model framework to map the research probability across the Brazilian Amazonia, while identifying the region's vulnerability to environmental change. 15%â18% of the most neglected areas in ecological research are expected to experience severe climate or land use changes by 2050. This means that unless we take immediate action, we will not be able to establish their current status, much less monitor how it is changing and what is being lost
COVID-19 symptoms at hospital admission vary with age and sex: results from the ISARIC prospective multinational observational study
Background:
The ISARIC prospective multinational observational study is the largest cohort of hospitalized patients with COVID-19. We present relationships of age, sex, and nationality to presenting symptoms.
Methods:
International, prospective observational study of 60â109 hospitalized symptomatic patients with laboratory-confirmed COVID-19 recruited from 43 countries between 30 January and 3 August 2020. Logistic regression was performed to evaluate relationships of age and sex to published COVID-19 case definitions and the most commonly reported symptoms.
Results:
âTypicalâ symptoms of fever (69%), cough (68%) and shortness of breath (66%) were the most commonly reported. 92% of patients experienced at least one of these. Prevalence of typical symptoms was greatest in 30- to 60-year-olds (respectively 80, 79, 69%; at least one 95%). They were reported less frequently in children (â€â18 years: 69, 48, 23; 85%), older adults (â„â70 years: 61, 62, 65; 90%), and women (66, 66, 64; 90%; vs. men 71, 70, 67; 93%, each Pâ<â0.001). The most common atypical presentations under 60 years of age were nausea and vomiting and abdominal pain, and over 60 years was confusion. Regression models showed significant differences in symptoms with sex, age and country.
Interpretation:
This international collaboration has allowed us to report reliable symptom data from the largest cohort of patients admitted to hospital with COVID-19. Adults over 60 and children admitted to hospital with COVID-19 are less likely to present with typical symptoms. Nausea and vomiting are common atypical presentations under 30 years. Confusion is a frequent atypical presentation of COVID-19 in adults over 60 years. Women are less likely to experience typical symptoms than men
Hydrochemistry of Cachoeira River (Bahia State, Brazil) HidroquĂmica do Rio Cachoeira (Bahia, Brasil)
AIM: The aim of this study is to evaluate the spatial-temporal changes of chemical elements in the surface waters of the Cachoeira River in order to evaluate the impacts of anthropogenic activities in water quality; METHODS: Samples were collected monthly between August 2008 and August 2009 at six collection points along the river. The abiotic parameters dissolved oxygen, pH, electrical conductivity and temperature were performed in the field using portable digital meters; concentration of ions nitrite (NO2-), nitrate (NO3-), ammonia (NH4+), phosphate (PO4-), sodium (Na+), calcium (Ca+2), potassium (K+), chloride (Cl-), magnesium (Mg+2), sulfate (SO4-2) were determined by ion chromatography and bicarbonate (HCO3-) was calculated by a model of ionic associations originated from alkalinity values; RESULTS: The spatial variations showed that anthropogenic activities and land use changes (cocoa crops and pasture) appear to be the major factors influencing the distribution of nutrients in the Cachoeira River; however, lithology seems to be the factor influencing the major ions; CONCLUSIONS: Variations in ion concentrations were directly related to drought and rainy periods, the geological formation, and the various land uses. The lack of treatment of domestic wastes and their incorrect disposal in water bodies has significantly contributed to the aggravation of environmental problems and consequently the health of the population.OBJETIVO: O objetivo do presente estudo foi avaliar as variaçÔes espaço temporais da quĂmica das ĂĄguas superficiais do Rio Cachoeira a fim de estabelecer os impactos das atividades antropogĂȘnicas na qualidade da ĂĄgua; MĂTODOS: As coletas foram realizadas mensalmente entre agosto de 2008 e agosto de 2009 em seis pontos de coleta ao longo do rio. Os parĂąmetros abiĂłticos oxigĂȘnio dissolvido, pH, condutividade elĂ©trica e temperatura foram determinados atravĂ©s de medidores portĂĄteis no campo; a concentração dos Ăons nitrito (NO2-), nitrato (NO3-), amĂŽnia (NH4+), fosfato (PO4-), sĂłdio (Na+), cĂĄlcio (Ca+2), potĂĄssio (K+), cloreto (Cl-), magnĂ©sio (Mg+2), sulfato (SO4-2) atravĂ©s da cromatografia iĂŽnica e o bicarbonato (HCO3-) atravĂ©s da alcalinidade; RESULTADOS: Os resultados referentes a variação espacial no Rio Cachoeira demonstraram que as atividades antropogĂȘnicas e os diferentes cultivos ao longo da bacia (cultivo de cacau e pastagem) sĂŁo os principais fatores que influenciam na distribuição dos nutrientes (N e P). No entanto, a litologia parece ser o principal responsĂĄvel pelas concentraçÔes dos Ăons maiores, nĂŁo havendo diferenças entre os pontos de coleta; CONCLUSĂES: As variaçÔes das concentraçÔes dos Ăons foram diretamente relacionadas aos perĂodos mais secos e mais chuvosos, a formação geolĂłgica e aos diversos usos da terra. A ausĂȘncia do tratamento de resĂduos domĂ©sticos e seu despejo imprĂłprio nos corpos de ĂĄgua tĂȘm contribuĂdo para o agravamento dos problemas ambientais e consequentemente Ă saĂșde da população
Hydrochemistry of Cachoeira River (Bahia State, Brazil)
AIM: The aim of this study is to evaluate the spatial-temporal changes of chemical elements in the surface waters of the Cachoeira River in order to evaluate the impacts of anthropogenic activities in water quality; METHODS: Samples were collected monthly between August 2008 and August 2009 at six collection points along the river. The abiotic parameters dissolved oxygen, pH, electrical conductivity and temperature were performed in the field using portable digital meters; concentration of ions nitrite (NO2-), nitrate (NO3-), ammonia (NH4+), phosphate (PO4-), sodium (Na+), calcium (Ca+2), potassium (K+), chloride (Cl-), magnesium (Mg+2), sulfate (SO4-2) were determined by ion chromatography and bicarbonate (HCO3-) was calculated by a model of ionic associations originated from alkalinity values; RESULTS: The spatial variations showed that anthropogenic activities and land use changes (cocoa crops and pasture) appear to be the major factors influencing the distribution of nutrients in the Cachoeira River; however, lithology seems to be the factor influencing the major ions; CONCLUSIONS: Variations in ion concentrations were directly related to drought and rainy periods, the geological formation, and the various land uses. The lack of treatment of domestic wastes and their incorrect disposal in water bodies has significantly contributed to the aggravation of environmental problems and consequently the health of the population
Litter inputs and standing stocks in riparian zones and streams under secondary forest and managed and abandoned cocoa agroforestry systems
Background Cocoa is an important tropical tree crop that is mainly cultivated in agroforestry systems (AFS). This system, known as cabruca in northeastern Brazil, holds promise to reconcile biodiversity conservation and economic development. However, since cocoa AFS alters forest structure composition, it can affect litter dynamics in riparian zones and streams. Thus, our objective was to determine litter inputs and standing stocks in riparian zones and streams under three types of forest: managed cocoa AFS, abandoned cocoa AFS, and secondary forest. Methods We determined terrestrial litter fall (TI), vertical (VI) and lateral (LI) litter inputs to streams, and litter standing stocks on streambeds (BS) in the Atlantic Forest of northeastern Brazil. Litter was collected every 30 days from August 2018 to July 2019 using custom-made traps. The litter was dried, separated into four fractions (leaves, branches, reproductive organs, and miscellaneous material) and weighed. Results Terrestrial litter fall was similar in all forests, ranging from 89 g mâ2 monthâ1 in secondary forest (SF) to 96 g mâ2 monthâ1 in abandoned cocoa AFS (AC). Vertical input were higher in AC (82 g mâ2 monthâ1) and MC (69 g mâ2 monthâ1) than in SF (40 g mâ2 monthâ1), whereas lateral input were higher in MC (43 g mâ2 monthâ1) than in AC (15 g mâ2 monthâ1) and SF (24 g mâ2 monthâ1). Standing stocks followed the order SF > AC > MC, corresponding to 425, 299 and 152 g mâ2. Leaves contributed most to all litter fractions in all forests. Reproductive plant parts accounted for a larger proportion in managed AFS. Branches and miscellaneous litter were also similar in all forests, except for higher benthic standing stocks of miscellaneous litter in the SF. Despite differences in the amounts of litter inputs and standing stocks among the forests, seasonal patterns in the abandoned AFS (AC) were more similar to those of the secondary forest (SF) than the managed AFS, suggesting potential of abandoned AFS to restore litter dynamics resembling those of secondary forests
Soil organic matter and CO<sub>2</sub> fluxes in small tropical watersheds under forest and cacao agroforestry
<div><p>Annual estimates of CO<sub>2</sub> and dissolved carbon concentrations in the soil profile provide valuable insight into the dynamics of organic matter in soil and the effect of changes to vegetation cover. The aim of this study was to observe the spatial influence of litter decomposition in the first few centimeters of the soil for CO<sub>2</sub> fluxes and to describe the processing of soil organic matter throughout the soil profile by comparing three small tropical watersheds. Data were collected biweekly for six months, from December 2015 to May 2016. CO<sub>2</sub> was measured using an infrared gas analyzer in fixed chambers and the dissolved carbon of soil solution was analyzed in a TOC analyzer. No differences were found in the total soil CO<sub>2</sub> fluxes (control flux treatments) between the three study areas. In both cacao agroforestry systems (managed and unmanaged), total CO<sub>2</sub> fluxes were influenced by the decomposition of litter. CO<sub>2</sub> emissions in the soil profile of the cacao agroforestry systems were highly variable, compared to the preserved forest, and highly dependent on the soil characteristics attributed to the type of vegetation cover. Although a definite pattern between the temperature and soil moisture was not identified, these parameters showed a strong relationship in controlling the release of CO<sub>2</sub> between treatments. The organic and inorganic dissolved carbon patterns in the soil solution of the three areas revealed different responses of soil organic matter processing related to soil characteristics and vegetation. The results confirm the hypothesis that the top of soils (total CO<sub>2</sub> fluxes) of both cacao agroforestry systems (managed and unmanaged) emits fluxes of CO<sub>2,</sub> which do not differ statistically from the preserved forest. However, depending on the soil characteristics, the cacao agroforestry system can result in an accumulation of CO<sub>2</sub> and dissolved inorganic carbon in the soil profile that is prone to being transported by hydrological routes to groundwater and stream water.</p></div
Land use effects on nutrient concentrations in a small watershed in northeast Brazil
Increases of N and P discharges from inland waters to coastal environments are the by-products of human activities such as agricultural practices. Therefore, the aim of this work is to evaluate the influence of land use change in nutrient concentrations in a small watershed in southern Bahia, Brazil. The study sites were characterized by secondary forest (P1), sand mining (P2), cocoa cultivation (P3), pasture (P4) and mangrove (P5). Dissolved forms of both nitrogen and phosphorus were higher than particulate forms in all sites. The DON concentration was higher than the DIN and the concentration of DON made up 60-73% of the total TDN. Seasonally, high variations between dry and rainy season were not observed in nutrient concentrations in Cururupe River Basin, with the exception of DON, which was higher in the rainy season. DIN, DON and PON export varies over the hydrological year indicating that fluxes were correlated with runoff. Even though the primary vegetation of The Cururupe River Basin was converted to different croplands, mainly cocoa production, the water quality presented low alterations in N and P export from upstream to downstream