S. T. Oliva

Exchange of short‐chain monocarboxylic acids by vegetation at a remote tropical forest site in Amazonia

[1] As part of the project LBA-EUSTACH (European Studies on Trace gases and Atmospheric Chemistry as a contribution to the Large-Scale Biosphere-Atmosphere experiment in Amazonia), the exchange of formic acid and acetic acid between vegetation and the atmosphere was investigated in the wet-to-dry season transition and the dry-to-wet season transition periods in 1999 in Rondonia, Brazil. Direct exchange measurements on the branch level mainly exhibited uptake of formic acid and acetic acid for all plant species in both seasons, although diel, seasonal, and interspecies variations were observed. Even though other physiological and physico-chemical parameters may have contributed, the uptake of organic acids was found to be primarily a function of the ambient atmospheric mixing ratios. The linear dependence suggests a bidirectional exchange behavior of the plants and calculated deposition velocities (0.17-0.23 cm s -1 ), compensation point mixing ratios (0.16-0.30 ppb), and potential emission rates under purified air conditions (0.013-0.031 nmol m -2 s -1 ) are discussed. Vertical profile measurements in and above the primary forest canopy further strengthened the assumption that the forest is rather a sink than a source for organic acids. The generally lower mixing ratios observed within the canopy were indicative of an uptake by vegetation and/or the soil surface. Continuous measurements of the ambient atmospheric mixing ratios at the canopy top revealed strong diel variations in both seasons and a marked seasonality with higher mixing ratios during the dry season, both being mirrored in the variation of observed uptake rates of the plants. High atmospheric concentrations during the dry season were attributed to biomass burning. During the wet season, when biomass burning activity was low, indirect emission by the vegetation, i.e., photochemical oxidation of primarily emitted biogenic reactive hydrocarbons, was assumed to dominantly contribute to the atmospheric burden of the organic acids. The high degree of correlation between atmospheric formic acid and acetic acid indicated that similar atmospheric processes were affecting their mixing ratios.

EXCHANGE OF SHORT-CHAIN ALDEHYDES BETWEEN AMAZONIAN VEGETATION AND THE ATMOSPHERE

As a part of the LBA-EUSTACH (EUropean Studies on Trace Gases and Atmospheric CHemistry as a contribution of the Large-scale Biosphere-Atmosphere ex- periment in Amazonia) project, the exchanges of formaldehyde (HCHO) and acetaldehyde (CH3CHO) between Amazonian vegetation and the atmosphere were investigated by branch enclosures and compared with gradient measurements during the wet-to-dry transition and dry-to-wet-transition periods at a remote forest site in Brazil, 1999. Branch enclosure measurements of several tree species showed emission as well as deposition of short-chain aldehydes, but fluxes were clearly dominated by deposition during both seasons. This bidirectional exchange was found to depend mainly on the actual ambient concentrations of these compounds and to exhibit a compensation point below 0.6 ppb of the compound in air with deposition velocities between 0.16 and 0.21 cm/s during the wet-to-dry season. During the dry-to-wet season, the deposition velocities and the compensation point in- creased. Under the clean air conditions of the wet-to-dry season, the major pathway for the aldehyde uptake was via leaf stomata. For HCHO, a mesophyll resistance of the same order of magnitude as the stomatal resistance contributed to the total leaf surface resistance, whereas the mesophyll resistance for CH3CHO was small, allowing a rapid uptake. This finding indicates a major contribution of metabolic consumption processes in addition to physical and chemical processes to the overall resistance. During the dry-to-wet period, when ambient air concentrations substantially increased, we found indications for an ad- ditional deposition to the leaf cuticle. Vertical gradient measurements of ambient air con- centrations in and above the canopy closely agreed with the branch enclosure studies and confirmed that the forest acts rather as a sink than as a direct source for HCHO and CH3CHO. Diel courses of ambient air concentrations and ratios of HCHO and CH3CHO above the canopy suggest photochemical oxidation of biogenically or pyrogenically emitted precursor compounds as the major sources for short-chain aldehydes in the tropical atmosphere.

Self-reported smoking status and urinary cotinine levels in patients with asthma

Objetivo: Descrever a frequência de tabagismo ativo entre pacientes com asma e indivíduos sem asma, usando questionários padronizados e dosagem da cotinina urinária. Métodos: Estudo transversal realizado em Salvador (BA), com 1.341 indivíduos, sendo 498 com asma grave, 417 com asma leve/moderada e 426 sem asma. O tabagismo foi identifi cado por meio de autorrelato utilizando questionários e por mensuração da cotinina urinária. Para a comparação das variáveis estudadas, utilizaram-se os testes do qui-quadrado e de Kruskal-Wallis. Resultados: Dos 55 participantes (4,1%) que se declararam tabagistas atuais, 5, 17 e 33 eram dos grupos asma grave, asma leve/ moderada e sem asma, respectivamente. Desses 55, 32 (58,2%) eram tabagistas diários e 23 (41,8%) eram tabagistas ocasionais. Observaram-se níveis elevados de cotinina urinária entre não fumantes autodeclarados e tabagistas pregressos, especialmente no grupo asma grave, o que sugere omissão do hábito atual de fumar. A carga tabágica entre os fumantes e a proporção de ex-tabagistas foram maiores no grupo asma grave do que no grupo asma leve/moderada. Conclusões: O tabagismo pregresso esteve associado à asma grave. Tabagismo atual também foi observado em alguns pacientes com asma grave e detectou-se omissão em alguns casos. A investigação de tabagismo deve ser meticulosa em pacientes com asma grave e a entrevista desses deve ser complementada por uma avaliação objetiva.

INVESTIGAÇÃO DA PRESENÇA DE HIDROCARBONETOS POLICÍCLICOS AROMÁTICOS EM POÇOS FREÁTICOS AO NORTE DO RECÔNCAVO DA BAHIA, BRASIL.

O norte do Reconcavo baiano abriga intensa atividade de petroleo. O objetivo deste trabalho foi verificar a presenca dos 16 Hidrocarbonetos Policiclicos Aromaticos (HPAs) considerados poluentes prioritarios pela Environmental Protection Agency (EPA), em amostras de agua de 12 pocos freaticos de uso individual e coletivo dos municipios de Sao Francisco do Conde e Candeias, Bahia, Brasil. Apos extracao liquido-liquido, os HPAs foram determinados por CG-MS (Metodo 8270- EPA). Dos pocos estudados, apenas um, localizado no municipio de Candeias, apresentou cinco HPAs em niveis acima dos padroes de qualidade para consumo humano estabelecidos pela Resolucao Conama 396/2008: benzo(a)pireno, benzo(b)fluoranteno, benzo(k)fluoranteno, dibenzoantraceno e indeno(1,2,3)pireno, com concentracoes medias encontradas de 0,14 μg.L-1, 0,15 μg.L-1, 0,17 μg.L-1, 0,08 μg.L-1, 0,13 μg.L-1, respectivamente. Considerando-se que os HPAs encontrados sao carcinogenicos e mutagenicos, e que existem mais de 80 pocos de uso individual e coletivo identificados nos municipios estudados, recomenda-se um estudo mais amplo, envolvendo todos os pocos, para que medidas adequadas de gestao sejam adotadas.

Phytochemical Profile of Seed Extracts of Plants Typical of the Brazilian Semiarid and their Potential Application in Brackish Water Desalination

The phytochemical profile of typical seeds from semiarid areas of Bahia was explored. The desalination capacity of the seeds discovered in previous studies considered the seeds potentially suitable for desalination of water. Coals composed of crushed seeds of umbu (Spondias tuberosa Arr. Cam.) and umburana (Amburana cearensis A. C. Sm.) were prepared by heating at 250 oC. As the desalination process using these materials involves ion exchange besides adsorption, it became necessary to study their chemical composition to check the possibility of transferring undesirable chemical species to the water during the contact between material and water. None of the tested metabolites were found in umbu coal, which enabled its use in desalination. However, the presence of coumarin and alkaloids in the umburana seeds coal indicated that this material is not suitable for that use.

Bioavailability assessment of toxic metals using the technique "acid-volatile sulfide (AVS)-simultaneously extracted metals (SEM)" in marine sediments collected in Todos os Santos Bay, Brazil.

This paper reports the bioavailability of the metals (cadmium, copper, zinc, lead, and nickel) in sediment samples collected in seven stations from the São Paulo Estuary, Todos os Santos Bay, Brazil. The bioavailability was determined by employing the technique “acid-volatile sulfide (AVS) and simultaneously extracted metal (SEM)”. The elements cadmium, copper, lead, and zinc were determined using differential pulse anodic stripping voltammetry (DPASV), while nickel was quantified utilizing electrothermal atomic absorption spectrometry (ET AAS). The accuracy of these methods was confirmed using a certified reference material of estuarine sediment (NIST 1646). The sulfide was quantified using potentiometry with selective electrode and the organic matter determination employing an indirect volumetric method using potassium dichromate and iron(II) sulfate solutions. The bioavailability of the metals was estimated by relationship between the concentration of AVS and the sum of the concentrations of the simultaneously extracted metals (ΣSEM), considering a significant toxicity when (ΣSEM)/(AVS) is higher than 1. The bioavailability values in the seven stations studied varied from 0.93 to 1.31 (June, 2014) and from 0.34 to 0.58 (September, 2014). These results demonstrated a critical condition of toxicity (bioavailability >1) in six of the seven sediment samples collected during the rainy season (June, 2014). In the other period (September, 2014), the bioavailability was always lower than 1 for all sediment samples collected in the seven stations. The individual values of the concentrations of the five metals were compared with the parameters PEL (probable effects level) and TEL (threshold effects level), which are commonly employed for characterization of ecological risk in environmental systems. This comparison revealed that all metals have concentrations lower than the PEL and only zinc and lead in some stations have contents higher than the TEL. The bioavailability evaluation and the concentrations achieved for the five elements in the sediments samples analyzed demonstrated that the ecosystem studied does not present an environmental risk.