A tethered balloon-sampling platform was used to study biogenic volatile organic compounds (BVOCs) in the atmospheric boundary layer in three distinct moist tropical forest ecoregions, as well as an extensive pasture area, in Amazonia. Approximately 24-40 soundings, including as many as four VOC samples collected simultaneously at various altitudes, were made at each site. Concentrations in the mixed layer increased during morning hours and were relatively constant midday through afternoon. Since most important meteorological and chemical parameters were very similar among the sites during the measurement periods, a BVOC canopy emission model was used with a model of the chemistry of the boundary layer to reproduce the atmospheric concentrations observed. The simulations indicated significantly different midday landscape isoprene and a-pinene emission rates for the three forest ecoregions (2200, 5300, 9800 lg m À2 h À1 isoprene and 90, 120, and 180 lg m À2 h À1 a-pinene for the three moist forest ecoregions studied, respectively). The differences in emissions among the ecoregions may be attributed to the species composition, which were markedly different and in which the percentage of isoprene and terpene emitting species also differed significantly.

Isoprene dominates global non-methane volatile organic compound emissions, and impacts tropospheric chemistry by influencing oxidants and aerosols. Isoprene emission rates vary over several orders of magnitude for different plants, and characterizing this immense biological chemodiversity is a challenge for estimating isoprene emission from tropical forests. Here we present the isoprene emission estimates from aircraft eddy covariance measurements over the Amazonian forest. We report isoprene emission rates that are three times higher than satellite top-down estimates and 35% higher than model predictions. The results reveal strong correlations between observed isoprene emission rates and terrain elevations, which are confirmed by similar correlations between satellite-derived isoprene emissions and terrain elevations. We propose that the elevational gradient in the Amazonian forest isoprene emission capacity is determined by plant species distributions and can substantially explain isoprene emission variability in tropical forests, and use a model to demonstrate the resulting impacts on regional air quality.

Abstract. Biogenic volatile organic compounds (BVOCs) are important components of the atmosphere due to their contribution to atmospheric chemistry and biogeochemical cycles. Tropical forests are the largest source of the dominant BVOC emissions (e.g. isoprene and monoterpenes). In this study, we report isoprene and total monoterpene flux measurements with a proton transfer reaction time-of-flight mass spectrometer (PTR-TOF-MS) using the eddy covariance (EC) method at the Tapajós National Forest (2.857∘ S, 54.959∘ W), a primary rainforest in eastern Amazonia. Measurements were carried out from 1 to 16 June 2014, during the wet-to-dry transition season. During the measurement period, the measured daytime (06:00–18:00 LT) average isoprene mixing ratios and fluxes were 1.15±0.60 ppb and 0.55±0.71 mg C m−2 h−1, respectively, whereas the measured daytime average total monoterpene mixing ratios and fluxes were 0.14±0.10 ppb and 0.20±0.25 mg C m−2 h−1, respectively. Midday (10:00–14:00 LT) average isoprene and total monoterpene mixing ratios were 1.70±0.49 and 0.24±0.05 ppb, respectively, whereas midday average isoprene and monoterpene fluxes were 1.24±0.68 and 0.46±0.22 mg C m−2 h−1, respectively. Isoprene and total monoterpene emissions in Tapajós were correlated with ambient temperature and solar radiation. Significant correlation with sensible heat flux, SHF (r2=0.77), was also observed. Measured isoprene and monoterpene fluxes were strongly correlated with each other (r2=0.93). The MEGAN2.1 (Model of Emissions of Gases and Aerosols from Nature version 2.1) model could simulate most of the observed diurnal variations (r2=0.7 to 0.8) but declined a little later in the evening for both isoprene and total monoterpene fluxes. The results also demonstrate the importance of site-specific vegetation emission factors (EFs) for accurately simulating BVOC fluxes in regional and global BVOC emission models.

Com o intuito de monitorar a concentração de ácido fólico (vitamina B9) em amostras de farinha de trigo, um método analítico simples e rápido foi desenvolvido e validado, utilizando a técnica de Cromatografia Líquida de Alta Eficiência com detecção por Espectrometria de Massas do tipo triplo quadrupolo (CLAE-EM/EM). O analito foi ionizado com fonte de ionização por electrospray no modo positivo e o espectrômetro de massas foi operado em modo de aquisição por Monitoramento Múltiplo de Reação (Multiple Reaction Monitoring -MRM), com o propósito de detectar duas trannsições de m/z, uma para quantificação e outra para confirmação. Um total de 83 amostras foram processadas para a validação do método de acordo como guia de procedimentos da Comissão Européia, referência 2002/657/EC, para análise de resíduos em alimentos. A performance do método foi avaliada através da linearidade, exatidão, precisão, sensibilidade e incerteza. O resultado das curvas analíticas na faixa de concentração de 1,0 a 50 µg L -1 apresentaram coeficientes de correlação (r 2 ) de 1,000. A reprodutibilidade do método foi obtida através do cálculo da somatória dos desvios padrão dos resultados de análises "intra-dias" e "inter-dias" e apresentou o valor de 5,6%, para o nível de fortificação de 1,50 µg g -1 . Além disso, dez amostras no nível de fortificação de 1,50 µg g -1 foram extraídas e analisadas com exatidão de 85% e precisão de 3% (coeficiente de variação). A sensibilidade do método foi expressa em limite de decisão (CC ) de 0,06 µg g -1 e capacidade de detecção (CC ) de 0,11 µg g -1 . A incerteza total calculada do método foi de + 0,11 µg g -1 . Diferentes marcas de farinha de trigo brasileiras foram avaliadas e reportadas.In order to monitor the fortification level of folic acid (vitamin B9) in wheat flour samples, we developed and validated a simple and fast analytical method using the liquid chromatography with tandem triple quadrupole mass spectrometry (LC-MS/MS) technique. The compound was ionized by an electrospray source in positive mode. The tandem MS/MS instrument was set in MRM (Multiple Reaction Monitoring) mode to detect two m/z transitions used for quantitation and confirmation purposes. A total of 83 samples were prepared to validate the method according to the regulatory guidelines from the Commission Decision 2002/657/EC for food residues analysis. The method performance was evaluated in regards to linearity, accuracy, precision, sensitivity, and uncertainty. The statistical analysis of the results showed a correlation coefficient (r 2 ) of 1.000 within the concentration range of 1.0 to 50 µg L -1. The method reproducibility of 5.6% was obtained by calculating the standard deviation sum of the intra-day and inter-day analysis at a fortification level limit of 1.50 µg g -1 of folic acid. In addition, ten blank spiked samples at the fortification level limit were extracted and analyzed with an accuracy of 85% and a precision of 3% (coefficient of variation). The method sensitivity was expressed in decision limit (CC ) of 0.06...

Since Levy (1971) postulated the importance of hydroxyl radicals (OH) in driving the photochemistry of the troposphere, numerous modeling, laboratory, and field studies have explored its roles in determining the chemical lifetimes of reactive trace gases and producing photochemical products such as ozone (O 3 ) and secondary aerosol precursors such as inorganic acids (HNO 3 and H 2 SO 4 ) and oxygenated volatile organic compounds (OVOCs). Tropospheric OH is primarily produced through O 3 photolysis and the following reaction of O ( 1 D) and water vapor (H 2 O). The OH level is sustained by recycling processes through nitric oxide (NO) oxidation to nitrogen dioxide (NO 2 ) by organic peroxy (RO 2 ) and hydroperoxy (HO 2 ) radicals, generated from the oxidation of VOCs (R1-R3). Cross (HO 2 + RO 2 ) or self-reactions (HO 2 + HO 2 or RO 2 + RO 2 ) between peroxy radicals compete with R2 and R3 to produce more stable compounds such as organic hydroxy peroxides. At low NO x and high VOC environments, regeneration of OH is suppressed by these chain terminating reactions. Therefore early studies of conventional chemistry speculated OH levels are depleted in remote tropical rain forests (Jacob & Wofsy, 1988;Logan et al., 1981). RH + OH + O2 → RO2 + H2O (R1) RO2 + NO + O2 → HO2 + RCHO + NO2 (R2) HO2 + NO → OH + NO2 (R3)