Qualidade da cachaça em função do tratamento do caldo e tipo de fermento

Pós-graduação em Microbiologia Agropecuária - FCAV

Electrocatalytic Activity of Pd, Pt, and Rh for the Electro-oxidation of Ethanol in Alkaline Electrolyte: An Online DEMS Study

The electro-oxidation of ethanol was investigated on electrodeposited layers of Pd, Pt, and Rh in alkaline electrolyte. The reaction products were monitored by experiments of online differential electrochemical mass spectrometry (DEMS). Potentiodynamic curves for the ethanol electro-oxidation catalyzed by these three different metal electrocatalysts showed similar onset potentials, but the highest Faradaic current peak was observed for the Pt electrocatalyst. Online DEMS experiments evidenced similar amounts of CO2 for the three different materials, but Pd presented the higher production of ethylacetate (acetic acid). This indicated that the electrochemical oxidation of ethanol on the Pd surface occurred to a higher extent. The formation of methane, which was observed for Pt and Rh, after potential excursions to lower potentials, was absent for Pd. On the basis of the obtained results, it was stated that, on Pt and Rh, the formation of CO2 occurs mainly via oxidation of CO and CH (x,ad) species formed after dissociative adsorption of ethanol or ethoxy species that takes place only at low potentials. This indicates that the dissociative adsorption of ethanol or ethoxy species is inhibited at higher potentials on Pt and Rh. On the other hand, on the Pd electrocatalyst, the reaction may occur via nondissociative adsorption of ethanol or ethoxy species at lower potentials, followed by oxidation to acetaldehyde and, after that, by a further oxidation step to acetic acid on the electrocatalyst surface. Additionally, in a parallel route, the acetaldehyde molecules adsorbed on the Pd surface can be deprotonated, yielding a reaction intermediate in which the carbon-carbon bond is less protected, and therefore, it can be dissociated on the Pd surface, producing CO2, after potential excursions to higher potentials.

Electro-oxidation of ethanol on Pt/C, Rh/C, and Pt/Rh/C-based electrocatalysts investigated by on-line DEMS

The ethanol electro-oxidation reaction was studied on carbon-supported Pt, Rh, and on Pt overlayers deposited on Rh nanoparticles. The synthesized electrocatalysts were characterized by TEM and XRD. The reaction products were monitored by on-line DEMS experiments. Potentiodynamic curves showed higher overall reaction rate for Pt/C when compared to that for Rh/C. However, on-line DEMS measurements revealed higher average current efficiencies for complete ethanol electro-oxidation to CO2 on Rh/C. The average current efficiencies for CO2 formation increased with temperature and with the decrease in the ethanol concentration. The total amount of CO2, on the other hand, was slightly affected by the temperature and ethanol concentration. Additionally, the CO2 signal was observed only in the positive-going scan, none being observed in the negative-going scan, evidencing that the C-C bond breaking occurs only at lower potentials. Thus, the formation of CO2 mainly resulted from oxidative removal of adsorbed CO and CHx,ad species generated at the lower potentials, instead of the electrochemical oxidation of bulk ethanol molecules. The acetaldehyde mass signal, however, was greatly favored after increasing the ethanol concentration from 0.01 to 0.1 mol L-1, on both electrocatalysts, indicating that it is the major reaction product. For the Pt/Rh/C-based electrocatalysts, the Faradaic current and the conversion efficiency for CO2 formation was increased by adjusting the amount of Pt on the surface of the Rh/C nanoparticles. The higher conversion efficiency for CO2 formation on the Pt1Rh/C material was ascribed to its faster and more extensive ethanol deprotonation on the Pt-Rh sites, producing adsorbed intermediates in which the C-C bond cleavage is facilitated. (C) 2012 Elsevier B.V. All rights reserved.

Development of Plurimetallic Electrocatalysts Prepared by Decomposition of Polymeric Precursors for EtOH/O-2 Fuel Cell

This work aimed to develop plurimetallic electrocatalysts composed of Pt, Ru, Ni, and Sn supported on C by decomposition of polymeric precursors (DPP), at a constant metal: carbon ratio of 40:60 wt.%, for application in direct ethanol fuel cell (DEFC). The obtained nanoparticles were physico-chemically characterized by X-ray diffraction (XRD) and energy dispersive X-ray spectroscopy (EDX). XRD results revealed a face-centered cubic crystalline Pt with evidence that Ni, Ru, and Sn atoms were incorporated into the Pt structure. Electrochemical characterization of the nanoparticles was accomplished by cyclic voltammetry (CV) and chronoamperometry (CA) in slightly acidic medium (0.05 mol L-1 H2SO4), in the absence and presence of ethanol. Addition of Sn to PtRuNi/C catalysts significantly shifted the ethanol and CO onset potentials toward lower values, thus increasing the catalytic activity, especially for the quaternary composition Pt64Sn15Ru13Ni8/C. Electrolysis of ethanol solutions at 0.4 V vs. RHE allowed determination of acetaldehyde and acetic acid as the main reaction products. The presence of Ru in alloys promoted formation of acetic acid as the main product of ethanol oxidation. The Pt64Sn15Ru13Ni8/C catalyst displayed the best performance for DEFC.

Chemical Selectivity during the Electro-Oxidation of Ethanol on Unsupported Pt Nanoparticles

In this paper we present results on the electro-oxidation of ethanol on unsupported (carbon free) platinum nanoparticles, considering the effects of the alcohol concentration. The case of the so-called dual pathway mechanism during the electro-oxidation of ethanol showed to be influenced by the surface coverage of adsorbed carbon monoxide (COad) at unsupported platinum. The influences of adsorbed intermediates were followed by in situ infrared spectroscopy (FTIR) and by electrochemical experiments. Unsupported platinum showed that the reaction leads to the formation of CO2 and acetic acid as main products at low concentrations of ethanol (0.01 to 0.1 mol L-1). At least in this case of 0.01 mol L-1 ethanol, most formation of CO2 occurred via COad (indirect pathway). At higher concentration of ethanol, however, most CO2 was formed via a reactive intermediate such as acetaldehyde (direct pathway). In addition, in this higher concentration of ethanol, the acetic acid was produced via formation of adsorbed acetaldehyde (via acetate) at higher overpotentials. In case of the acetic acid formation, a dual pathway was identified during the electro-oxidation of ethanol at low alcohol concentrations, whereas a parallel pathway occurred without the formation of adsorbed acetate intermediates at low overpotentials. (C) 2012 The Electrochemical Society. [DOI: 10.1149/2.101203jes] All rights reserved.

Performance and selectivity of PtxSn/C electro-catalysts for ethanol oxidation prepared by reduction with different formic acid concentrations

Carbon supported Pt-Sn catalysts were prepared by reduction of Pt and Sn precursors with formic acid and characterized in terms of structure, morphology and surface properties. The electrocatalytic activity for ethanol oxidation was studied in a direct ethanol fuel cell (DEFC) at 70 degrees C and 90 degrees C. Electrochemical and physico-chemical data indicated that a proper balance of Pt and Sn species in the near surface region was necessary to maximize the reaction rate. The best atomic surface composition, in terms of electrochemical performance, was Pt:Sn 65:35 corresponding to a bulk composition 75:25 namely Pt3Sn1/C. The reaction products of ethanol electro-oxidation in single cell and their distribution as a function of the nature of catalyst were determined. Essentially, acetaldehyde and acetic acid were detected as the main reaction products; whereas, a lower content of CO2 was formed. The selectivity toward acetic acid vs. acetaldehyde increased with the increase of the Sn content and decreased by decreasing the concentration of the reducing agent used in the catalyst preparation. According to the recent literature, these results have been interpreted on the basis of ethanol adsorption characteristics and ligand effects occurring for Sn-rich electrocatalysts. (C) 2012 Elsevier Ltd. All rights reserved.

CHEMICAL CONSTITUENTS FROM RED ALGAE Bostrychia radicans (Rhodomelaceae): NEW AMIDES AND PHENOLIC COMPOUNDS

This study describes the isolation and structural determination of two amides, isolated for the first time: N,4-dihydroxy-N-(2'-hydroxyethyl)-benzamide (0.019%) and N, 4-dihydroxy-N-(2'-hydroxyethyl)-benzeneacetamide (0.023%). These amides, produced by the red macroalgae Bostrychia radicans, had their structures assigned by NMR spectral data and MS analyses. In addition, this chemical study led to the isolation of cholesterol, heptadecane, squalene, trans-phytol, neophytadiene, tetradecanoic and hexadecanoic acids, methyl hexadecanoate and methyl 9-octadecenoate, 4-(methoxymethyl)-phenol, 4-hydroxybenzaldehyde, methyl 4-hydroxybenzeneacetate, methyl 2-hydroxy-3-(4-hydroxyphenyl)-propanoate, hydroquinone, methyl 4-hydroxymandelate, methyl 4-hydroxybenzoate, 4-hydroxybenzeneacetic acid and (4-hydroxyphenyl)-oxo-acetaldehyde. This is the first report concerning these compounds in B. radicans, contributing by illustrating the chemical diversity within the Rhodomelaceae family.

New Approaches for the Ethanol Oxidation Reaction of Pt/C on Carbon Cloth Using ATR-FTIR

This work describes the study of the ethanol oxidation reaction of a Pt/C Etek electrocatalyst that was supported on different substrates, such as gold, glassy carbon and carbon cloth treated with PTFE. In the ethanol oxidation reaction, the activity varies with the substrate, as well as the pathways for ethanol oxidation, as studied by an ATR-FTIR in situ setup using the carbon cloth as the electrocatalyst support. The electrocatalyst Pt/C supported on gold starts acetaldehyde production from ethanol oxidation at an onset potential of 0.1 V less than that observed for the same process on Teflon-treated carbon cloth. The Pt/C supported on the carbon cloth starts its CO2 production for the same oxidation process at 0.2 V less than on the Pt/C supported on gold substrate. The differences in catalytic activity for the ethanol oxidation reaction depend not only on the electrocatalyst but also on various electrode factors, such as the substrate, the roughness of the electrode and the charge transfer resistance.

Probiotic yogurts manufactured with increased glucose oxidase levels: Postacidification, proteolytic patterns, survival of probiotic microorganisms, production of organic acid and aroma compounds

We investigated the effect of increased glucose oxidase concentration as a technological option to decrease oxidative stress during the processing of probiotic yogurts. Probiotic yogurts were produced with increased concentrations of glucose oxidase (0, 250, 500, 750, or 1,000 mg/kg) and submitted to physicochemical and microbiological analysis at 1, 15, and 30 d of refrigerated storage. Higher concentrations of glucose oxidase (750 and 1,000 mg/kg) and a longer storage time were found to have an influence on the characteristics of the probiotic yogurt, contributing to more extensive post-acidification, an increase in the dissolved oxygen level, and higher proteolysis. In addition, increased production of aroma compounds (diacetyl and acetaldehyde) and organic acids (mainly lactic acid) and a decrease in the probiotic bacteria count were reported. The use of glucose oxidase was a feasible option to minimize oxidative stress in probiotic yogurts. However, supplementation with excessive amounts of the enzyme may be ineffective, because insufficient substrate (glucose) is present for its action. Consumer tests should be performed to evaluate changes in the sensory attributes of the probiotic yogurts with increased supplementation of glucose oxidase. In addition, packaging systems with different permeability to oxygen should be evaluated.

Chemical constituents from red algae Bostrychia radicans (Rhodomelaceae): new amides and phenolic compounds

This study describes the isolation and structural determination of two amides, isolated for the first time: N,4-dihydroxy-N-(2'-hydroxyethyl)-benzamide (0.019%) and N,4-dihydroxy-N-(2'-hydroxyethyl)-benzeneacetamide (0.023%). These amides, produced by the red macroalgae Bostrychia radicans, had their structures assigned by NMR spectral data and MS analyses. In addition, this chemical study led to the isolation of cholesterol, heptadecane, squalene, trans-phytol, neophytadiene, tetradecanoic and hexadecanoic acids, methyl hexadecanoate and methyl 9-octadecenoate, 4-(methoxymethyl)-phenol, 4-hydroxybenzaldehyde, methyl 4-hydroxybenzeneacetate, methyl 2-hydroxy-3-(4-hydroxyphenyl)-propanoate, hydroquinone, methyl 4-hydroxymandelate, methyl 4-hydroxybenzoate, 4-hydroxybenzeneacetic acid and (4-hydroxyphenyl)-oxo-acetaldehyde. This is the first report concerning these compounds in B. radicans, contributing by illustrating the chemical diversity within the Rhodomelaceae family.

Development of plurimetallic electrocatalysts prepared by decomposition of polymeric precursors for EtOH/O2 fuel cell

This work aimed to develop plurimetallic electrocatalysts composed of Pt, Ru, Ni, and Sn supported on C by decomposition of polymeric precursors (DPP), at a constant metal:carbon ratio of 40:60 wt.%, for application in direct ethanol fuel cell (DEFC). The obtained nanoparticles were physico-chemically characterized by X-ray diffraction (XRD) and energy dispersive X-ray spectroscopy (EDX). XRD results revealed a face-centered cubic crystalline Pt with evidence that Ni, Ru, and Sn atoms were incorporated into the Pt structure. Electrochemical characterization of the nanoparticles was accomplished by cyclic voltammetry (CV) and chronoamperometry (CA) in slightly acidic medium (0.05 mol L-1 H2SO4), in the absence and presence of ethanol. Addition of Sn to PtRuNi/C catalysts significantly shifted the ethanol and CO onset potentials toward lower values, thus increasing the catalytic activity, especially for the quaternary composition Pt64Sn15Ru13Ni8/C. Electrolysis of ethanol solutions at 0.4 V vs. RHE allowed determination of acetaldehyde and acetic acid as the main reaction products. The presence of Ru in alloys promoted formation of acetic acid as the main product of ethanol oxidation. The Pt64Sn15Ru13Ni8/C catalyst displayed the best performance for DEFC.

Reaction intermediates of ethanol electro-oxidation on platinum investigated by SFG spectroscopy

Although electrochemical oxidation of simple organic molecules on metal catalysts is the basic ingredient of fuel cells, which have great technological potential as a renewable source of electrical energy, the detailed reaction mechanisms are in most cases not completely understood. Here, we investigate the ethanol-platinum interface in acidic aqueous solution using infrared-visible sum frequency generation (SFG) spectroscopy and theoretical calculations of vibrational spectra in order to identify the intermediates present during the electro-oxidation of ethanol. The complex vibrational spectrum in the fingerprint region imply on the coexistence of several adsorbates. Based on spectra in ultra-high-vacuum (UHV) and electrochemical environment from the literature and our density functional theory (DFT) calculations of vibrational spectra, new adsorbed intermediates, never before observed with conventional infrared (IR) spectroscopy, are proposed here: g2-acetaldehyde, g2-acetyl, ethylidyne, monodentate acetate, methoxy, tertiary methanol derivative, COH residue, g2-formaldehyde, mono and bidentate formate, CH3 and CH2 residues. In addition, we present new evidences for an ethoxy intermediate, a secondary ethanol derivative and an acetyl species, and we confirm the presence of previously observed adsorbates: a tertiary ethanol derivative, bidentate acetate, and COad. These results indicate that the platinum surface is much more reactive, and the reaction mechanism for ethanol electro-oxidation is considerably more complex than previously considered. This might be also true for many other molecule-catalyst systems.

Study of the components of quality in SO2-free wines obtained by innovative vinification protocols. Evaluation of the pre-fermentative addition of lysozyme and oenological tannins.

The research performed during the PhD candidature was intended to evaluate the quality of white wines, as a function of the reduction in SO2 use during the first steps of the winemaking process. In order to investigate the mechanism and intensity of interactions occurring between lysozyme and the principal macro-components of musts and wines, a series of experiments on model wine solutions were undertaken, focusing attention on the polyphenols, SO2, oenological tannins, pectines, ethanol, and sugar components. In the second part of this research program, a series of conventional sulphite added vinifications were compared to vinifications in which sulphur dioxide was replaced by lysozyme and consequently define potential winemaking protocols suitable for the production of SO2-free wines. To reach the final goal, the technological performance of two selected yeast strains with a low aptitude to produce SO2 during fermentation were also evaluated. The data obtained suggested that the addition of lysozyme and oenological tannins during the alcoholic fermentation could represent a promising alternative to the use of sulphur dioxide and a reliable starting point for the production of SO2-free wines. The different vinification protocols studied influenced the composition of the volatile profile in wines at the end of the alcoholic fermentation, especially with regards to alcohols and ethyl esters also a consequence of the yeast’s response to the presence or absence of sulphites during fermentation, contributing in different ways to the sensory profiles of wines. In fact, the aminoacids analysis showed that lysozyme can affect the consumption of nitrogen as a function of the yeast strain used in fermentation. During the bottle storage, the evolution of volatile compounds is affected by the presence of SO2 and oenological tannins, confirming their positive role in scaveging oxygen and maintaining the amounts of esters over certain levels, avoiding a decline in the wine’s quality. Even though a natural decrease was found on phenolic profiles due to oxidation effects caused by the presence of oxygen dissolved in the medium during the storage period, the presence of SO2 together with tannins contrasted the decay of phenolic content at the end of the fermentation. Tannins also showed a central role in preserving the polyphenolic profile of wines during the storage period, confirming their antioxidant property, acting as reductants. Our study focused on the fundamental chemistry relevant to the oxidative phenolic spoilage of white wines has demonstrated the suitability of glutathione to inhibit the production of yellow xanthylium cation pigments generated from flavanols and glyoxylic acid at the concentration that it typically exists in wine. The ability of glutathione to bind glyoxylic acid rather than acetaldehyde may enable glutathione to be used as a ‘switch’ for glyoxylic acid-induced polymerisation mechanisms, as opposed to the equivalent acetaldehyde polymerisation, in processes such as microoxidation. Further research is required to assess the ability of glutathione to prevent xanthylium cation production during the in-situ production of glyoxylic acid and in the presence of sulphur dioxide.

Emissions of volatile organic compounds from tropical savanna vegetation and biomass burning

This dissertation focuses on characterizing the emissions of volatile organic compounds (VOCs) from grasses and young trees, and the burning of biomass mainly from Africa and Indonesia. The measurements were performed with a proton-transfer-reaction mass spectrometer (PTR-MS). The biogenic emissions of tropical savanna vegetation were studied in Calabozo (Venezuela). Two field campaigns were carried out, the first during the wet season (1999) and the second during the dry season (2000). Three grass species were studied: T. plumosus, H. rufa and A. canescens, and the tree species B. crassifolia, C. americana and C. vitifolium. The emission rates were determined with a dynamic plant enclosure system. In general, the emissions increased exponentially with increasing temperature and solar radiation. Therefore, the emission rates showed high variability. Consequently, the data were normalized to a standard temperature of 30°C, and standard emission rates thus determined allowed for interspecific and seasonal comparisons. The range of average daytime (10:00-16:00) emission rates of total VOCs measured from green (mature and young) grasses was between 510-960 ngC/g/h. Methanol was the primary emission (140-360 ngC/g/h), followed by acetaldehyde, butene and butanol and acetone with emission rates between 70-200 ngC/g/h. The emissions of propene and methyl ethyl ketone (MEK) were <80 ngC/g/h, and those of isoprene and C5-alcohols were between 10-130 ngC/g/h. The oxygenated species represented 70-75% of the total. The emission of VOCs was found to vary by up to a factor of three between plants of the same species, and by up to a factor of two between the different species. The annual source of methanol from savanna grasses worldwide estimated in this work was 3 to 4.4 TgC, which could represent up to 12% of the current estimated global emission from terrestrial vegetation. Two of the studied tree species, were isoprene emitters, and isoprene was also their primary emission (which accounted for 70-94% of the total carbon emitted) followed by methanol and butene + butanol. The daytime average emission rate of isoprene measured in the wet season was 27 mgC/g/h for B. crassifolia, and 123 mgC/g/h for C. vitifolium. The daytime emissions of methanol and butene + butanol were between 0.3 and 2 mgC/g/h. The total sum of VOCs emission measured during the day in the wet season was between 30 and 130 mgC/g/h. In the dry season, in contrast, the methanol emissions from C. vitifolium saplings –whose leaves were still developing– were an order of magnitude higher than in the wet season (15 mgC/g/h). The isoprene emission from B. crassifolia in the dry season was comparable to the emission in the wet season, whereas isoprene emission from C. vitifolium was about a factor of three lower (~43 mgC/g/h). Biogenic emission inventories show that isoprenoids are the most prominent and best-studied compounds. The standard emission rates of isoprene and monoterpenes of the measured savanna trees were in the lower end of the range found in the literature. The emission of other biogenic VOCs has been sparsely investigated, but in general, the standard emissions from trees studied here were within the range observed in previous investigations. The biomass burning study comprised the measurement of VOCs and other trace-gas emissions of 44 fires from 15 different fuel types, primarily from Africa and Indonesia, in a combustion laboratory. The average sum of emissions (excluding CO2, CO and NO) from African fuels was ~18 g(VOC)/kg. Six of the ten most important emissions were oxygenated VOCs. Acetic acid was the major emission, followed by methanol and formaldehyde. The emission of methane was of the same order as the methanol emission (~5 g/kg), and that of nitrogen-containing compounds was ~1 g/kg. An estimate of the VOC source from biomass burning of savannas and grasslands worldwide suggests that the sum of emissions is about 56 Tg/yr, of which 34 Tg correspond to oxygenated VOCs, 14 Tg to unsaturated and aromatic compounds, 5 Tg to methane and 3 Tg to N-compounds. The estimated emissions of CO, CO2 and NO are 216, 5117 and 9.4 Tg/yr, respectively. The emission factors reported here for Indonesian fuels are the first results of laboratory fires using Indonesian fuels. Acetic acid was the highest organic emission, followed by acetol, a compound not previously reported in smoke, methane, mass 97 (tentatively identified as furfural, dimethylfuran and ethylfuran), and methanol. The sum of total emissions of Indonesian fuels was 91 g/kg, which is 5 times higher than the emissions from African fuels. The results of this study reinforces the importance of oxygenated compounds. Due to the vast area covered by tropical savannas worldwide, the biogenic and biomass burning emission of methanol and other oxygenated compounds may be important for the regional and even global tropospheric chemistry.

Measurement of volatile organic compounds and total OH reactivity in the atmosphere

Volatile organic compounds play a critical role in ozone formation and drive the chemistry of the atmosphere, together with OH radicals. The simplest volatile organic compound methane is a climatologically important greenhouse gas, and plays a key role in regulating water vapour in the stratosphere and hydroxyl radicals in the troposphere. The OH radical is the most important atmospheric oxidant and knowledge of the atmospheric OH sink, together with the OH source and ambient OH concentrations is essential for understanding the oxidative capacity of the atmosphere. Oceanic emission and / or uptake of methanol, acetone, acetaldehyde, isoprene and dimethyl sulphide (DMS) was characterized as a function of photosynthetically active radiation (PAR) and a suite of biological parameters, in a mesocosm experiment conducted in the Norwegian fjord. High frequency (ca. 1 minute-1) methane measurements were performed using a gas chromatograph - flame ionization detector (GC-FID) in the boreal forests of Finland and the tropical forests of Suriname. A new on-line method (Comparative Reactivity Method - CRM) was developed to directly measure the total OH reactivity (sink) of ambient air. It was observed that under conditions of high biological activity and a PAR of ~ 450 μmol photons m-2 s-1, the ocean acted as a net source of acetone. However, if either of these criteria was not fulfilled then the ocean acted as a net sink of acetone. This new insight into the biogeochemical cycling of acetone at the ocean-air interface has helped to resolve discrepancies from earlier works such as Jacob et al. (2002) who reported the ocean to be a net acetone source (27 Tg yr-1) and Marandino et al. (2005) who reported the ocean to be a net sink of acetone (- 48 Tg yr-1). The ocean acted as net source of isoprene, DMS and acetaldehyde but net sink of methanol. Based on these findings, it is recommended that compound specific PAR and biological dependency be used for estimating the influence of the global ocean on atmospheric VOC budgets. Methane was observed to accumulate within the nocturnal boundary layer, clearly indicating emissions from the forest ecosystems. There was a remarkable similarity in the time series of the boreal and tropical forest ecosystem. The average of the median mixing ratios during a typical diel cycle were 1.83 μmol mol-1 and 1.74 μmol mol-1 for the boreal forest ecosystem and tropical forest ecosystem respectively. A flux value of (3.62 ± 0.87) x 1011 molecules cm-2 s-1 (or 45.5 ± 11 Tg CH4 yr-1 for global boreal forest area) was derived, which highlights the importance of the boreal forest ecosystem for the global budget of methane (~ 600 Tg yr-1). The newly developed CRM technique has a dynamic range of ~ 4 s-1 to 300 s-1 and accuracy of ± 25 %. The system has been tested and calibrated with several single and mixed hydrocarbon standards showing excellent linearity and accountability with the reactivity of the standards. Field tests at an urban and forest site illustrate the promise of the new method. The results from this study have improved current understanding about VOC emissions and uptake from ocean and forest ecosystems. Moreover, a new technique for directly measuring the total OH reactivity of ambient air has been developed and validated, which will be a valuable addition to the existing suite of atmospheric measurement techniques.