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1.
PLoS One ; 13(12): e0208825, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-30532234

RESUMO

The emissions of BVOCs from oilseed rape (Brassica napus), both when the plant is exposed to clean air and when it is fumigated with ozone at environmentally-relevant mixing ratios (ca. 135 ppbv), were measured under controlled laboratory conditions. Emissions of BVOCs were recorded from combined leaf and root chambers using a recently developed Selective Reagent Ionisation-Time of Flight-Mass Spectrometer (SRI-ToF-MS) enabling BVOC detection with high time and mass resolution, together with the ability to identify certain molecular functionality. Emissions of BVOCs from below-ground were found to be dominated by sulfur compounds including methanethiol, dimethyl disulfide and dimethyl sulfide, and these emissions did not change following fumigation of the plant with ozone. Emissions from above-ground plant organs exposed to clean air were dominated by methanol, monoterpenes, 4-oxopentanal and methanethiol. Ozone fumigation of the plants caused a rapid decrease in monoterpene and sesquiterpene concentrations in the leaf chamber and increased concentrations of ca. 20 oxygenated species, almost doubling the total carbon lost by the plant leaves as volatiles. The drop in sesquiterpenes concentrations was attributed to ozonolysis occurring to a major extent on the leaf surface. The drop in monoterpene concentrations was attributed to gas phase reactions with OH radicals deriving from ozonolysis reactions. As plant-emitted terpenoids have been shown to play a role in plant-plant and plant-insect signalling, the rapid loss of these species in the air surrounding the plants during photochemical pollution episodes may have a significant impact on plant-plant and plant-insect communications.


Assuntos
Brassica napus/metabolismo , Fumigação , Ozônio/farmacologia , Componentes Aéreos da Planta/metabolismo , Raízes de Plantas/metabolismo , Compostos Orgânicos Voláteis/metabolismo , Brassica napus/parasitologia , Componentes Aéreos da Planta/parasitologia , Raízes de Plantas/parasitologia
4.
Trends Ecol Evol ; 32(6): 438-451, 2017 06.
Artigo em Inglês | MEDLINE | ID: mdl-28359572

RESUMO

Forest canopies are dynamic interfaces between organisms and atmosphere, providing buffered microclimates and complex microhabitats. Canopies form vertically stratified ecosystems interconnected with other strata. Some forest biodiversity patterns and food webs have been documented and measurements of ecophysiology and biogeochemical cycling have allowed analyses of large-scale transfer of CO2, water, and trace gases between forests and the atmosphere. However, many knowledge gaps remain. With global research networks and databases, and new technologies and infrastructure, we envisage rapid advances in our understanding of the mechanisms that drive the spatial and temporal dynamics of forests and their canopies. Such understanding is vital for the successful management and conservation of global forests and the ecosystem services they provide to the world.


Assuntos
Biodiversidade , Florestas , Atmosfera , Ecossistema , Árvores
8.
Sci Rep ; 5: 12064, 2015 Jul 13.
Artigo em Inglês | MEDLINE | ID: mdl-26165168

RESUMO

Despite the known biochemical production of a range of aromatic compounds by plants and the presence of benzenoids in floral scents, the emissions of only a few benzenoid compounds have been reported from the biosphere to the atmosphere. Here, using evidence from measurements at aircraft, ecosystem, tree, branch and leaf scales, with complementary isotopic labeling experiments, we show that vegetation (leaves, flowers, and phytoplankton) emits a wide variety of benzenoid compounds to the atmosphere at substantial rates. Controlled environment experiments show that plants are able to alter their metabolism to produce and release many benzenoids under stress conditions. The functions of these compounds remain unclear but may be related to chemical communication and protection against stress. We estimate the total global secondary organic aerosol potential from biogenic benzenoids to be similar to that from anthropogenic benzenoids (~10 Tg y(-1)), pointing to the importance of these natural emissions in atmospheric physics and chemistry.


Assuntos
Atmosfera/análise , Benzeno/química , Combustíveis Fósseis/análise , Árvores/metabolismo , Compostos Orgânicos Voláteis/química , Clima , Ecossistema , Estresse Fisiológico/fisiologia
9.
Environ Pollut ; 185: 44-51, 2014 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-24212233

RESUMO

Urban form controls the overall aerodynamic roughness of a city, and hence plays a significant role in how air flow interacts with the urban landscape. This paper reports improved model performance resulting from the introduction of variable surface roughness in the operational air-quality model ADMS-Urban (v3.1). We then assess to what extent pollutant concentrations can be reduced solely through local reductions in roughness. The model results suggest that reducing surface roughness in a city centre can increase ground-level pollutant concentrations, both locally in the area of reduced roughness and downwind of that area. The unexpected simulation of increased ground-level pollutant concentrations implies that this type of modelling should be used with caution for urban planning and design studies looking at ventilation of pollution. We expect the results from this study to be relevant for all atmospheric dispersion models with urban-surface parameterisations based on roughness.


Assuntos
Poluentes Atmosféricos/análise , Poluição do Ar/estatística & dados numéricos , Modelos Químicos , Movimentos do Ar , Cidades , Planejamento de Cidades , Humanos
10.
Philos Trans R Soc Lond B Biol Sci ; 366(1582): 3177-95, 2011 Nov 27.
Artigo em Inglês | MEDLINE | ID: mdl-22006961

RESUMO

We report measurements of atmospheric composition over a tropical rainforest and over a nearby oil palm plantation in Sabah, Borneo. The primary vegetation in each of the two landscapes emits very different amounts and kinds of volatile organic compounds (VOCs), resulting in distinctive VOC fingerprints in the atmospheric boundary layer for both landscapes. VOCs over the Borneo rainforest are dominated by isoprene and its oxidation products, with a significant additional contribution from monoterpenes. Rather than consuming the main atmospheric oxidant, OH, these high concentrations of VOCs appear to maintain OH, as has been observed previously over Amazonia. The boundary-layer characteristics and mixing ratios of VOCs observed over the Borneo rainforest are different to those measured previously over Amazonia. Compared with the Bornean rainforest, air over the oil palm plantation contains much more isoprene, monoterpenes are relatively less important, and the flower scent, estragole, is prominent. Concentrations of nitrogen oxides are greater above the agro-industrial oil palm landscape than over the rainforest, and this leads to changes in some secondary pollutant mixing ratios (but not, currently, differences in ozone). Secondary organic aerosol over both landscapes shows a significant contribution from isoprene. Primary biological aerosol dominates the super-micrometre aerosol over the rainforest and is likely to be sensitive to land-use change, since the fungal source of the bioaerosol is closely linked to above-ground biodiversity.


Assuntos
Agricultura , Atmosfera/química , Árvores/química , Aerossóis/química , Poluentes Atmosféricos/química , Aeronaves , Anisóis/química , Arecaceae/química , Arecaceae/fisiologia , Atmosfera/análise , Bornéu , Butadienos/química , Carbono/química , Hemiterpenos/química , Radical Hidroxila/química , Indústrias , Malásia , Monoterpenos/química , Óxidos de Nitrogênio/química , Ozônio/química , Pentanos/química , Fotoquímica , Árvores/fisiologia , Compostos Orgânicos Voláteis/química
11.
Philos Trans R Soc Lond B Biol Sci ; 366(1582): 3210-24, 2011 Nov 27.
Artigo em Inglês | MEDLINE | ID: mdl-22006963

RESUMO

We present results from the OP3 campaign in Sabah during 2008 that allow us to study the impact of local emission changes over Borneo on atmospheric composition at the regional and wider scale. OP3 constituent data provide an important constraint on model performance. Treatment of boundary layer processes is highlighted as an important area of model uncertainty. Model studies of land-use change confirm earlier work, indicating that further changes to intensive oil palm agriculture in South East Asia, and the tropics in general, could have important impacts on air quality, with the biggest factor being the concomitant changes in NO(x) emissions. With the model scenarios used here, local increases in ozone of around 50 per cent could occur. We also report measurements of short-lived brominated compounds around Sabah suggesting that oceanic (and, especially, coastal) emission sources dominate locally. The concentration of bromine in short-lived halocarbons measured at the surface during OP3 amounted to about 7 ppt, setting an upper limit on the amount of these species that can reach the lower stratosphere.


Assuntos
Poluição do Ar/análise , Arecaceae/química , Atmosfera/química , Árvores/química , Agricultura , Arecaceae/fisiologia , Atmosfera/análise , Bornéu , Bromo/química , Butadienos/química , Carbanilidas/análise , Carbanilidas/química , Simulação por Computador , Formaldeído/química , Hemiterpenos/química , Malásia , Óxidos de Nitrogênio/química , Oxirredução , Ozônio/química , Pentanos/química , Árvores/fisiologia , Clima Tropical , Compostos Orgânicos Voláteis/química
12.
Proc Natl Acad Sci U S A ; 106(44): 18447-51, 2009 Nov 03.
Artigo em Inglês | MEDLINE | ID: mdl-19841269

RESUMO

More than half the world's rainforest has been lost to agriculture since the Industrial Revolution. Among the most widespread tropical crops is oil palm (Elaeis guineensis): global production now exceeds 35 million tonnes per year. In Malaysia, for example, 13% of land area is now oil palm plantation, compared with 1% in 1974. There are enormous pressures to increase palm oil production for food, domestic products, and, especially, biofuels. Greater use of palm oil for biofuel production is predicated on the assumption that palm oil is an "environmentally friendly" fuel feedstock. Here we show, using measurements and models, that oil palm plantations in Malaysia directly emit more oxides of nitrogen and volatile organic compounds than rainforest. These compounds lead to the production of ground-level ozone (O(3)), an air pollutant that damages human health, plants, and materials, reduces crop productivity, and has effects on the Earth's climate. Our measurements show that, at present, O(3) concentrations do not differ significantly over rainforest and adjacent oil palm plantation landscapes. However, our model calculations predict that if concentrations of oxides of nitrogen in Borneo are allowed to reach those currently seen over rural North America and Europe, ground-level O(3) concentrations will reach 100 parts per billion (10(9)) volume (ppbv) and exceed levels known to be harmful to human health. Our study provides an early warning of the urgent need to develop policies that manage nitrogen emissions if the detrimental effects of palm oil production on air quality and climate are to be avoided.


Assuntos
Agricultura , Poluição do Ar/análise , Arecaceae/fisiologia , Nitrogênio/análise , Ozônio/análise , Óleos Vegetais/análise , Clima Tropical , Aeronaves , Butadienos/análise , Geografia , Hemiterpenos/análise , Monoterpenos/análise , Óxido Nítrico/análise , Dióxido de Nitrogênio/análise , Óleo de Palmeira , Pentanos/análise , Ácido Peracético/análogos & derivados , Ácido Peracético/análise , Fatores de Tempo
13.
Plant Cell Environ ; 32(1): 31-45, 2009 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-19076530

RESUMO

This study examined whether two genotypes of hybrid poplar (Populus deltoides x Populus trichocarpa), previously classified as ozone tolerant and ozone sensitive, had differing physiological and biochemical responses when fumigated with 120 nL L(-1) ozone for 6 h per day for eight consecutive days. Isoprene emission rate, ozone uptake and a number of physiological and biochemical parameters were investigated before, during and after fumigation with ozone. Previous studies have shown that isoprene protects plants against oxidative stress. Therefore, it was hypothesized that these two genotypes would differ in either their basal isoprene emission rates or in the response of isoprene to fumigation by ozone. Our results showed that the basal emission rates of isoprene, physiological responses and ozone uptake rates were all similar. However, significant differences were found in visible damage, carotenoids, hydrogen peroxide (H(2)O(2)), thiobarbituric acid reactions (TBARS) and post-fumigation isoprene emission rates. It is shown that, although the classification of ozone tolerance or sensitivity had been previously clearly and carefully defined using one particular set of parameters, assessment of other key variables does not necessarily lead to the same conclusions. Thus, it may be necessary to reconsider the way in which plants are classified as ozone tolerant or sensitive.


Assuntos
Butadienos/metabolismo , Hemiterpenos/metabolismo , Estresse Oxidativo , Ozônio/farmacologia , Pentanos/metabolismo , Populus/metabolismo , Ácido Ascórbico/metabolismo , Carotenoides/metabolismo , Clorofila/metabolismo , Clorofila A , Genótipo , Peróxido de Hidrogênio/metabolismo , Peroxidação de Lipídeos , Folhas de Planta/efeitos dos fármacos , Folhas de Planta/genética , Folhas de Planta/metabolismo , Populus/efeitos dos fármacos , Populus/genética , Tiobarbitúricos/metabolismo
14.
J Environ Monit ; 5(1): 1-7, 2003 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-12619749

RESUMO

Proton transfer reaction-mass spectrometry (PTR-MS) is a new and emerging technique for the measurement and monitoring of volatile organic compounds (VOCs) at low concentrations in gaseous samples in more-or-less real time. Utilising chemical ionisation, it combines the desirable attributes of high sensitivity and short integration times with good precision and accuracy. Recently it has been exploited in applications related to atmospheric science. Here, the principles of operation of the PTR-MS are described, its advantages and disadvantages discussed, its inherent uncertainties highlighted, some of its uses in atmospheric sciences reviewed, and some suggestions made on its future application to atmospheric chemistry.


Assuntos
Poluentes Atmosféricos/análise , Monitoramento Ambiental/métodos , Espectrometria de Massas/métodos , Compostos Orgânicos/análise , Prótons , Volatilização
15.
Environ Sci Technol ; 36(7): 1554-60, 2002 Apr 01.
Artigo em Inglês | MEDLINE | ID: mdl-11999066

RESUMO

Data illustrating the performance characteristics of a proton transfer reaction-mass spectrometer (PTR-MS) under both laboratory and field conditions are presented. Under laboratory conditions, we demonstrate that PTR-MS measures (within 10%) a 2.6 ppbv concentration of gaseous dimethyl sulfide. Using a stepwise dilution of a gaseous isoprene standard, we demonstrate the linearity of the response of PTR-MS across 3 orders of magnitude of mixing ratios, from 100 ppbv to less than 100 pptv. By combining this data set with that of its monosubstituted 13C isotopic analogue, we demonstrate the ability of the instrumentto reliably measure concentrations as low as approximately 50 pptv and to detect concentrations at significantly lower levels. We conclude our laboratory characterization by investigating the components of the instrument noise signal (drift, mean, and range) and develop an expression (noise statistic) that reliably predicts the instrumental noise associated with any signal across a wide range of masses. In the field, we deployed a PTR-MS at a clean-air coastal site and an urban kerbside monitoring station to demonstrate the measurement of atmospheric dimethyl sulfide and benzene concentrations, respectively. At both sites, we were able to monitor diurnal variations in concentrations at unprecedented temporal resolutions (<5 min between successive measurements). We then demonstrate how the noise statistic can be applied to enable real fluctuations in atmospheric VOC concentrations to be reliably distinguished from instrument noise. We conclude by demonstrating how PTR-MS can be used to measure real-time VOC emission rate changes from vegetation in response to external forcing by examining the effect varying photon-flux density has upon emissions of isoprene from a Sitka spruce tree.


Assuntos
Poluentes Atmosféricos/análise , Espectrometria de Massas/métodos , Compostos Orgânicos/análise , Prótons , Reprodutibilidade dos Testes , Sensibilidade e Especificidade , Sulfetos/análise , Volatilização
16.
J Environ Monit ; 2(2): 133-8, 2000 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-11253032

RESUMO

Considerable uncertainties are associated with the experimental estimates of emission rates of different volatile organic compound (VOC) species from the biosphere to the atmosphere. Some of this uncertainty derives from the sampling and analytical procedures used in emission rate measurements. A calibration system was developed in order to evaluate possible errors in the measurements of biogenic emission rates using a branch enclosure system. Two types of calibration procedures were tested, a standard additions technique and an internal standard procedure. Both techniques were used to evaluate possible losses while sampling isoprene and monoterpenes, which are the most abundant VOCs of biogenic origin. The losses to Teflon lines and the empty sampling system were tested and losses to the branch enclosure system installed on two VOC emitting plant species were evaluated. A considerable loss of isoprene (approximately 18% of inflow concentration 65 ng l(-1)) to the empty enclosure system and to the system installed on the plant was measured, but no losses of monoterpenes were observed.


Assuntos
Monitoramento Ambiental/métodos , Poluentes Ambientais/análise , Compostos Orgânicos/análise , Calibragem , Reprodutibilidade dos Testes , Sensibilidade e Especificidade , Volatilização
17.
Environ Pollut ; 88(1): 19-26, 1995.
Artigo em Inglês | MEDLINE | ID: mdl-15091565

RESUMO

One-year-old cherry trees were fumigated with propene and gas-phase hydrogen peroxide, singly and in combination, in controlled-environment chambers for an 8-week period during the summer season. A UV light source was included with the combined propene and hydrogen peroxide regime to provide a source of hydroxyl radicals and ozone, and thus all the constituents of a photochemical smog. Measurements were made of soluble protein concentration and of glutathione reductase activity in leaf extracts from two or three leaf classes in plants from each treatment regime at the end of each fumigation period. Significant increases in soluble protein concentration with respect to the controls were found in plants fumigated with propene and hydrogen peroxide. The occurrence and extent of these differences depended on the leaf class and on the timing of the fumigation period over the summer with respect to bud break. The activity of glutathione reductase was found to be significantly increased in mature lower leaves of plants which had been fumigated with hydrogen peroxide. This effect was independent of the timing of fumigation with respect to bud break. Enzyme activity was also increased in propene and in propene plus hydrogen peroxide treatments, but only when plants were fumigated early in the growth season.

18.
Environ Sci Technol ; 29(9): 2405-13, 1995 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-22280285
19.
Air Waste ; 44(11): 1299-302, 1994 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-15736344

RESUMO

A recycling exposure system, which has characteristics of dynamic and static systems, has been designed and constructed for calibrating passive sampling tubes. This system is very easy to set up and maintain. Organic vapors inside the system are generated by syringe injection, and homogeneous vapors are circulated by a metal-bellows pump. The concentrations of light hydrocarbons (e.g., isoprene) may decrease slightly after circulating for longer than 10 hours; however, this system is very stable for C5-C8 hydrocarbons for at least eight hours. The system has been used successfully to calibrate Perkin-Elmer diffusion tubes packed with Chromosorb 106 for collecting benzene vapor at low exposure doses (< 70 ppmv x min). The entire system can be easily and effectively cleaned by circulating through a U-tube packed with activated carbon.


Assuntos
Poluentes Atmosféricos/análise , Monitoramento Ambiental/métodos , Hidrocarbonetos/análise , Calibragem , Monitoramento Ambiental/normas , Desenho de Equipamento , Volatilização
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