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1.
2.
Sci Rep ; 9(1): 16975, 2019 11 18.
Artigo em Inglês | MEDLINE | ID: mdl-31740689

RESUMO

Deforestation rates have declined substantially across the Brazilian Legal Amazon (BLA) over the period from 2000-2017. However, reductions in fire, aerosol and carbon dioxide have been far less significant than deforestation, even when accounting for inter-annual variability in precipitation. Our observations and analysis support a decoupling between fire and deforestation that has exacerbated forest degradation in the BLA. Basing aerosol and carbon dioxide emissions on deforestation rates, without accounting for forest degradation will bias these important climate and ecosystem-health parameters low, both now and in the future. Recent increases in deforestation rate since 2014 will enhance such degradation, particularly during drought-conditions, increasing emissions of aerosol and greenhouse gases. Given Brazil's committed Nationally Determined Contribution under the Paris Agreement, failure to account for forest degradation fires will paint a false picture of prior progress and potentially have profound implications for both regional and global climate.

3.
Environ Sci Technol ; 53(19): 11112-11121, 2019 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-31423774

RESUMO

The size-resolved properties of atmospheric black carbon (BC) importantly determine its absorption capacity and cloud condensation nuclei (CCN) ability. This study reports comprehensive vertical profiles of BC size-related properties over the Beijing area (BJ) and Continental Europe (CE). BC mass loadings over CE were in the range of clean background over BJ. For both planetary boundary layer (PBL) and lower free troposphere, the BC mass median core diameter over BJ during the cold season was 0.21 ± 0.02 µm, larger than the warm season over BJ and CE (0.18 ± 0.01 µm), which may reflect seasonal differences in emissions. The BC coatings were positively correlated with the pollution level, with background BC having a smaller coated count median diameter (0.19 ± 0.01 µm). The modeled absorption enhancement (Eabs) due to coatings was 1.23 ± 0.14 for the background but in the PBL following a linear expression (Eabs = 0.13 × MassBC,surface + 1.26). The CCN ability of BC was significantly enhanced in the polluted PBL, due to both enlarged size and increased hygroscopicity. In polluted BJ at predicted supersaturations, ∼0.08% half of the BC number could be activated, whereas the cleaner environment needs ∼0.14%. The results here suggest that the highly coated and absorbing BC can be efficiently incorporated into clouds and can exert important indirect radiative impacts over the polluted East Asia region.


Assuntos
Poluentes Atmosféricos , Aerossóis , Atmosfera , Carbono , Monitoramento Ambiental , Europa (Continente) , Extremo Oriente
4.
Nat Commun ; 10(1): 423, 2019 01 24.
Artigo em Inglês | MEDLINE | ID: mdl-30679429

RESUMO

Organic nucleation is an important source of atmospheric aerosol number concentration, especially in pristine continental regions and during the preindustrial period. Here, we improve on previous simulations that overestimate boundary layer nucleation in the tropics and add changes to climate and land use to evaluate climate forcing. Our model includes both pure organic nucleation and heteromolecular nucleation of sulfuric acid and organics and reproduces the profile of aerosol number concentration measured in the Amazon. Organic nucleation decreases the sum of the total aerosol direct and indirect radiative forcing by 12.5%. The addition of climate and land use change decreases the direct radiative forcing (-0.38 W m-2) by 6.3% and the indirect radiative forcing (-1.68 W m-2) by 3.5% due to the size distribution and number concentration change of secondary organic aerosol and sulfate. Overall, the total radiative forcing associated with anthropogenic aerosols is decreased by 16%.

5.
Sci Rep ; 8(1): 15680, 2018 10 24.
Artigo em Inglês | MEDLINE | ID: mdl-30356119

RESUMO

Even modest ash-rich volcanic eruptions can severely impact a range of human activities, especially air travel. The dispersal of ash in these eruptions depends critically on aggregation and sedimentation processes - however these are difficult to quantify in volcanic plumes. Here, we image ash dynamics from mild explosive activity at Santiaguito Volcano, Guatemala, by measuring the depolarisation of scattered sunlight by non-spherical ash particles, allowing the dynamics of diffuse ash plumes to be investigated with high temporal resolution (>1 Hz). We measure the ash settling velocity downwind from the main plume, and compare it directly with ground sampled ash particles, finding good agreement with a sedimentation model based on particle size. Our new, cost-effective technique leverages existing technology, opening a new frontier of integrated ash visualisation and ground collection studies which could test models of ash coagulation and sedimentation, leading to improved ash dispersion forecasts. This will provide risk managers with improved data quality on ash location, reducing the economic and societal impacts of future ash-rich eruptions.

6.
Environ Sci Technol ; 52(17): 10134-10143, 2018 09 04.
Artigo em Inglês | MEDLINE | ID: mdl-30064212

RESUMO

Designs of "improved" stoves are introduced recently to benefit the solid fuel consumption of cooking activities in developing countries, but the uncertainties concerning the combustion processes and particulate emissions remain poorly characterized. To help understand this, combustion in three examples of "improved" African cookstoves was investigated in the laboratory. A typical European heating stove was included for comparison purpose. Detailed aerosol emissions were studied in real-time with an Aerosol Mass Spectrometer and Single Particle Soot Photometer, to explore interactions between black carbon (BC) and organic carbon aerosols, which were parametrized according to modified combustion efficiency (MCE), a common metric used within the atmospheric emission community. Greater than 50% of the total organic matter (OM) was found in BC-containing particles when MCE was >0.95 for dry oak and coal fuels, whereas at lower MCE, over 80% of the total OM for most of the fuels existed in particles without detectable BC. When the OM mass fraction of total particulate matter (PM1) > 0.9, the mass ratio of OM to refractory BC in BC-containing particles was about 2-3, but only ∼0.8 when OM mass fraction <0.9. These findings are not currently included in models and such information should be considered in the future emission scenarios.


Assuntos
Poluentes Atmosféricos , Aerossóis , Carvão Mineral , Material Particulado , Fuligem
7.
Environ Sci Technol ; 52(9): 5308-5318, 2018 05 01.
Artigo em Inglês | MEDLINE | ID: mdl-29619820

RESUMO

Food-cooking organic aerosols (COA) are one of the primary sources of submicron particulate matter in urban environments. However, there are still many questions surrounding source apportionment related to instrumentation as well as semivolatile partitioning because COA evolve rapidly in the ambient air, making source apportionment more complex. Online measurements of emissions from cooking different types of food were performed in a laboratory to characterize particles and gases. Aerosol mass spectrometer (AMS) measurements showed that the relative ionization efficiency for OA was higher (1.56-3.06) relative to a typical value of 1.4, concluding that AMS is over-estimating COA and suggesting that previous studies likely over-estimated COA concentrations. Food-cooking mass spectra were generated using AMS, and gas and particle food markers were identified with filter inlets for gases and aerosols-chemical ionization mass spectrometer (CIMS) measurements to be used in future food cooking-source apportionment studies. However, there is a considerable variability in both gas and particle markers, and dilution plays an important role in the particle mass budget, showing the importance of using these markers with caution during receptor modeling. These findings can be used to better understand the chemical composition of COA, and they provides useful information to be used in future source-apportionment studies.


Assuntos
Poluentes Atmosféricos , Aerossóis , Culinária , Monitoramento Ambiental , Material Particulado
8.
Environ Sci Technol ; 51(24): 14072-14082, 2017 Dec 19.
Artigo em Inglês | MEDLINE | ID: mdl-29131606

RESUMO

Refractory black carbon (rBC) aerosol is an important climate forcer, and its impacts are greatly influenced by the species associated with rBC cores. However, relevant knowledge is particularly lacking at the Tibetan Plateau (TP). Here we report, for the first time, highly time-resolved measurement results of rBC and its coating species in central TP (4730 m a.s.l), using an Aerodyne soot particle aerosol mass spectrometer (SP-AMS), which selectively measured rBC-containing particles. We found that the rBC was overall thickly coated with an average mass ratio of coating to rBC (RBC) of ∼7.7, and the coating species were predominantly secondarily formed by photochemical reactions. Interestingly, the thickly coated rBC was less oxygenated than the thinly coated rBC, mainly due to influence of the transported biomass burning organic aerosol (BBOA). This BBOA was relatively fresh but formed very thick coating on rBC. We further estimated the "lensing effect" of coating semiquantitatively by comparing the measurement data from a multiangle absorption photometer and SP-AMS, and found it could lead to up to 40% light absorption enhancement at RBC > 10. Our findings highlight that BBOA can significantly affect the "lensing effect", in addition to its relatively well-known role as light-absorbing "brown carbon."


Assuntos
Aerossóis , Poluentes Atmosféricos , Fuligem , Biomassa , Carbono , Tibet
12.
Nature ; 546(7659): 485-491, 2017 06 22.
Artigo em Inglês | MEDLINE | ID: mdl-28640263

RESUMO

Aerosols have a potentially large effect on climate, particularly through their interactions with clouds, but the magnitude of this effect is highly uncertain. Large volcanic eruptions produce sulfur dioxide, which in turn produces aerosols; these eruptions thus represent a natural experiment through which to quantify aerosol-cloud interactions. Here we show that the massive 2014-2015 fissure eruption in Holuhraun, Iceland, reduced the size of liquid cloud droplets-consistent with expectations-but had no discernible effect on other cloud properties. The reduction in droplet size led to cloud brightening and global-mean radiative forcing of around -0.2 watts per square metre for September to October 2014. Changes in cloud amount or cloud liquid water path, however, were undetectable, indicating that these indirect effects, and cloud systems in general, are well buffered against aerosol changes. This result will reduce uncertainties in future climate projections, because we are now able to reject results from climate models with an excessive liquid-water-path response.

13.
Proc Natl Acad Sci U S A ; 113(21): 5781-90, 2016 May 24.
Artigo em Inglês | MEDLINE | ID: mdl-27222566

RESUMO

The effect of an increase in atmospheric aerosol concentrations on the distribution and radiative properties of Earth's clouds is the most uncertain component of the overall global radiative forcing from preindustrial time. General circulation models (GCMs) are the tool for predicting future climate, but the treatment of aerosols, clouds, and aerosol-cloud radiative effects carries large uncertainties that directly affect GCM predictions, such as climate sensitivity. Predictions are hampered by the large range of scales of interaction between various components that need to be captured. Observation systems (remote sensing, in situ) are increasingly being used to constrain predictions, but significant challenges exist, to some extent because of the large range of scales and the fact that the various measuring systems tend to address different scales. Fine-scale models represent clouds, aerosols, and aerosol-cloud interactions with high fidelity but do not include interactions with the larger scale and are therefore limited from a climatic point of view. We suggest strategies for improving estimates of aerosol-cloud relationships in climate models, for new remote sensing and in situ measurements, and for quantifying and reducing model uncertainty.

14.
Environ Sci Technol ; 46(24): 13093-102, 2012 Dec 18.
Artigo em Inglês | MEDLINE | ID: mdl-23163290

RESUMO

Characteristic organic aerosol (OA) emission ratios (ERs) and normalized excess mixing ratios (NEMRs) for biomass burning (BB) events have been calculated from ambient measurements recorded during four field campaigns. Normalized OA mass concentrations measured using Aerodyne Research Inc. quadrupole aerosol mass spectrometers (Q-AMS) reveal a systematic variation in average values between different geographical regions. For each region, a consistent, characteristic ratio is seemingly established when measurements are collated from plumes of all ages and origins. However, there is evidence of strong regional and local-scale variability between separate measurement periods throughout the tropical, subtropical, and boreal environments studied. ERs close to source typically exceed NEMRs in the far-field, despite apparent compositional change and increasing oxidation with age. The absence of any significant downwind mass enhancement suggests no regional net source of secondary organic aerosol (SOA) from atmospheric aging of BB sources, in contrast with the substantial levels of net SOA formation associated with urban sources. A consistent trend of moderately reduced ΔOA/ΔCO ratios with aging indicates a small net loss of OA, likely as a result of the evaporation of organic material from initial fire emissions. Variability in ERs close to source is shown to substantially exceed the magnitude of any changes between fresh and aged OA, emphasizing the importance of fuel and combustion conditions in determining OA loadings from biomass burning.


Assuntos
Aerossóis/análise , Biomassa , Fogo , Compostos Orgânicos/análise , África Ocidental , Monóxido de Carbono/análise , Fatores de Tempo
15.
Environ Sci Technol ; 46(19): 10805-11, 2012 Oct 02.
Artigo em Inglês | MEDLINE | ID: mdl-22913288

RESUMO

Growing concern over emissions from increased airport operations has resulted in a need to assess the impact of aviation related activities on local air quality in and around airports, and to develop strategies to mitigate these effects. One such strategy being investigated is the use of alternative fuels in aircraft engines and auxiliary power units (APUs) as a means to diversify fuel supplies and reduce emissions. This paper summarizes the results of a study to characterize the emissions of an APU, a small gas turbine engine, burning conventional Jet A-1, a fully synthetic jet fuel, and other alternative fuels with varying compositions. Gas phase emissions were measured at the engine exit plane while PM emissions were recorded at the exit plane as well as 10 m downstream of the engine. Five percent reduction in NO(x) emissions and 5-10% reduction in CO emissions were observed for the alternative fuels. Significant reductions in PM emissions at the engine exit plane were achieved with the alternative fuels. However, as the exhaust plume expanded and cooled, organic species were found to condense on the PM. This increase in organic PM elevated the PM mass but had little impact on PM number.


Assuntos
Aeronaves , Material Particulado , Emissões de Veículos , Poluentes Atmosféricos , Monóxido de Carbono/análise
16.
Environ Sci Technol ; 46(19): 10812-9, 2012 Oct 02.
Artigo em Inglês | MEDLINE | ID: mdl-22913312

RESUMO

The work characterizes the changes in volatile and semivolatile PM emissions from a gas turbine engine resulting from burning alternative fuels, specifically gas-to-liquid (GTL), coal-to-liquid (CTL), a blend of Jet A-1 and GTL, biodiesel, and diesel, to the standard Jet A-1. The data presented here, compares the mass spectral fingerprints of the different fuels as measured by the Aerodyne high resolution time-of-flight aerosol mass spectrometer. There were three sample points, two at the exhaust exit plane with dilution added at different locations and another probe located 10 m downstream. For emissions measured at the downstream probe when the engine was operating at high power, all fuels produced chemically similar organic PM, dominated by C(x)H(y) fragments, suggesting the presence of long chain alkanes. The second largest contribution came from C(x)H(y)O(z) fragments, possibly from carbonyls or alcohols. For the nondiesel fuels, the highest loadings of organic PM were from the downstream probe at high power. Conversely, the diesel based fuels produced more organic material at low power from one of the exit plane probes. Differences in the composition of the PM for certain fuels were observed as the engine power decreased to idle and the measurements were made closer to the exit plane.


Assuntos
Aeronaves , Material Particulado , Emissões de Veículos , Aerossóis , Poluentes Atmosféricos/química , Alcanos/química , Biocombustíveis , Carvão Mineral , Desenho de Equipamento , Combustíveis Fósseis , Espectrometria de Massas/instrumentação , Material Particulado/química , Volatilização
17.
Philos Trans A Math Phys Eng Sci ; 370(1974): 4217-62, 2012 Sep 13.
Artigo em Inglês | MEDLINE | ID: mdl-22869798

RESUMO

The idea behind the marine cloud-brightening (MCB) geoengineering technique is that seeding marine stratocumulus clouds with copious quantities of roughly monodisperse sub-micrometre sea water particles might significantly enhance the cloud droplet number concentration, and thereby the cloud albedo and possibly longevity. This would produce a cooling, which general circulation model (GCM) computations suggest could-subject to satisfactory resolution of technical and scientific problems identified herein-have the capacity to balance global warming up to the carbon dioxide-doubling point. We describe herein an account of our recent research on a number of critical issues associated with MCB. This involves (i) GCM studies, which are our primary tools for evaluating globally the effectiveness of MCB, and assessing its climate impacts on rainfall amounts and distribution, and also polar sea-ice cover and thickness; (ii) high-resolution modelling of the effects of seeding on marine stratocumulus, which are required to understand the complex array of interacting processes involved in cloud brightening; (iii) microphysical modelling sensitivity studies, examining the influence of seeding amount, seed-particle salt-mass, air-mass characteristics, updraught speed and other parameters on cloud-albedo change; (iv) sea water spray-production techniques; (v) computational fluid dynamics studies of possible large-scale periodicities in Flettner rotors; and (vi) the planning of a three-stage limited-area field research experiment, with the primary objectives of technology testing and determining to what extent, if any, cloud albedo might be enhanced by seeding marine stratocumulus clouds on a spatial scale of around 100×100 km. We stress that there would be no justification for deployment of MCB unless it was clearly established that no significant adverse consequences would result. There would also need to be an international agreement firmly in favour of such action.

18.
Science ; 331(6022): 1273-4, 2011 Mar 11.
Artigo em Inglês | MEDLINE | ID: mdl-21393532
19.
Vet J ; 174(1): 42-53, 2007 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-16904353

RESUMO

There is strong evidence to suggest that foot-and-mouth disease (FMD) can be transmitted by airborne virus up to many kilometres from a virus source. Atmospheric dispersion models are often used to predict where this disease might spread. This study investigated whether FMD virus (FMDV) aerosol has specific characteristics which need to be taken into consideration in these models. The characteristics and infectiousness of particles emitted by 12 pigs have been studied pre- and post-infection with O UKG 2001 FMDV. Aerosol generated by individual pigs was found log normally distributed in the range 0.015-20.0microm with concentrations between 1000 and 10000cm(-3) at the smallest size and <1cm(-3) above 10microm. No differences in either the total number of particles produced or their size distribution were detected between uninfected and infected pigs. However, a correlation between aerosol concentration and animal activity was found with a more active pig producing significantly greater concentrations than those that were less active. Viable virus was found up to a maximum of 6.3 log TCID(50)/24h/animal. The virus was distributed almost equally across the three size ranges; <3, 3-6 and >6microm. No correlation could be established between the production of virus and animal activity. In general the production of airborne virus closely followed the detection of viraemia in the blood and the presence of clinical symptoms. However, in one instance a pig excreted as much airborne virus as the other animals in the study, but with less virus detected in its blood. The results suggest that there is little merit in including a sophisticated virus release pattern based on physical activity periods or FMDV aerosol size spectrum, together with the appropriate dry deposition calculations, in models used to predict airborne spread of FMD. An estimate of the total daily virus production based on the clinical assessment of disease and virus strain is sufficient as input.


Assuntos
Microbiologia do Ar , Surtos de Doenças , Vírus da Febre Aftosa/crescimento & desenvolvimento , Febre Aftosa/transmissão , Doenças dos Suínos/virologia , Animais , Transmissão de Doença Infecciosa/veterinária , Feminino , Febre Aftosa/virologia , Vírus da Febre Aftosa/química , Tamanho da Partícula , Suínos , Doenças dos Suínos/transmissão
20.
Faraday Discuss ; 130: 341-62; discussion 363-86, 519-24, 2005.
Artigo em Inglês | MEDLINE | ID: mdl-16161793

RESUMO

We present an analysis of recent field data to investigate the variation in the organic component of atmospheric aerosol and its behaviour in the moist environment. In all locations the degree of oxygenation of the organic material increases with photochemical age, as does the particulate hygroscopicity. These changes will generally occur in spatial scales comparable to a single cell in global models at representative boundary layer wind speeds. Using ADDEM, a new model of the equilibrium state of multicomponent aerosol, we show that inorganic component changes must be responsible for the increase in particulate hygroscopicity with photochemical age. It is suggested that a common representation of nearfield and background organic aerosol composition is sufficient to describe the behaviour of organic components in a variety of field experiments; nearfield small mode organics being dominated by a combustion-derived unoxidised signature, whilst the background accumulation mode is more oxygenated and dominates in air masses with a photochemical age of more than a couple of days. This representation may be used within the sub-saturated regime to predict the behaviour of ambient particulates in the moist atmosphere. Whether a similar common representation can be used for cloud activation prediction in supersaturated environments, or for investigation of gas-to-particle partitioning, should be investigated.


Assuntos
Poluentes Atmosféricos/análise , Atmosfera/química , Monitoramento Ambiental/métodos , Compostos Orgânicos/análise , Aerossóis/análise , Atmosfera/análise , Geografia , Incineração , Compostos Inorgânicos/análise , Oxidantes Fotoquímicos/análise , Oxirredução , Oxigênio/química , Termodinâmica , Vento
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