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Environ Sci Technol ; 49(20): 12568-75, 2015 Oct 20.
Artigo em Inglês | MEDLINE | ID: mdl-26422536


Measurements of particle number and mass concentrations and number size distribution of particles from a ship running on liquefied natural gas (LNG) were made on-board a ship with dual-fuel engines installed. Today there is a large interest in LNG as a marine fuel, as a means to comply with sulfur and NOX regulations. Particles were studied in a wide size range together with measurements of other exhaust gases under different engine loads and different mixtures of LNG and marine gas oil. Results from these measurements show that emissions of particles, NOX, and CO2 are considerably lower for LNG compared to present marine fuel oils. Emitted particles were mainly of volatile character and mainly had diameters below 50 nm. Number size distribution for LNG showed a distinct peak at 9-10 nm and a part of a peak at diameter 6 nm and below. Emissions of total hydrocarbons and carbon monoxide are higher for LNG compared to present marine fuel oils, which points to the importance of considering the methane slip from combustion of LNG.

Gás Natural , Navios , Emissões de Veículos/análise , Monóxido de Carbono/análise , Óleos Combustíveis , Gases , Hidrocarbonetos/análise , Tamanho da Partícula
Environ Sci Technol ; 46(21): 11660-9, 2012 Nov 06.
Artigo em Inglês | MEDLINE | ID: mdl-22985264


Limonene has a strong tendency to form secondary organic aerosol (SOA) in the atmosphere and in indoor environments. Initial oxidation occurs mainly via ozone or OH radical chemistry. We studied the effect of O(3) concentrations with or without a OH radical scavenger (2-butanol) on the SOA mass and thermal characteristics using the Gothenburg Flow Reactor for Oxidation Studies at Low Temperatures and a volatility tandem differential mobility analyzer. The SOA mass using 15 ppb limonene was strongly dependent on O(3) concentrations and the presence of a scavenger. The SOA volatility in the presence of a scavenger decreased with increasing levels of O(3), whereas without a scavenger, there was no significant change. A chemical kinetic model was developed to simulate the observations using vapor pressure estimates for compounds that potentially contributed to SOA. The model showed that the product distribution was affected by changes in both OH and ozone concentrations, which partly explained the observed changes in volatility, but was strongly dependent on accurate vapor pressure estimation methods. The model-experiment comparison indicated a need to consider organic peroxides as important SOA constituents. The experimental findings could be explained by secondary condensed-phase ozone chemistry, which competes with OH radicals for the oxidation of primary unsaturated products.

Butanóis/química , Cicloexenos/química , Radical Hidroxila/química , Oxidantes/química , Ozônio/química , Terpenos/química , Aerossóis , Simulação por Computador , Limoneno , Modelos Químicos , Temperatura , Volatilização , Água/química
Proc Natl Acad Sci U S A ; 109(34): 13503-8, 2012 Aug 21.
Artigo em Inglês | MEDLINE | ID: mdl-22869714


The Multiple Chamber Aerosol Chemical Aging Study (MUCHACHAS) tested the hypothesis that hydroxyl radical (OH) aging significantly increases the concentration of first-generation biogenic secondary organic aerosol (SOA). OH is the dominant atmospheric oxidant, and MUCHACHAS employed environmental chambers of very different designs, using multiple OH sources to explore a range of chemical conditions and potential sources of systematic error. We isolated the effect of OH aging, confirming our hypothesis while observing corresponding changes in SOA properties. The mass increases are consistent with an existing gap between global SOA sources and those predicted in models, and can be described by a mechanism suitable for implementation in those models.

Aerossóis/química , Compostos Orgânicos/química , Atmosfera , Radicais Livres , Radical Hidroxila , Espectrometria de Massas/métodos , Modelos Químicos , Oxigênio/química , Ozônio , Reprodutibilidade dos Testes , Solventes/química , Raios Ultravioleta
J Phys Chem A ; 115(42): 11671-7, 2011 Oct 27.
Artigo em Inglês | MEDLINE | ID: mdl-21910406


Amines are widely used and originate from both anthropogenic and natural sources. Recently, there is, in addition, a raised concern about emissions of small amines formed as degradation products of the more complex amines used in CO(2) capture and storage systems. Amines are bases and can readily contribute to aerosol mass and number concentration via acid-base reactions but are also subject to gas phase oxidation forming secondary organic aerosols. To provide more insight into the atmospheric fate of the amines, this paper addresses the volatility properties of aminium nitrates suggested to be produced in the atmosphere from acid-base reactions of amines with nitric acid. The enthalpy of vaporization has been determined for the aminium nitrates of mono-, di-, trimethylamine, ethylamine, and monoethanolamine. The enthalpy of vaporization was determined from volatility measurements of laboratory generated aerosol nanoparticles using a volatility tandem differential mobility analyzer set up. The determined enthalpy of vaporization for aminium nitrates range from 54 up to 74 kJ mol(-1), and the calculated vapor pressures at 298 K are around 10(-4) Pa. These values indicate that aminium nitrates can take part in gas-to-particle partitioning at ambient conditions and have the potential to nucleate under high NO(x) conditions, e.g., in combustion plumes.

Aerossóis/química , Poluentes Atmosféricos/química , Aminas/química , Atmosfera/química , Monitoramento Ambiental/métodos , Nanopartículas/química , Atmosfera/análise , Gases , Nitratos/química , Ácido Nítrico/química , Óxidos de Nitrogênio/química , Oxirredução , Tamanho da Partícula , Termodinâmica , Volatilização
J Phys Chem A ; 114(13): 4586-94, 2010 Apr 08.
Artigo em Inglês | MEDLINE | ID: mdl-20235543


The enthalpy of sublimation has been determined for nine carboxylic acids, two cyclic (pinonic and pinic acid) and seven straight-chain dicarboxylic acids (C(4) to C(10)). The enthalpy of sublimation was determined from volatility measurements of nano aerosol particles using a volatility tandem differential mobility analyzer (VTDMA) set-up. Compared to the previous use of a VTDMA, this novel method gives enthalpy of sublimation determined over an extended temperature range (DeltaT approximately 40 K). The determined enthalpy of sublimation for the straight-chain dicarboxylic acids ranged from 96 to 161 kJ mol(-1), and the calculated vapor pressures at 298 K are in the range of 10(-6)-10(-3) Pa. These values indicate that dicarboxylic acids can take part in gas-to-particle partitioning at ambient conditions and may contribute to atmospheric nucleation, even though homogeneous nucleation is unlikely. To obtain consistent results, some experimental complications in producing nanosized crystalline aerosol particles were addressed. It was demonstrated that pinonic acid "used as received" needed a further purification step before being suspended as a nanoparticle aerosol. Furthermore, it was noted from distinct differences in thermal properties that aerosols generated from pimelic acid solutions gave two types of particles. These two types were attributed to crystalline and amorphous configurations, and based on measured thermal properties, the enthalpy of vaporization was 127 kJ mol(-1) and that of sublimation was 161 kJ mol(-1). This paper describes a new method that is complementary to other similar methods and provides an extension of existing experimental data on physical properties of atmospherically relevant compounds.

Aerossóis/química , Atmosfera/química , Ácidos Dicarboxílicos/química , Aerossóis/análise , Poluentes Atmosféricos/análise , Poluentes Atmosféricos/química , Ácidos Dicarboxílicos/análise , Ácidos Graxos/análise , Ácidos Graxos/química , Estrutura Molecular , Ácidos Pimélicos/análise , Ácidos Pimélicos/química , Termodinâmica , Volatilização