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.
The formation of secondary organic aerosols (SOA) has been investigated intensively during the last two decades in numerous field and laboratory studies and a general understanding exists about the ...major particle-phase products. However, recent studies show that several new product classes, such as esters, peroxides or organosulfates, also have to be considered in order to understand the detailed chemical mechanisms leading to SOA as well as to predict the aerosol mass loadings. For the identification and quantification of these three compound classes as well as for carboxylic SOA compounds, liquid chromatography (LC)/mass spectrometry (MS) is the most appropriate analytical method. In this article we try to summarize briefly the work that has been done for the determination of SOA-related carboxylic acids and we present new LC/tandem MS results on the characterization of esters, peroxides and organosulfates. In contrast to earlier work, the mass-spectrometric characterization of the individual compounds is always based on the comparison with authentic reference compounds.
Like chalk and cheese: Although the model put forward by Lahav and Leiserowitz may be quite reasonable for the crystallization of glycine in the presence of amino acids, it is not the case for the ...crystallization of CaCO3 (see picture). In the latter case, the amino acids present cannot be considered to be innocent molecules as they are involved as ligands in the coordination chemistry of Ca2+. New results indicate that homochiral impurities are not the driving force for the phase selection: When added intentionally, they annihilate the observed phase selectivity rather than promote it.
The formation of secondary organic aerosols (SOA) has been investigated intensively during the last two decades in numerous field and laboratory studies and a general understanding exists about the ...major particle-phase products. However, recent studies show that several new product classes, such as esters, peroxides or organosulfates, also have to be considered in order to understand the detailed chemical mechanisms leading to SOA as well as to predict the aerosol mass loadings. For the identification and quantification of these three compound classes as well as for carboxylic SOA compounds, liquid chromatography (LC)/mass spectrometry (MS) is the most appropriate analytical method. In this article we try to summarize briefly the work that has been done for the determination of SOA-related carboxylic acids and we present new LC/tandem MS results on the characterization of esters, peroxides and organosulfates. In contrast to earlier work, the mass-spectrometric characterization of the individual compounds is always based on the comparison with authentic reference compounds.
The formation of secondary organic aerosols (SOA) has been investigated intensively during the last two decades in numerous field and laboratory studies and a general understanding exists about the ...major particle-phase products. However, recent studies show that several new product classes, such as esters, peroxides or organosulfates, also have to be considered in order to understand the detailed chemical mechanisms leading to SOA as well as to predict the aerosol mass loadings. For the identification and quantification of these three compound classes as well as for carboxylic SOA compounds, liquid chromatography (LC)/mass spectrometry (MS) is the most appropriate analytical method. In this article we try to summarize briefly the work that has been done for the determination of SOA-related carboxylic acids and we present new LC/tandem MS results on the characterization of esters, peroxides and organosulfates. In contrast to earlier work, the mass-spectrometric characterization of the individual compounds is always based on the comparison with authentic reference compounds.
Wie Tag und Nacht: Das Modell von Lahav und Leiserowitz mag für die Kristallisation von Glycin in Gegenwart von Aminosäuren sinnvoll sein – für die Kristallisation von CaCO3 (siehe Bild) ist es dies ...nicht, denn hier können die Aminosäuren nicht als „unschuldige“ Moleküle betrachtet werden, da sie mit Ca2+ Komplexe bilden können. Nach neuen Ergebnissen sind homochirale Verunreinigungen nicht die Triebkraft der Phasenselektion: Absichtlich zugegeben fördern sie die Phasenselektivität nicht, sondern unterdrücken sie.
PDF
