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Neutral molecular cluster formation of sulfuric acid-dimethylamine observed in real time under atmospheric conditions.

ABSTRACT: For atmospheric sulfuric acid (SA) concentrations the presence of dimethylamine (DMA) at mixing ratios of several parts per trillion by volume can explain observed boundary layer new particle formation rates. However, the concentration and molecular composition of the neutral (uncharged) clusters have not been reported so far due to the lack of suitable instrumentation. Here we report on experiments from the Cosmics Leaving Outdoor Droplets chamber at the European Organization for Nuclear Research revealing the formation of neutral particles containing up to 14 SA and 16 DMA molecules, corresponding to a mobility diameter of about 2 nm, under atmospherically relevant conditions. These measurements bridge the gap between the molecular and particle perspectives of nucleation, revealing the fundamental processes involved in particle formation and growth. The neutral clusters are found to form at or close to the kinetic limit where particle formation is limited only by the collision rate of SA molecules. Even though the neutral particles are stable against evaporation from the SA dimer onward, the formation rates of particles at 1.7-nm size, which contain about 10 SA molecules, are up to 4 orders of magnitude smaller compared with those of the dimer due to coagulation and wall loss of particles before they reach 1.7 nm in diameter. This demonstrates that neither the atmospheric particle formation rate nor its dependence on SA can simply be interpreted in terms of cluster evaporation or the molecular composition of a critical nucleus.

SUBMITTER: Kurten A

PROVIDER: S-EPMC4210346 | biostudies-literature | 2014 Oct

REPOSITORIES: biostudies-literature

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Neutral molecular cluster formation of sulfuric acid-dimethylamine observed in real time under atmospheric conditions.

Kürten Andreas A Jokinen Tuija T Simon Mario M Sipilä Mikko M Sarnela Nina N Junninen Heikki H Adamov Alexey A Almeida João J Amorim Antonio A Bianchi Federico F Bianchi Federico F Breitenlechner Martin M Dommen Josef J Donahue Neil M NM Duplissy Jonathan J Ehrhart Sebastian S Flagan Richard C RC Franchin Alessandro A Hakala Jani J Hansel Armin A Heinritzi Martin M Hutterli Manuel M Kangasluoma Juha J Kirkby Jasper J Laaksonen Ari A Lehtipalo Katrianne K Leiminger Markus M Makhmutov Vladimir V Mathot Serge S Onnela Antti A Petäjä Tuukka T Praplan Arnaud P AP Riccobono Francesco F Rissanen Matti P MP Rondo Linda L Schobesberger Siegfried S Seinfeld John H JH Steiner Gerhard G Tomé António A Tröstl Jasmin J Winkler Paul M PM Williamson Christina C Wimmer Daniela D Ye Penglin P Baltensperger Urs U Carslaw Kenneth S KS Kulmala Markku M Worsnop Douglas R DR Curtius Joachim J

Proceedings of the National Academy of Sciences of the United States of America 20141006 42

For atmospheric sulfuric acid (SA) concentrations the presence of dimethylamine (DMA) at mixing ratios of several parts per trillion by volume can explain observed boundary layer new particle formation rates. However, the concentration and molecular composition of the neutral (uncharged) clusters have not been reported so far due to the lack of suitable instrumentation. Here we report on experiments from the Cosmics Leaving Outdoor Droplets chamber at the European Organization for Nuclear Resear ...[more]

PMID: 25288761

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Project description:An understanding of the biosynthesis and metabolism of dimethylamine (DMA) is important because it is a precursor of dimethylnitrosamine (nitroso-DMA). DMA is the major short-chain aliphatic amine in human and rat urine. DMA is formed from trimethylamine (TMA), which, in turn, is a breakdown product of dietary choline. Enzymes within gut bacteria catalyse both of these reactions; it is not known whether mammalian cells can form DMA. To determine the relative importance of dietary choline, bacteria and other mechanisms for the formation of DMA, we measured DMA excretion in the urine of rats fed on a diet devoid of choline, and in urine of rats with no bacterial colonization of the intestines. We also describe an improved gas-chromatographic method for the measurement of methylamines in biological fluids. In control rats there were significant amounts of DMA within several biological fluids [urine, 54.2 +/- 3.0 mumol/kg body wt. per 24 h (556.2 +/- 37.5 nmol/ml); blood, 18.8 +/- 1.9 nmol/ml; gastric juice, 33.5 +/- 10.5 nmol/ml; means +/- S.E.M.]. Animals eating a diet containing no choline excreted as much MMA and DMA as did choline-supplemented rats (25-35 mumol/kg per 24 h), and they excreted slightly less TMA (2 versus 2.5 mumol/kg per 24 h). Rats with no gut bacteria excreted the same amount of DMA in their urine as did the control animals (45-55 mumol/kg per 24 h). They excreted much less MMA (16.3 +/- 1.5 versus 40.3 +/- 2.6 mumol/kg per 24 h; mean +/- S.E.M.; P less than 0.01), TMA (0.7 +/- 0.2 versus 2.5 +/- 0.5 mumol/kg per 24 h; mean +/- S.E.M.; P less than 0.01) and piperidine (2.0 +/- 0.3 versus 6.3 +/- 0.6 mumol/kg per 24 h; mean +/- S.E.M.; P less than 0.01) in their urine. From our studies we conclude that DMA is present in significant amounts within gastric fluid, an environment that is ideal for nitrosamine formation (under acidic conditions, nitroso-DMA is chemically formed by the reaction of nitrite with DMA). Results also indicate that dietary choline was not the sole precursor for DMA formation and that gut bacteria are not essential for the formation of DMA. Hence in mammals there must be endogenous pathways that are capable of forming DMA; however, these endogenous mechanisms remain unidentified.

Dataset Information

Neutral molecular cluster formation of sulfuric acid-dimethylamine observed in real time under atmospheric conditions.

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Neutral molecular cluster formation of sulfuric acid-dimethylamine observed in real time under atmospheric conditions.

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