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Chemical and Morphological Characterisation of Aerosol Particles in the Tropopause Region

Nguyen Ngoc, Hung LU (2007)
Abstract (Swedish)
Popular Abstract in Swedish

Små partiklar i form av vätska eller fast material mellan 0.001 till 100 µm i diameter, kan sväva i luften och kallas då aerosolpartiklar. De påverkar direkt på klimatet genom att reflektera solstrålar ut till rymden. Detta gör att vi får ett kallare klimat. Indirekt kan de påverka klimatet genom att verka som kondensationskärnor vid molnbildning. Med detta påverkar de molnens strålningsegenskaper och livstid. Trots deras viktiga roll för klimat är kunskap om dem mycket mager. Min forskning gick ut på att utvidga den befintliga kunskapen om aerosolernas kemiska sammansättning, deras morfologi och ursprung. För detta syfte utvecklades en aerosolprovtagare, en ny metod för att kunna göra... (More)
Popular Abstract in Swedish

Små partiklar i form av vätska eller fast material mellan 0.001 till 100 µm i diameter, kan sväva i luften och kallas då aerosolpartiklar. De påverkar direkt på klimatet genom att reflektera solstrålar ut till rymden. Detta gör att vi får ett kallare klimat. Indirekt kan de påverka klimatet genom att verka som kondensationskärnor vid molnbildning. Med detta påverkar de molnens strålningsegenskaper och livstid. Trots deras viktiga roll för klimat är kunskap om dem mycket mager. Min forskning gick ut på att utvidga den befintliga kunskapen om aerosolernas kemiska sammansättning, deras morfologi och ursprung. För detta syfte utvecklades en aerosolprovtagare, en ny metod för att kunna göra kvantitativ analys på huvudämnen (C, N och O) som finns i aerosolpartiklar och en ny metodik för att studera enskilda aerosolpartiklars morfologi och kemiska sammansättning.



I det första arbetet analyserades prover som samlades under 60 flygningar mellan 1999 till 2002 för selektiva grundämnen med hjälp av den känsliga PIXE-metoden. Analysresultat användes sedan för att studera egenskaper av och källa till aerosoler i den lägsta delen av stratosfären vid norra jordklotets mittlatitud. Det visade sig att kalium och järn som finns på aerosol partiklar i den lägsta delen av stratosfären kommer från troposfären over tropopausen. Resultatet visade också att svavel transporterades till den lägsta delen av stratosfären från högre nivå i stratosfären samt från troposfären över tropopausen.



En mångkanalprovtagare utvecklades och kalibrerades för användning inom ett internationellt projekt, CARIBIC (Civil Aircraft for Regular Investigations of the atmosphere Based on an Instrument Container). Med den här provtagaren förbättrades tidsupplösningen för provtagning av aerosol. Dessutom kan prov samlas för både kvantitativ analys och individuell partikelanalys. Vidare är insamlingseffektivitet 97 % för partiklar med diameter större än eller lika med 0.2 µm. Den är ett effektivt instrument for karakterisering av aerosolpartikel från ett flygplan.



Utveckling av en ny metod för analys av kol, kväve och syre baserad på PESA-metod (particle elastic scattering analysis) genomfördes. Med den här metoden kan man analysera t.ex. ett kolrikt ämne som finns på ett underlag som just innehåller ämnet. Med hjälp av metoden kan man för första gången kvantitativt studera kol, kväve och syre i partiklar från övre troposfären och lägsta stratosfären. Mätningarna visar bl.a. att de här ämnena tillsammans med svavel är huvudämnen på aerosoler i tropopausområdet.



Slutlighen har jag utvecklat en ny metodik för att studera individuella partiklar från tropopausen och mellan södra och norra jordklotet. Den går ut på att klassificera enskilda partiklars utseende och kemiska sammansättning längs flygrutten. Partiklarnas morfologi och kemiska sammansättning varierade med position där de samlades. Bland annat kan man hitta stora partiklar med komplicerad struktur på norra jordklotet och södra jordklotets midlatituder. Partiklar i över troposfären kan ha bildats där uppe genom koagulation och olika gas-till- partikelprocesser. Partiklar i den lägsta delen av stratosfären visade sig vara mer grenad struktur än de som fanns på övre troposfären. Detta beror troligen på att stratosfäriska partiklar befanns sig en längre tid i atmosfären än troposfäriska partiklar. (Less)
Abstract
The aim of this work was to study atmospheric aerosols, focusing on the chemical composition, the morphology and the origin of the aerosol in the upper troposphere and lowermost stratosphere. An aerosol sampler was developed for this purpose. A new method for quantitative analysis of the major components of the aerosol, i.e. C, N and O was developed, and methodologies for single-particle analysis to gain information on particle morphology and chemical composition were adapted and used for the aerosol samples.



Samples collected during 60 intercontinental flights from 1999 to 2002 were analysed with regard to elemental composition with particle-induced X-ray emission. The results were used to study the properties and the... (More)
The aim of this work was to study atmospheric aerosols, focusing on the chemical composition, the morphology and the origin of the aerosol in the upper troposphere and lowermost stratosphere. An aerosol sampler was developed for this purpose. A new method for quantitative analysis of the major components of the aerosol, i.e. C, N and O was developed, and methodologies for single-particle analysis to gain information on particle morphology and chemical composition were adapted and used for the aerosol samples.



Samples collected during 60 intercontinental flights from 1999 to 2002 were analysed with regard to elemental composition with particle-induced X-ray emission. The results were used to study the properties and the origin of the aerosol in the lowermost stratosphere at northern mid-latitudes, focusing on the sulphur concentration. The results of this study show that particulate potassium and iron in the lowermost stratosphere originate in the troposphere and are transported across the tropopause, whereas particulate sulphur has a strong stratospheric origin in addition to transport across the tropopause. Approximately half of the mass of particulate sulphur transported from the stratospheric overworld to the lowermost stratosphere was formed from carbonyl sulphide the remainder being dominated by particulate sulphur and sulphur dioxide that was transported across the tropical tropopause. The production of particulate sulphur in the stratosphere was estimated to be 0.066 Tg S/y.



A new multi-channel aerosol sampler was developed and calibrated for the second phase of the CARIBIC project, which improved the time resolution and produced samples for quantitative and individual particle analyses. It was found that the collection efficiency of the sampler was as high as 97% for particles larger than approximately 0.2 µm in diameter, and the cut-off was 0.08 µm at the calibration conditions. The time resolution of each sample was 1.5 hours. This sampler is a powerful tool for aerosol characterization from an aircraft.



A new method for the analysis of carbon, nitrogen and oxygen based on the use of PESA has been developed for use on CARIBIC samples, which are collected on an organic backing film. For example, the detection limits of C, N O, S and Fe are 3, 1, 2, 2 and 0.1 ng/m3, normalized to STP. This analytical protocol is truly unique because it offers low detection limits and high analytical capability over a wide range of elements. Moreover, it yields quantitative information. This is the first quantitative measurement of the concentration of the carbonaceous aerosol component and other components such as N and O in the upper troposphere and the lowermost stratosphere. It was found that they, together with sulphur, are the major constituents of the aerosol in this region.



Individual particles? characteristics have also been studied based on classification of individual particles with respect to morphology and composition along a transect from 50º N to 30º at 10 km altitude. The classification comprised of more than 30 particle types. Their morphology is complex and varied. A dependence of morphology on the location where they were collected was found. For further investigation of these aerosol particles, chemical analysis was undertaken. Two techniques, PIXE and PESA, were used to quantitatively determine the concentration of carbon and sulphur. Then the particulate carbon to sulphur ratio was used to express the composition of the samples. This ratio varied over the aerosol samples in a range 0.5 to 3.5. The largest value of this ratio appears at around the equator, south of ITCZ, whereas the lowest one was found in the lowermost stratosphere. Further chemical investigation using EFTEM was made to reveal the distributions of carbonaceous and sulphurous matter of individual particles. The results were used to explain the complex structures and the large variation in morphology of the aerosol from different regions. Particles with satellite patterns usually are interpreted as being composed of sulfuric acid. Analyses by EFTEM presented here show that these particles have a central particle composed of both carbonaceous and sulfurous matter and the satellites are composed of carbonaceous matter. Hence a morphological analysis alone could erroneously classify these mixed particles as being pure sulfuric acid. (Less)
Please use this url to cite or link to this publication:
author
supervisor
opponent
  • Prof. Dr. Maenhaut, Willy, Ghent University (UGent), Belgium
organization
publishing date
type
Thesis
publication status
published
subject
keywords
CARIBIC, Physics, Singel particle analysis TEM and EFTEM, Carbon and Sulphur, Light element analysis, Aerosol sampler, Chemical Characterisation, Aerosol in the Tropopause Region, Nuclear physics, Technological sciences, Fysik, Teknik, Kärnfysik, Fysicumarkivet A:000
publisher
Nuclear Physics (Faculty of Technology)
defense location
In Lecture Hall B at Fysikum, Professorsgatan 1, Lund University Faculty of Engineering
defense date
2007-11-30 13:45
ISBN
978-91-628-7332-5
language
English
LU publication?
yes
id
e0aa6e3e-4236-43fa-8422-cb8211a1264b (old id 599268)
date added to LUP
2007-11-13 08:43:54
date last changed
2016-09-19 08:45:09
@misc{e0aa6e3e-4236-43fa-8422-cb8211a1264b,
  abstract     = {The aim of this work was to study atmospheric aerosols, focusing on the chemical composition, the morphology and the origin of the aerosol in the upper troposphere and lowermost stratosphere. An aerosol sampler was developed for this purpose. A new method for quantitative analysis of the major components of the aerosol, i.e. C, N and O was developed, and methodologies for single-particle analysis to gain information on particle morphology and chemical composition were adapted and used for the aerosol samples.<br/><br>
<br/><br>
Samples collected during 60 intercontinental flights from 1999 to 2002 were analysed with regard to elemental composition with particle-induced X-ray emission. The results were used to study the properties and the origin of the aerosol in the lowermost stratosphere at northern mid-latitudes, focusing on the sulphur concentration. The results of this study show that particulate potassium and iron in the lowermost stratosphere originate in the troposphere and are transported across the tropopause, whereas particulate sulphur has a strong stratospheric origin in addition to transport across the tropopause. Approximately half of the mass of particulate sulphur transported from the stratospheric overworld to the lowermost stratosphere was formed from carbonyl sulphide the remainder being dominated by particulate sulphur and sulphur dioxide that was transported across the tropical tropopause. The production of particulate sulphur in the stratosphere was estimated to be 0.066 Tg S/y.<br/><br>
<br/><br>
A new multi-channel aerosol sampler was developed and calibrated for the second phase of the CARIBIC project, which improved the time resolution and produced samples for quantitative and individual particle analyses. It was found that the collection efficiency of the sampler was as high as 97% for particles larger than approximately 0.2 µm in diameter, and the cut-off was 0.08 µm at the calibration conditions. The time resolution of each sample was 1.5 hours. This sampler is a powerful tool for aerosol characterization from an aircraft.<br/><br>
<br/><br>
A new method for the analysis of carbon, nitrogen and oxygen based on the use of PESA has been developed for use on CARIBIC samples, which are collected on an organic backing film. For example, the detection limits of C, N O, S and Fe are 3, 1, 2, 2 and 0.1 ng/m3, normalized to STP. This analytical protocol is truly unique because it offers low detection limits and high analytical capability over a wide range of elements. Moreover, it yields quantitative information. This is the first quantitative measurement of the concentration of the carbonaceous aerosol component and other components such as N and O in the upper troposphere and the lowermost stratosphere. It was found that they, together with sulphur, are the major constituents of the aerosol in this region.<br/><br>
<br/><br>
Individual particles? characteristics have also been studied based on classification of individual particles with respect to morphology and composition along a transect from 50º N to 30º at 10 km altitude. The classification comprised of more than 30 particle types. Their morphology is complex and varied. A dependence of morphology on the location where they were collected was found. For further investigation of these aerosol particles, chemical analysis was undertaken. Two techniques, PIXE and PESA, were used to quantitatively determine the concentration of carbon and sulphur. Then the particulate carbon to sulphur ratio was used to express the composition of the samples. This ratio varied over the aerosol samples in a range 0.5 to 3.5. The largest value of this ratio appears at around the equator, south of ITCZ, whereas the lowest one was found in the lowermost stratosphere. Further chemical investigation using EFTEM was made to reveal the distributions of carbonaceous and sulphurous matter of individual particles. The results were used to explain the complex structures and the large variation in morphology of the aerosol from different regions. Particles with satellite patterns usually are interpreted as being composed of sulfuric acid. Analyses by EFTEM presented here show that these particles have a central particle composed of both carbonaceous and sulfurous matter and the satellites are composed of carbonaceous matter. Hence a morphological analysis alone could erroneously classify these mixed particles as being pure sulfuric acid.},
  author       = {Nguyen Ngoc, Hung},
  isbn         = {978-91-628-7332-5},
  keyword      = {CARIBIC,Physics,Singel particle analysis TEM and EFTEM,Carbon and Sulphur,Light element analysis,Aerosol sampler,Chemical Characterisation,Aerosol in the Tropopause Region,Nuclear physics,Technological sciences,Fysik,Teknik,Kärnfysik,Fysicumarkivet A:000},
  language     = {eng},
  publisher    = {ARRAY(0x9babd80)},
  title        = {Chemical and Morphological Characterisation of Aerosol Particles in the Tropopause Region},
  year         = {2007},
}