701-1262-00L  Atmospheric Chemistry Lab Work

SemesterSpring Semester 2019
LecturersC. Marcolli, U. Krieger, T. Peter
Periodicityyearly recurring course
Language of instructionEnglish



Courses

NumberTitleHoursLecturers
701-1262-00 PAtmospheric Chemistry Lab Work
Das Praktikum findet nach Vereinabrung im CHN D57 statt.
5 hrsC. Marcolli, U. Krieger, T. Peter

Catalogue data

AbstractExperiments are carried out to investigate the freezing of water droplets and ice cloud formation. Water-in-oil emulsions are prepared and cooled in a DSC (differential scanning calorimeter). The measured freezing temperatures are put in context with cloud formation in the atmosphere.
ObjectiveThis practical course offers the opportunity to get to know lab work on a topic of atmospheric importance.
ContentCirrus clouds play an important role in the radiative budget of the Earth. Due to scattering and absorption of the solar as well as terrestrial radiation the cirrus cloud cover may influence significantly the Earth climate. How the cirrus clouds exactly form, is still unknown. Ice particles in cirrus clouds may form by homogeneous ice nucleation from liquid aerosols or via heterogeneous ice nucleation on solid ice nuclei (IN). The dihydrate of oxalic acid (OAD) acts as a heterogeneous ice nucleus, with an increase in freezing temperature between 2 and 5K depending on solution composition. In several field campaigns, oxalic acid enriched particles have been detected in the upper troposphere with single particle aerosol mass spectrometry. Simulations with a microphysical box model indicate that the presence of OAD may reduce the ice particle number density in cirrus clouds by up to ~50% when compared to exclusively homogeneous cirrus formation without OAD.
The goal of this atmospheric chemistry lab work is to expand the knowledge about the influence of oxalic acid in different aqueous solution systems for the heterogeneous ice nucleation process. Experiments of emulsified aqueous solutions containing oxalic acid will be performed with a differential scanning calorimeter (DSC, TA Instruments Q10). Water-in-oil emulsions contain a high number of micrometer-sized water droplets. Each droplet freezes independently which allows the measurement of homogeneous freezing for droplets without heterogeneous IN and heterogeneous freezing in the presence of an IN. OAD is formed in-situ in a first freezing cycle and will act as an IN in a second freezing cycle. This experiment will be performed in the presence of different solutes. In general, the presence of a solute leads to a decrease of the freezing temperature. However, also more specific interactions with oxalic acid are possible so that e.g. the formation of OAD is inhibited.
In the atmospheric chemistry lab work experiments, emulsified aqueous oxalic acid solutions are prepared and investigated in the DSC during several freezing cycles. The onset of freezing is evaluated. Freezing onsets in the presence and absence of OAD are compared. This is done for pure oxalic acid solutions and oxalic acid solutions containing a second solute (e.g. another dicarboxylic acid). The quality of the emulsions is checked in an optical microscope.
Lecture notesHand-outs will be distributed during the course
LiteratureOxalic acid as a heterogeneous ice nucleus in the upper troposphere and its indirect aerosol effect,
B. Zobrist C. Marcolli, T. Koop, B. P. Luo, D. M. Murphy, U. Lohmann, A. A. Zardini, U. K. Krieger, T. Corti, D. J. Cziczo, S. Fueglistaler, P. K. Hudson, D. S. Thomson, and T. Peter
Atmos. Chem. Phys., 6, 3115–3129, 2006.
Prerequisites / NoticeThis module may be attended by 8 students at most. Practical work is carried out in groups of 2, max. 3.

Performance assessment

Performance assessment information (valid until the course unit is held again)
Performance assessment as a semester course
ECTS credits2.5 credits
ExaminersC. Marcolli, U. Krieger, T. Peter
Typeungraded semester performance
Language of examinationEnglish
RepetitionRepetition only possible after re-enrolling for the course unit.

Learning materials

No public learning materials available.
Only public learning materials are listed.

Groups

No information on groups available.

Restrictions

Places8 at the most
PriorityRegistration for the course unit is until 14.02.2020 only possible for the primary target group
Primary target groupAtmospheric and Climate Science MSc (661000)
Environmental Sciences MSc (736000)
Waiting listuntil 28.02.2020

Offered in

ProgrammeSectionType
Atmospheric and Climate Science MasterLaboratory and Field CoursesWInformation
Environmental Sciences MasterLaboratory and Field CoursesWInformation