Research Interests

Reactive Indoor Air Chemistry

The importance of atmospheric reaction processes in the indoor air has been previously neglected but quite recently obtained recognition. The chemistry occurring indoors is fundamentally the same as occurring outdoors; the time available for chemical reactions indoors is determined by the ventilation rate of the building. Indoor organic air pollutants arise from number of sources such as building materials, carpets, paints, cleaning products, plants and flowers. The organic compounds indoors are present at higher levels compared with that outdoors. Ozone, initiating reactions with organic compounds itself, is infiltrated via the ventilation systems together with NO₂, usually at comparable concentration levels indoors as outdoors. Reaction between O₃ and NO₂ yields NO₃, a free radical effectively reacting especially with unsaturated hydrocarbons such as limonene. OH radicals normally require sunlight for their formation, however they might be formed in specific reactions between terpenes and ozone indoors in levels comparable to ambient concentrations. 

Formation of ultrafine particles from the gas-phase chemical reaction between ozone and terpenes under conditions relevant for indoor environments has been studied using the available chambers. The goal of the project: Chemical reactions in indoor air as a source of ultrafine particles” is to develop a simple mathematical model that describes and quantifies the fraction of ultrafine particles formed indoors.

Preliminary results from this project have been presented:

S. Langer, K. Pointet, J. Moldanová, E. Ljungström, L. Ekberg, 2005. ”Formation of Ultrafine Particles by Chemical Reactions in Indoor Air”, EGU 2005 General Assembly, 24-29 April 2005, Vienna, Austria.

S. Langer, K. Pointet, J. Moldanová, E. Ljungström, L. Ekberg, 2006. ”Formation of ultrafine particles by chemical reactions in indoor air: Effect of ventilation and relative humidity”, EGU 2006 General Assembly, 2-7 April 2006, Vienna, Austria.

S. Langer and L. Ekberg, 2006. ”Small particles indoors and particle transportation through ventilation (in Swedish)”, Proceedings Inomhusklimat Örebro 2006, pp. 134-145, 14-15 March 2006, Örebro, Sweden.

Figure: Particle number concentration in a ventilated experiment. ACR = 2.,05 h-1, steady state concentrations: [ozone] = 103 ppb, [limonene] = 16 ppb, T = 23 oC, RH = 20%.

APCI MS of gaseous air pollutants

Measurement of the nitric acid (MW = 63.01) in the gas phase on-line is under development using Atmospheric Pressure Chemical Ionization Mass Spectroscopy. The instrument is a Micromass Quattro Micro with specially designed gas inlet. The flow through the inlet is initially set at 70 ml/min. Negative ionization mode is used to generate Cl^- from gaseous chloroform:

Ion masses of the formed adducts are m/z = 98 for ³⁵Cl - H – ONO₂^- and m/z = 100 for ³⁷Cl - H – ONO₂^-. They are scanned in the first quadrupole. The important parameters on the instrument inlet are the voltages on the corona needle and the inlet cone into the mass spectrometer in order to maximize the formation of the Cl^- and dissociation of the adduct in argon in a collision cell and the daughter ion monitoring (m/z = 62)  in the third quadrupole.

A generation system for the nitric acid and chloroform has been developed. The system consists of permeation or diffusion tubes as a source of the substances and a dilution system for air controlled by mass flow regulators. The emission rates of the substances are determined by periodic weighing of the permeation/diffusion tubes (ng/min) and the diluting air flow is measured in Liter/min.

Example of the mass spectrum. Chloroform + approx 7000 ppb of HNO3. Clear excess of HNO3.

m/z 35 and m/z 37:                ³⁵Cl^- and ³⁷Cl^-
m/z 62 and m/z 125:              NO₃^- and HNO₃ -NO₃^-
m/z 98 and m/z 100:              ³⁵Cl-HNO₃ and ³⁷Cl-HNO₃

Characterization of organic content of aerosol particles

Organic compounds in samples of atmospheric aerosol have been determined by Direct Thermal Extraction Gas Chromatography/Mass Spectrometry/Flame Ionization Detection. The samples are heated in Automated Thermal Desorber and the released compounds are injected into a chromatographic column. The compounds are identified by mass spectrometry and quantified by flame ionization detector.

As an example, a NIST certified dust sample “1649a Urban Dust (Organics)” has been analyzed by this method.

NIST dust 2003-06-24