Physical and chemical evolution of atmospheric components in Antarctic troposphere

Measurements of trace components relevant to atmospheric chemistry, in gas
phase such as nitric acid, nitrous acid, hydrochloric acid, bromidic acid,
sulphur dioxide, nitrogen dioxide, peroxyacetyl nitrate and other organic
nitrates (NOy) and particulate matter such as nitrate, nitrite, chloride,
bromide, sulphate, calcium, sodium, ammonium, potassium, magnesium, were
carried out at BTN (Icaro Camp) in austral summers from 1990 to 2004. Total
Gaseous Mercury (TGM) and Total Particulate Matter (TPM) levels were also
measured during November-December 1999 and 2000. The determinations of trace
components were carried out by sampling air through a diffusion annular
denuder/filter patch sampling system, followed by extraction and analysis by
ion chromatography. The annular denuder technique allows the simultaneous and
selective collection of chemical species of interest with a precision and
accuracy never achieved with other commercial instruments. In addition, this
sampling technique follows a multi-step Quality Control and Assurance (QC/QA)
procedure, which ranges from the denuder pre-treatment to the final analysis of
the data. Aerosol samples were also collected using a low-pressure impactor
which divides particles into 12 size fraction over the aerodynamic particle
diameter range 0.035-15.9 micrometers. After sampling, the impaction surfaces
were analysed using the same procedures used for the filters and the denuders
and the mass size distribution were determined. The sampling times were 12, 24
and 48h. TGM samples were taken every 24h using the manual gold trap method
based on the gold-trap amalgamation technique and analysed using the CVAFS
technique. TPM concentrations were obtained collecting airborne particles on
micro-quartz fibre filters mounted in a quartz tube for 48h and analysed by
CVAFS technique. Finally, high sensitivity instruments for nitrous acid (HONO)
was tested in November and December 2003. The CNR-Institute for Atmospheric
Pollution has been developed an automatic sampling system to measure HONO with
two coil samplers, based on derivatization by 2,4-Dinitrophenylhydrazine (DNPH)
and on high performance liquid chromatographic (HPLC) analysis with UV
detection at 309 nm. This instrument allowed the HONO measurements with a
sample integration time of 3 min, with a sampling frequency of 10 min and with
a detection limit of 1 pptv, proper in the polar areas. Atmospheric
measurements of HONO were carried out in parallel with the micrometeorological
data in order to define the local behaviours of physical parameters and to
determine the surface fluxes.