3.3 Pump sampling
The experiments on the recovery rates of PAH congeners from the PU foam
sampling devices in the pump sampling procedure were throughout above
90% (supplementary Table S2). The average respiratory volume of a
person at rest is about 750 L h-1 and may reach 1
m3 h-1 after light exercise such as
climbing a staircase. Based on the idea that a visitor would stay on the
premises for less than one hour air was sampled for one hour for each
determination of airborne PAHs. Fig. 4 comprises the results of pump
sampling on the drip floor. PAH concentrations are given separately for
the PU foams and the respective quartz filters. The standard deviations
of the triplicate determinations are generally below 20% and may reach
50% in cases where airborne congener concentration were below 5 ng
m-3. In exceptional cases the very low concentrations
sampled on quartz filter may display standard deviation up to 100%.
There is no obvious difference between intraday and interday
repeatabilities and they are reasonably small to allow assessment of
airborne PAH concentrations and the influence of temperature. The
complete set of data separately for PU foams and quartz filters are
collected in supplementary Tables S7 and S8.
Figure 4: PAH concentrations in air determined after pump
sampling at the wall (see Fig. 1, position P) in PU foams and quartz
filters, means and standard deviations (n=3). Intraday 1: 29 July;
intraday 2: 11 September; interday: 30 July – 1 August.
As for the stir bar sorptive extraction the pattern of relative congener
abundance is biased towards the congeners with lower molecular weight
and higher vapor pressures when compared with the congener pattern of
the source (Table 1). Supplementary Figure S2 juxtaposes the PAH
congener patterns in the source, on the SBSE devices, on the PU foams
and on the quartz filters.
The three pump sampling sequences (intraday 1 and 2, interday) reveal
the expected dependence of airborne PAH content on the room temperature
(20 °C, 15 °C, 19 – 20 °C). The observation of highest naphthalene
abundance on the quartz filter on the coolest sampling day (interday 2)
may be attributed to the temperature susceptibility of the vapor
pressure of this congener. With increasing temperature, naphthalene
bound to the particles captured on the quartz filter should be blown
into the PU foam by the constant pump flow. This effect is likely to
occur in case of all PAH congeners though it should decrease with vapor
pressure of the respective congener. However, there are obviously
significantly different affinities among PAH congeners towards particles
independent from the respective vapor pressure as may be concluded from
the high abundance of acenaphthene on the quartz filter that exceed as
sole congener even that in the PU foam.