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.