Direct collection of HNO3 and HCl by a diffusion scrubber without inlet tubes

Laboratory and field studies were conducted to evaluate the transmittance losses and interactions of atmospheric HNO3 and/or HCl through inlet tubings at a flow rate of 1.0 l min−1. Approximately 80% of HNO3 and 70% of HCl in the dry standard gas were lost through the stainless steel tubing (3 mm i.d., 1.5 m). The loss of HCl through PFA tubing (3 mm i.d., 10 m length) under the given dry and humid conditions was negligible. As for HNO3 on PFA tubing, although the loss was negligible at <50% RH, relative humidity increased the loss up to about 10% at 77% RH. When an HNO3/HCl mixed standard gas passed through the PFA tubing which had been exposed to the marine atmosphere, the loss of HNO3 was enhanced up to 50% at 77% RH, and HCl artifact was simultaneously produced by the reaction of HNO3 with deposited NaCl sea-salt particles. To eliminate the loss and interaction of HNO3 and HCl through inlet tubing, direct collection without inlet tubing was performed by installing an outdoor diffusion scrubber that was connected to an indoor ion chromatograph (direct DS-IC system). HNO3 and HCl in the marine atmosphere were measured by the direct DS-IC system along with another DS-IC system connecting PFA inlet tubing (3 mm i.d., 10 m length) prior to the diffusion scrubber (tubing DS-IC system). As a result, there were a reduction of 22–53% of HNO3 and an increase of 15–106% of HCl through the PFA tubing, which were the negative and positive artifacts produced by the reaction of HNO3 with the deposited NaCl. Thus, inlet tubing should not be used for collecting atmospheric HNO3 and HCl especially in marine environments. The direct DS-IC system is useful for their measurements.