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 1.01min^-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.