Comparison of Sampling Resistance for One to Three Sheets of Membrane Type Passive Sampler

Field measurements were conducted using one to three sheets of a poly-tetrafluoroethylene (PTFE) membrane resistance-type passive sampler (N type sampler) and diffusion length resistance-type sampler (O type sampler) to compare sampling resistance. Acidic gases such as nitric acid (HNO3), hydrochloric acid (HCl), sulfur dioxide (SO2), ozone (O3), ammonia (NH3), nitrogen dioxide (NO2), and nitrogen oxides (NO X ) were sampled using five types of capturing filter paper: plain polyamide filter (ϕ47 mm) and cellulose filters (ϕ14.5 mm) impregnated with NaNO2 + K2CO3, H3PO4, triethanolamine (TEA), and TEA + 3-oxo-2-phenyl-4,4,5,5-tetramethylimidazolin-1-oxyl (PTIO). Four sets of the samplers were exposed to the atmosphere for 4 or 5 weeks through four seasons in FY 2006. The amount of gas components captured occurred in the order of NO X > O3 > NO2 > NH3 > SO2 > HCl > HNO3 for all of the filters in spring and autumn. However, the amount of NH3 captured was large in summer and the amount of NO X was large in winter. The relative standard deviations (RSDs) were less than 10% except for NH3 with the O type sampler in spring and autumn, and for HCl of both type samplers in winter. The RSDs were not dependent on the numbers of PTFE sheets for gas species and season. When the N type sampler mounted on one PTFE sheet was normalized to unit, the resistance values of two and three PTFE sheets for HNO3 were 2.3–2.4 and 4.2–6.1, respectively, while the values of two and three sheets for SO2, O3, HCl, and NH3, were 1.1–1.5 and 1.3–1.9, respectively. There was little variation in resistance for NO2 and NO X , as shown by the values of 1.0–1.1 and 0.9–1.2, respectively. For comparison with the O type sampler, the resistances values for SO2, O3, HCl, NH3, NO2 and NOX were 4.9–5.8, 2.5–3.2, 2.7–4.5, 4.1–12.6, 1.4–1.9, and 1.2–2.4, respectively. The resistance values of the O type sampler were larger than those of the N type samplers. The collection of HNO3 was decreased 25% per PTFE sheet, while the decreases for SO2, O3, HCl and NH3 were moderate at 12–17%. In contrast, collection of NO2 and NO X was minimally affected by the number of PTFE sheets. The concentration of HNO3, SO2, HCl and NH3 in the N type passive sampling method was compared with that of the four-stage filter pack method. The passive method for HNO3, SO2 and HCl was in fair agreement with the filter pack method. For NH3, the concentration by passive method was lower than that by the active method.