The hydrogen-sulfur correlation, by PIXE plus PESA, and aerosol source identification

Abstract

The use of hydrogen-free thin teflon filters for particulate sampling has allowed us to simultaneously measure sulfur (and other elements) by PIXE and hydrogen by PESA. Particulate hydrogen in nonvolatile forms (since all analyses are in vacuum) is an important component of aerosols, totalling typically about 1 3 of all atoms. The hydrogen is measured at the same time as PIXE by placing a surface barrier detector at 30° in the forward direction, allowing the (p, p) kinematic energy shift to safely resolve hydrogen from the unresolved peaks of C, N, O, and heavier elements. The method is absolute and simple, with no important corrections. Sensitivity on 400 μg cm2 teflon filters is about 5 ng cm2 H in 100s. This technique was introduced to the National Park Service 31 station network in June. 1984, and immediately proved enormously valuable in separating natural aerosols from anthropogenic aerosols. For example, at Great Smoky NP, the H/S correlation was excellent, > 0.90, while the molar ratio was 10:1 (note: (NH4)2SO4) has a ratio 8:1), while at North Cascades NP, there was essentially no correlation and the H S molar ratio was 37:1. In the former, most hydrogen is tied to presumably anthropogenic sulfur species, while at North Cascades NP, the converse is true. Evidence of H2SO4) aerosols from Arctic studies will also be shown. © 1987.