Characterization of ions at Alpine waterfalls

P Kolarž,M Gaisberger,W Hofmann,P Madl,M Ritter,A Hartl

doi:10.5194/acp-12-3687-2012

P Kolarž, M Gaisberger + Show 4 more

Open Access

https://doi.org/10.5194/acp-12-3687-2012

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Abstract

Abstract. During a three-year field campaign of measuring waterfall generated ions, we monitored five different waterfalls in the Austrian Alps. Most measurements were performed at the Krimml waterfall (Salzburg, Austria), which is the biggest waterfall in Europe, and the Gartl waterfall (Mölltal, Austria). We characterized spatial, time and size distributions of waterfall-generated ions under the influence of surrounding topography. The smallest ions with boundary diameters of 0.9, 1.5 and 2 nm, were measured with a cylindrical air ion detector (CDI-06), while ion sizes from 5.5 to 350 nm were measured using a modified Grimm SMPS aerosol spectrometer. High negative ion concentration gradients are detected in the vicinity of the waterfalls, whereas the increase of positive ions was only moderate. Ions in the nano range were the most abundant at 2 nm, and at 120 nm in the sub-micrometer range.

Highlights

1.1 Air ions in the environmentThe term “air ions” refers to all charged airborne particles with electrical mobility
Most measurements were performed at the Krimml waterfall (Salzburg, Austria), which is the biggest waterfall in Europe, and the Gartl waterfall (Molltal, Austria)
The size range of ions from 0.36 to 350 nm was measured at 2 WFs in the Austrian Alps, using a Gerdian-type ion counter and a Scanning Mobility Particle Sizer, adapted for negative ion counting purposes

Summary

Introduction

The term “air ions” refers to all charged airborne particles with electrical mobility. They are continually created by natural sources such as cosmic rays, radioactive decay of noble gases (such as radon) in the air, and radioactive minerals of the ground. Primary ions evolve after ionization, which typically occurs within microseconds via a process of hydration and ion cluster formation into complexes, known as small air ions (charged nano-aerosols) with a typical lifetime of 5–60 s (Horrak et al, 2000). The central ion of a cluster can contain one inorganic molecule and can be surrounded by one layer of water molecules. In highly pure waters, such inoculation cores are largely absent in the aerosols, at is the case in the waterfalls investigated in this study. The small air ion concentration (n±) itself is determined by the following balance equation:

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