Fog collection and deposition modelling - EcoCatch Lunz

Author(s)

M. W. Koller, C. Ramírez-Santa Cruz, K. Leder, H. Bauer, M. Dorninger, F. Hofhansl, W. Wanek, A. Kasper-Giebl

Abstract

The area of Lunz am See (N 047.855°, E 015.068°, 650 m a.s.l.)

in Lower Austria has been subject to long term monitoring of

meteorological parameters as well as wet deposition. Even though Lunz is

known for its good air quality, with about 200 days of precipitation per

year reaching an annual average of 1500 mm deposition, immission fluxes

reach levels of critical loads. For instance, nitrogen input from wet

deposition of nitrate and ammonium is > 14 kg ha-1 a-1, and sulphur

input from sulphate is 5 kg ha-1 a-1. In the framework of the

EcoCatch project1) wet, dry and occult deposition have been investigated

in detail in an alluvial forest near the Biological Station (Lunz/See)

since September 2008. The overall contribution of dry and occult

deposition was expected to be comparably low and only of importance in

times of decreased wet deposition. Collection of fog samples was

performed with an active fog sampler, regulated by a Vaisala PWD-12

sensor monitoring visibility. Temperature, relative humidity, wind speed

and direction were logged by a HOBO weather station. Filter stacks were

used for sampling of aerosol particles and gaseous components and a Wet

And Dry Only Sampler (WADOS) was used to sample precipitation. Solute

analysis was carried out via ion chromatography. Alkali and earth alkali

metals, chloride as well as ammonium, sulphate and nitrate were

quantified in rain, aerosol and fog samples on an event basis. In

addition dry deposition included nitrogen oxide and dioxide, sulphur

dioxide and ammonia measurements. A site specific relation of liquid

water content (LWC) to visibility was established using the collection

rate and the known collection efficiency of the fog sampler. A modified

version of the fog deposition resistance model devised by G.M. Lovett

was used to quantify occult deposition onto the alluvial forest. The

surface area index of local vegetation was measured with a SunScan

System and tree height was determined using a Vertex IV/GS. Between

September 2008 and October 2009 roughly 560 hours of fog were observed

and about 380 hours thereof were sampled. Duration, frequency as well as

density of fog events showed strong seasonal variations. As expected,

spring and autumn seasons exhibited the highest frequencies and

durations of fog events. Concentrations of nitrate in fog samples during

the cold season (Nov-Mar) were 10-fold higher than in rain, reaching

monthly averages of 50 mg L-1 in January and February. With 15-25 mg

L-1, sulphate was 11-fold higher in fog compared to rain. Ammonium

reached on average 14 mg L-1 in fog samples and was thus 15-fold higher

than in rain. 1)EcoCatch - Understanding the effects of global change

on ecosystem processes and services at catchment scale (funded by Amt

der Niederösterreichischen Landesregierung, and Clean Air

Commission, Austrian Academy of Sciences).

Organisation(s)

Department of Meteorology and Geophysics, Aerosol Physics and Environmental Physics

External organisation(s)

Technische Universität Wien

Pages

101

No. of pages

1

Publication date

07-2010

Austrian Fields of Science 2012

105206 Meteorology

Portal url

https://ucrisportal.univie.ac.at/en/publications/fog-collection-and-deposition-modelling--ecocatch-lunz(d8e43ee1-5f81-4a7e-a7e9-fa8a91040b6c).html