Environmental Engineering Reference
In-Depth Information
Previous study of precipitation chemistry in Croatia (Špoler Čanić et al., 2009)
had shown significant increase of the trend of the annual volume weighted
averages (VWA) of calcium concentration after 1995. It was associated with the
post-war recovery. Nevertheless, Löye-Pilot et al. (1986) have shown that only
calcium concentration and pH value are consistently affected by Saharan dust in
rain water. In addition, some researchers (e.g. Goudie and Middleton, 1992) have
shown that dust storm occurrence increased. For those reasons, the observed increase
in calcium concentration could be due to more frequent mud rains. Therefore, in
this work we also investigated the contribution of mud rains to the above mentioned
increase in calcium concentration.
2. Data and Methods
2.1. Sampling sites
We analyzed episodes of mud rain over Croatia for two mountainous, background
sites (
Fig. 1)
. Those sites are parts of Co-operative Programme for the Monitoring
and Evaluation of the Long-Range Transmission of Air Pollutants in Europe (EMEP)
network. The Site 1 (1594 m) is situated in a protected area (i.e. the National Park
Northern Velebit). The nearest pollution sources are in industrial area of the city
of Rijeka, about 60 km north-westward. The Site 2 (988 m) is situated in the
Nature Park Medvednica and about 10 km far from the city of Zagreb.
2.2. Precipitation data
In this work we used the data from the daily bulk precipitation samples collected
during the period 2001-2005 at Site 1 (676 samples) and 2 (555 samples). The
samples were collected in open polyethylene buckets in accordance with the
precipitation measurement protocol, from 07:00 to 07:00 CET. In precipitation
samples pH values and electrical conductivity were measured, as were concentrations
of main ions. Analysis details are given in Špoler Čanić et al. (2009).
2.3. Aerosol index (AI)
AI was used for mud rains identification. AI is a measure of how much the wave-
length dependence of backscattered UV radiation from an atmosphere containing
aerosols differs from that of a pure molecular atmosphere. Therefore, AI represents
an ideal tool for monitoring intensity and pathway of desert dust on daily basis
(Herman et al., 1997). The daily maps and data of AI were downloaded from:
http://toms.gsfc.nasa.gov. The resolution of the AI data over globe is 1.25° in
longitude and 1.00° in latitude.
