Long-term assessment of the wet precipitation chemistryin Austria (1984–1999)

H. Puxbaum a, V. Simeonov b,*, M. Kalina a, S. Tsakovski b, H. L€ooffler c,G. Heimburger d, P. Biebl e, A. Weber f, A. Damm g

a Institute for Analytical Chemistry, Vienna University of Technology, Getreidemarkt 9/151, A-1060 Vienna, Austriab Chair of Analytical Chemistry, Faculty of Chemistry, University of Sofia ‘‘St. Kl. Okhridski’’, J. Bourchier Blvd. 1, 1164 Sofia, Bulgaria

c Department of Environmental Protection, City of Vienna, Rinnb€oockstraße 15, A-1100 Vienna, Austriad Department of Environmental Protection and Engineering, Carinthian Regional Government, Flatschacherstraße 70,

A-9021 Klagenfurt, Austriae Amt der Salzburger Landesregierung, Abteilung Umweltschutz, Ulrich Schreier Straße 18, A-5020 Salzburg, Austria

f Amt der Tiroler Landesregierung, Landesforstdirektion Tirol, B€uurgerstraße 36, A-6020 Innsbruck, Austriag Amt der Nieder€oosterreichische Landesregierung, Abteilung WA5, Landhausplatz 1, A-3109 St. P€oolten, Austria

Received 6 July 2001; received in revised form 15 February 2002; accepted 13 March 2002

Abstract

The aim of the present study was to determine the long-time trends in concentrations and depositions of major ions

in wet precipitation samples collected at 11 sampling sites from the Austrian precipitation chemistry network in the

period 1984–1999. The analytical results were treated by the use of least square linear regression method. It is shown

that a serious decrease of sulfate (between 30% and 60% for the period) and hydrogen ion (between 60% and 102% for

the period) concentrations and depositions is achieved at almost all sampling sites and in most of these cases the linear

trend proves to be statistically significant. Nitrogen containing ions and base cations do not reveal a distinct trend of

changing and in the majority of the sites the linear models are not adequate. In principle, an overall slight concentration

and deposition decrease for these major ions is observed (up to 30% for the period of observation) but some substantial

exceptions are also found (site Haunsberg or site Lobau). The changes in chloride concentration and deposition, too, do

not indicate significant linear trend and, in general, are decreasing for the period of monitoring. In order to give some

explanation of the exceptional behaviour of some of the major ions in several sites, an additional comparison with

Austrian emission data (sulfur dioxide, nitrogen oxides, ammonium) and with data from five EMEP sites from

neighbouring countries is performed. A significant West–East trend of acidity increase is found as well as a good

correlation with the emission trends. Therefore, both transboundary and specific local factors could be substantial

factors in the wet precipitation chemistry in the region.

� 2002 Elsevier Science Ltd. All rights reserved.

Keywords: Trend analysis; Wet precipitation; Chloride; Nitrate; Sulfate; Ammonium; Sodium; Potassium; Calcium; Magnesium;

Acidity; Austrian precipitation chemistry network

1. Introduction

The Austrian Precipitation Sampling Network was

established in the early 80s based on daily sampling ac-

tivity with wet only collectors with seven sampling sites

in Tyrol, Salzburg and Burgenland counties followed

Chemosphere 48 (2002) 733–747

www.elsevier.com/locate/chemosphere

*Corresponding author. Fax: +359-296-25438.

E-mail address: vsimeonov@chem.uni-sofia.bg (V. Simeo-

nov).

0045-6535/02/$ - see front matter � 2002 Elsevier Science Ltd. All rights reserved.

PII: S0045-6535 (02 )00125-X

by the other federal counties (BMGU, 1984; Gehak and

Chalupa, 1985; Kalina and Puxbaum, 1996). But syste-

matic studies of the rainwater composition began much

earlier with only one station as part of the European

Air Chemistry Network (EACN) and of the World

Meteorological Organization (WMO) Background Air

Pollution Monitoring Network (BAPMON). In the de-

veloped framework of the national monitoring system

more and more stations were developed and engaged

with the assessment of the wet precipitation chemistry.

Now 33 sampling stations are available, three of which

are also part of the EMEP Network (co-operative pro-

gramme for monitoring and evaluation of long-range

transmission of air pollutants in Europe). Due to the

complex terrain in Austria the altitudes of the sampling

sites from the net reach from 155 m asl in the East to

3106 m asl at high elevation sites in the Central Alps and

the annual precipitation amounts range from 260 to

2100 mm.

In its integrity the Austrian Precipitation Sampling

Network is designed to estimate the wet deposition loads

of the wet precipitation major ions and to determine the

trends in all chemical components of the rainwater for

Austria. The wet precipitation data collection is impor-

tant not only for evaluation of the soil and forest con-

ditions in the country, but also for comparison of time

trends in the precipitation chemistry in Austria and

other countries from Central and Western Europe and

North America. In several already published studies

during the 80s and 90s (Granat, 1978; Rohde and

Granat, 1984; Hedin et al., 1987; Dillon et al., 1988;

Puxbaum et al., 1988; Erisman et al., 1989; Fay et al.,

1989; Schulze et al., 1990; Fricke and Beilke, 1993; Ru-

ijgork and R€oomer, 1993; Hedin et al., 1994; Lynch et al.,1995; Sanusi et al., 1995; West and Feagley, 1995; Avila,

1996; Hovmad and Kemp, 1996; Lynch et al., 1996) it

was found by all authors despite the differences in time

periods of sampling and in sampling locations that the

overall pH values increase and sulfate concentrations

decrease in the wet precipitation. This is considered as

the reason for the total acid deposition decrease in

countries like USA, Canada, The Netherlands, Den-

mark, Germany, France, Spain, Switzerland, Sweden,

Norway, Finland and Austria. In most of the cited

studies the time trends are determined just for a limited

number of sites and for time intervals not exceeding

a decade. Besides, there is a lack of reliable information

about the relationships between locally observed trends

in the major ion concentrations and additional sub-

stantial components of the environment like total

emission amount for a certain pollutant or influence of

emissions from neighbouring regions. Only the careful

consideration of observation over a really long time

period and over a large part of the sampling net and

successive linking of the observed trends in the wet

precipitation major ions with local and more global in-

fluences gives a chance to interpret in a reliable way the

wet precipitation chemistry on a national scale. Since

many local institutions in Austria are interested of the

preservation of a clean environment, another significant

purpose of a large-scale trend study is to present in a

simple way an environment situation dated more than a

decade ago and the present one with some future per-

spectives.

The aim of the present study is perform trend anal-

ysis of wet precipitation data collections from 11 sam-

pling sites all over Austria (Tyrol, Salzburg, Lower

Austria, Carinthia and Vienna counties) for the period

1984–1999. Additionally, the trend analysis results will

be compared and interpreted with respect to data from

the total emission loads of pollutants in Austria for the

same period (sulfur dioxide, ammonia, nitrogen oxides)

and from EMEP sampling stations located in the neigh-

bouring countries Switzerland, Germany, Hungary,

Czech Republic and Italy.

2. Experimental

2.1. Sampling sites

Eleven sampling sites (Reutte, Kufstein, Innervill-

graten, Haunsberg, Werfenweng, Sonnblick, Nasswald,

Litschau, Lunz, Nassfeld and Lobau) were chosen from

the Austrian Wet Only Precipitation Network as they

provide almost complete data collections for a long

sampling period (between 9 and 16 years within the time

interval 1984–1999 as follows: 16 years of monitoring

for the sites Haunsberg and Werfenweng; 15 years of

monitoring for the sites Reutte, Kufstein and Innervill-

graten; 12 years of monitoring for the sites Sonnblick

and Lobau; 11 years of monitoring for site Nasswald;

nine years of monitoring for the rest of the sites Nass-

feld, Lunz and Litschau). Additionally, the trend anal-

ysis for each site and each major ion was performed for

that particular period for which no missing data were

found. Thus, each linear model is calculated for the

specific time period assuring a complete data set. The

first three sites are located in the Austrian province

Tyrol, the next three in Salzburg, the following three

in Lower Austria, Nassfeld in Carinthia and the last,

Lobau, in Vienna region. The sampling site locations

(all of them background stations) are presented in

Fig. 1. Additionally, the location of five sites from the

EMEP measurement network (T€aanikon––Switzerland,Brotjacklriegel––Germany, Kosetice––Czech Republic,

Ispra––Italy and K-puszta––Hungary) is given for com-

parison of wet precipitation data and trends with the

Austrian sites. Some location characteristics of all Aus-

trian sites are given in Table 1 (co-ordinates and alti-

tude).

734 H. Puxbaum et al. / Chemosphere 48 (2002) 733–747

2.2. Sampling equipment

The Austrian Wet Only Precipitation Network is

equipped with the wet and dry only precipitation sam-

pler (WADOS) (Winkler et al., 1989). A slightly heated

resistance sensor coupled to a lid ensures the collection

of wet only precipitation samples in sampling bottles

protected from the light. Local observers carry out the

daily control of the samples usually in the morning

hours. The collection procedure is performed according

to the recommendation of the Austrian Ministry of

Health and Environment (BMGU, 1984). The samples

are transferred and stored in polyethylene bottles at 0–4

�C, transported in biweekly intervals to the Institute of

Analytical Chemistry, Vienna University of Technology,

and analysed generally within 1–4 weeks after receipt.

The sampler efficiency was determined to be 96% in an

international comparison test (Winkler et al., 1989), and

there is a good correlation between the amount of rain

sampled by WADOS and the total amount of rain in the

respective region determined by the meteorological

teams (r ¼ 0:96). Missing data are evaluated by checking

Fig. 1. Location of the sampling sites in the Austrian precipitation-monitoring network (legend to the sites: 11, Reutte; 13, Kufstein;

14, Innervillgraten; 21, Haunsberg; 25, Werfenweng; 27, Sonnblick; 32, Nasswald; 33, Litschau; 36, Lunz; 61, Nassfeld; 43, Lobau).

Table 1

Characteristics of the sampling sites

Site code Site Longitude (E) Latitude (N) Altitude (asla) Period

Tyrol

11 Reutte 10�4005400 47�2901100 930 1984–1999

13 Kufstein 12�1303800 47�3904700 680 1984–1999

14 Innervillgraten 12�2101000 46�4900600 1730 1984–1999

Salzburg

21 Haunsberg 13�0100000 47�5702300 520 1984–1999

25 Werfenweng 13�1501200 47�2501800 940 1984–1999

27 Sonnblick 12�5703200 47�0301500 3106 1987–1998

Lower Austria

32 Nasswald 15�4202600 47�4600400 600 1988–1999

33 Litschau 15�0202000 48�5702000 560 1989–1998

36 Lunz 15�0400700 47�5101800 618 1990–1998

Vienna

43 Lobau 16�3005100 48�1101500 155 1987–1998

Carinthia

61 Nassfeld 13�1603300 46�3303700 1530 1990–1997

a asl: above sea-level.

H. Puxbaum et al. / Chemosphere 48 (2002) 733–747 735

the precipitation data (precipitation amount) from the

meteorological service to evaluate the rain event and ion

concentrations are calculated by regression analysis

from already available measurements. The missing ion

concentrations were estimated only for samples with

partial analysis.

2.3. Chemical analysis

The samples were analysed for the anions chloride,

nitrate and sulfate and the monovalent cations ammo-

nium, sodium and potassium by ion chromatography

(IC) as described by Kalina and Puxbaum (Kalina and

Puxbaum, 1996). The system was a Dionex-Quc Ana-

lyser for cations and a Dionex GMP-2 for anions. The

columns were Dionex Ion Pac CS 12 and AS4A-SC,

respectively, with precolumns CG 12 and AG4A-SC.

The eluents used were 17 mM methane sulfonic acid

(MSA) (cations) or 1.8 mM sodium carbonateþ 1:7mM sodium bicarbonate (anions). Respective suppres-

sors were Dionex CSRS I 4 mm or ASRS I 4 mm

(electrochemical). Detection was performed through

conductivity measurements. Sample loop volumes were

20 or 30 ll, respectively. The divalent cations calcium

and magnesium were determined by atomic absorp-

tion spectroscopy (Perkin–Elmer 403, flame atomizer,

photomultiplier PM detector). The pH was determined

electrochemically according to the procedure of the

Austrian Ministry of Health and Environment (BMGU,

1984).

The detection limits calculated according to the three

standard deviations of the blank values were 0.01 lg l�1

for ammonium, chloride, magnesium, potassium and

sodium, 0.02 lg l�1 for calcium and 0.03 lg l�1 for ni-

trate and sulfate.

Quality control of the analytical data was performed

by comparing calculated vs. measured conductivities and

by cation vs. anion balances of the individual samples.

If the differences were less than 10%, it was assumed that

all major ions had been analysed. The majority of the

samples presented an anion deficit, probably due to the

lack of bicarbonate and the quantity of short-chain or-

ganic acids (Puxbaum et al., 1991).

The wet precipitation weighted annual mean con-

centrations for all major ions measured at all sampling

sites in the periods of observation are available at re-

quest from the authors. The analytical measurements

and the precipitation amount values were used for the

trend study both for major ion concentrations and de-

positions.

2.3.1. Statistical data treatment

The trend analysis was performed by the use of

least-squares linear regression approach to the non-

normalized raw data (both for mean annual weighted

concentrations and depositions). Squaring of the re-

gression coefficient performs the goodness of fit, thus

presenting the percent of variance explained. The

regression coefficient significance was determined after

estimation of their standard errors at p < 0:05 and

p < 0:01 and respective estimation of the residuals by

F-test. The validity of the linear model was checked by

the value of r2.

3. Results and discussion

The most important features of the trend analysis are

presented in Tables 2 and 3 for concentrations and de-

positions, respectively. In the tables the changes (total

and per year in %) in major ion concentrations and

depositions for the period of monitoring are given for

each site. The quality of the model fit is illustrated by the

value of the r2, whose value indicates the percentage ofexplained variance.

3.1. Trend analysis of concentrations

It was of substantial interest to determine the changes

in major ion concentrations for each sampling site

from the Austrian wet precipitation-monitoring net-

work. These results could be readily compared to previ-

ously published data of acidic reduction in Western

Europe and North America like studies for Spain (19%

decrease of sulfate concentrations and depositions for

five years means and median pH increase from 4.74 to

5.50 for 10 years, Avila, 1996); for Canada (average

annual decrease in sulfate concentrations in the period

of 10 years of 29%, Dillon et al., 1988); for The Neth-

erlands (decrease in total acid deposition nearly 19%

for five-year period, Erisman et al., 1989); for USA

(approximately 28% sulfate decrease and 40% hydrogen

decrease within period of 13 years of observation); for

Germany (up to 50% acidity decrease) etc. Most of the

cited studies are limited with respect to time period of

monitoring or number of sites under observation or even

discussion about the concentration changes of all major

ions of the wet precipitation, just to mention the general

comment that base cation changes are out of the scope

of the trend study.

In the present study an effort is done to summarize

the trend of all major ions in the wet precipitation at a

large number of sites and for a relative long time period.

This approach reveals a more complete and reliable as-

sessment of the wet precipitation chemistry in Austria.

3.2. Hydrogen

As a whole, significant linear trends are found for

hydrogen ion concentrations at 7 out of 11 sites (at

Litschau the trend is calculated as statistically significant

736 H. Puxbaum et al. / Chemosphere 48 (2002) 733–747

Table 2

Summary for major ion concentration (mg l�1) changes and trend significance at all sites

Ion/site Predicted first

year

Predicted final

year

Total change

in %

Change per year

in %

R2 and trend

significance

Hþ

Reutte 0.02 0.005 �77.7 �5.2 0.43

Kufstein 0.04 0.01 �68.5 �4.6 0.66

Innervillgraten 0.02 0.002 �91.0 �6.1 0.64

Haunsberg 0.03 0.004 �85.4 �5.4 0.71

Werfenweng 0.02 0.0006 �102.9 �6.4 0.69

Sonnblick 0.02 0.01 �64.0 �5.3 0.63

Nasswald 0.02 0.03 60.6 5.5 0.14 (n.s.)

Litschau 0.04 0.01 �63.7 �6.4 0.61

Lunz 0.032 0.03 �6.9 �0.8 0.01 (n.s.)

Lobau 0.02 0.003 �85.7 �7.1 0.41

Nassfeld 0.01 0.02 6.5 0.8 0.01 (n.s.)

NHþ4

Reutte 0.43 0.428 �0.3 0.02 0.01 (n.s.)

Kufstein 0.60 0.64 7.2 0.5 0.03 (n.s.)

Innervillgraten 0.41 0.47 16.7 1.1 0.05 (n.s.)

Haunsberg 0.95 0.84 �11.4 �0.7 0.03 (n.s.)

Werfenweng 0.59 0.40 �31.0 �1.9 0.14 (n.s.)

Sonnblick 0.36 0.19 �46.9 �3.9 0.56

Nasswald 0.50 0.49 �1.6 �0.2 0.01 (n.s.)

Litschau 1.27 0.79 �38.2 �3.8 0.49

Lunz 0.71 0.53 �25.8 �2.9 0.36

Lobau 1.19 0.52 �56.4 �4.7 0.74

Nassfeld 0.63 0.55 �12.5 �1.6 0.02 (n.s.)

Cl�

Reutte 0.56 0.34 �38.6 �2.6 0.07 (n.s.)

Kufstein 0.36 0.25 �31.0 �2.1 0.20 (n.s.)

Innervillgraten 0.30 0.25 �15.8 �1.1 0.01 (n.s.)

Haunsberg 0.50 4.07 720.5 45.0 0.22 (n.s.)

Werfenweng 0.66 0.35 �47.5 �3.0 0.49

Sonnblick 0.39 0.20 �47.2 �3.9 0.24 (n.s.)

Nasswald 1.59 0.44 �72.2 �6.6 0.59

Litschau 0.70 0.85 22.1 2.2 0.01 (n.s.)

Lunz 0.36 0.21 �42.2 �4.7 0.36 (n.s.)

Lobau 1.06 0.18 �83.4 �7.0 0.61

Nassfeld 0.99 0.41 �58.8 �7.4 0.61

Naþ

Reutte 0.23 0.11 �52.0 �3.5 0.08 (n.s.)

Kufstein 0.14 0.13 �7.7 �0.5 0.01 (n.s.)

Innervillgraten 0.104 0.096 �7.9 �0.5 0.01 (n.s.)

Haunsberg 0.25 0.36 45.3 3.0 0.03 (n.s.)

Werfenweng 0.45 0.21 �53.5 �3.8 0.49

Sonnblick 0.11 0.19 71.9 6.0 0.14 (n.s.)

Nasswald 0.21 0.24 14.5 1.3 0.01 (n.s.)

Litschau 0.12 0.32 179.4 17.9 0.40 (n.s.)

Lunz 0.15 0.12 �19.7 �2.2 0.14 (n.s.)

Lobau 0.21 0.17 �17.1 �1.4 0.05 (n.s.)

Nassfeld 0.53 0.28 �47.7 �6.0 0.24 (n.s.)

Kþ

Reutte 0.10 0.07 �33.9 �2.3 0.04 (n.s.)

Kufstein 0.07 0.06 �7.1 �0.5 0.01 (n.s.)

Innervillgraten 0.05 0.10 93.4 6.2 0.20 (n.s.)

Haunsberg 0.15 0.16 5.0 0.3 0.01 (n.s.)

Werfenweng 0.17 0.15 �14.1 �1.0 0.01 (n.s.)

(continued on next page)

H. Puxbaum et al. / Chemosphere 48 (2002) 733–747 737

Table 2 (continued)

Ion/site Predicted first

year

Predicted final

year

Total change

in %

Change per year

in %

R2 and trend

significance

Sonnblick 0.08 0.03 �64.1 �5.3 0.62

Nasswald 0.16 0.14 �12.2 �1.1 0.01 (n.s.)

Litschau 0.17 0.10 �42.2 �4.2 0.10 (n.s.)

Lunz 0.06 0.07 7.9 0.9 0.01 (n.s.)

Lobau 1.42 1.38 �3.2 �0.3 0.01 (n.s.)

Nassfeld 0.08 0.07 �10.2 �1.3 0.01 (n.s.)

Ca2þ

Reutte 0.88 0.31 �65.3 �5.9 0.87

Kufstein 0.41 0.19 �53.7 �4.9 0.67

Innervillgraten 0.47 0.27 �41.3 �3.8 0.14 (n.s.)

Haunsberg 0.75 2.76 268.6 16.8 0.23 (n.s.)

Werfenweng 1.02 0.94 �7.2 �0.5 0.01 (n.s.)

Sonnblick 0.58 0.27 �53.3 �4.4 0.37

Nasswald 1.20 0.74 �38.7 �3.5 0.09 (n.s.)

Litschau 0.62 0.87 40.0 4.0 0.04 (n.s.)

Lunz 1.07 0.0001 �109.2 �12.1 0.43 (n.s.)

Lobau 1.83 0.92 �49.8 �4.5 0.42

Nassfeld 1.10 0.57 �48.5 �6.1 0.15 (n.s.)

Mg2þ

Reutte 0.11 0.05 �55.4 �5.0 0.91

Kufstein 0.06 0.02 �58.8 �5.4 0.73

Innervillgraten 0.08 0.05 �41.0 �3.7 0.24 (n.s.)

Haunsberg 0.12 0.06 �49.1 �3.1 0.30

Werfenweng 0.20 0.26 27.7 1.7 0.02 (n.s.)

Sonnblick 0.06 0.02 �62.8 �5.2 0.68

Nasswald 0.10 0.12 19.7 1.8 0.01 (n.s.)

Litschau 0.0792 0.0791 �0.1 (�0.01) 0.01 (n.s.)

Lunz 0.08 0.03 �56.3 �6.3 0.45 (n.s.)

Lobau 0.3093 0.3094 0.1 (0.01) 0.01 (n.s.)

Nassfeld 0.15 0.11 �27.4 �3.4 0.03 (n.s.)

NO�3

Reutte 0.34 0.33 �1.2 �0.1 0.01 (n.s.)

Kufstein 0.48 0.50 2.7 0.2 0.01 (n.s.)

Innervillgraten 0.26 0.28 5.8 0.4 0.02 (n.s.)

Haunsberg 0.63 0.57 �9.5 �0.6 0.04 (n.s.)

Werfenweng 0.45 0.43 �5.1 �0.3 0.01 (n.s.)

Sonnblick 0.24 0.19 �19.8 �1.7 0.17 (n.s.)

Nasswald 0.41 0.74 82.0 7.5 0.10 (n.s.)

Litschau 0.66 0.58 �11.9 �1.2 0.17 (n.s.)

Lunz 0.61 0.53 �12.9 �1.4 0.07 (n.s.)

Lobau 0.77 0.62 �19.9 �1.7 0.28 (n.s.)

Nassfeld 0.48 0.53 9.2 1.2 0.06 (n.s.)

SO2�4

Reutte 0.53 0.32 �40.9 �2.7 0.49

Kufstein 0.71 0.37 �47.7 �3.2 0.41

Innervillgraten 0.63 0.28 �55.9 �3.7 0.53

Haunsberg 1.15 0.53 �53.5 �3.4 0.61

Werfenweng 0.80 0.33 �59.3 �3.7 0.65

Sonnblick 0.55 0.26 �53.4 �4.5 0.72

Nasswald 0.79 0.75 �4.9 �0.5 0.01 (n.s.)

Litschau 1.31 0.76 �41.7 �4.2 0.62

Lunz 0.84 0.52 �37.8 �4.2 0.42 (n.s.)

Lobau 1.74 0.80 �53.9 �4.5 0.80

Nassfeld 0.98 0.72 �26.2 �3.3 0.07 (n.s.)

738 H. Puxbaum et al. / Chemosphere 48 (2002) 733–747

Table 3

Summary for major ion deposition (kg ha�1) changes and trend significance at all sites

Ion/site Predicted first

year

Predicted final

year

Total change

in %

Change per year

in %

R2 and trend

significance

Hþ

Reutte 0.23 0.06 �75.6 �5.0 0.43

Kufstein 0.39 0.13 �66.3 �4.4 0.53

Innervillgraten 0.16 0.01 �92.8 �6.2 0.46

Haunsberg 0.25 0.02 �93.9 �5.8 0.74

Werfenweng 0.14 0.01 �95.3 �6.0 0.64

Sonnblick 0.18 0.09 �48.1 �4.0 0.33 (n.s.)

Nasswald 0.19 0.22 13.7 1.3 0.01 (n.s.)

Litschau 0.15 0.07 �50.1 �5.0 0.37 (n.s.)

Lunz 0.35 0.39 10.7 1.2 0.01 (n.s.)

Lobau 0.09 0.01 �90.5 �7.5 0.36

Nassfeld 0.21 0.20 �0.3 (�0.03) 0.01 (n.s.)

NHþ4

Reutte 0.2 0.1 �26.0 �1.7 0.01 (n.s.)

Kufstein 5.9 6.5 8.7 0.6 0.03 (n.s.)

Innervillgraten 2.8 2.5 �12.2 �0.8 0.03 (n.s.)

Haunsberg 8.0 5.5 �31.1 �1.9 0.25

Werfenweng 3.6 3.1 �15.9 �1.0 0.08 (n.s.)

Sonnblick 3.7 3.0 �17.8 �1.5 0.03 (n.s.)

Nasswald 5.2 3.0 �41.3 �3.8 0.37

Litschau 5.7 3.9 �31.3 �3.1 0.18 (n.s.)

Lunz 8.2 7.3 �11.9 �1.3 0.04 (n.s.)

Lobau 4.0 2.2 �45.6 �3.8 0.35

Nassfeld 8.3 6.5 �21.8 �2.7 0.12 (n.s.)

(continued on next page)

Table 2 (continued)

Ion/site Predicted first

year

Predicted final

year

Total change

in %

Change per year

in %

R2 and trend

significance

NHþ4 þ NO�

3

Reutte 0.92 0.90 �2.2 �0.1 0.01 (n.s.)

Kufstein 1.08 1.14 5.6 0.4 0.01 (n.s.)

Innervillgraten 0.67 0.75 11.9 0.8 0.03 (n.s.)

Haunsberg 1.58 1.41 �10.8 �0.7 0.04 (n.s.)

Werfenweng 1.04 0.84 �19.2 �1.3 0.06 (n.s.)

Sonnblick 0.50 0.38 �24.0 �2.0 0.49

Nasswald 0.91 1.21 33.0 3.0 0.17 (n.s.)

Litschau 1.93 1.37 �29.0 �3.8 0.26 (n.s.)

Lunz 1.32 1.05 �20.5 �2.6 0.17 (n.s.)

Lobau 1.95 1.15 �41.0 �3.4 0.50

Nassfeld 1.05 1.06 1.0 0.1 0.01 (n.s.)

Base cations

Reutte 0.94 0.38 �60.0 �5.5 0.64

Kufstein 0.56 0.44 �21.8 �2.0 0.12 (n.s.)

Innervillgraten 0.68 0.51 �15.7 �1.4 0.09 (n.s.)

Haunsberg 2.36 4.52 91.8 6.1 0.32 (n.s.)

Werfenweng 1.75 1.03 �42.8 �3.1 0.09 (n.s.)

Sonnblick 0.74 0.61 �17.3 �1.4 0.24 (n.s.)

Nasswald 1.48 0.50 �66.8 �6.1 0.65

Litschau 1.29 1.80 39.4 4.4 0.01 (n.s.)

Lunz 0.91 0.25 �73.3 �9.2 0.31 (n.s.)

Lobau 1.41 0.94 �33.6 �3.1 0.01 (n.s.)

Nassfeld 2.27 1.32 �41.7 �5.2 0.33 (n.s.)

n.s. means non-significant trend.

H. Puxbaum et al. / Chemosphere 48 (2002) 733–747 739

Table 3 (continued)

Ion/site Predicted first

year

Predicted final

year

Total change

in %

Change per year

in %

R2 and trend

significance

Cl�

Reutte 6.6 3.9 �40.7 �2.7 0.07 (n.s.)

Kufstein 3.5 2.4 �30.6 �2.0 0.17 (n.s.)

Innervillgraten 1.9 0.9 �50.2 �3.4 0.43

Haunsberg 4.8 29.3 505.9 31.6 0.11 (n.s.)

Werfenweng 4.7 2.3 �52.2 �3.3 0.24 (n.s.)

Sonnblick 4.2 3.1 �27.1 �2.3 0.08 (n.s.)

Nasswald 15.5 1.2 �92.1 �8.4 0.76

Litschau 3.4 4.3 28.5 2.9 0.01 (n.s.)

Lunz 4.7 2.4 �49.7 �5.5 0.22 (n.s.)

Lobau 3.6 0.4 �90.0 �7.5 0.60

Nassfeld 15.1 5.5 �63.4 �7.9 0.46 (n.s.)

Naþ

Reutte 0.2 0.1 �26.4 �1.8 0.01 (n.s.)

Kufstein 1.2 1.2 4.0 0.3 0.01 (n.s.)

Innervillgraten 0.7 0.4 �36.0 �2.4 0.25 (n.s.)

Haunsberg 2.2 2.6 18.3 1.2 0.01 (n.s.)

Werfenweng 3.3 1.1 �66.0 �4.4 0.36

Sonnblick 1.0 2.8 194.7 16.2 0.30 (n.s.)

Nasswald 2.1 1.3 �36.6 �3.3 0.14 (n.s.)

Litschau 0.4 1.5 280.7 28.1 0.35 (n.s.)

Lunz 1.53 1.54 0.2 (0.02) 0.01 (n.s.)

Lobau 0.7 0.5 �20.3 �1.7 0.11 (n.s.)

Nassfeld 6.7 3.6 �46.3 �5.8 0.19 (n.s.)

Kþ

Reutte 1.2 0.8 �34.5 �2.3 0.05 (n.s.)

Kufstein 0.7 0.6 �5.3 �0.4 0.01 (n.s.)

Innervillgraten 0.3 0.5 76.4 5.1 0.11 (n.s.)

Haunsberg 1.2 0.9 �25.4 �1.7 0.04 (n.s.)

Werfenweng 1.3 0.9 �27.5 �1.8 0.06 (n.s.)

Sonnblick 0.8 0.5 �41.3 �3.4 0.21 (n.s.)

Nasswald 1.5 0.8 �44.1 �4.0 0.25 (n.s.)

Litschau 0.8 0.4 �53.4 �5.3 0.12 (n.s.)

Lunz 0.5 1.0 106.3 11.8 0.34 (n.s.)

Lobau 1.4 1.3 �3.2 �0.3 0.01 (n.s.)

Nassfeld 1.2 0.7 �37.4 �4.7 0.09 (n.s.)

Ca2þ

Reutte 10.3 3.6 �64.6 �5.4 0.71

Kufstein 3.8 2.2 �41.5 �3.8 0.48

Innervillgraten 2.4 1.6 �33.1 �3.0 0.14 (n.s.)

Haunsberg 7.2 19.1 165.8 10.4 0.10 (n.s.)

Werfenweng 7.5 6.6 �11.4 �0.7 0.01 (n.s.)

Sonnblick 5.9 3.9 �34.3 �2.9 0.20 (n.s.)

Nasswald 11.5 3.0 �74.2 �6.8 0.50

Litschau 2.8 4.0 46.3 4.6 0.04 (n.s.)

Lunz 16.3 0.01 �116.3 �12.9 0.34 (n.s.)

Lobau 5.9 3.1 �46.5 �4.2 0.23 (n.s.)

Nassfeld 12.7 7.4 �41.9 �5.2 0.14 (n.s.)

Mg2þ

Reutte 1.1 0.6 �48.4 �4.0 0.53

Kufstein 0.5 0.3 �49.2 �4.5 0.64

Innervillgraten 0.3 0.2 �26.6 �2.4 0.15 (n.s.)

Haunsberg 0.9 0.4 �57.7 �3.6 0.49

Werfenweng 1.4 1.2 �13.2 �0.8 0.01 (n.s.)

Sonnblick 0.5 0.3 �39.8 �3.3 0.35

740 H. Puxbaum et al. / Chemosphere 48 (2002) 733–747

Table 3 (continued)

Ion/site Predicted first

year

Predicted final

year

Total change

in %

Change per year

in %

R2 and trend

significance

Nasswald 1.0 0.4 �58.4 �5.3 0.53

Litschau 0.4 0.3 �0.8 �0.1 0.01 (n.s.)

Lunz 0.9 0.4 �52.7 �5.9 0.25 (n.s.)

Lobau 1.0 0.9 �9.9 �0.9 0.01 (n.s.)

Nassfeld 1.4 1.0 �28.2 �3.5 0.09 (n.s.)

NO�3

Reutte 3.7 3.8 2.0 0.1 0.01 (n.s.)

Kufstein 4.5 4.7 5.6 0.4 0.01 (n.s.)

Innervillgraten 1.7 1.4 �19.1 �1.3 0.11 (n.s.)

Haunsberg 5.5 3.4 �38.2 �2.4 0.48

Werfenweng 3.0 2.7 �10.1 �0.6 0.06 (n.s.)

Sonnblick 2.5 2.8 14.4 1.2 0.07 (n.s.)

Nasswald 4.1 3.4 �17.3 �1.6 0.10 (n.s.)

Litschau 2.6 2.5 �3.7 �0.4 0.01 (n.s.)

Lunz 6.4 7.2 12.5 1.4 0.04 (n.s.)

Lobau 2.5 2.1 �15.2 �1.3 0.04 (n.s.)

Nassfeld 5.3 5.2 �0.7 �0.1 0.01 (n.s.)

SO2�4

Reutte 6.1 3.6 �41.7 �2.8 0.44

Kufstein 7.1 3.7 �47.1 �3.1 0.36

Innervillgraten 4.5 1.5 �67.4 �4.5 0.57

Haunsberg 9.7 3.1 �67.7 �4.2 0.81

Werfenweng 5.8 2.2 �61.6 �3.9 0.65

Sonnblick 5.4 4.0 �25.4 �2.1 0.32 (n.s.)

Nasswald 8.5 4.3 �49.4 �4.5 0.49

Litschau 5.7 3.3 �41.3 �4.1 0.53

Lunz 10.3 6.8 �33.9 �3.8 0.18 (n.s.)

Lobau 6.1 3.0 �50.9 �4.2 0.48

Nassfeld 11.2 9.8 �12.9 �1.6 0.01 (n.s.)

NHþ4 þ NO�

3

Reutte 8.7 8.8 0.9 0.1 0.01 (n.s.)

Kufstein 10.4 11.2 7.4 0.5 0.02 (n.s.)

Innervillgraten 4.5 3.8 �14.8 �1.0 0.12 (n.s.)

Haunsberg 13.5 8.9 �34.0 �2.1 0.37

Werfenweng 6.6 5.7 �13.3 �0.8 0.09 (n.s.)

Sonnblick 9.0 7.0 �22.3 �1.9 0.24 (n.s.)

Nasswald 9.3 6.5 �30.6 �2.8 0.28 (n.s.)

Litschau 8.4 6.5 �22.6 �2.3 0.15 (n.s.)

Lunz 14.6 14.4 �1.3 �0.1 0.01 (n.s.)

Lobau 6.5 4.3 �33.8 �2.8 0.23 (n.s.)

Nassfeld 13.5 11.7 �13.7 �1.7 0.04 (n.s.)

Base cations

Reutte 16.5 4.7 �71.4 �6.5 0.64

Kufstein 6.0 4.5 �24.4 �2.2 0.14 (n.s.)

Innervillgraten 3.6 2.9 �20.3 �1.9 0.08 (n.s.)

Haunsberg 12.0 23.0 92.3 6.2 0.06 (n.s.)

Werfenweng 14.9 9.3 �37.7 �2.7 0.04 (n.s.)

Sonnblick 12.4 10.6 �14.9 �1.2 0.06 (n.s.)

Nasswald 16.0 5.5 �65.7 �6.0 0.55

Litschau 4.3 6.3 45.3 4.53 0.07 (n.s.)

Lunz 19.3 0.3 �98.4 �10.9 0.31 (n.s.)

Lobau 9.3 5.8 �37.9 3.4 0.15 (n.s.)

Nassfeld 22.1 12.7 �42.1 �5.3 0.18 (n.s.)

n.s means non-significant trend.

H. Puxbaum et al. / Chemosphere 48 (2002) 733–747 741

due to one outlier, the rest of the average annual con-

centrations for the site show very close values). In all

cases (except for the sites Nasswald and Nassfeld) a se-

rious hydrogen ion concentration decrease is found

varying between 7% and 102% for the whole period of

monitoring (or between 0.8% and 6.5% per year). If the

extremely low change at site Lunz is eliminated as well

as the increasing statistically non-significant trends at

Nasswald and Nassfeld, then an average hydrogen

concentration decrease of about 80% for the period of

monitoring is observed. It means a annual decrease of

�5%. It is worth noting that the increase at the site

Nassfeld is relatively small (6.5% for the whole period or

0.8% per year; it could be stated that no real change is

observed) and the only substantial exception in the ob-

served overall tendency is the hydrogen ion concentra-

tion increase at the site Nasswald (over 60% for the

period or 5.5% per year). In principle, a serious free

acidity reduction is constantly observed at sites located

in the Western part of Austria (Reutte, Kufstein, In-

nervillgraten, Sonnblick, Haunsberg, Werfenweng from

counties Salzburg and Tyrol) since at sites located in the

middle of the country or its eastern part the free acidity

reduction is either less or no significant change is regis-

tered.

3.3. Sulfate

The sulfate ion concentration decreases at all 11 sites.

Statistically significant linear trend is found at eight

of the sites, exceptions are only Nasswald, Lunz and

Nassfeld being sites located in the eastern part of the

country. The concentration decrease ranges between 5%

and 60% for the period of observation (average annual

change between 0.5% and 4.5%). This is a very con-

vincing illustration of the overall acidity decrease in

many countries from Western Europe and North Amer-

ica. On the other hand, it is important confirmation of

the long postulated influence of emissions from Eastern

European countries, which although seriously reduced

in the last decade, still determine the relatively higher

wet precipitation acidity in Eastern Austria. However,

the differences in the predicted with respect to the linear

regression model sulfate concentrations (1999) between

these two major conditionally separated Austrian re-

gions do not exceed a factor of 2.5.

3.4. Ammonium and nitrate

The linear regression analysis for both major ions has

indicated that no serious changes in their concentrations

throughout the long-time period of observation could be

found. For instance, ammonium concentrations exhibit

a slight decrease (between 0.3% and 55% for the whole

period of monitoring) at almost all sites except for

Kufstein and Innervillgraten, where an increase is found

of about 7% and 17%, respectively. The linear models,

however, are statistically significant only at Sonnblick,

Litschau and Lobau, indicating in this way that the ob-

served changes are rather sporadic fluctuations around

a average value than a serious linear trend. Again, the

maximal differences in the concentration values for the

period of monitoring are around 2–2.5.

For nitrate ions the situation seems even more con-

stant. No statistically significant trend is proved for any

of the sites and the calculated concentration changes are

in fact result of the non-adequateness of the linear

regression models and indicate a relative stability over

a long-time observation. The appearance of outliers

among the average annual concentrations leads some-

times to estimation of overall increase or decrease (e.g.

about 82% increase at Nasswald or 20% decrease at

Lobau for the whole period).

For both ions could be concluded that the long-term

assessment reveals an almost constant level of their

concentrations in the wet precipitation. This is proved

by the simultaneous regression of the ammonium and

nitrate concentrations (sum of both N-containing ion

concentrations). Again, no statistically significant linear

trend is found for 10 out of all 11 sites.

3.5. Chloride

Chloride concentration decreases at 10 out of 11 sites

(between 1% and 7% per year). At four sites the trend is

significant. This situation indicates that the chloride

concentration, similar to those of ammonium and ni-

trate is relatively constant over the long time period of

observation. The chloride concentration increases only

at Haunsberg (with 45% per year) and this is obviously

due to specific local conditions. The slight chloride

concentration decrease is in good agreement with the

estimated trend in USA for an earlier period (up to

1992).

3.6. Base cations (sodium, potassium, calcium, magne-

sium)

In a previously published study on long-term trend

determination of wet precipitation data from the USA,

Lynch et al. found a decrease in the base cations con-

centration (between 2% and 3% per year) in various

sampling sites. In Europe similar trends was detected in

Sweden and The Netherlands. Due to this situation

Lynch postulated a base cations ‘‘offset’’ including the

combined effect of the changes in cation and anion

concentrations.

In this study a slight base cation concentration de-

crease is observed in almost all sampling sites (ex-

ceptions are Haunsberg and Litschau) with changes

742 H. Puxbaum et al. / Chemosphere 48 (2002) 733–747

between 1% and 10% per year. The concentration

increase for the two sites mentioned above is between

4% and 6% per year. Since the statistically signifi-

cant linear trend is calculated only at 2 out of 11 sites, it

may be accepted that in fact the real changes are small

and represent rather the unavoidable concentration

fluctuations caused by local factors than a stable time

trend.

Nevertheless, some important assumptions about

role of different local factors in the acidity decrease

could be suggested. Three main groups of sites are

formed with respect to the changes in sulfate and hy-

drogen concentrations. The first group includes sites

with relatively higher level of hydrogen ion concentra-

tion decrease as compared to the sulfate ion concentra-

tion decrease (Innervillgraten, Haunsberg, Werfenweng,

Nasswald). In the second group (Luntz, Nassfeld,

Lobau) exactly the opposite situation is observed. This

second case indicates that for such a situation, the base

cation ‘‘offset’’ influences the acidity changes. In the

third group (Reutte, Kufstein, Sonnblick, Litschau) the

free acidity decrease is probably due to the overall

reduction of the sulfur oxide emissions in Europe.

3.7. Trend analysis of depositions

The results from the linear regression analysis of data

for the changes in deposition are presented in Table 3.

The deposition data reflect with higher level of signifi-

cance the changes in the overall acidity, base cations and

nitrogen containing ions from the wet precipitation data

since they take into account the precipitation amount

throughout the monitoring.

3.8. Hydrogen

As it could be readily seen, the trend observed for the

concentrations at the different sampling sites is almost

the same for the hydrogen deposition. Statistically

significant decline is proved for 6 out of 11 sites and it

varies between 4% and 7% decrease per year. Exceptions

are sites Lunz and Sonnblick with a statistically non-

significant hydrogen ion deposition increase of about 1%

per year, which is an indication for deposition stability

all over the monitoring period.

3.9. Sulfate

Again, a very dominant decreasing trend for sulfate

depositions at all sampling sites is observed (varying

between 1.6% and 4.5% per year). The trend is statisti-

cally significant in 8 out of 11 sites (Lunz and Nassfeld

are again sites with non-significant linear trend as it

was in the concentration estimation; instead of site

Sonnblick indicating non-significant trend for sulfate

concentration change, Nasswald is the site with non-

significance of the deposition trend).

The substantial decrease of the overall acidity for the

whole net of sampling sites in case of deposition change

estimation is an indication that the precipitation amount

is not the factor, which influences substantially the trend

of the acidity reduction.

3.10. Ammonium and nitrate

No differences are observed in comparison with the

concentration considerations. The statistical significance

of the linear trend for the majority of the sites is absent

and it is an indication for a relatively constant level of

the deposition amount over the years of monitoring for

almost all sampling sites. The deposition amount tends

to a slight decrease and the same holds true for the sum

of both nitrogen-containing ions.

3.11. Chloride

The only exceptions of the observed chloride depo-

sition changes are at sites Haunsberg and Litschau

where a significant increase of chloride deposition for

the period of monitoring is found (totally over 500% or

about 30% per year for Haunsberg and much less but

still exceptional for Litschau––28% totally and about 3%

per year). This is an indication for specific local condi-

tions since at all other sampling sites (although rarely

possessing linear trend significance) a deposition de-

crease (between 2% and 8% per year). It is important to

note that this specific increase is related to the deposition

increase of base cations at the same sampling sites

confirming in this way the local factor influence.

3.12. Base cations (sodium, potassium, calcium, magne-

sium)

In general, the base cations deposition changes cor-

respond closely to the deposition changes of chlo-

ride––statistically non-significant trend of decrease in 9

out of 11 sites (significant linear trend is found only for

Reutte and Nasswald, both cases with decreasing de-

positions) and for two sites (Haunsberg and Litschau)

base cation deposition increase (6% and 4.5% per year,

respectively). As mentioned above, this is an indication

for specific local conditions.

3.13. Site identity

The overall changes in major ion concentrations and

depositions of the wet precipitation monitoring data

from the Austrian monitoring network need a more

careful discussion with respect to the sampling site lo-

cation. It is obvious that, on one side, the global ten-

dency of acidic reduction is followed but, on the other

H. Puxbaum et al. / Chemosphere 48 (2002) 733–747 743

side, local conditions also determine the wet precipita-

tion chemistry. It was assumed that the summarizing of

several possible reasons for influences on the chemical

content of the wet precipitation in the region of interest

could be of use.

In Fig. 2 the changes in the emissions from SO2, NOx

and NH3 during the last 20 years for Austria (Um-

weltbundesamt, 2001) are presented.

The rapid decrease of the sulfur dioxide emissions

after the mid 80s are well documented and it corre-

sponds very close with the sulfate concentration and

deposition changes in all sampling sites (in Fig. 3a and b

the changes in site Sonnblick and site Werfenweng are

presented as representative for the region of interest).

If the gross annual average data (for the whole period

of monitoring) for concentrations or depositions at each

site are simultaneously plotted, one could easily cluster

the sampling sites into three main groups depending on

the average values of concentrations or depositions. The

first group is formed by the sites with relatively highest

levels of concentrations or depositions (Haunsberg and

Lobau); the second group contains sites with middle

levels of concentrations or depositions (Litschau, Luntz,

Nasswald, Nassfeld and Werfenweng); the last cluster

includes the sites with lowest average concentrations

and depositions (Reutte, Innervillgraten, Sonnblick and

Kufstein). It could be concluded that the sites from the

Tyrol county are clustered separately and represent a

region with lower level of atmospheric pollution since

the site Lobau, which is located far east is with highest

level of pollution.

This situation required a more careful consideration

of the dependence of the chemical composition of the

wet precipitation with the special location of the sam-

pling sites. It was also interesting to compare the annual

average values for the long-term trends with values from

sites from neighbouring countries, which could influence

the atmospheric state through transboundary transfer

Fig. 2. Trend in air polluting emissions of SO2, NOx and NH3 in Austria (1980–1999).

Fig. 3. (a) Trend in sulfate concentration at site Sonnblick

(1987–1998). (b) Trend in sulfate concentration at site Wer-

fenweng (1984–1999).

744 H. Puxbaum et al. / Chemosphere 48 (2002) 733–747

processes. Five sites from the EMEP network (co-

operative programme for monitoring and evaluation

of long range transmission of air pollutants in Eu-

rope) located in Switzerland (T€aanikon), Czech Republic

(Kosetice), Hungary (K-puszta), Germany (Brotjackl-

riegel) and Italy (Ispra) were considered as suitable and

data for average monthly and annual concentrations

and depositions were compared with the gross average

values for the Austrian sites (Meteorological Synthesiz-

ing Centre-West of EMEP, 2000). The plotting is per-

formed with respect to the geographical location of each

sampling site. A very distinctive West–East decreasing

trend was observed (Fig. 4a and b) for sulfate concen-

trations and depositions. The linear trend is statistically

significant and the regression line is presented on the

plot for comparison.

This confirms to high extent the clustering of the

Austrian sampling sites into three well-defined groups.

The Alpine character of the western background sites

supposes a lower level of acidic components in the wet

precipitation since the transboundary atmospheric trans-

fer causes enhanced acidification of the eastern Austrian

sites.

A more special case in this configuration is site

Haunsberg. The site is located in Salzburg county and

lies closer to the western sites than to the eastern ones.

Nevertheless, the levels of acidic components, N-con-

taining ions and base cations are much higher than those

of the neighbouring sites and resemble more the eastern

sites than the local stations. Obviously, as already men-

tioned above, quite specific local factors determine the

wet chemistry at this site, e.g. building activities, crustal

influences etc.

3.14. Regional patterns and trends

If the different counties are separately considered,

it could be concluded that (in case of concentration

changes; same trend is kept for the deposition changes)

that the highest level of acidity decrease (hydrogen and

sulfate concentration per year) is found for the Vienna

site Lobau (nearly 7% and 4.5% per year, respectively).

All other counties (Tyrol, Salzburg, Lower Austria and

Carinthia) have similar figures for mean annual acidity

decrease of about 5% per year for hydrogen and about

3–3.5% per year for sulfate (average for the whole re-

gion). The Tyrol and Salzburg sites as a whole indicate

quite similar trends. The same holds true for site simi-

larity from Lower Austria and the Carinthian site

Nassfeld. But local influences and factors create differ-

ences in the site concentration or deposition patterns like

strongly enhanced potassium concentration at Innerv-

illgraten more than 6% per year, very high levels of

chloride and calcium with strongly increasing trend at

Haunsberg (up to 45% per year and over 17% per year,

respectively), serious acidity increase at Nasswald (about

5% per year as hydrogen ion concentration) and high

sodium increasing trend at Litschau (about 18% per

year). These typical ‘‘outliers’’ in the data set, which

influence the general patterns of site similarities, have to

be carefully treated in final decision making.

As seen from the trend Tables 2 and 3 the lowest

average acidic (sulfate) concentrations and depositions

for the whole period of monitoring are in Tyrolean and

Salzburg sites and the highest––in Vienna region. The

same holds true for the N-containing ions and base ca-

tions. This is another confirmation of the West–East

acidity increasing trend for the whole region.

4. Conclusions

The trend study of the rainwater data sets made it

possible to determine the trend of the major ion con-

centrations and depositions over a long period of mon-

itoring (1984–1999) for 11 sampling sites of the Austrian

monitoring network. The choice of the time period was a

result of the availability of data with good quality and

Fig. 4. (a) West–East acidity increasing trend (sulfate concen-

trations). (b) West–East acidity increasing trend (sulfate depo-

sitions). Legend: CH, Switzerland; H, Hungary; G, Germany;

CZ, Czech Republic; I, Italy; RE, Reutte; KU, Kufstein; IN,

Innervillgraten; HA, Haunsberg; WE, Weerfenweng; SB, Son-

nblick; NW, Nasswald; LI, Litschau; LU, Lunz; NF, Nassfeld;

LO, Lobau.

H. Puxbaum et al. / Chemosphere 48 (2002) 733–747 745

without missing data. For most of the sites, a statisti-

cally significant decrease in sulfate concentrations (be-

tween 30% and 60% for the whole period except for the

outlier Nasswald) and depositions (between 25% and

68% for the whole period except for the outlier Nassfeld)

is observed. Thus, the trend observed in previous studies

from Western Europe (including Austria) and North

America is confirmed. The same tendency holds true for

changes in hydrogen ion concentrations and depositions,

which reveals a constant reduction of the overall wet

precipitation acidity. Another features of the trend study

are related to the changes of the nitrogen containing

major ions nitrate and ammonium, of the chloride

ions and of the base cations. In the first case no serious

changes both in concentrations or depositions are de-

tected neither for ammonium and nitrate ions, nor for

their sum (changes between 13% and 34% for the whole

period of monitoring for the deposition sum except for

the outliers Reutte, Kufstein, Lunz). The linear trends

are insignificant at most of the sites and only slight de-

crease of the average values throughout the period of

monitoring is found. The same situation is observed for

chloride ions and for base cations. Slight, often statis-

tically non-significant trends of decrease, characterize

the changes in these ions both for concentrations and

depositions. Since some of the sampling sites deviate

from the general scheme of changes (Haunsberg,

Lobau), additional considerations were made to classify

the site location. It was found that a distinct West–East

gradient of concentration and deposition increase exists

not only for the sites of the Austrian monitoring net-

work but for five neighbouring station from the EMEP

network. This is an obvious indication for the trans-

boundary influence on the wet precipitation chemistry of

the region. The local influences and relationships were

indicated by comparison of the observed reduction of

the overall acidity of the wet precipitation with the long-

term decrease of sulfur dioxide emission decrease in

Austria.

Acknowledgements

One of the authors (V. Simeonov) would like to ex-

press his sincere gratitude to the Austrian South Euro-

pean Institute (OSI), Sofia branch for the constant

interest in this environmental research and the financial

support.

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