Marko Kaasik
Institute of Environmental Physics, University of Tartu, Estonia mkaasik@ut.ee
, http://rubiin.physic.ut.ee/~mkaasik/
Jüri Ivask, Tiiu Alliksaar
Institute of Geology, Tallinn University of Technology
Methods
Deposition fluxes were measured using the snow sampling method originally developed for fly ash deposition studies in the oil shale processing region, northeastern part of Estonia (Sofiev et al., 2003, Jaknin et al., 2002, Kaasik et al., 2000,
Kaasik & Sõukand, 2000). Snow was collected from natural surface keeping in mind distinguishable layers as markers of snow accumulation periods (especially good marker was the crust formed after heavy thawing period, April 22). 6 sampling sites were chosen representing variable landscapes: open and forested landscape, valley, valley-bottom.
Snow samples were collected using plastic instruments, thawed at Värriötunturi monitoring station in hermetically closed plastic (high-pressure polyethylene) bags and then stored in bottles of the same material. Both bags and bottles were previously washed with nitric acid and rinsed with Milli-Q water. Then water samples were transported to Estonia and analysed in the Institute of Geology at Tallinn University of Technology for the composition of major ions and spheroidal fly ash particles.
Spheroidal fly-ash particles are specific chemically inert markers of high-temperature combustion of fossil fuels (Alliksaar et al., 1998), thus originating from anthropogenic sources (energy production and other industrial processes using fuels). For the fly-ash particle analyse and for measuring atmospherically deposited dry matter in snow cover the settled residues of thawed samples were subjected to treatment with 32% hydrogen peroxide in order to digest possible organic material fallen down from tree canopies. This was followed by washing the samples with distilled water and then filtered on pre-weighted filter papers. Dried filters were weighed then with the residues and the amount of dry matter deposited in snow-cover was calculated. After that filters were analysed under the stereomicroscope (magnification 100x) and flyash particles larger than 5μm were counted.
The apparatus (Ivask & Pentchuk, 1997) used for detection of ions (Ca
2+
, Mg
2+ ,Na + ,K + , Cl ,SO
4
2, NO
3
2) was an IAK-12 analytical chromatograph with conductivity detector (INKROM Ltd., Estonia). The separation columns used were an ion chromatography cation and anion columns 3 x 150 mm, packed with cation- or anion exchange resins. The chromatographic experiment was performed with a flow rate of 1.0 ml/min. The sample volume used was 0.2 ml. The column, loop injector and the cell of the conductivity detector were maintained at 35 °C. Cation separation was performed with 7.5 mM tartaric acid + 0.8 mM pyridine-2,6-dicarbonic acid eluent and anion separation with 2.0 mM potassium hydrogen phthalate eluent (pH =
4.01).
All the reagents used were of analytical grade (Merck KGaA, Germany).
Standard solutions were prepared by dilution of individual stock solutions at 1000

ppm (µg/g) with concentration ratios chosen to be similar to those in ice samples.
Standard solutions for calibration were prepared a few minutes before usage and their concentrations were checked using ion reference solution (Alltech, US).
Meteorological data were gathered from freely accessible Internet site of NOAA Air
Resources Laboratory (http://www.arl.noaa.gov/ready). Wind directions and speeds at higher levels (925 hPa isobaric height, i.e. about 500 – 700 m a.s.l.; 850 hPa isobaric height, i.e. about 1300 – 1500 m a.s.l.) are important to decide about the direction of propagation v. spread of air masses.
Results
Snow-based deposition fluxes of major ions and spheroidal particles for two episodes during measurement campaign in Värriötunturi are presented in Table 1 and Figure 1.
Fluxes were clearly (several times, for Ca and NO
3
-
more than 10 times) higher during
April 22 – 27 than during April 28 – May 1. Chloride is the only strong exception.
Ammonium does not show significant differences, concentrations of Na and K in snow water are close to the detection limit.
Meteorological data (Figure 2) suggest that during the first snow sampling period
(April 22 – 27) wind was blowing from northern and western directions, during the second period (April 28 – May 1) from southern and eastern directions. It is evident that during the second period there are much more anthropogenic pollution sources upwind: southern Finland and all the Eastern Europe in south, metallurgy industries at
Kola peninsula (Russia) in East. Higher fluxes of chloride during the first period are natural in the air mass passing the Golf stream with high evaporation rate of marine water.
Conclusions
Measurement method initially developed for high anthropogenic pollution loads is sensitive enough to be applied in remote polar areas. Moreover, for polar regions there is possible to achieve more representative results about deposition fluxes due to long-lasting snow cover and sparser thawing events during the winter.
The measurements can be proceeded in depth, applying snow samples to analyse the deposition patterns in inhomogenous landscapes like forest and open land patches, complex terrain (Kaasik et al., 2004), giving contribution to both ecological impact studies and understanding the mechanisms of atmospheric deposition.
The obtained results allow to conclude that further cooperation in (1) analysing the data from Vörriötunturi aerosol campaign integrating the in-air and deposition measurements and (2) research projects at polar and remote areas of Finland is highly recommended. A possible innovative step would be air pollution transport and deposition modelling study along the Värriötunturi and possible further campaigns.
Suitable models for that are e.g. SILAM (FMI) and AEROPOL (Universtity of Tartu, for shorter range transport).
Acknowledgements
The analysis was supported by Estonian Science Foundation, Grant No. 5002 “The interaction of forest and atmospheric fly ash influx”.

References
T. Alliksaar, P. Hörstedt, I. Renberg (1998) Characteristic fly-ash particles from oilshale combustion found in lake sediments, Water, Air, and Soil Pollution , 104 , 149-
160.
Ivask, J., Pentchuk, J. (1997) Analysis of Ions in Polar Ice Core Samples by use of
Large Injection Volumes in Ion Chromatography. – Journal of Chromatography , 770 ,
20, 125-127.
Jaknin, E., Goltsova, N., Tomilina, O., Kaasik, M., Sõukand, Ü, Hongisto, M. (2002)
Atmospheric depositions on the north-eastern areas of Estonia and in the west of
Leningrad district (based on the data of snow cover), Ecological Chemistry , 11 , 3, pp.
145-156 (in Russian, summary in English).
Kaasik, M., Alliksaar, T. (2004) Dry deposition of coarse solid particles in patchy sub-boreal landscape. Accepted to Air Pollution Modelling and its Applications,
NATO “Challenges of modern society”, XVI.
Kaasik, M., Sõukand, Ü. (2000) Balance of alkaline and acidic pollution loads in the area affected by oil shale combustion. Oil Shale , 17 , 2, pp. 113-128.
Kaasik, M., Rõõm, R., Røyset, O., Vadset, M., Sõukand, Ü., Tõugu, K., Kaasik
, H.
(2000) Elemental and base anions deposition in the snow cover of north-eastern
Estonia. The impact of industrial emissions , Water, Air, and Soil Pollution , 121 , pp.
324-366.
Sofiev, M., Kaasik M., Hongisto M. (2003) Distribution of alcaline particles over the
Baltic Sea basin. Water, Air, Soil Pollution, 146 , pp.211-223 .