ISSN 1875-3728, Geography and Natural Resources, 2013, Vol. 34, No. 2, pp. 151-157. © Pleiades Publishing, Ltd., 2013. Original Russian Text © V.A. Obolkin, O.G. Netsvetaeva, L.P. Golobokova, V.L. Potemkin, E.A. Zimnik, U.G. Filippova, T.V. Khodzher, 2013, published in Geography and Natural Resources, 2013, Vol. 34, No. 2, pp. 66-73.
RESEARCH IN THE BAIKAL WATERSHED
Results of Long-Term Investigations on Acid Deposition in the Area of South Baikal V. A. Obolkin, O. G. Netsvetaeva, L. P. Golobokova, V. L. Potemkin, E. A. Zimnik, U. G. Filippova, and T. V. Khodzher
Limnological Institute, Siberian Branch, Russian Academy of Sciences, Irkutsk, Russia e-mail:
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[email protected] Received June 29, 2012
Abstract—We examine the acid deposition monitoring results (2000−2010) for the southern territory of East Siberia (the Irkutsk-Angarsk industrial center). It is established that acid deposition events are most frequently recorded in the area of South Baikal (70−100 km south-east of the Irkutsk-Angarsk industrial center), with the acidity of precipitation continuing to increase. Atmospheric precipitation acidity data are compared with longterm monitoring results for Europe. DOI: 10.1134/S1875372813020078 Keywords: monitoring, sulfur and nitrogen oxides, pH, acid deposition, Southeastern Siberia.
INTRODUCTION Acidification of natural environments is a challenging ecological problem. Europe was one of the first to face it during the 1970s–1980s when unregulated atmospheric emissions, primarily from coal-fired thermoelectric plants, led to an increase in acidity of atmospheric deposition and, hence, to a gradual degradation of terrestrial and aquatic ecosystems in the most vulnerable areas of this territory [1, 2]. Subsequently, European countries resorted to measures for monitoring and abatement of emissions of oxides of sulfur and nitrogen. As a result, SO2 concentrations in Europe showed a consistent trend toward a decrease, so that the ecological situation as regards acid depositions has bettered substantially. In Siberia, this issue does not receive the attention it needs. It is thought that the specific SO2 emissions with respect to the region’s huge territory are considerably lower than in Europe, so that there must be no problems with acidification of atmospheric depositions and natural ecosystems. Some of the regions of Siberia, however, have a highly advanced, power-intensive industries and, hence, produce significant amounts of acidifying gases. In this connection, it can be anticipated that some natural territories can experience a negative influence from acid deposition. In particular, such a risk exists for the western slopes of the Khamar-Daban Range facing the northwesterly transport of air masses from the area of Irkutsk. Earlier work pointed out repeatedly the low
pH values (< 5.0) for the snow cover in this area which, together with large amounts of precipitation (1200– 1400 mm/year) can lead to an excess of allowable critical acid loads on forest ecosystems [3, 4]. The goal of this paper is to assess the present situation and the tendencies concerning acid deposition in the south-east of Siberia, based on analyzing results from an 11-year-long regional monitoring of the atmosphere by comparison with how matters stood in a number of countries of Northern Europe which have been most heavily affected by acid deposition. STUDY AREA AND METHODS Located in the south-west of Siberia, Irkutsk oblast is a major industrial region of Russia. Nowadays, the atmospheric emissions from the coal-fueled thermoelectric plants around Angarsk and Irkutsk amount to 100–110 and 60–70 thou t of SO2 and NOx, respectively, every year [5], or as much as 80–90% of the emissions of these gases from the entire Irkutsk oblast. Such amounts of emissions compare with the SO2 emissions in a number of countries in Northern Europe, namely: Norway – 140 and 50 thou t in the 1980s and 2000s, Sweden – 400 and about 50 thou t, and Latvia – 118 and 18 thou t, respectively [6–8]. Thus today’s emissions of acidifying pollutants only from Irkutsk and Angarsk are comparable with the total emissions from the three European countries:
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Norway, Sweden, and Latvia. The zone of the most likely atmospheric influence of the Irkutsk-Angarsk industrial complex, with the northwesterly transport of air masses predominating, extends along the direction toward South Baikal. Therefore, a monitoring of the atmosphere on a regular basis is very important in this area. In this connection, for year-round observations of atmospheric pollutants, including acid deposition, we selected the following sites: Irkutsk (52° 14′ N., 104° 15′ E) as one of the main sources of anthropogenic pollution in the region; settlement of Listvyanka (51° 51′ N, 104° 54′ E) as a rural area in the path of prevailing transport of air masses from Irkutsk (the settlement is situated on the shore of Lake Baikal a short distance from the source of the Angara river, 70 km south-east of Irkutsk), and st. Mondy (51° 40′ N, 101° 0′ E) as a background area (the station is located in a mountainous area at an altitude of 2005 m above the sea level, 300 km south-west of Irkutsk). The three stations were included in the international program “Acid Deposition Monitoring Network in Asia (EANET). The air and atmospheric precipitation sampling and analysis methods in use at the stations are unified with the commonly accepted techniques for the entire network of stations within this program [9]. The accuracy of chemical analyses, and the quality of data obtained are checked by conducting annual interlaboratory intercalibrations within the EANET program. Analysis of the composition of aerosols and gases uses the filter sampling method by drawing air samples at a rate of 1–2 L/min for a week through four filters that are arranged in series. The first filter collects aerosol, and the other three filters collect gaseous impurities. Subsequent to sampling, concentrations of four gases (SO2, HNO3, HCl, and NH3) and nine basic ions (SO42-, NO3-, Cl-, HCO3-, NH4+, Ca2+, Na+, Mg2+, and K+) are determined in the laboratory. Wet deposition (atmospheric precipitation) is sampled using a wet-only deposition collector (model US–320, manufactured in Japan, with the funnel 300 mm in diameter). For every deposition event, the procedure involved determining the concentrations of basic ions, the pH value, and specific conductivity using state-of-the-art standard techniques (ion chromatography, atomic absorption spectrophotometry, potentiometry, and conductometry) in the Certified Laboratory of atmospheric hydrochemistry and chemistry, Limnological Institute, Siberian Branch, Russian Academy of Sciences (http://www.lin.irk.ru). After a statistical processing, mean monthly data are sent to the Institute of Global Climate and Ecology operated by Rosgidromet RF (Federal Service for Hydrometeorology and Environmental Monitoring of Russia) and become available on the official website of EANET (http://www.eanet.cc). In addition to these methods shared by all EANET stations, concentrations of SO2, NO and NO2 gases
were measured at stations Irkutsk and Listvyanka using automatic high-resolution gas analyzers С310 and А310 (“OPTEC”, Russia). The gas analyzers feature a sensitivity not below 1 μg/m3 and a temporal resolution of 1–2 min, thereby enabling a more detailed analysis of the correlation between concentrations of the gases used in the analysis and wind directions. DISCUSSION Seasonal Year-To-Year SO2 Concentration Variability in the Atmosphere It is common knowledge that the main acidification sources for atmospheric deposition consist of gaseous oxides of sulfur and nitrogen supplied to the atmosphere from the burning of fossil fuels, mostly coal. In Siberia, the volumes of annually burned fuels depend on a season, and on climatic conditions. Fig. 1, (a) plots the variability in mean annual SO2 concentrations for three monitoring stations in Southeastern Siberia for the entire observing period as well as mean annual air temperatures for st. Irkutsk. The SO2 concentrations at stations Irkutsk and Listvyanka, as a rule, increase during cold years and decrease during warm years (the correlation coefficient 0.62). It is obvious that such a correlation is partially accounted for by an increase in the volumes of burned fuels during cold years, and vice versa. However, variability in mean annual sulfur dioxide concentrations is considerably higher than that in regional SO2 emissions (see Fig. 1, (b)). What this means is that, apart from air temperature, variability in sulfur dioxide concentrations is also influenced by other meteorological factors, primarily a worsening of the dispersal and transformation conditions for impurities during cold years as well as by variability in wind direction. At the Mondy background station, mean annual SO2 concentrations and their year-to-year variability are substantially lower when compared with the other stations, which points to a minimal anthropogenic influence upon atmospheric pollution in this area. For comparison: Fig. 2, (b) plots the year-toyear variability in SO2 concentration as observed at monitoring stations in Sweden [7], where there arose problems with acidification of the ecosystems of small lakes and forests during the 1970s–1980s. It is seen that the current mean annual sulfur dioxide concentrations at stations Irkutsk and Listvyanka have the same order of magnitude and about the same high year-to-year variability as those observed at the Swedish stations in the 1980s; however, their trends differ greatly. In Sweden (as is the case with the whole of Europe), the mean annual concentrations of this gas had decreased many times by the 2000s to reach today’s identically low values as observed at the background Siberian st. Mondy. At the urban and the rural monitoring stations in Southeastern Siberia, for the 11-year observing period
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Fig. 1. Dynamics of mean annual SO2 concentrations at monitoring stations in Southeastern Siberia (а) and Northern Europe (b). Stations of Southeastern Siberia: (1) Irkutsk, (2) Mondy, (3) Listvyanka. (4) air temperature. Stations of Northern Europe: (5) Bredkalen, (6) Hoburgen, (7) Vavihill, (8) Rørvik.
Fig. 2. Seasonal SO2 concentration variability at monitoring stations in Southeastern Siberia (а) and Northern Europe (b). Stations: (1) Irkutsk, (2) Listvyanka, (3) Mondy, (4) Stoke Ferry (1982–1984), (5) Stoke Ferry (1999–2001), (6) Tange (1979– 1981), (7) Tange (1999–2001).
the trend of sulfur dioxide content in the atmospheric air has a tendency toward an increase, rather than an increase. Seasonal variability in sulfur dioxide concentrations in the atmosphere of urbanized and rural areas of Siberia is also correlated with the seasonal behavior of air temperature (Fig. 2, (а)). In such areas, the wintertime SO2 concentrations, as a rule, are many times higher than the summertime concentrations. A similar situation was observed in the 1980s in Northern Europe (see Fig. 2, (b)). By the 2000s, European countries managed to decrease the SO2 emissions to such an extent that the wintertime concentrations of this gas came to equal the summertime concentrations. In East Siberia, such a seasonal dynamics was observed only in the area of the background st. Mondy (see Fig. 2, (а)). Thus the current situation with sulfur dioxide concentrations in the air of large cities and rural areas in the south-east of Siberia (as exemplified by the city of Irkutsk and the settlement of Listvyanka) closely GEOGRAPHY AND NATURAL RESOURCES
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resembles the one that was emerging on the territory of Northern Europe in the 1980s. Hence there is a risk that identical problems (associated with acid deposition) may well arise also in separate areas of Siberia, specifically across South Baikal. Analysis of the relation between SO2 concentrations in the air and wind directions makes it apparent that the main sources supplying sulfur dioxide to South Baikal are located to the west of it (Fig. 3). In summers, it is a rather broad spectrum from south-west to north, with approximately similar mean concentrations (3–4 μg/ m3), suggesting the uncertain location of these sources. More likely they constitute well-mixed air masses, including emissions not only from Irkutsk and Angarsk but also from the more distant sources. In winters, on the contrary, higher concentrations are recorded in the northwestern sector (about 100 μg/m3) within which Irkutsk and Angarsk are situated. The narrowness of this sector, coupled with the high SO2 concentrations in the air, points to the main contribution from the sources No. 2
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Fig. 3. Mean SO2 concentrations (μg/m3) at st. Listvyanka for different wind directions. (а) summer, (b) winter.
Fig. 4. Distribution density (%) of different SO2 (μg/m3) concentrations at st. Listvyanka. (1) winter, (2) summer.
located in these cities, to the wintertime transport of these gas pollutants to South Baikal. The SO2 concentration distribution densities also differ substantially in the summer and winter periods at st. Listvyanka (Fig. 4). In summers, the distribution shows only one mode: 1–2 μg/m3 (with maximum values reaching 20–30 μg/m3), indicating a good mixing of air masses, and a weak influence of any local sources. In winters, there occur two modes: one in the range 5–10 μg/m3, and the other in the range 30–40 μg/m3. The former mode seems to be associated with a long-range transport or with a global background (about 16%), and the latter mode — with the regional transport (Angarsk–Irkutsk, and other nearby sources). The highest SO2, concentrations were recorded at st. Listvyanka in the wintertime to reach, sometimes, 350 μg/m3. Acidity of Atmospheric Precipitation Monitoring observations showed that acid deposition events are most often recorded in the area
of South Baikal (settlement of Listvyanka) (Table 1). During 2005–2007, the precipitation amount with рН below 5.0 at this station exceeded 50%. The same time interval showed the highest SO2 concentrations at all atmospheric monitoring stations (see Fig. 1). Low рН values of wet deposition are persistently recorded also at Irkutsk, with the range of variation in acid-alkali index exceeding substantially the one at Listvyanka (see Table 1). Potentially, acidity of atmospheric precipitation at Irkutsk is higher than at Listvyanka; unlike rural areas, however, the excessive acidity in the industrial sector is more effectively neutralized by an excess of alkaline components permanently present in the air. The lowest occurrence frequency of acid deposition events is observed at the background st. Mondy – less than 8%. Hence, the most likely zone of maximal acid loads, associated with regional anthropogenic sources, extends from the industrial complexes of the Angara region to South Baikal. Routine data on acidity of atmospheric precipitation that have been accumulated for 11 years permit us to make preliminary estimates of long-term trends (Fig. 5). At stations Listvyanka and Irkutsk, the trend of precipitation pH is seen to have a tendency toward a decrease (an increase in acidity). Furthermore, the trend for the settlement of Listvyanka is statistically reliable (R2 = 0.59). As regards Irkutsk, because of a high yearto-year variability in pH, the statistical significance of the trend is inadequate, although the situation with acid deposition in this case seems also to worsen. For comparison: Fig. 5, (b) presents the long-term statistically significant positive trends of atmospheric precipitation pH for two stations of Northern Europe, showing the actual result from a planned reduction in emissions of acidifying gases in Europe in general. In contrast, data on emissions from Irkutsk and Angarsk (see Table 1) for the period under consideration are indicative of a slow increase, in agreement with the trend for an increase in deposition acidity in the region.
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Table 1. The recurrence frequency of atmospheric precipitation with рН < 5, the range of pH variation at monitoring stations in East Siberia (2000–2010), and annual volumes of emissions of acid-forming gases from the cities of Irkutsk and Angarsk Irkutsk
Listvyanka
Emissions, thou t/year
pH
Year 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010
Mondy
%
range
%
range
%
range
14 16 20 7 11 19 15 20 18 5 9
3.65–8.26 3.99–7.53 4.30–7.52 4.68–7.90 4.09–7.74 4.30–7.22 3.73–7.44 4.11–7.30 4.10–7.69 4.54–7.20 3.60–7.37
29 32 50 36 30 67 65 56 51 41 47
4.27–6.69 4.30–6.93 4.32–6.46 4.29–6.40 4.35–6.71 4.20–6.48 3.14–6.10 3.87–6.60 4.14–7.10 4.25–6.52 4.31–7.83
3 4 7 5 3 0 0 0 7 0 8
4.86–6.62 4.97–7.00 4.89–6.99 4.76–6.53 4.96–6.51 5.02–6.33 5.07–7.10 5.12–6.96 4.92–7.14 5.11–6.55 4.85–6.28
SO2 73 69 73 84 65 82 89 92 120 104 158
NOx 34 34 37 45 33 30 33 49 77 67 80
Fig. 5. Long-term trends of atmospheric precipitation pH in Southeastern Siberia (а) and in Sweden (b) [7]. Stations: (1) Irkutsk, (2) Listvyanka, (3) Rørvik, (4) Vavihill.
For determining the particular anions that make the main contribution to acidification of atmospheric precipitation on South Baikal, a correlation analysis was made of the correlation between monthly pH values of atmospheric precipitation and the ratio of basic anions and cations (Table 2). Direct correlations of pH with concentrations of sulfates and nitrates were found to be very low because, apart from anions, the pH value is also influenced by basic cations: Са2+ and Mg2+. Correlations of pH with the mutual relationship of anions and cations are more significant. An important correlation was revealed between precipitation pH and contents of three ions: Ca2+, NO3-, and SO42- (see Table 2). Also, for a cold period the precipitation pH value depends substantially on the relationship of GEOGRAPHY AND NATURAL RESOURCES
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calcium and nitrate concentrations, i.e. acidification of wintertime precipitation at Listvyanka is caused by an increase in NO3- content and a decrease in Са2+. The role of sulfates was of a minor nature. In the summer period, on the contrary, the main contribution to acidification of precipitation in the area of Listvyanka is made by the SO42- anion. The NO3- anion also has a significant influence; however, the correlation with it is twice as low as with sulfates. Hence, in spite of the fact that the maximum of anthropogenic emissions of sulfur and nitrogen is observed in winters, acidification of wintertime precipitation generally proceeds somewhat more weakly (рН = 5.0) than of summertime precipitation (рН = 4.8), and this is mainly determined by the ratio of No. 2
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Table 2. Correlation of atmospheric precipitation pH at st. Listvyanka with the basic cation and anion concentration ratio (the Pearson correlation) (2000–2009) Season
Number of months
рН
Winter (December–March)
38
Summer (June–August)
30
r Ca /SO4
Ca /NO3–
Ca2+/(SO42+ + NO3–)
5.07 (5.00–5.15)
–0.05
0.71 (0.50–0.84)
0.67 (0.45–0.81)
4.84 (4.74–4.94)
0.64 (0.36–0.81)
0.31 (0.01–0.56)
0.60 (0.30–0.79)
2+
2–
2+
Note. r – corelation coefficient of pH equivalent ion concentration ratios; in brackets – confidence level of mean values with 95% probability.
the Са2+/NO3- ion ratio. The contribution of sulfates to acidification of wintertime precipitation on South Baikal is very small. In summers, on the contrary, acidification of atmospheric precipitation is mainly influenced by sulfates, the contribution from nitrates is twice as small, and the correlation is near the significance limit. What has been said above is also corroborated by the analysis of the chemical composition of snow cover sampled along the Irkutsk – Listvyanka – South Baikal water area route (Table 3). Snow cover gives a more detailed insight into the picture of variability in ion composition and atmospheric precipitation acidity with the distance from large sources of anthropogenic pollution of the atmosphere. As is evident from Table 3, the sulfate-ion concentration in the snow with the distance from Irkutsk by 30 km decreases by a factor of 3–4, whereas the nitrate-ion concentration, on the contrary, increases gradually, and at 40–50 km from the city it begins to exceed the SO42- concentration. A predominance of nitrates over sulfates in the snow was also observed on the eastern shore of South Baikal, opposite the Angara Table 3. The pH value and density distribution of basic ions (mg/dm3) in snow cover along the Irkutsk–Listvyanka–South Baikal water area direction. Winter 2005/2006 Distance from Irkutsk, km
рН
0
6.4
6.2
1.9
3.1
1.1
2.8
4
6.4
5.9
1.9
3.1
0.4
2.6
9
6.3
4.3
1.8
1.9
1.2
2.9
19
5.4
2.3
1.8
1.4
0.1
0.0
29
5.2
2.1
2.0
1.2
0.1
0.0
39
5.0
1.7
2.0
1.0
0.1
0.0
51
5.0
1.4
2.0
0.8
0.1
0.0
63
5.2
2.4
2.1
1.2
0.2
0.0
67
5.0
2.0
2.8
1.3
0.1
0.0
70
4.8
2.7
3.2
1.4
0.0
0.0
74
5.0
1.6
2.7
1.1
0.0
0.0
81
4.8
2.6
3.5
1.7
0.0
0.0
SO42– NO3–
Ca2+
NH4+ HCO3–
valley [10]. This can imply that acidification of SO2 to sulfates in the wintertime proceeds more slowly than does acidification of NO and NO2 to NO3-. This is also suggested by the high wintertime SO2 concentrations at Listvyanka comparable with the concentrations at Irkutsk (see Figs. 1–3). Thus the main contribution to acidification of the snow cover on South Baikal is made not so much by sulfur dioxide emissions as nitrogen oxides emissions, although it is not inconceivable that, with the distance from the sources of these components, the influence of sulfates (after acidification of SO2) will be increasing to become the main factor again. Overall, the monitoring results considered above testify to the fact that acid deposition events in the study area most often occur in the area of South Baikal, which is determined by the westerly transport of emissions of sulfur and nitrogen oxides. In the wintertime, the main source of atmospheric pollution is provided by the large coal-fired thermoelectric plants in the area of Irkutsk and Angarsk, while acidification in the summertime appears to be due to effects from enterprises not only of the regional but also more distant industrial centers of Siberia. Proper account must also be taken of such a round-year source of nitrogen oxides as the motor transport, with ever increasing numbers of vehicles. In accordance with their natural conditions (acid soils, and little mineralized waters of rivers and lakes), some areas of South Baikal, specifically the drainage basin of the Pereemnaya river, exhibit high sensitivity to acid precipitation. Although today’s acid loads for this region still do not exceed critical ones [11], the observed long-term tendency provokes concern. Thus, according to the research [10] done during 1996–2003, the relative ion composition in the water of the rivers in this area underwent a change when compared with the 1950s [12]: the contribution from the SO42- ion and from НСО3- ions increased and decreased, respectively. The waters of the Pereemnaya river, with its drainage basin situated on the slope of Khamar-Daban, opposite the Angara river valley, currently exhibit the pH value within the range 6.6–6.8 (with a standard value > 7), and the alkalinity of 0.15 mg eq/L (0.05 mg eq/L is considered critical). In the future, the ecological situation in this area will be gradually worsening unless appropriate measures are undertaken for a limitation of
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atmospheric emissions of SO2 and NOx by the coalfired thermoelectric plants of Irkutsk and Angarsk, and by other large sources located in Siberia. CONCLUSIONS The results from the 11-year monitoring of the levels of acidifying impurities in the atmosphere over the southern part of East Siberia show that the influence zone of the region’s major industrial centers show a tendency for a gradual increase in acidity of atmospheric deposition. Such a tendency brings the most serious threat to South Baikal’s natural objects, especially to the slopes of the Khamar-Daban Range which are in the path of atmospheric transport of pollutants from regional anthropogenic sources. This threat is enhanced by significant amounts of atmospheric precipitation, and by high sensitivity of the natural objects themselves in this area to acid deposition. Hence, special emphasis should be attached to a routine monitoring of regional transports of atmospheric pollutants, and to the state of natural objects in the south of Baikal as well as to the control over the measures for a reduction in atmospheric emissions of sulfur and nitrogen oxides from large enterprises of Irkutsk oblast. Experience of European countries suggests that the problem of reducing these emissions is actually quite solvable and that it is best to take measures for a reduction of emissions of acid gases in the region rather than eliminating their eventual consequences in the future.
4.
5. 6.
7.
8.
9.
10.
11.
REFERENCES 1. Wright, R.F., Acidification of Freshwaters in Europe,
Water Qual. Bull., 1983, vol. 8, no. 3, pp. 137–142. 2. Abrahamsen, G., Stuanes, A.O. and Tveite, B., Effects of Long Range Transported Air Pollutants in Scandinavia, Water Qual. Bull., 1983, vol. 8, no. 2, pp. 89–95. 3. Obolkin, V.A., Khodzher, T.V., Anokhin, Yu.A., and Prokhorova, T.A., Acidity in Atmospheric Depositions
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12.
No. 2
157
in the Baikal Region, Meteorologiya i gidrologiya, 1991, no. 1, pp. 55–60 [in Russian]. Kokorin, A.O. and Politov, S.V., Deposition of Pollutants From the Atmosphere With Precipitation in the Southrn Baikal Region, Meteorologiya i gidrologiya, 1991, no. 1, pp. 48–54 [in Russian]. National Report “On the State and Protection of Natural Environment in Irkutsk Oblast for 2007”, Irkutsk, 2008 [in Russian]. Schaug, J.S., Soberg, S., Tørseth, K., Barrett, K., Hole, L., and Aas, W., National Assessments Norway, in EMEP Assessment, Part II, National Contributions, ed. by J. Bartnicki and G. Lövblad, Oslo: Norwegian Meteorological Institute, 2004, pp. 157–173. Lövblad, G., Henningsson, E., Sjöberg, K., BrorströmLundén, E., Lindskog, A., and Munthe, J., Trends in Swedish Background Air 1980−2000, in EMEP Assessment. Part II, National Contributions, ed. by J. Bartnicki and G. Lövblad, Oslo: Norwegian Meteorological Institute, 2004, pp. 211–220. Lyulko, I., Frolova, M., Indriksone, I., and Berga P., Assessment Report on the Latvian EMEP Data 1985–2000, in EMEP Assessment. Part II, National Contributions, ed. by J. Bartnicki and G. Lövblad, Oslo: Norwegian Meteorological Institute, 2004, pp. 122–132. Guidelines for Acid Deposition Monitoring in East Asia, 2nd Interim Scientific Advisory Group (ISAG) Meeting of EANET (March 13−15, 2000, Jakarta), Niigata: ADORC, 2000. Sorokovikova, L.M., Netsvetaeva, O.G., Tomberg, I.V., Khodzher, T.V., and Pogodaeva, T.V., Effect of Atmospheric Precipitation on the Chemical Composition of River Waters in the South Baikal, Atmospheric and Oceanic Optics, 2004, vol. 17, nos. 5–6, pp. 373–377. Semenov, M.Yu., Khodzher, T.V., Obolkin, V.A., Domysheva, V.M., Golobokova, L.P., Kobeleva, N.A., Netsvetaeva, O.G., Potemkin, V.L., Grieken, R. van., and Fukuzaki, N., Assessing the Acidification Risk in the Lake Baikal Region, Chemistry and Ecology, 2006, vol. 22, no. 1, pp. 1–11. Votintsev, K.K., Glazunov, I.V. and Tolmachea, A.P., Hydrochemistry of Rivers Witin the Lake Baikal Watershed Basin, Moscow: Nauka, 1965 [in Russian].
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