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Mass Balance between Emission and Deposition of Airborne Contaminants P A T R I C E D E C A R I T A T , * ,† CLEMENS REIMANN,† VIKTOR CHEKUSHIN,‡ IGOR BOGATYREV,§ HEIKKI NISKAVAARA,| AND JEAN BRAUN⊥ Geological Survey of Norway, P.O. Box 3006, Lade, N-7002 Trondheim, Norway
Quantification of (1) the total mass of airborne pollutants deposited around pollution emitters, (2) the contaminated radius around these point sources, and (3) the proportion of emissions available for long-range transport remains challenging for environmental scientists. Here, we present a simple method for comparing yearly airborne emission figures from any point source with observed deposition estimates from the surrounding area. First, the depositiondistance function D(x) around the smokestack must be defined. This requires the empirical determination of total (water soluble + particulate) annual deposition at several locations away from the source and of the extent of the smokestack “shadow” zone. Secondly, the loading function L(x) is obtained by integrating D(x) around the point-source. This allows estimation of the yearly mass of a contaminant deposited within an area corresponding to that of a circle of radius x around the point source. Thus, emission, deposition, and (long-range) transport of airborne contaminants can be assessed quantitatively. Preliminary results from the Kola Peninsula, Russia, suggest that deposition of trace metals overwhelmingly occurs within 200 km from the source.
Introduction Worldwide, industrial activity releases trace metals (1), sulfur dioxide (2), and other gases and compounds to the atmosphere, polluting the local, regional, and global air, land, and water resources (arctic haze, acid precipitation, lake eutrophication, etc.) (3-10). Reliable quantification of industrial emissions to the atmosphere, of the extent of the region they affect or of the proportion of these emissions transported afar, remain challenging tasks for environmental scientists. We present a method for estimating the total loading mass as a function of radius around point-source emitters on the basis of total yearly deposition values around a point-source emitter and illustrate it in the case of the Monchegorsk smelter complex on the Kola Peninsula, Russia. The advantage of the method is that the total mass (in kilograms) of airborne pollutants deposited around, and attributable to, a given source (loading) can be calculated independently of emission figures (also in kilograms), allowing direct comparison between loading and emission. * Corresponding author. E-mail:
[email protected]. † Geological Survey of Norway. ‡ Central Kola Expedition, Fersman St. 26, 184200 Apatity, Russia. § Kola Geological Information Laboratory Centre, Fersman St. 26, 184200 Apatity, Russia. | Geological Survey of Finland, P.O. Box 77, FIN-96101 Rovaniemi, Finland. ⊥ Research School of Earth Sciences, Australian National University, ACT 0200, Canberra, Australia.
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Kola Peninsula Industrial activity on the western Kola Peninsula in Russia includes nickel-copper smelting in Nikel and Monchegorsk and nickel-copper ore roasting in Zapoljarniy (Figure 1). For many years this industry has been a major world source of emissions of sulfur dioxide, heavy metals, and other trace elements to the atmosphere (e.g., refs 2 and 11-13). In the immediate vicinity of the Nikel and Monchegorsk smelters, ecosystems have been destroyed, leading to growing “technogenic deserts” (e.g., refs 14, and 15) devoid of most plants and humus, and prone to severe soil erosion. Since 1991, the Central Kola Expedition (CKE) and the Geological Surveys of Finland (GTK) and Norway (NGU) have collaborated in multimedia, multielement studies of the environmental impacts of the smelting and associated industry on the Kola Peninsula. The three phases of the “Kola Ecogeochemistry” project (see Supporting Information) have been (1) a pilot project of geochemical mapping of a 12 000 km2 area around the Nikel smelter, Zapoljarniy ore concentrating plant and mine (2) a detailed investigation of element sources, sinks, and pathways in eight small catchments, and (3) a regional geochemical mapping phase of a 188 000 km2 area in northwest Russia, northern Finland, and northeastern Norway (Figure 1). As part of this regional geochemical mapping phase, terrestrial moss was collected at 644 locations selected on the basis of previous knowledge of bedrock, drift, vegetation, and soil distributions. The resulting average sample density is one sample per 300 km2, ranging from 1 per 100 km2, where steep gradients were expected, to 1 per 600 km2 in remote background areas. The moss samples were dried, milled, sieved, and finally, digested in concentrated HNO3 in a microwave oven prior to analysis by ICP-AES and ICP-MS at the GTK laboratory. QA/QC procedures included (1) collection of field duplicates every 15th locality (46 in total), (2) calibration with international reference samples, (3) duplicate analysis of every 10th moss sample, and (4) inclusion of an internal standard, split from a very large field sample, every 15th analysis. Precision was generally better than 2-3% for most elements. The GTK laboratory is accredited according to ISO 9001 and ISO-Guide 25. More details about the moss survey are given elsewhere (16-18).
Deposition Function Atmospheric deposition for 1994 was estimated using snow and rain water analyses (19) obtained from eight catchments (C1 to C8) located at different distances from the industrial sources (Figure 1). Whereas C1-C6 show some influence of industrial airborne contamination, C7 and C8 can be considered as background areas, as evidenced, among others, by precipitation chemistry (20, 21) and regional geochemical mapping of moss chemistry (16-18). The resulting total (water soluble + particulate) yearly deposition estimates for Co, Cu, Ni, S, and V in the catchments under the influence of emissions from Monchegorsk (C2, C4, C3, and C7) are presented in Table 1, together with the official emission values. Deposition D(x) (kilograms per squared kilometer) of industrial contaminants was found to decrease with distance x (kilometers) away from the source, according to power-law best-fit deposition curves of the type
ln D(x) ) κ ln x + b
(1)
or, after exponentiation
D(x) ) D1xκ
(2)
where κ is the (element and industry specific) dispersion coefficient [ln (kilograms per squared kilometer)/ln kilometer]
S0013-936X(97)00193-4 CCC: $14.00
1997 American Chemical Society
FIGURE 1. Location map showing the pilot project area (small frame), the main mapping project area (large frame), and the eight studied catchments (circles numbered 1, Zapoljarniy; 2, Monchegorsk; 3, Kirovsk; 4, Kurka; 5, Skjellbekken; 6, Kirakka; 7, Naruska; and 8, Pallas). Major point-source emitters are found in Zapoljarniy (Ni-Cu ore roasting plant), Nikel and Monchegorsk (Ni-Cu smelters). Other subordinate sources of atmospheric pollution exist both in Norway (the Fe mine at Bjørnevaten and the nearby Fe mill in Kirkenes) and in Russia (the Ni-Cu mine near Zapoljarniy, the industry and naval operations in Murmansk, the Fe mine in Olenegorsk, the coal-fired power plant and apatite processing plant in Apatity, the apatite mine in Kirovsk, the Fe mine and mill in Kovdor, the nuclear power plant near Kandalaksha, and the Al smelter in Kandalaksha). Also shown are major lakes and rivers, selected townships; the windrose for the Monchegorsk area is from (25).
TABLE 1. Official Emission Figures (1994) from Monchegorsk (23; see ref 21), Field-Based Total Deposition (1994) in Four Catchments (19), and Best-Fit Parameters of Deposition-Distance Relationships [D(x) ) D1xK] for Co, Cu, Ni, S, and V Co
Cu
81 500
933 700
C2 C3 C4 C7
60.3 0.205 4.944 0.038
κ D1 r
-2.2271 2527.54 -0.99
Ni Emission (1994, in kg) 1 618 800
Deposition (1994, in kg km-2) 494 845 3.28 4.68 49.4 66.3 0.626 0.22 -2.0031 14 220.67 -0.99
Best-Fit Parameters -2.4074 58 751.77 -0.99
reflecting the rate at which deposition decreases with distance, and D1 ) eb is the deposition (kilogram per squared kilometer) at x ) 1 km. The best-fit parameters (Table 1) were determined by linear regression of the natural log-transformed data. The deposition-distance relationships for the five
S
48 904 277 654 375 311 189 -0.3212 1040.06 -0.91
V
16 741 19.3 3.090 2.781 0.240 -1.1626 134.39 -0.94
elements of concern here are illustrated in Figure 2. Ni, Cu, and Co have steep deposition gradients, while S and V have gentler deposition gradients. Knowing the deposition gradient for any element away from an atmospheric pollution source, one can estimate the
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FIGURE 2. Deposition (kilograms per squared kilometer) vs distance (kilometer) for Ni, Cu, S, and V in the four studied catchments around Monchegorsk (C2, C4, C3, and C7), with best-fit regressions (note log-log axes). D(x) into two domains DA(x) and DB(x), with D(x) ) DA(x) + DB(x) (Figure 3). Within the inner domain, i.e., between x ) 0 and x ) x′, deposition DA(x) is assumed to be a linear function of distance according to
DA(x) )
FIGURE 3. Conceptual model for the deposition-distance relationship, shown with linear axes. total deposited mass or loading L(x) (kilograms) that occurs within 1 year inside a given radius x around the source.
Loading Modeling We use a simple model for the loading function L(x), based on the analogy of the volume obtained by rotating the deposition function D(x) around the ordinate. Since deposition as defined in eq 1 or 2 cannot increase to infinity as the distance decreases toward the source, we must define a critical distance x′ (kilometer) to separate the deposition function
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[
]
D1(x′)κ - D0 x + D0 x′
(3)
where D0 is the deposition at x ) 0, which can be chosen to be 0, D′ [)D(x ) x′)] or >D′ (respectively, giving positive, zero, or negative slopes within this domain), or some intermediate value best matching any existing field evidence (see Figure 3). Deposition in the outer domain (where x > x′) obeys eq 2, i.e., DB(x) ) D1xκ, and decreases as a power law of x with increasing x, as observed empirically (Figure 2). The physical significance of x′ is the deposition “shadow” afforded by the height of the smoke stack(s); x′ is expected to be a function of the industrial process, physical characteristics of the smokestack, chemical element (including its particle size distribution), meteorological and topographic characteristics of the area, etc. The loading model is thus defined as
∫ xD(x) dx ) 2π∫ xD (x) dx + 2π∫ xD (x) dx
L(x) ) 2π
x
0
x′
0
x
A
x′
B
(4)
Expanding DA(x) and DB(x), as shown above, and integrating yields the general solution (for x > x′):
{
L(x) ) 2π
D1 κ+2 D1 κ+2 D0 2 (x′) + (x′) + [x - (x′)κ+2] 3 6 κ+2
}
(5)
FIGURE 4. Modeled loading curves (L, in kilograms) of Ni, Cu, Co, S, and V (for x′ values of 0.1, 0.2, and 0.3 km) as a function of distance (kilometers) away from the Monchegorsk source. The horizontal dashed lines indicate emission values (E, in kilograms). The radii equivalent to the area delineated by the 50th percentile (median) value on the moss maps is indicated for Ni, Cu, Co, and V by the vertical black arrows on the abscissa. In the special case where κ ) -2, the third term on the RHS of eq 5 must be replaced by D1 ln (x/x′). We now have the opportunity to estimate the radius of influence an industrial center has for a given element, assuming that all the yearly emissions (kilograms) are deposited as yearly loading (kilograms) within an area corresponding to that of a circle of radius x around the sources. Alternatively, we can define from our regional geochemical maps for moss (16-18) the size of the polluted areas and from there derive x′. If the latter parameter can be established independently, the amount of emission available for longrange transport can be determined.
Discussion Figure 4 shows the results of the emission-deposition modeling (using D0 ) 0), in terms of the total mass of element deposited within an area equivalent to that of a circle of radius x around Monchegorsk. Modeling, i.e., solving eq 5, was carried out with three different x′ values (0.1, 0.2, and 0.3 km). Here, the intention is primarily to present the new method of quantitative assessment of deposited pollutants. Regional moss geochemical maps for the elements under investigation (Figure 5) (see also refs 16 and 18) show, in the vicinity of the emission sources, patterns reflecting to a large extent deposition of airborne pollutants. They allow to approach the question of balancing emission and deposition from another angle: given the areal extent of pollution, what is the matching minimum emission figure? We circumscribed on the Co, Cu, Ni, and V geochemical maps for moss the areas defined by the 50th percentile (median) value of the metal concentration recorded within the 188 000 km2 region
surveyed (see above for details), assuming that these provide a conservative (minimum) estimate for the extent of pollution. These areas are ellipses centred on Monchegorsk, elongated in the directions of dominant winds (NNE-SSW). The radius xmed of the equivalent-area circle, marked on Figure 4, is the average of the long and short ellipse axes. That the choice of the 50th percentile contour is a cautious (minimum) choice for how far pollution from Monchegorsk reaches is exemplified in Figure 6 for Ni. Here, an east-west transect at the latitude of Monchegorsk shows that the median value of the whole data set (4.4 mg/kg) definitively is at the higher end of, if not above, the range within which natural, background concentrations of Ni vary in this region (ca. >200 km west of Monchegorsk). It is interesting to note in this context that median Ni concentrations in moss in Norway and Finland (1995 data) are both around 1.6 mg/kg (22), i.e., well below our conservative choice of 4.4 mg/kg. If an area greater than the median contour were chosen, it is clear that an even greater mass of deposited pollutant (loading) would be obtained. Results, shown in Table 2, indicate that for Co and Ni, we obtain a good match between emission and loading for reasonably small x′ values (best fits are 0.24 and 0.28 km, respectively). Loading of Ni from Monchegorsk appears to be very sensitive to the x′ value chosen, with the range x′ ) 0.1-0.3 km covering the whole range of loading radii from 1 to 1000 km (Figure 4). Emissions of Co can be fully deposited within a radius of 8-800 km. For Cu, even the smallest x′ value chosen is too high to yield a sensible loading radius with respect to the known deposition patterns. Modeling has shown that we need to decrease x′ to ca. 10 m to obtain realistic loading radii for Cu.
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FIGURE 5. Regional geochemical map of Ni in moss, presented as a block-kriged color surface map based on 598 analysed samples (field duplicates removed). See text for details. Al, aluminum; Ap, apatite; Au, gold; Fe, iron; Ni, nickel-copper industrial sites. As mentioned above, x′ values are expected to vary from element to element due to different particles size distributions and thus settling characteristics. If, however, we assume that the extent of the “shadow” zone for Cu is in the same range as that observed for Co and Ni (0.2-0.3 km), Cu emissions should only be of the order of 600 000 kg. The official V emission figures from the Monchegorsk smelters are insufficient to explain the deposition pattern and loading observed; this is explained by the fact that there are other important sources of airborne V in the area, namely
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activities related to mining in Kirovsk and Kovdor and activities in Kandalaksha (12 200, 5550, and 5400 kg V emitted in 1994, respectively, see refs 21 and 23). The curves for S on Figure 4 suggest a dispersion of this element over several hundreds of kilometers. Unfortunately, the pattern of S in moss does not readily lend itself to estimation of a radius of influence, because of its irregularity. This is probably a consequence of this element being an essential nutrient for plants, and being mobilised to the ground and surface waters (mostly as SO42-).
support of the ideas presented in this paper and their careful and constructive reviews of earlier drafts.
Supporting Information Available
FIGURE 6. East-west transect of the concentration of Ni in moss (milligrams/kilogram) through Monchegorsk, showing the raw data (circles) and a smoothed fit (curve). Note the logarithmic ordinate (minor ticks at 2.5, 5, and 7.5 × major tick).
TABLE 2. Calculated Loadings (kg) of Co, Cu, Ni, and V within Area Defined by the Median Values on the Geochemical Maps (xmed) for Three Different Values of x′ around Monchegorsk xmed, km x′ ) 0.1 km x′ ) 0.2 km x′ ) 0.3 km
Co
Cu
Ni
V
140 104 132 85 650 76 113
170 691 758 629 389 592 966
145 2 510 270 1 863 329 1 561 437
130 59 304 59 220 59 144
Modeling was also carried out for the Nikel/Zapoljarniy source, but the situation here is complicated by the existence of a smelter source (Nikel) and an ore roasting source (Zapoljarniy) separated by a distance of 24 km; the very different types of industrial processes lead to different emission characteristics. In addition, the 3 km long open-pit Jdanovska mine (3 km SSW of Zapoljarniy) and its impressive spoil and waste heaps are a source of windblown dust. When the Nikel and Zapoljarniy emissions were combined, we needed to use large x′ values (up to a few kilometers) to get a reasonable match with the official emission figures and our moss maps. When we modeled the loading from Nikel separately, we derived similar x′ values as for the Monchegorsk case (both are nickel-copper smelters). Compared with existing methods of estimating contaminant dispersion from point sources, which include Gaussian plume models (e.g., ref 24), the present method is mathematically and conceptually simpler: it does not physically track pollutant transport downwind along erratic eddies and turbulence patterns. In addition, the method averages wind conditions and other transport and deposition parameters over a full year and hence yields robust, annual loading values. Once characteristics of pollutant deposition in the immediate vicinity of a point-source emitter (D0, x′) are reliably established, the method allows for independent emission control and quantification of element masses available for long-range transport.
Acknowledgments The concept of mass balancing emission and deposition was developed during the Kola Ecogeochemistry project, for which financial support was received from the Norwegian Ministry of the Environment with special project funds from the Norwegian Ministry of Foreign Affairs. We wish to extend our thanks to all project participants for their assistance and insight. We are grateful to E. M. Cameron and F. Agterberg, three anonymous reviewers, the editors, and associate editor S. M. Japar, Environmental Science & Technology, for their
The three phases of the Kola Ecogeochemistry project (also included at http://www.ngu.no/Kola) (53 pages) will appear following these pages in the microfilm edition of this volume of the journal. Photocopies of the Supporting Information from this paper or microfiche (105 × 148 mm, 24× reduction, negatives) may be obtained from Microforms Office, American Chemical Society, 1155 16th St. NW, Washington, DC 20036. Full bibliographic citation (journal, title of article, names of authors, inclusive pagination, volume number, and issue number) and prepayment, check or money order for $85.50 for photocopy ($87.50 foreign) or $12.00 for microfiche ($13.00 foreign), are required. Canadian residents should add 7% GST. Supporting Information is also available via the World Wide Web at URL http://www.chemcenter.org. Users should select Electronic Pubications and then Environmental Science and Technology under Electronic Editions. Detailed instructions for using this service, along with a description of the file formats, are available at this site. To download the Supporting Information, enter the journal subscription number from your mailing label. For additional information on electronic access, send electronic mail to
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(18) Reimann, C.; A¨ yra¨s, M.; Chekushin, V. A.; Bogatyrev, I.; Boyd, R.; de Caritat, P.; Dutter, R.; Finne, T. E.; Halleraker, J. H.; Jæger, Ø.; Kashulina, G.; Niskavaara, H.; Lehto, O.; Pavlov, V.; Ra¨isa¨nen, M. L.; Strand, T.; Volden, T. Environmental Geochemical Atlas of the Central Barents Region; NGU-GTK-CKE Special Publication, Geological Survey of Norway: Trondheim, Norway; manuscript in preparation. (19) Chekushin, V. A.; Bogatyrev, I. V.; de Caritat, P.; Niskavaara, H.; Reimann, C. Annual atmospheric deposition of 16 elements in eight catchments of the central Barents region; manuscript in preparation. (20) A¨ yra¨s, M.; de Caritat, P.; Chekushin, V. A.; Niskavaara, H.; Reimann, C. Water, Air, Soil Pollut. 1995, 85, 749-754. (21) Reimann, C.; de Caritat, P.; Halleraker, J. H.; Volden, T.; A¨ yra¨s, M.; Niskavaara, H.; Chekushin, V. A.; Pavlov, V. A. Atmos. Environ. 1997, 31, 159-170. (22) Ru ¨ hling, Å.; Steinnes, E.; Berg, T. Atmospheric heavy metal desposition in northern Europe 1995; Report Nord 1996:37. Nordic Council of Ministers, Copenhagen, Denmark, 1996; 46 pp.
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(23) Murmansk Region Committee of Ecology and Nature Resources; Review of pollutant fallouts in the atmosphere on the territory of the Murmansk region in 1994; Murmansk, Russia, 1995. (24) Boubel, R. W.; Fox, D. L.; Turner, D. B.; Stern, A. C. Fundamentals of Air Pollution, 3rd ed.; Academic Press: San Diego, 1994; 574 pp. (25) Ma¨kinen, A. Biomonitoring of atmospheric deposition in the Kola Peninsula (Russia) and Finnish Lapland, based on the chemical analysis of mosses; Report 4/1994. Finnish Ministry of the Environment, 1994; 83 pp.
Received for review March 4, 1997. Revised manuscript received June 10, 1997. Accepted June 16, 1997.X ES970193Z X
Abstract published in Advance ACS Abstracts, August 1, 1997.
