ISSN 10642293, Eurasian Soil Science, 2011, Vol. 44, No. 3, pp. 286–296. © Pleiades Publishing, Ltd., 2011. Original Russian Text © A.A. Shelepchikov, E.S. Brodskii, D.B. Feshin, V.G. Zhil’nikov, E.Ya. MirKadyrova, S.P. Balashova, 2011, published in Pochvovedenie, 2011, No. 3, pp. 317–328.
SOIL CHEMISTRY
Polychlorinated DibenzopDioxins, Dibenzofurans, and Biphenyls in Soils of Moscow A. A. Shelepchikova, E. S. Brodskiia, D. B. Feshina, V. G. Zhil’nikova, E. Ya. MirKadyrovaa, and S. P. Balashovab a
Severtsov Institute of Ecology and Evolution, Russian Academy of Sciences, pr. Leninskii 33, Moscow, 119071 Russia Email: eco
[email protected] b Glavekspertiza Rossii, per. Furkasovskii 12/5, Moscow, 101990 Russia Received March 4, 2010
Abstract—The contents of polychlorinated dibenzopdioxins (PCDDs), dibenzofurans (PCDFs), and biphenyls (PCBs) in the soils of Moscow were estimated. The concentrations of PCDDs and PCDFs mainly vary in the range of 0.27–16.1 ng WHOTEQ/kg with single points of very high contamination up to 57.3 ng WHOTEQ/kg; the concentrations of PCBs are in the range of 2.1–50.8 ng/g with sites of high contamina tion up to 4020 ng/g. The contribution of dioxinlike PCBs to the total dioxin toxic equivalent is very high: from 16 to 85%. The high levels of PCDDs and PCDFs in the soils indicate the strong contamination of the atmospheric air. The main source of these compounds is apparently motor transport. DOI: 10.1134/S1064229311030124
INTRODUCTION The contamination of the environment with persis tent organic pollutants (POPs) is one of the most important ecological problems. POPs primarily include polychlorinated dibenzopdioxins (PCDDs), dibenzofurans (PCDFs), and biphenyls (PCBs). These compounds and eight pesticides are included on the list of the Stockholm Convention on Persistent Organic Pollutants, to which Russia is a signatory. POPs are characterized by high toxicity, a long half life period, and capacity for bioaccumulation and transboundary transfer. The intensive study of dioxin like compounds started in the world in the 1970s– 1980s. It was found that the main sources of PCDDs/PCDFs in the environment are various chemical and metallurgical industries and waste burn ing plants. Therefore, strongly polluted areas needing cleaning exist in any industrial country [15–17, 30]. In Russia, the study of environmental contamina tion with dioxins started only after 1985. The available information on technogenic catastrophes with the emission of dioxins and other POPs into the environ ment attracted close attention to this problem. Some preliminary studies were conducted [3, 5, 11, 31], but almost no regular work was done in this field, and the scope of the dioxin pollution remains unknown even for large industrial centers. In 2005–2006, we determined, with the support of the Moscow Government, the contents of a wide range of organic compounds (including PCDDs/PCDFs, PCBs,
polyaromatic hydrocarbons (PAHs), pesticides, and other compounds) in soil samples taken at different points in the city. The results of these studies are pre sented in this paper. EXPERIMENTAL The concentrations of the PCDDs/PCDFs and PCBs were determined by gas chromatography and high resolution mass spectrometry using standardized procedures [6, 9]. A mixture of internal standards (Wellington Laboratories) containing 13C12labeled PCDDs/PCDFs and dioxinlike PCBs was added to a soil sample of about 10 g. The sample was extracted by continuous flow extraction [8] and passed through a multilayer column consisting of continuous potassium silicate and silica gel impregnated with sulfuric acid layers separated by anhydrous sodium sulfate layers. The eluate was fractionated on a column packed with activated carbon and on a combined column with acti vated basic aluminum oxide and silica gel. The pre pared extract was concentrated to 10 µl with addition of tridecane and recovery standards, then analyzed for PCDDs/PCDFs and coplanar PCBs (77, 81, 126, 169). Other PCB congeners were determined in the fraction eluted from the carbonfilled column and the aluminafilled column after additional purification in a multilayer column and Florisil. All the solvents, sor bents, and glassware were preliminarily checked for the absence of the components to be determined. The following equipment was used: an HP 6890 Plus gas
286
POLYCHLORINATED DIBENZOpDIOXINS, DIBENZOFURANS
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60
50 ~ ~ 20 15 10 5 0
MO45 (CAD) MO117 (CAD) M661 (CAD) M662 (CAD) M672 (CAD) MO1 (NAD) MO71 (NAD) M627 (NAD) M647 (NAD) MO91 (NEAD) MO196 (NEAD) M693 (NEAD) MO13 (EAD) MO60 (EAD) MO123 (EAD) MO201 (EAD) M660 (EAD) M683 (EAD) M694 (EAD) MO3 (SEAD) MO39 (SEAD) MO52 (SEAD) M664 (SEAD) M670 (SEAD) MO14 (SAD) MO69 (SAD) MO70 (SAD) MO237 (SAD) M663 (SAD) M659 (SAD) MO120 (SWAD) M667 (SWAD) M668 (SWAD) M681 (SWAD) MO38 (WAD) MO124 (WAD) MO166 (WAD) M653 (WAD) M685 (WAD) M698 (WAD) M686 (NWAD)
PCDDs/PCDFs, ng WHOTEQ/kg
55
Sample code (sampling site)
Fig. 1. Total dioxin toxic equivalent for PCDDs/PCDFs in soil samples; the dotted line denotes the average value for all the sam ples; the solid line denotes the same without the two most contaminated samples.
chromatograph, a Finnigan MAT 95XP massspec trometer, and SGE BPX5 (diameter 0.22 mm, phase thickness 0.25 µm, column length 25 m) and SGE HT8 columns (diameter 0.22 mm, phase thickness 0.25 µm, column length 30 m). The analysis was per formed at a resolution of about 10000 using multiion detection and recording of two isotopes from the molecular ion cluster for each compound to be deter mined. The identification was based on the retention times and isotope ratios; the quantification was based on the peak ratios of the congener determined and the corresponding isotopelabeled standard. The total dioxin toxic equivalent (TEQ) was cal culated using two systems of dioxin toxicity coeffi cients used in world practice: the international sys tem (ITEQ) and a newer WHO system (WHOTEQ) [36]. The values lower than the detection limit were considered zero in the calculation of the TEQ. The names of the congeners correspond to the IUPAC sys tem. RESULTS AND DISCUSSION Because of the different construction and garden ing operations, the urban soils compose a relatively EURASIAN SOIL SCIENCE
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dynamic environment; therefore, the time of the exposure of a soil layer on the surface frequently can not be estimated during the soil sampling. The results are inevitably characterized by a large spread. The content of the PCDDs/PCDFs was determined in 41 soil samples. This number of samples is insufficient for a detailed conclusion about the environmental sit uation in such a large city as Moscow, but a general estimation is possible. The average concentration of PCDDs/PCDFs in all the soil samples was 8.2 ng WHOTEQ/kg, or 6.9 ng/kg when the most contaminated sample was excluded. The levels of contamination for most of the samples were in the range of 2–6 pg WHOTEQ/g, which was lower than the average value (Fig. 1). The highest concentrations were found in two samples from the industrial areas between Budennogo Avenue and Entuziastov Road in the Eastern Administrative District (EAD) (48.2 pg WHOTEQ/g) and at Tagil’skaya Street 10 (57.3 pg WHOTEQ/g). Con centrations below 1 pg WHOTEQ/g were found in three samples, two of which were taken in the indus trial zones of the Eastern and Southeastern adminis trative districts, and the third sample was taken on a
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waste area beyond the Moscow Ring Road (Priozer naya Street). The concentrations of dioxins in the samples taken beyond the Moscow Ring Road were lower than the average values for Moscow: 0.27 and 0.89 pg WHOTEQ/g on Priozernaya Street and in the Novokosino district, respectively. At the third point beyond the MRR (settlement of Severnyi), the con centration was 3.8 pg WHOTEQ/g, which could be related to the proximity of a waste burning plant and the northern steam power plant. The obtained data show an increase in the content of PCDDs/PCDFs in the soils when going from the northwest to southeast and from the west to east (Fig. 2). The difference in the contents of the dioxins in the park belts in the western and eastern regions of the city is very demonstrative. For example, the concentration of dioxins was 1.9 pg WHOTEQ/g in the region of Osennii Boulevard compared to 11.2 pg WHOTEQ/g in the Kuz’minki forest park, as well as 3.8 pg WHO TEQ/g in the soils of allotments in the settlement of Severnyi compared to 12.4 pg WHOTEQ/g in the Yasenevo forest park. The general predominance of PCDFs was observed, which indicated the predominant contribu tion of combustion products (exhaust gases from vehi cles, waste combustion plants, and other hightemper ature processes). The city areas can be divided into three categories: industrial, park, and generalpurpose ones. The last category includes courtyard areas, waste areas, lawns, public gardens, boulevards, and motorways. This is a quite conventional classification, because residential areas and industrial enterprises are neighboring in Moscow, as well as in other large cities. The data in Table 1 show that the average concentrations of PCDDs/PCDFs are similar for all the soil categories. A slightly higher level of contamination is observed in the park belts, which can be related to the longer time of accumulation and to the fact that the fallen leaves adsorbing dust and pollutants are not removed from these areas. The contamination at two points with the highest concentrations of PCDDs/PCDFs is appar ently due to specific local sources. To characterize the concentrations of different environmental pollutants, they are frequently com pared to the MPC values. In the Soviet Union, the USSR Ministry of Health order no. 697 of September 8, 1986, established the MPC at a level of 0.33 ng/kg. This was the most stringent value in the world, which was practically inaccessible for the soils of megapo lises. The current norms of the Russian Federation do not regulate the content of dioxinlike compounds in soils. The norms of other countries differ significantly from one another (Table 2). This is partly related to the
fact that the source of the contamination and the potential of the pollutants’ transfer from the soil to the trophic chains and humans, rather than the concen tration, are of importance for dioxins (to a greater degree than for other substances). In the soil, dioxins can persist without almost any change for tens of years [35]. It is believed that they are sorbed in the topsoil, and their extremely low solubility in water hampers their penetration deep into the soil [21, 37]. We and other authors found experimental disproof of this statement [4, 8, 24], but it should be recognized that the main mechanisms of dioxin migration in soils are rain erosion and, to a lesser degree, wind transfer [29, 30]. Therefore, if the polluted soils are not used for agriculture and if erosion control measures are taken, the risk for the inhabitants of these areas is low. How ever, if the permanent deposition of dioxins from the atmosphere is the source of pollution, this indicates the aerial contamination and constitutes a direct threat to the population’s health. This is the case for Moscow, where the deposition from the atmosphere is the main source of the pollution, although there are also local spills of hazardous preparations. The contamination levels of the urban soils can be conventionally divided into three categories: 10 pg WHO TEQ/g. The values lower than 1 pg WHOTEQ/g indicate a low level of contamination, and the values higher than 10 pg WHOTEQ/g are indicative of a high anthropogenic load. The levels of the soil con tamination in Moscow cannot be classified as cata strophic, but they call for close attention to the prob lem. The observed levels of contamination correspond to those detected in such European cities as London, Birmingham, Leeds, Sheffield, and Salzburg [12, 17] or in the zone of chemical plants in the Great Denver region [16], but they are higher than those in the region of oilprocessing plants in Tarragona (Spain) [25, 32, 33], where the average concentrations of PCDDs/PCDFs did not exceed 3 pg WHOTEQ/g in the industrial zones and 1.5 pg WHOTEQ/g in the residential areas. For comparison, in the town of Chapaevsk in Samara oblast, where different chlori nated organic compounds were produced for more than 30 years, the concentration of PCDDs/PCDFs in the soils of the residential area in 2006–2007 was in the range 1.8–54.1 pg WHOTEQ/g with the average value being 15.3 pg WHOTEQ/g [34]. The state eco logical expertise classified Chapaevsk as an environ mentally neglected area. In distinction from dioxins, PCBs originally were products of industrial synthesis. The main sources of their input into the environment are leakages from transformers and other industrial equipment. Because of the wide use of this equipment and the volatility and EURASIAN SOIL SCIENCE
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MO1 MO91
NEAD
NAD M693 M647
5 EAD MO71 M686
MO196
NWAD
M660
MO60
M627 M672 MO38 M662
MO124
M683 MO123
MO45 MO166
M694 MO201
MO13
M661 M685
MO117 M653
MO39
WAD MO14 M663 MO237
M698
M670 MO52 MO69
M664
MO3
SEAD
M667
M681 MO120 M659
SWAD MO70
SAD
M668
Fig. 2. Levels of PCDDs/PCDFs (ng/kg WHOTEQ) in different districts of Moscow. EURASIAN SOIL SCIENCE
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Table 1. Concentration of PCDDs and PCDFs in soils of different functional areas of Moscow, pg/g Soil category parks
generalpurpose
industrial
Congener min–max
mean
min–max
7 2,3,7,8TetraCDD
mean 20
min–max
mean
12*
12(14)
0–1.6
0.43
0–1.6
0.21
0–1.8
0.45(0.46)
1,2,3,7,8PentaCDD
0.54–3.1
1.4
0–2.3
1.0
0–2
0.64(0.76)
1,2,3,4,7,8HexaCDD
0.31–4.1
1.1
0–1.7
0.76
0–1.8
0.7(0.78)
1,2,3,6,7,8HexaCDD
0.79–8.2
2.4
0–2.8
1.3
0.17–3.2
1,2,3,7,8,9HexaCDD
0.66–6.8
1.9
0–2.2
1.0
0–10.8
1.4(1.5) 1.8(1.7)
1,2,3,4,6,7,8HeptaCDD
0–17.6
8.1
0–29.3
9.4
0–21
10.6(11.9)
OctaCDD
0–54
29.4
0–403
57.9
0–94.7
49.1(54.2)
2,3,7,8TetraCDF
0.8–9.3
4.4
0.31–12.7
3.2
0.86–21.7
4.5(11.1)
1,2,3,7,8PentaCDF
1.9–7
3.2
0.18–10.6
2.8
0.54–11.7
3.1(7.7)
2,3,4,7,8PentaCDF
2.2–10.4
4.4
0.41–11.9
3.8
0.61–10.4
3.5(8.9)
1,2,3,4,7,8HexaCDF
2.5–9.2
4.6
0–11.8
3.9
0.72–20.5
6.0(16.6)
1,2,3,6,7,8HexaCDF
1.7–10.9
4.1
0–11.1
3.3
0.44–9.5
3.9(9.6)
1.3
0–3.3
0.97
0–2.4
1.3(7.1)
4.2
0–12.4
3.2
0.36–7.7
3.5(7.6)
12.5
0–660
48.6
1.8–54
24.6(52.3)
2.3
0–5.9
2.0
0.44–8.2
2.3(8.6)
1,2,3,7,8,9HexaCDF 2,3,4,6,7,8HexaCDF 1,2,3,4,6,7,8HeptaCDF 1,2,3,4,7,8,9HeptaCDF
0.43–3 1.7–12 0–30.3 0.66–6.7
OctaCDF
0–55.5
27.2
0–439
75.1
12–221
62.5(178)
Other TetraCDD
0–21.8
10.9
0–30
13.3
0–11
5.3(5.6)
Other PentaCDD
6.5–56
25.1
0–41
15.2
1.6–27
11.6(11.9)
Other HexaCDD
9.2–91
28.8
0–37
16.7
2.4–31
13.3(14.2)
Other HeptaCDD
5.1–48
14.7
0.8–31
10.6
1.7–21
9.5(11.6)
0–73
35.5
0–180
42.4
0–52
23.0(36.5)
Other TetraCDF Other PentaCDF
25.1–110
47.5
2–120
35.0
4.8–50
26.2(42.4)
Other HexaCDF
11.1–51
22.9
1.3–286
29.2
0–41
19.5(36.5)
Other HeptaCDF
1.1–19
6.8
0.6–491
31.4
0.9–28
9.7(20.9)
ITEQ
3.4–14.1
6.2
0.27–14.4
5.2
0.79–15.3
5.5(12.3)
WHOTEQDF
3.6–15.7
6.8
0.27–15.4
5.6
0.67–16.1
5.7(12.4)
* Excluding the two most contaminated samples. Note: Here and in Table 3, the number of samples is italicized.
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stability of PCBs, these compounds can be considered the most prevalent POPs. They are rated the fifth most hazardous for the health of Americans after arsenic, lead, mercury, and vinyl chloride [14]. The first of the PCDDs/PCDFs occupies only the 73rd position on this list.
Table 2. Maximum permissible concentrations established for dioxins in soils in different countries
PCBs can also form simultaneously with PCDDs/PCDFs in waste burning plants and in other hightemperature processes. The emission from these sources is usually not predominant in terms of the total contamination with PCBs, but it results in an increase in the proportion of coplanar PCBs, including the most toxic congeners PCB126 and PCB169 [26].
Canada
In Russia, the provisional permissible concentra tion (PPC) of total PCBs in soils is 60 ng/g; higher PPC values are established for separate components: 30, 60, and 100 ng/g for tri, tetra, and pentachloro bipenyl, respectively [7]. A more reliable and informa tive method of estimating the level of contamination is the use of indicator congeners: the individual PCBs typical for different PCB mixtures. In Europe, conge ners 28, 52, 101, 138, 153, and 180 are usually used for this purpose; their total concentration of 20 ng/g char acterizes the safe contamination level of soils and bot tom sediments in the Netherlands [18]. If the contam ination is caused by Sovtol and Sovol (the PCB mix tures most prevalent in Russia), the Netherlands norm is close to the Russian PPC for the total PCBs. The results of the analysis presented in Fig. 3 show that the concentration of PCBs in the sample taken in the industrial zone (point M660, Tagil’skaya Street 10A, EAD) exceeds the PPC by more than 130 times and is 4 times higher than the level requiring the remediation of the area in the Netherlands (1 µg/g for the sum of PCBs 28, 52, 101, 118, 138, 153, and 180). A high level of PCDDs/PCDFs was also found in the same sample, and the total toxicity coefficient for the PCDDs/PCDFs and PCBs was 388.5 pg WHOTEQ/g. The contami nation of other samples was relatively low: no more than 2 MPC was observed in only 3 cases, and the PCB concentration in 34 samples was in the range from 0.1 to 1 MPC (Table 3). When the sample with the very high contamination level was excluded from the con sideration, the average content of the six indicator PCBs was 8.7 ng/g. As for the PCDDs/PCDFs, the concentrations of the PCBs in the different functional zones were similar. However, a decrease in their con centration was observed in the following series: indus trial, park, and urban soils. This observation agrees with the distance from the emission sources and the longer exposure of the soils in the park areas. The contribution of the most hazardous PCB con geners having dioxinlike properties to the total toxic equivalent is 16 to 85% (Fig. 3). The low correlation EURASIAN SOIL SCIENCE
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Country
Soil categor
MPC, ng ITEQ/kg [18, 19, 27, 28] 4
United States
1000
Japan
1
Finland
2
Germany
Italy
agricultural
5–40
playgrounds
100
residential zones
1000
industrial zones
10000
residential zones
10
industrial zones
100
The Nether residential and agricultur lands al zones dairy farms
Sweden
Finland
1000
10
safe level
1
susceptibl
10
less susceptible
250
proposed levels
2
maximum permissible (agricultural, residential zones)
500
between the total content of indicator congener PCBs and congener 126 (the most toxic dioxinlike planar PCB) is noteworthy (Fig. 4). At the same time, the concentration of congener 126 well correlates with the total toxicity equivalent for PCDDs/PCDFs (Fig. 4); i.e., it can be supposed that their sources can coincide. As was shown above, PCDDs/PCDFs are present in the soils of different functional zones of the city, and no visible differences in the distribution of the conge ners are observed. This suggests that the contamina tion is due to multiple distributed onetype sources.
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SHELEPCHIKOV et al. 25 331.2 + 57.3 WHOTEQ, ng/kg
20
15
10
5
MO117 (CAD) M661 (CAD) M662 (CAD) M672 (CAD) MO1 (NAD) MO71 (NAD) M627 (NAD) M647 (NAD) MO91 (NEAD) M693 (NEAD) MO60 (EAD) MO201 (EAD) M660 (EAD) M683 (EAD) M694 (EAD) M664 (SEAD) M670 (SEAD) MO237 (SAD) M663 (SAD) M659 (SAD) MO120 (SWAD) M667 (SWAD) M668 (SWAD) M681 (SWAD) MO124 (WAD) MO166 (WAD) M653 (WAD) M685 (WAD) M698 (WAD) M686 (NWAD)
0
Sample code (sampling site) PCDDs/PCDFs
PCBs
Fig. 3. Total toxic equivalent of PCDDs/PCDFs and dioxinlike PCBs in soils of Moscow (pg WHOTEQ/g).
The observed distribution of the PCDDs/PCDFs characterized by the predominance of dibenzofurans can be due to a combination of emissions from differ ent hightemperature processes; however, motor transport is the most evident common source of con tamination for the entire city. The emission factors for PCDDs/PCDFs from dif ferent automobile engines strongly depend on the fuel type and the automobile construction (Table 4) [15, 23]. Our measurements showed that the emission factor of the ZIL Bychok diesel automobile in the idlerun engine mode is 113 pg ITEQ/kg fuel [1]. Although the production and circulation of ethylated gasoline has been prohibited in the Russian Federation since June 1, 2003, according to the Federal Customs Ser vice data, about 4735 t of tetraethyl lead was imported into Russia in 2004, which was larger than in 2003 by almost 50%. In 2006, the State Duma proposed to the Chairman of the Government to prohibit the import of tetraethyl lead, but this was not done [2, 10]. Thus, taking into consideration the high probability of ethy lated gasoline use and the large proportion of adulter ated fuel, the expected spread of the emission factor values should be no lower than in other countries. If the range from 100 to 1000 pg/kg fuel is used, the
emission will be 0.3–3 g TEQ for the annual con sumption of about 3 million tons of motor fuel. As was noted above, the dioxinlike compounds present in the atmospheric air usually constitute a greater threat for health than those accumulated in soils. PCDDs and PCDFs, as well as other POPs, are capable of transboundary transfer thousands kilome ters from the sources of the emissions. During a short time period, most of them are deposited onto the soil at small distances from the emission sources. From the levels of the soil contamination alone, the deposition flux of pollutants onto the area studied cannot be exactly determined, but the lower limits of its values can be estimated. Under the supposition that all the PCDDs/PCDFs are accumulated without transfor mation in the upper 15cm thick soil layer with a dry density of 1.5 g/cm3, the annual deposition flux should be 18–90 ng/m2 to reach a concentration of 4 pg/g after exposure for 10–50 years. For the city area equal to 1000 km2, the total annual deposition is 18–90 g TEQ, which is comparable to the emissions in some European countries (Fig. 5). With consideration for the intensity of the earthworks in the city, which decrease the period of exposure, and the partial removal of the contamination with rain and melt water EURASIAN SOIL SCIENCE
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Table 3. Concentrations of PCBPs in soils of different functional groups in Moscow Parks min–max
Urban soils mean
min–max
Industrial soils*
mean
min–max
mean
Soil category Dioxinlike congeners, pg/g 9
36 124
6–465
8
PCB77
10–344
PCB81
0–15
PCB105
212–3280
PCB114
3.8–236
PCB118
416–6440
PCB123
7–65
32.6
3–395
61.8
39–183(3250)
84.7
PCB126
0–62
21.8
0–73
15.0
0–93(890)
26.4
PCB156
42–754
PCB157
11–194
PCB167
4.9
116
0–25
1240
5.4
120–7010
56.5
1460
0–529
2560
81.4
284–12300
140
0–15(180)
4.4
201–5730(351000) 15–264(24900) 773–10900(1278000)
1870 91.3 3800
16–1740
373
70–1850(104000)
565
61.2
5–1050
133
19–531(25650)
186
11–291
89.2
4–3780
243
29–681(30900)
256
PCB169
0–13
2.3
0–63
3.4
PCB189
0–38
7.5
0–155
20.6
0.29–7.3
2.8
0.07–9.7
2.3
WHOTEQ
240
2880
15–499(6980)
0–61(20)
10.2
0–463(3630)
99.9
0.16–12(330)
3.8
Indicator congeners, ng/g 7 PCB28
26
0.04–6.3
7
1.1
0.02–4.4
0.8
0.05–0.7(16.6)
0.3
PCB52
0.2–10.9
2.2
0.02–5.0
1.4
0.09–1.6(414)
0.8
PCB101
0.3–6.4
1.8
0.03–4.7
1.3
0.2–6.2(735)
1.9
PCB138
0.3–4.8
1.9
0.1–6.0
2.0
0.5–15.8(761)
4.1
PCB153
0.5–5.0
2.0
0.2–5.6
1.9
0.5–14.7(769)
4.0
PCB180
0.03–0.7
0.2
0.03–0.8
0.3
0.8–2.5(50.2)
0.6
Total 6**
2.3–34.0
9.3
1.7–26.4
7.8
3.2–39.9(2746)
11.7
Total 7***
2.8–40.5
11.4
2.1–32.2
10.0
3.9–50.8(4020)
14.8
Notes:
* Excluding the most contaminated sample (its values are given in parentheses). ** Total concentration of PCBs: 28, 52, 101, 138, 153, and 180. *** Total concentration of PCBs: 28, 52, 101, 118, 138, 153, and 180.
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60
g, ITEQ 4500 3981 4000 3500 2744 3000 2500 2000 1500 873 661 1000 486 569 334 290 500 22 29 39 42 112 150 181 0
(a)
50 40
Y = 0.34X + 6.63 R2 = 0.46
30 20 10 0
20
80
100
(b)
18 16 14 12 10 8 6 4 2 0
40 60 PCB 126, pg/g
Sweden Austria Denmark Slovakia Hungary Australia Switzerland Canada Germany Holland Great Britain Belgium France United States Japan
Total PCBs28, 52, 101, 118, 138, 153 и 180, ng/g
294
Fig. 5. Emission of PCDDs and PCDFs to the atmosphere in 1995.
Y = 0.21X + 1.41 R2 = 0.85
e.g., waste burning plants, and the underestimation of the emission factors of the automobile engines.
10
20
30
50 40 PCB126
60
70
80
Fig. 4. Correlation of the congener PCB 126 with (a) the total content of six indicator PCB congeners and (b) the total toxic equivalent for the PCDDs/PCDFs (WHOTEQ) in the soils of Moscow, pg/g.
into the drainage system, the actual deposition could be higher by several times. An additional method of estimating the deposition rate of the pollutants is the analysis of the snow cover. Our analysis of a snow sample from the Kozhukhovo microdistrict (EAD) taken in late February of 2008 showed a distribution profile of congener PCDDs/PCDFs similar to that revealed in the city’s soils; the level of contamination was 33 pg WHO TEQ/kg. If the residual snow cover mass is taken equal to 100 kg/m2, the precipitation will be more than 3 ng TEQ/m2 in this area for the winter period (2.5 months), which exceeds the norm of 2.55 ng WHOTEQ/m2 per year specified by the EU strategy [22]. The calculated precipitation values of the PCDDs/PCDFs exceed the estimates for the emis sions from motor transport, which can be due to the presence of more intensive contamination sources,
CONCLUSIONS All the territory of Moscow is subjected to contam ination with PCDDs and PCDFs. Although areas with very high levels of contamination were revealed in the industrial zones, the general character of the contam ination and the observed concentrations are similar throughout the city. The relatively high concentrations of dioxins in the soils indicative of the contamination of the atmospheric air constitute the threat that the population will be exposed to dioxins because of the direct contact with the soil (especially for children) and the inhalation with dust and soil particles trans ferred by the wind [20]. Contamination with PCBs is also typical for the major part of Moscow soils; its level is extremely high in some industrial zones. The contribution with dioxinlike PCBs compared to the total toxic equiva lent is 16 to 85%, and these compounds apparently have the same sources of emission as the PCDDs/PCDFs. Motor transport is one of the main contamination sources. The amount of dioxinlike compounds formed during the combustion of motor fuel strongly depends on the dopes used; therefore, the total prohi bition of the production and sale of ethylated gasoline and fuels containing other hazardous dopes should strongly decrease the emission. A gradual decrease in the level of dioxins in the surface soil layers can also be expected because of the reduced number of industrial enterprises within the city and the mitigation of the EURASIAN SOIL SCIENCE
Vol. 44
No. 3
2011
POLYCHLORINATED DIBENZOpDIOXINS, DIBENZOFURANS
295
Table 4. Emission factors for different automobile engines Emission factor Country, year
Fuel pg ITEQ/km
United States, 1987
ethylated gasoline
203
diesel Sweden, 1987
380–4900
pg ITEQ/l 1794 5904–24440
nonethyleated gasoline
