ISSN 01476874, Moscow University Soil Science Bulletin, 2012, Vol. 67, No. 2, pp. 85–90. © Allerton Press, Inc., 2012. Original Russian Text © E.S. Brodskii, A.A. Shelepchikov, D.B. Feshin, E.S. Efimenko, G.I. Agapkina, 2012, published in Vestnik Moskovskogo Universiteta. Pochvovedenie, 2012, No. 2, pp. 35–40.

CHEMISTRY OF SOILS

The Profile of Congeners of Polychlorinated Biphenyls in Soils of Moscow E. S. Brodskiia, A. A. Shelepchikova, D. B. Feshina, E. S. Efimenkob, and G. I. Agapkinac a

Severtsov Institute of Ecology and Evolution, Russian Academy of Sciences, Moscow, 117071 Russia b Physical Technical Institute, Moscow State University, Moscow, Russia cDepartment of Soil Science, Moscow State University, Moscow, Russia email: [email protected], [email protected], [email protected], [email protected], [email protected] Received June 2, 2011

Abstract—The profiles of 19 indicative and dioxinlike congeners of polychlorinated biphenyls (PCBs) in the surface soils of distinct types of land use in Moscow are investigated. The penta and hexachlorobiphenyls (46.7 and 31.6%, respectively) contribute significantly to the PCB spectrum. They used to make up the bulk of coolants and insulating fluids for electrical equipment, especially transformers. Among the congeners, the indicative PCB101, 110, 138, and 153 and dioxinlike congeners PCB105 and 118 dominate. They pos sess extremely high persistence and capability of bioaccumulation and exert harmful toxic influence, which should be taken into account when estimating an urban ecosystem’s ecotoxicological state. Keywords: urban ecosystems, soil contamination, polychlorinated biphenyls, profile of 19 indicative and dioxinlike congeners. DOI: 10.3103/S0147687412020020

INTRODUCTION Polychlorinated biphenyls (PCBs) are listed as one of the very harmful pollutants that are subject to strict control in urban ecosystem soils [15]. High stability in the environment, possibility of worldwide distribution in the biosphere, enhanced accumulation in organ isms, lack of evolutionary adaptation of the human organism to these xenobiotics, and the existence of a toxic effect even at extremely low concentrations both allowed some of them to be included in the list of per sistent organic pollutants (POPs) and permitted them to be classed as special dioxinlike superecotoxicants [8, 9, 12–14, 17]. The major danger of PCBs is caused by their persistent toxicity, which provokes distur bances in the immune status and reproductive func tion of the organism; teratogenic and carcinogenic effects; and diseases of the liver, kidney, nerve system, and skin, etc. Their most harmful effects on the human organism arise from the mutagenic action, which has a negative impact on the health of subse quent human generations [1, 4, 5, 12–14, 21, 22]. The emission of PCBs into the environment is linked to their commercial production, which began in 1930, and use in dielectrics; heattransfer systems; coolants; and insulating and hydraulic fluids, such as paint, glue, lacquer, and plasticizer components, and plastic filling compounds [7, 9, 12–14, 18]. PCB production is currently banned in many developed countries, including Russia. Nevertheless, according to an expert evaluation, about a third of the

commercially produced PCBs have entered the envi ronment, with only 4% of them having decomposed [9, 19]. The rest are kept in urban ecosystems hidden in electrical appliances, materials, and waste products. Transformers contain the most percentage of PCBs (up to 61%) [26]. In addition, PCBs are a byproduct of waste material combustion and many industrial processes [12–14]. Therefore, these superecotoxi cants continue to enter the environment and actively circulate in it. Consequences of this are both the for mation of areas with an elevated contamination level in urban ecosystems due to local sources and global biosphere pollution due to the transboundary PCB transport [9–14, 16, 20, 25]. Information on contam ination sources, distribution, and content level and the peculiarities of the PCB profile in the soils of urban ecosystems, particularly Moscow, is of the highest interest. At present, these data are limited [27]. We previously studied PCB content in the soils of various types of land use of Moscow and estimated the risk of contamination levels based on the domestic and foreign permissible exposure limits [2]. However, the total content of the given ecotoxicants in the compo nents of ecosystem, including the soil, is not the only indicator of the ecosanitary conditions of urban envi ronment. The contribution of some congeners (com pounds with a varying number and position of the chlorine atom in a biphenyl molecule) to their profile (the composition of the spectrum of all the com pounds) also provides significant information on pos 85

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Table 1. The contribution of 7 indicative and 12 dioxinlike congeners to the profile of PCBs in soils of Moscow PCB conge ner

Relative content of a congener in the PCB profile, % average

PCB28/31 PCB52 PCB81 PCB77 PCB101 PCB110 PCB123 PCB118 PCB114 PCB105 PCB126 PCB153 PCB138 PCB167 PCB156 PCB157 PCB169 PCB180 PCB189

minimal

Trichlorobiphenyls 9.0 0.3 Tetrachlorobiphenyls 9.9 0.3 0.0 0.0 0.7 0.1 Pentachlorobiphenyls 9.4 0.7 14.6 5.4 0.4 0.1 14.9 8.2 0.3 0.0 6.9 3.4 0.1 0.0 Hexachlorobiphenyls 14.2 5.5 14.4 4.8 0.6 0.1 1.9 0.5 0.6 0.2 0.0 0.0 Heptachlorobiphenyls 1.9 0.1 0.2 0.0

maximal

33.2 30.9 0.5 2.0 24.4 26.0 3.0 38.3 0.8 16.2 0.7 34.7 28.1 1.5 3.5 1.5 0.0 5.8 5.8

sible harmful effects of PCBs on humans and other inhabitants of urban ecosystems. The ecological risk of single congeners depends on their homologous series classification (from di and trichlorobiphenyls to hep tachlorobiphenyls) and structural differences (planar, mono and orthosubstituted, and nonplanar com pounds) that affect such properties of congeners as toxicity, volatility, lipophilicity, interaction with soil components, resistance to microbial activity, bioaccu mulation, transpiration by plants, etc. The peculiari ties of the PCB profile also allow a judgment made regarding the sources of emission and the pathways of ecotoxicant migration in the environment that is important for designing projects to prevent contami nation or reduce the present burden on the environ ment, including the development of safe PCB decom position approaches. The aim of the present work is to study the profile of PCB in the soils of distinct landuse types of Mos

cow, identification of its relation to possible sources of contamination, and estimation of potential harm for inhabitants. MATERIALS AND METHODS The objects for the investigation were surface soils (0–5 cm) of different soil types (n = 40) including dis tinct land use types of the city: recreational land use (n = 12), residential land use (n = 13), transportation land use (n = 5), industrial land use (n = 7), and vacant space land use (n = 2). The technique and locations of sampling points were previously described [2]. The ranges of PCB compounds identified in the soil samples of seven indicative and 12 dioxinlike congeners are considered. The technique of congener specific analysis of the samples was previously given in works [2]. The contribution of each of the 19 conge ners to the PCB profile was estimated as the ratio of its concentration to the sum of concentrations of these compounds. In the case of 12 dioxinlike PCBs, the contribution of each congener to the profile was assessed as the relative fraction of a congener in the total toxic equivalency. The PCB congeners are desig nated according to the IUPAC chemical nomencla ture. RESULTS AND DISCUSSION Based on data of the content of individual PCB congeners in the soils of Moscow, their profile was analyzed both for the entire area of the city (Table 1) and for individual landuse types (Fig. 1). Calculation showed that, in urban soil; trichlorobi phenyls28/31; tetrachlorobiphenyl52; pentachloro biphenyls101, 105, 110, and 118; and hexachloro biphenyls138 and 153 dominate. The presence of low chlorinated PBCs in the profile reflects a tendency toward global distribution of the most volatile com pounds with lower molecular weight in the biosphere. Due to the atmospheric precipitation onto the soil cover, the presence of these compounds is typical of background surface and agricultural lands and the principal factor influencing the bioaccumulation of contaminants in the soil is the content of the organic substance [10, 25]. The highest relative content of trichlorobiphenils28/31 (20.0%) in the PCB profile is shown for the soils of transportation land use of Mos cow; at the same time, in the residential, industrial, and recreational land use types, this value varies in the range of 7.4–9.1% (Fig. 1). The elevated content of low chlorinated PCBs in the upper layers of lawns near roadways may be determined by the periodic introduc tion of peatcontaining mixtures into them. The major contribution into the PCB profile is made up by high chlorinated congeners, mainly, penta and hexachlorobiphenyls, the percentage of which is 46.7 and 31.6% of the total content of all con geners, respectively (Table 1). At the same time, the

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(a)

15 10

Relative content of congeners in the PCB profile, %

5 0 20

(b)

15 10 5 0 20

(c)

15 10 5 0 15

(d)

10 5 0

PCB 28/31

PCB 101

PCB 81

PCB 123

PCB 114

PCB 126

PCB 138

PCB 156

PCB 169

PCB 189

Fig. 1. The contribution of 19 congeners to the profile of PCBs in the soils of distinct landuse types of Moscow: (a) transporta tion, (b) residential, (c) industrial, and (d) recreational.

relative content of tetra, penta, and hexachlorobi phenyls in the PCB profile for soils of urban areas of distinct landuse types is similar (figure). The consid erable contribution of highchlorinated compounds into the PBC profile, including PCB101, 105, 110, 118, 138, and 153, indicates the possibility of urban environment contamination by Sovol and Sovtol tech nical fluids, i.e., heatexchanging and dielectric fluids for transformers, and the Trichlorodiphenyl technical fluid in condensers, which were widely used in the Soviet Union and then in Russia up to 1995 [7–14, 16, 18]. For example, Sovol (OST 6012485) contained 23% of tetrachlorobiphenyls, 53% of pentachlorobi phenyls, and 22% of hexachlorobiphenyls [6, 21, 23, 24]. According to other research, the distribution of PCBs between the fractions of tetra, penta, and hexachlorobiphenyls in this fluid corresponded to 16, 52, and 28% [26]. At the same time, PCB101 (8.7%), 110 (9.6%), 118 (8.6%), 105 (4.1%), 153 (5.9%), MOSCOW UNIVERSITY SOIL SCIENCE BULLETIN

and 138 (8.7%) dominated in the profile of polychlo robiphenyls. Tri (0.49%) and heptachlorobiphenyls (2.4%) were also found in this technical fluid in small quantities. Therefore, the prevalence of indicative PCB101, 110, 138, and 153, which belong to penta and hexachlorobiphenyls, is typical of the soils of PCBcontaining transformer locations [10]. The significant presence of trichlorobiphenyls 28/31 and tetrachlorobiphenyl52 in PCB profile in the soils of Moscow may also be related to soilcover contamination with the Trichlorodiphenyl technical fluid in the locations of service and storage of PCB containing condensers, e.g., in industrial land use. This technical fluid was used for condenser isolation impregnation, and it was 49% trichlorobiphenyls, 32% tetrachlorobiphenyls, and 14% dichlorobiphenyls [10, 21, 24]. The prevalence of high chlorinated congeners PCB138 (+158) (11.0%), 110 (11.0%), 52 (8.3%), Vol. 67

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Table 2. The profile of dioxinlike PCBs in soils of Moscow PCB congener code

structure according to the IUPAC

Relative contribution of a congener to the PCB profile, % ITEF

average

minimal

maximal

Planar congeners PCB81

3,3',4,4'TCB

0.0001

0.06

0.00

0.34

PCB77

3,4,4',5TCB

0.0005

4.93

0.57

21.12

PCB126

3,3',4,4',5PECB

0.1

39.45

0.00

93.67

PCB169

3,3',4,4',5,5'HHCB

0.01

0.20

0.00

4.68

Monoorthosubstituted PCB105

2,3,3',4,4'PECB

0.0001

10.26

0.66

19.41

PCB114

2,3,4,4',5PECB

0.0005

2.66

0.00

10.71

PCB118

2,3,4,4',5PECB

0.0001

22.34

1.60

55.13

PCB123

2',3,4,4',5PECB

0.001

0.75

0.01

6.80

PCB156

2,3,3',4,4',5HHCB

0.0005

14.22

1.09

34.43

PCB157

2,3,3',4,4',5'HHCB

0.0005

4.51

0.27

13.58

PCB167

2,3',4,4',5,5'HHCB

0.00001

0.10

0.01

0.33

PCB189

2,3,3',4,4',5,5'HPCB

0.0001

0.52

0.00

14.53

118 (8.2%), and 101 (8.1%) was also found for the soils of grassland?and forest systems of Moscow oblast, and their percentage in the spectrum declined with increasing distance from Moscow [27]. It is likely that the source of contamination may also have been the Sovol and Trichlorodiphenyl technical mixtures. The toxic action mechanism of 12 dioxinlike PCBs, as well as polychlorinated dibenzopdioxins and dibenzofurans (PCDD/PCDF), is mediated by the induction of the P450 cytochromecontaining monooxygenase system that controls the oxidative metabolism of xenobiotics and endogenous hydro phobic compounds in the organism [1, 8, 12, 21]. Pla nar PCBs with four, five, and six chlorine atoms (which do not contain chlorine atom in the ortho position) exert the greatest toxic effect, and mono orthosubstituted ones (with one chlorine atom in the orthoposition) produce a weaker effect. The toxicity of each of these compounds is assessed compared to the 2,3,7,8tetrachlorodibenzondioxin (2,3,7,8 TCDD) using toxic equivalency factors (ITEF), and the total toxic equivalency is expressed as a toxic equivalent quantity (ITEQ), similarly as to in PCDD/PCDF risk assessment. The analysis of 12 dioxinlike PBCs in soils of Moscow showed that the most toxic PECB126 (I TEF = 0.1), as well as PECBs118 and 105 (ITEF = 0.0001) and PECB156 (ITEF = 0.0005), dominate in total toxic equivalency (Table 2).

CONCLUSIONS We revealed a clear prevalence of high chlorinated congeners (penta and hexachlorobiphenyls), which are typical of PCBcontaining Sovol and Sovtol tech nical mixtures used in electrical appliances, especially in transformers, in the profile of PCBs in soil cover of all the landuse types of Moscow. The relatively uni form distribution of ecotoxicants in the soil cover of the whole city may be a consequence of PBC evapora tion and migration with air flows in the forms of vapor and aerosols and transfer with waste and surface water from the areas of local contamination indicated in the area of Moscow [2]. The prevalence of high chlorinated biphenyls in the PCB profile in the surface soil layers of Moscow testi fies that, although the total content of PCBs in urban soils mainly correspond to the permissible ecosanitary exposure limits [2], they represent a potential threat to the health of the inhabitants. Due to the high inertness of PCBs, abiotic mineralization and enzymatic pro cesses with their involvement occur very slowly. According various literature data, the halflife of PCBs in soil lies within the range of 5–15 years, depending on the natural conditions and the profile of congeners [5, 14, 16, 19]. A decrease in PCB concentration in terrestrial ecosystems occurs mainly through vapor ization and biphenyl biotransformation with a low content of chlorine atoms [3, 4, 7, 12, 20]. Under nat ural conditions, biological degradation of biphenyls is considered impossible from 4–5chlorosubstituted congeners [1]. Bioremediation of objects contami

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nated with high chlorinated PCBs is only achieved during successive anaerobical–aerobic treatment [3]. Therefore, the most stable and lipophilic high chlori nated congeners, the concentration of which con stantly increases from lower to higher levels of the trophic chain, are of the highest danger for organisms [1, 7, 9]. Even when congeners with two or three chlo rine atoms dominate in the abiotic components of ecosystems, the profile of PCBs is mainly represented by biphenyls with six or seven chlorine atoms in the organisms of high trophic levels. PCBs can become eliminated from the human organism only in 7–8 years [21]. Congeners of PCBs that dominate in the surface soils of Moscow are characterized not only by extremely high stability and ability of bioaccumulation and biomagnification, but also by highly harmful forms of toxic action. A high relative content of mono orthosubstituted PCBs105 and 118 in the profile of dioxinlike PCBs is of special interest, which signifi cantly contributes to the total toxic equivalence of dioxinlike PCBs. REFERENCES 1. Avkhimenko, M.M., Environment Pollution by Poly chlorinated Biphenyls: Medical and Ecological After maths, in Polikhlorirovannye bifenily. Supertoksikanty XXI veka (Polychlorinated Biphenyls. Supertoxins of 21st Century), Moscow, 2000, issue 5. 2. Agapkina, G.I., Efimenko, E.S., Brodskii, E.S., et al., Concentration and Distribution of Polychlorinated Biphenyls in Soils of Moscow, Moscow Univ. Soil Sci. Bull., 2011, vol. 66, no. 1, p. 36. 3. Vasil’eva, G.K. and Strijakova, E.R., Bioremediation of Soils and Sediments Contaminated by Polychlorinated Biphenyls, Microbiol., 2007, vol. 76, no. 6, p. 639. 4. Vrednye khimicheskie veshchestva. Galogen i kislorod soderzhashchie organicheskie soedineniya: Sprav. izd. (Hazardous Substances. Halogen and Oxygen Con tenting Organic Compounds. Handbook), Filov, V.A., Ed., St. Petersburg, 1994. 5. Informatsionnoe pis’mo Minzdrava SSSR (Information Letter of the USSR Department of Public Health) Dioxine. Hygienic Aspects, Moscow, 1990. 6. Zabelina, O.N., Reactivity of Polychlorinated Biphe nyls and Identification of Products Caused by Their Chemical Transformations, Extended Abstract of Cand. Sci. (Chem.) Dissertation, Yekaterinburg, 2007. 7. Isidorov, V.A., Vvedenie v khimicheskuyu ekotok sikologiyu: Ucheb. posobie (Introduction into Chemical Ecotoxicology: Student’s Book), St. Petersburg, 1999. 8. Klyuev, N.A., Ekologoanaliticheskii kontrol’ stoikikh organicheskikh zagryaznenii v okruzhayushchei srede (Ecological–Analytical Monitoring of Stable Organic Pollutants in the Environment), Moscow, 2000. 9. Klyuev, N.A. and Bordskii, E.S., Polychlorinated Biphenyls Detection in the Environment and Biota, in Polikhlorirovannye bifenily. Supertoksikanty XXI veka (Polychlorinated Biphenyls. Supertoxins of 21st Cen tury), Moscow, 2000, issue 5. MOSCOW UNIVERSITY SOIL SCIENCE BULLETIN

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