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Railway transportation as a source of soil pollution
Transportation Research Part D 57 (2017) 124–129
Contents lists available at ScienceDirect
Transportation Research Part D journal homepage: www.elsevier.com/locate/trd
Railway transportation as a source of soil pollution a,⁎
a
Natasa Stojic , Mira Pucarevic , Gordan Stojic a b
MARK
b
Faculty for Environmental Protection, University Educons, Vojvode Putnika 87, 21208 Sremska Kamenica, Serbia Faculty of Technical Sciences, University of Novi Sad, Trg Dositeja Obradovića 6, 21000 Novi Sad, Serbia
AR TI CLE I NF O
AB S T R A CT
Keywords: Environment Heavy metals PCB Pollution Railway
Surface soil (0–10 cm) samples from 60 sampling sites along the length of railway tracks on the territory of Srem (the western part of the Autonomous Province of Vojvodina, itself part of Serbia) were collected and analyzed for seven polychlorinated biphenyls (PCBs) and ten heavy metals in order to see how the distance from the railroad affects the concentration of some organic and inorganic pollutants in the soil. Samples were taken at a distance of 0.03–4.19 km from the railway. For the soil extraction was used USEPA 3540S method. The extracts were purified on a silica-gel column (USEPA 3630C). The analysis of the extracts was performed by gas chromatography with tandem mass spectrometry. PCBs were not detected only at two locations. Mean total concentration of PCBs for all other sampling locations was 0.0043 ppm dry weight (dw) with a range of 0.0005–0.0227 ppm dw. According to values of Nemerow pollution index Cu, Co, Zn and Ni were the most ubiquitous heavy metals in the area near railroad. Based on these results, it can be said that railway transport is a potential source of PCBs and some heavy metals.
1. Introduction Soil is one of the most important natural resources. It is the reason we are able to sustain ourselves. But, unfortunately, the pollution of soil is a common thing these days. In recent years scientific workers draw attention to a series of restrictive factors that threaten the quality of soil such as degradation of chemical, physical and biological properties of soil (De Haan, 1987; Baumhardt et al., 2015). If the degradation of soil does not get adequate attention, especially when we talk about contamination with heavy metals, pesticides and other organic pollutants, might come to the occurrence of so-called “chemical time bomb”. Polychlorinated biphenyls (PCBs) belong to the group of chemicals of concern because they persist in soil and sediment for decades, perhaps centuries, and are locked away in the fatty tissues of animals (Webster et al., 2013), building up in food webs. There are a variety of potential PCB sources in addition to more commonly recognized sources such as electrical transformer and capacitor oils and fluorescent light ballasts (Martínez et al., 2005). PCBs were released (both accidentally and intentionally) into the atmosphere, water, and land through sewers, smokestacks, stormwater runoff, spills, and direct application to the environment. Large volumes of PCBs have been introduced to the environment through the burning of PCB-containing products, vaporization from PCBcontaining coatings and materials, releases into sewers and streams, improper disposal of PCB-containing equipment in non-secure landfill sites and municipal disposal facilities, and by other routes (such as ocean dumping) (ATSDR, 2001). The current primary sources of PCB contamination are limited to outdated or illegal landfills and scrap yards and leaks or explosions of electrical equipment and other equipment (such as locomotive transformers) that may still contain PCBs (ATSDR, 2001). According to NIP (national implementation plan) (NIP, 2015), public company Railways of Serbia in 2015th year possessed 110 capacitors and 491
⁎
Corresponding author. E-mail address: [email protected] (N. Stojic).
http://dx.doi.org/10.1016/j.trd.2017.09.024
1361-9209/ © 2017 Elsevier Ltd. All rights reserved.
Transportation Research Part D 57 (2017) 124–129
N. Stojic et al.
transformers based on PCB fluid, whereby the 3.6% of the transformers have been identified as contaminated (> 50 ppm of PCBs). Therefore it is assumed that railroad can be a source of polychlorinated biphenyls, which were used in transformers, capacitors and electric locomotives. The question is are there PCBs accumulated in the soils in the vicinity of railway lines? Are the soils beyond 1000 m away from the railroad also polluted by PCBs? Are there other pollutants, for example, heavy metals (Jian-Hua et al., 2009), accumulated in the soils on railroad? In this article, railroad sections in Srem district of Vojvodina, part of Serbian Railroad, were chosen as the study section. The length of the sampling section was extended to 4 km from the railroad. The aims of the study were to investigate the combined pollution of PCBs and heavy metals in the railroad-side soils. 2. Materials and methods 2.1. Study area The study area is in the northwest of Serbia with temperate continental climate with clear alternation of the seasons. The average temperature is about 10.9 °C and the mean relative humidity is about 75.5%. The study sections, located between Stara Pazova–Novi Sad and Stara Pazova-Ruma-Sremska Mitrovica, were constructed about 130 years ago. Sections were used for passenger and cargo traffic. The area around the sampling section was used mainly for the cultivation of corn but there were also present farmlands with cabbage, soybean, sunflower, wheat, sugar beet, vegetables and alfalfa. There were no industrial objects near sampling area. Some physical and chemical properties of the sampled soils were: pH about 7.1; percent of humus about 2.9%; average percentage of carbonates 2.93%; average of total nitrogen was 0.21% and 32.9% of phosphates. Samples were chernozem and meadow black soil types mainly used as arable land but there are also a couple of neglected lands and one meadow. Average height of the railroad bed compared to the surrounding farmland was about 2 m. 2.2. Soil sampling To review the content of hazardous and harmful substances in the soils near the railway tracks in the area of Srem, 60 soil samples were collected. Soil samples were taken in disturbed state under the provisions of the System soil fertility control, with agrochemical probe to a depth of 30 cm, on a circular control plots. Various geomorphological types, actually, lower systematic units of the soil, as well as different forms of land use, were covered during sampling. 2.3. Method The sampled soils were tested for the presence of the following PCB congeners: Bal 28, Bal 52, Bal 101, Bal 118, Bal 138, Bal 153 and Bal 180, and heavy metals: Cu, Zn, Mn, Pb, Co, Cr, Ni, Cd, As and Hg. 2.3.1. Polychlorinated byphenils Samples were taken from a depth of 0–30 cm. The sample area was created from twenty subsamples taken properly distributed from defined areas. The soil was dry at room temperature, stones and the remains of vegetation were removed and then the soil was ground up and stored until analysis in sealed cardboard boxes. The Soxhlet extraction (United States Environmental Protection Agency - USEPA 3540C) was used, then the extracts were purified on a silica-gel column (USEPA 3630C). The analysis of the extracts was performed by gas chromatography with tandem mass spectrometry, using the device 1300 Thermo Scientific Trace ISQ with automatic injector AI 1310, on a HP-5-MS column (30 m × 0.25 mm × 25 μm). The method of selected ion monitoring (SIM) was used for detection of congeners. The working conditions of the mass spectrometer and temperature mode of the column were described in previous published paper (Stojić et al., 2014). 2.3.2. Heavy metals Total content of trace elements and heavy metals Cu, Zn, Mn, Pb, Co, Cr, Ni, Cd, As and Hg in soil extract with concentrated HNO3, was determined using inductively coupled plasma ICP-OES VistaPro Varian, while the content of Fe was determined by AAS. 3. Results and discussion 3.1. Concentrations of PCBs in soil Fig. 1 shows the concentrations of PCBs in the soil samples. There were only three samples with concentrations od sum of PCBs higher than 0.02 ppm which is limit value defined by the Soil Regulation in Serbia (Official Gazette of RS 88/2010). These are two samples taken near the railway line in the municipality of Ruma and third sampled in the municipality of Šabac. All three samples were sampled at a distance up to 1 km from the railway track. At this distance, there were four more samples with a total PCBs concentration between 0.005 and 0.02 ppm. In the other twelve samples, from this distance group, PCBs concentration was below 0.005 ppm. Thirty-two soil samples were taken at a distance from 1 to 4 km of railroad. In seven of those samples concentration of PCBs was in the range between 0.005 and 0.02 ppm. In all other samples PCBs concentration was lower. Nearly the same was the situation with 125
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Fig. 1. Study area with concentrations of PCBs.
a group of samples taken at a distance of over 4 km. Only in 22% of the soil samples the concentration of PCBs was in the range between 0.005 and 0.02 ppm. In all other samples the concentration was lower than 0.005 ppm. Due to the small number of samples with increased concentration of PCBs, sampling area was thoroughly analyzed. One of those samples was taken at industrial area in Ruma. In the industrial zone are located around 15 facilities involved in the production and trade of auto tires, pneumatics, plumbing pipes, PVC pipes, mattress… So, it can be assumed that there is relatively big impact from the industry on the quality of the soil in that area. Highway is about 15 km away from sampling area, so it is not expected to affect the concentration of PCBs. Second soil sample with 0.02 ppm of total PCBs was taken at the area which was on 2.5 km from highway and there were no landfills and industrial facilities near. Therefore it can be concluded that the greatest impact on the soil quality has a railway transport. Third sample with a total PCBs concentration over 0.02 ppm lies between the railway line and the highway, therefore, we can expect a mutual influence on soil contamination with organic and inorganic pollutants. 3.2. Concentrations of heavy metals in soil Research results of heavy metals are shown in Table 1. The concentrations of Co and Ni at almost all sampling sites were elevated compared to the maximum allowable concentration - MAC (according to national regulations - Official Gazette of RS 88/2010). Increased concentrations of Cu and Zn occurred only in samples up to 1 km indicating the obvious impact of railroad traffic on the accumulation of those metals in the soil near railroad (Fig. 2). For the construction and maintenance of thresholds, rails and crossovers there are standards issued by the competent ministry in the field of transport. In the last decade, these standards are harmonized with the EU directives and the standards are approved by the competent state institution (ministerial) for environmental protection. But in the previous period, on the observed railroads were built-in the wooden sleepers. Only on railways of international significance in the last decade the wooden sleepers were replaced by sleepers made of pre-stressed reinforced concrete. Wooden sleepers are made of oak and beech wood. The impregnation process is used to extend the lifetime of sleepers. During the impregnation antiseptic agents are imprinted in the wood cells with the intention of preventing the development of fungus, thereby preventing rotting and at the same time preventing the insect's harmful activity. There are two types of antiseptics: water-soluble and insoluble in water. The most commonly used water-soluble antiseptics are zinc chloride with copper and chromium salts and a salt mixture according to Volman. Volman's salts consist of sodium fluoride, sodium chloride, sodium arsenate and dinitrophenol. Bearing this in mind, the assumption is that the increased concentration of Zn and Cu next to the railway line is the result of the process of impregnation of the wood sleepers. On the contrary, the concentrations of Mn, As, Cr and Fe at all the soil samples were lower than MAC. Cd and Pb were increased only at one soil sample taken at the distance up to 1 km. The% CVs of Cu, Ni, Cd and Zn in the samples that were closer to the railroad was higher than in those who were sampled at a distance greater than 1 km. To remove the possibility of occurrence of this result because of different sample numbers the average coefficient of variations (ACV) of these elements was calculated and presented in Table 1. The results showed that Cu, Zn, Ni and Pb, in that order, varied greatly along the railroad. This result leads us to the conclusion that the concentration of Cu, Zn, Ni and Pb in soil 126
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Table 1 Descriptive statistics of metal concentrations by the distance of the soil samples from the railroad (mg kg−1). Distance (km)
Cu
Co
Mn
As
Cr
Ni
Cd
Pb
Zn
Fe
0–0.5
MIN MAX AVERAGE CV%
8.73 215.7 41.46 133.3
4.82 18.13 12.79 30.28
223.99 977.84 549.48 36.45
2.99 9.08 7.00 28.36
10.32 64.26 36.46 37.45
14.16 115.5 48.99 51.21
0.08 0.74 0.38 41.49
12.91 36.44 24.16 32.81
12.69 191.4 61.27 70.46
20,610 33,250 26,133 13.72
0.5–1
MIN MAX AVERAGE CV%
14.41 50.66 27.59 42.06
6.93 20.49 12.58 35.25
253.34 1041.2 544.05 41.36
2.62 9.66 7.13 27.30
20.58 49.77 34.19 33.36
23.91 82.35 44.13 46.99
0.26 0.88 0.47 50.43
16.63 48.08 26.76 41.74
34.04 147.2 77.79 77.71
16,005 27,970 23924.3 16.41
1–2
MIN MAX AVERAGE CV%
18.49 63.85 27.85 45.19
9.94 17.42 12.93 14.64
498.26 1023.7 651.83 22.24
6.23 9.67 8.30 11.84
23.34 53.69 33.49 22.38
30.12 61.02 42.15 24.21
0.29 0.58 0.40 17.36
17.79 95.71 27.30 66.29
36.12 129.08 63.24 35.92
19,170 34,245 26073.8 14.61
2–3
MIN MAX AVERAGE CV%
2.83 32.49 21.83 30.81
4.56 24.13 13.69 33.93
147.50 1464.5 621.94 52.33
1.76 11.22 7.57 34.14
9.19 80.76 37.48 41.05
9.70 119.2 49.50 48.80
0.05 0.54 0.38 33.48
10.69 31.80 22.80 25.38
5.85 80.82 55.30 36.44
22,585 31,250 26,250 9.13
>3
MIN MAX AVERAGE CV% ACV%
17.06 28.28 21.79 20.91 60.35
9.47 18.26 12.99 26.67 26.71
399.32 809.72 572.94 26.21 31.57
5.26 9.65 7.44 19.77 21.82
23.70 67.30 41.38 41.64 33.71
30.68 90.02 53.62 41.37 40.94
0.26 0.52 0.39 23.14 33.10
15.54 25.69 21.02 16.55 39.35
34.32 73.87 50.79 31.45 53.89
22730.0 29845.0 27058.7 9.51 13.56
Average ĐŽŶĐeŶƚraƟŽŶ (mg kg-1)
V - Coefficient of variation, ACV - average coefficient of variations.
70
Cu
60
Zn
50 40 30 20 10 0
1
2
3
4
Distance (km) Fig. 2. Concentration of Cu and Zn depending on the distance from the railroad.
is probably most associated with human activities along the railroad. Data on concentrations of heavy metals were also analyzed using analysis of variance (ANOVA). The results obtained by ANOVA showed that, for the significance level of 0.05 (α = 0.05), p-value is less than α, so the hypothesis of independence of concentration of heavy metals and distance from the railway (H0) can be rejected, which means that the concentration of heavy metals in the soil changes depending on the distance from the railroad. 3.3. Evaluation of degree of pollution Pollution index can be calculated according to Eq. (1):
Pi = Ci/ Cref
(1)
Pi is the single pollution index, Ci is the measured contamination value of heavy metal i and Cref indicates the evaluation criteria values (Official Gazette of RS 88/2010). The adopted evaluation criteria for this study were the recommended values for soil by the Ministry of Agriculture and Environmental Protection of Serbia. According to Pi values, we can determine which type of heavy metal has been excessively more in all monitored areas, and to define what are the most serious pollutants depending on the distance from the railroad. The evaluation grading standards (Hong-gui et al., 2012) of the single pollution index method are shown in Table 2. The results show that Cu, Co and Ni are the most ubiquitous heavy metals in the area near railroad. Pollution of the soil with Cu is the most visible at the distance smaller than 1 km (see Table 3). On the other hand, Co and Ni have the same pollution index at all sampling areas so it can be assumed that the railway is not the 127
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N. Stojic et al.
Table 2 The evaluation grading standards of the single pollution index method. Sub index
Pi < 1
1 ≤ Pi < 2
2 ≤ Pi < 3
3 ≤ Pi
Quality grade
Clean
Potential pollution
Slight pollution
Heavy pollution
Table 3 The pollution index of each heavy metal in a sampling area. Distance (km)/heavy metals
Cu
Co
Mn
As
Cr
Ni
Cd
Pb
Zn
Fe
0–1 1–2 2–3 >3
1.017 0.773 0.606 0.605
1.413 1.436 1.521 1.443
0.274 0.326 0.311 0.286
0.243 0.286 0.261 0.256
0.357 0.335 0.375 0.414
1.351 1.204 1.414 1.532
0.519 0.501 0.477 0.487
0.295 0.321 0.268 0.247
0.479 0.452 0.395 0.363
0.507 0.521 0.525 0.541
only source of heavy metals in this area and that Co and Ni are distributed at a distance of more than 1 km.
3.3.1. Nemerow pollution index The Nemerow pollution index can reflect pollution status of the surface soils by the heavy metals. The formula of Nemerow index (Pc) is shown as Eq. (2):
Pc =
(Pi )2 + (Pimax )2 2
(2)
Pi is the average value of each pollution index, Pimax is the maximum of the pollution index. According to some authors (Liu et al., 2012) the pollution level standard of Nemerow index is shown in Table 5. In accordance with the average values of Pc of the heavy metals from the sampling sites, pollution of soil near railroads with Mn, As, Cr, Cd, Pb, Zn and Fe is at the warning level. Pollutions of Cu in the soil samples distant from the railway about 0–2 km were at the light level and with increasing of distance from the railway the values of pollution index decreased (see Table 4). The Pc of Co and Ni in all soil samples were between 1 and 2 which means that all sampling sites were polluted with Co and Ni regardless of the distance from the railway. According to the Pearson’s matrix of correlation, Nemerow indices for Cu, Cd, Pb, Zn and Fe were strongly negatively related to the distances from the railroad, which indicates that railway affects the concentrations of these metals in the soil.
4. Conclusions Operations performed during the use and maintenance of trains have a relevant impact on the environment (Wierzbicka et al., 2015; Wilkomirski et al., 2012). This paper demonstrates the influence of railway on the soil quality with particular emphasis on organic pollutants like PCBs and heavy metals. In this research higher concentrations of PCBs were measured in the soil samples taken at the distance up to 1 km from the railway track. Samples with concentration higher than 0.02 ppm were taken near rail station in municipality of Ruma and Šabac. PCBs at the other samples did not exceed admissible pollution levels. The assumption is that this is a result of the activities of transhipment of goods, maintenance and washing of trains that occurs in the railway stations. Among the analyzed heavy metals, concentrations of Co and Ni were over MAC at almost all sampling sites. In the samples taken at a distances up to 1 km from railroad, concentrations of Cu, Zn, Cd and Pb were higher than those measured in soil sampled at larger distances. Nemerow index values for ten heavy metals confirm the light and medium levels of soil contamination near the railway line. Despite the fact that in most of the samples pollutants do not exceed acceptable levels of pollution (except in the case of Co and Ni), there are indications that the current amount of organic and inorganic pollutants is a potential threat to the environment, so routinely monitoring of soil in the area around the railway track and railway stations is justified. Table 5 Pollution level standard of Nemerow index. Level
Pc
Pollution level
Pollution condition
1 2 3 4 5
Pc ≤ 0.7 0.7 ≤ Pc≤1 1 ≤ Pc≤2 2 ≤ Pc≤3 3 ≤ Pc
Safety Warning Light Medium level Serious
Non-pollution Little pollution Light pollution Medium level pollution Serious pollution
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Table 4 Nemerow pollution index for ten heavy metals. Distance (km)/heavy metals
Cu
Co
Mn
As
Cr
Ni
Cd
Pb
Zn
Fe
0–1 1–2 2–3 >3
1.315 1.051 0.930 0.912
1.161 1.138 1.198 1.146
0.789 0.802 0.841 0.765
0.731 0.746 0.753 0.736
0.836 0.810 0.869 0.855
1.221 1.100 1.232 1.192
0.941 0.883 0.870 0.867
0.805 0.902 0.752 0.724
0.965 0.903 0.833 0.815
0.874 0.880 0.870 0.868
Acknowledgements The present work was supported by the Ministry of Education, Science and Technological Development of the Republic of Serbia, under the Project No. III 43004. References Agency for Toxic Substances and Disease Registry ATSDR 2001. Polychlorinated Biphenyls. < http://www.atsdr.cdc.gov/tfacts17.html > . Baumhardt, R.L., Stewart, B.A., Sainju, U.M., 2015. North American soil degradation: processes, practices, and mitigating strategies. Sustainability 7, 2936–2960. De Haan, F.A.M., 1987. Effects of Agricultural Practices on the Physical. In: In Barth, H., L’Hermite, P. (Eds.), Chemical and Biological Properties of Soils: Part III—Chemical Degradation of Soil as the Result of the Use of Mineral Fertilizers and Pesticides: Aspects of Soil Quality Evaluation, Book Title Scientific Basis for Soil Protection in the European Community. Springer, Netherlands, pp. 211–236. Hong-gui, D., Teng-feng, G., Ming-hui, L., Xu, D., 2012. Comprehensive assessment model on heavy metal pollution in soil. Int. J. Electrochem. Sci. 7, 5286–5296. Jian-Hua, M.A., Chun-Jie, C.H.U., Jian, L., Bo, S., 2009. Heavy metal pollution in soils on railroad side of Zhengzhou – Putian section of longxi-haizhou railroad, China. Pedosphere 19 (1), 121–128. Liu, J., Yinan, L., Ting, Z., 2012. The analysis and evaluation on heavy metal pollution of Topsoil in Chinese large-scale cities. Energy Procedia 16, 1084–1089. Martínez, H.A.R., Rodríguez, G.C., Castillo, D.H., 2005. Determination of PCBs in transformers oil using gas chromatography with mass spectroscopy and aroclors (A1254:A1260). J. Mex. Chem. Soc. 49 (3), 263–270. NIP, 2015. Project: Updating the National Implementation Plan for the Implementation of the Stockholm Convention on Persistent Organic Pollutants (POPs), GEF ID 5001. < http://www.eko.minpolj.gov.rs/wp-content/uploads/hemikalije/FINAL_ANIP_april_SREDJENO_05_06_2015.pdf > . Official Gazette of RS 88/2010, 2010. Regulation on the Systematic Monitoring of Soil Quality Indicators for Assessment of the Risk of Soil Degradation and Methodology for Development of Remediation Programs. < http://www.sepa.gov.rs/download/Uredba_o_programu_pracenja_kvaliteta_zemljista.pdf > . Stojić, N., Pucarević, M., Mrkajić, D., Kecojević, I., 2014. Transformers as a potential for soil contamination. Metalurgija 53 (4), 689–692. US EPA 3540C, 1996. Soxhlet Extraction. U.S. EPA, Washington DC, US. US EPA 3630C, 1996. Silica Gel Cleanup. U.S. EPA, Washington DC, US. Webster, L., Roose, P., Bersuder, P., Kotterman, M., Haarich, M., Vorkamp, K., 2013. Determination of polychlorinated biphenyls (pcbs) in sediment and biota. ICES Tech. Marine Environ. Sci. 53, 1–23. Wierzbicka, M., Bemowska-Kałabun, O., Gworek, B., 2015. Multidimensional evaluation of soil pollution from railway tracks. Ecotoxicology 24, 805–822. Wilkomirski, B., Galera, H., Sudnik-Wójcikowska, B., Staszewski, T., Malawska, M., 2012. Railway tracks—habitat conditions, contamination, floristic settlement—a review. Environ. Natl. Resour. Res. 2, 86–95.
129
Contents lists available at ScienceDirect
Transportation Research Part D journal homepage: www.elsevier.com/locate/trd
Railway transportation as a source of soil pollution a,⁎
a
Natasa Stojic , Mira Pucarevic , Gordan Stojic a b
MARK
b
Faculty for Environmental Protection, University Educons, Vojvode Putnika 87, 21208 Sremska Kamenica, Serbia Faculty of Technical Sciences, University of Novi Sad, Trg Dositeja Obradovića 6, 21000 Novi Sad, Serbia
AR TI CLE I NF O
AB S T R A CT
Keywords: Environment Heavy metals PCB Pollution Railway
Surface soil (0–10 cm) samples from 60 sampling sites along the length of railway tracks on the territory of Srem (the western part of the Autonomous Province of Vojvodina, itself part of Serbia) were collected and analyzed for seven polychlorinated biphenyls (PCBs) and ten heavy metals in order to see how the distance from the railroad affects the concentration of some organic and inorganic pollutants in the soil. Samples were taken at a distance of 0.03–4.19 km from the railway. For the soil extraction was used USEPA 3540S method. The extracts were purified on a silica-gel column (USEPA 3630C). The analysis of the extracts was performed by gas chromatography with tandem mass spectrometry. PCBs were not detected only at two locations. Mean total concentration of PCBs for all other sampling locations was 0.0043 ppm dry weight (dw) with a range of 0.0005–0.0227 ppm dw. According to values of Nemerow pollution index Cu, Co, Zn and Ni were the most ubiquitous heavy metals in the area near railroad. Based on these results, it can be said that railway transport is a potential source of PCBs and some heavy metals.
1. Introduction Soil is one of the most important natural resources. It is the reason we are able to sustain ourselves. But, unfortunately, the pollution of soil is a common thing these days. In recent years scientific workers draw attention to a series of restrictive factors that threaten the quality of soil such as degradation of chemical, physical and biological properties of soil (De Haan, 1987; Baumhardt et al., 2015). If the degradation of soil does not get adequate attention, especially when we talk about contamination with heavy metals, pesticides and other organic pollutants, might come to the occurrence of so-called “chemical time bomb”. Polychlorinated biphenyls (PCBs) belong to the group of chemicals of concern because they persist in soil and sediment for decades, perhaps centuries, and are locked away in the fatty tissues of animals (Webster et al., 2013), building up in food webs. There are a variety of potential PCB sources in addition to more commonly recognized sources such as electrical transformer and capacitor oils and fluorescent light ballasts (Martínez et al., 2005). PCBs were released (both accidentally and intentionally) into the atmosphere, water, and land through sewers, smokestacks, stormwater runoff, spills, and direct application to the environment. Large volumes of PCBs have been introduced to the environment through the burning of PCB-containing products, vaporization from PCBcontaining coatings and materials, releases into sewers and streams, improper disposal of PCB-containing equipment in non-secure landfill sites and municipal disposal facilities, and by other routes (such as ocean dumping) (ATSDR, 2001). The current primary sources of PCB contamination are limited to outdated or illegal landfills and scrap yards and leaks or explosions of electrical equipment and other equipment (such as locomotive transformers) that may still contain PCBs (ATSDR, 2001). According to NIP (national implementation plan) (NIP, 2015), public company Railways of Serbia in 2015th year possessed 110 capacitors and 491
⁎
Corresponding author. E-mail address: [email protected] (N. Stojic).
http://dx.doi.org/10.1016/j.trd.2017.09.024
1361-9209/ © 2017 Elsevier Ltd. All rights reserved.
Transportation Research Part D 57 (2017) 124–129
N. Stojic et al.
transformers based on PCB fluid, whereby the 3.6% of the transformers have been identified as contaminated (> 50 ppm of PCBs). Therefore it is assumed that railroad can be a source of polychlorinated biphenyls, which were used in transformers, capacitors and electric locomotives. The question is are there PCBs accumulated in the soils in the vicinity of railway lines? Are the soils beyond 1000 m away from the railroad also polluted by PCBs? Are there other pollutants, for example, heavy metals (Jian-Hua et al., 2009), accumulated in the soils on railroad? In this article, railroad sections in Srem district of Vojvodina, part of Serbian Railroad, were chosen as the study section. The length of the sampling section was extended to 4 km from the railroad. The aims of the study were to investigate the combined pollution of PCBs and heavy metals in the railroad-side soils. 2. Materials and methods 2.1. Study area The study area is in the northwest of Serbia with temperate continental climate with clear alternation of the seasons. The average temperature is about 10.9 °C and the mean relative humidity is about 75.5%. The study sections, located between Stara Pazova–Novi Sad and Stara Pazova-Ruma-Sremska Mitrovica, were constructed about 130 years ago. Sections were used for passenger and cargo traffic. The area around the sampling section was used mainly for the cultivation of corn but there were also present farmlands with cabbage, soybean, sunflower, wheat, sugar beet, vegetables and alfalfa. There were no industrial objects near sampling area. Some physical and chemical properties of the sampled soils were: pH about 7.1; percent of humus about 2.9%; average percentage of carbonates 2.93%; average of total nitrogen was 0.21% and 32.9% of phosphates. Samples were chernozem and meadow black soil types mainly used as arable land but there are also a couple of neglected lands and one meadow. Average height of the railroad bed compared to the surrounding farmland was about 2 m. 2.2. Soil sampling To review the content of hazardous and harmful substances in the soils near the railway tracks in the area of Srem, 60 soil samples were collected. Soil samples were taken in disturbed state under the provisions of the System soil fertility control, with agrochemical probe to a depth of 30 cm, on a circular control plots. Various geomorphological types, actually, lower systematic units of the soil, as well as different forms of land use, were covered during sampling. 2.3. Method The sampled soils were tested for the presence of the following PCB congeners: Bal 28, Bal 52, Bal 101, Bal 118, Bal 138, Bal 153 and Bal 180, and heavy metals: Cu, Zn, Mn, Pb, Co, Cr, Ni, Cd, As and Hg. 2.3.1. Polychlorinated byphenils Samples were taken from a depth of 0–30 cm. The sample area was created from twenty subsamples taken properly distributed from defined areas. The soil was dry at room temperature, stones and the remains of vegetation were removed and then the soil was ground up and stored until analysis in sealed cardboard boxes. The Soxhlet extraction (United States Environmental Protection Agency - USEPA 3540C) was used, then the extracts were purified on a silica-gel column (USEPA 3630C). The analysis of the extracts was performed by gas chromatography with tandem mass spectrometry, using the device 1300 Thermo Scientific Trace ISQ with automatic injector AI 1310, on a HP-5-MS column (30 m × 0.25 mm × 25 μm). The method of selected ion monitoring (SIM) was used for detection of congeners. The working conditions of the mass spectrometer and temperature mode of the column were described in previous published paper (Stojić et al., 2014). 2.3.2. Heavy metals Total content of trace elements and heavy metals Cu, Zn, Mn, Pb, Co, Cr, Ni, Cd, As and Hg in soil extract with concentrated HNO3, was determined using inductively coupled plasma ICP-OES VistaPro Varian, while the content of Fe was determined by AAS. 3. Results and discussion 3.1. Concentrations of PCBs in soil Fig. 1 shows the concentrations of PCBs in the soil samples. There were only three samples with concentrations od sum of PCBs higher than 0.02 ppm which is limit value defined by the Soil Regulation in Serbia (Official Gazette of RS 88/2010). These are two samples taken near the railway line in the municipality of Ruma and third sampled in the municipality of Šabac. All three samples were sampled at a distance up to 1 km from the railway track. At this distance, there were four more samples with a total PCBs concentration between 0.005 and 0.02 ppm. In the other twelve samples, from this distance group, PCBs concentration was below 0.005 ppm. Thirty-two soil samples were taken at a distance from 1 to 4 km of railroad. In seven of those samples concentration of PCBs was in the range between 0.005 and 0.02 ppm. In all other samples PCBs concentration was lower. Nearly the same was the situation with 125
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Fig. 1. Study area with concentrations of PCBs.
a group of samples taken at a distance of over 4 km. Only in 22% of the soil samples the concentration of PCBs was in the range between 0.005 and 0.02 ppm. In all other samples the concentration was lower than 0.005 ppm. Due to the small number of samples with increased concentration of PCBs, sampling area was thoroughly analyzed. One of those samples was taken at industrial area in Ruma. In the industrial zone are located around 15 facilities involved in the production and trade of auto tires, pneumatics, plumbing pipes, PVC pipes, mattress… So, it can be assumed that there is relatively big impact from the industry on the quality of the soil in that area. Highway is about 15 km away from sampling area, so it is not expected to affect the concentration of PCBs. Second soil sample with 0.02 ppm of total PCBs was taken at the area which was on 2.5 km from highway and there were no landfills and industrial facilities near. Therefore it can be concluded that the greatest impact on the soil quality has a railway transport. Third sample with a total PCBs concentration over 0.02 ppm lies between the railway line and the highway, therefore, we can expect a mutual influence on soil contamination with organic and inorganic pollutants. 3.2. Concentrations of heavy metals in soil Research results of heavy metals are shown in Table 1. The concentrations of Co and Ni at almost all sampling sites were elevated compared to the maximum allowable concentration - MAC (according to national regulations - Official Gazette of RS 88/2010). Increased concentrations of Cu and Zn occurred only in samples up to 1 km indicating the obvious impact of railroad traffic on the accumulation of those metals in the soil near railroad (Fig. 2). For the construction and maintenance of thresholds, rails and crossovers there are standards issued by the competent ministry in the field of transport. In the last decade, these standards are harmonized with the EU directives and the standards are approved by the competent state institution (ministerial) for environmental protection. But in the previous period, on the observed railroads were built-in the wooden sleepers. Only on railways of international significance in the last decade the wooden sleepers were replaced by sleepers made of pre-stressed reinforced concrete. Wooden sleepers are made of oak and beech wood. The impregnation process is used to extend the lifetime of sleepers. During the impregnation antiseptic agents are imprinted in the wood cells with the intention of preventing the development of fungus, thereby preventing rotting and at the same time preventing the insect's harmful activity. There are two types of antiseptics: water-soluble and insoluble in water. The most commonly used water-soluble antiseptics are zinc chloride with copper and chromium salts and a salt mixture according to Volman. Volman's salts consist of sodium fluoride, sodium chloride, sodium arsenate and dinitrophenol. Bearing this in mind, the assumption is that the increased concentration of Zn and Cu next to the railway line is the result of the process of impregnation of the wood sleepers. On the contrary, the concentrations of Mn, As, Cr and Fe at all the soil samples were lower than MAC. Cd and Pb were increased only at one soil sample taken at the distance up to 1 km. The% CVs of Cu, Ni, Cd and Zn in the samples that were closer to the railroad was higher than in those who were sampled at a distance greater than 1 km. To remove the possibility of occurrence of this result because of different sample numbers the average coefficient of variations (ACV) of these elements was calculated and presented in Table 1. The results showed that Cu, Zn, Ni and Pb, in that order, varied greatly along the railroad. This result leads us to the conclusion that the concentration of Cu, Zn, Ni and Pb in soil 126
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Table 1 Descriptive statistics of metal concentrations by the distance of the soil samples from the railroad (mg kg−1). Distance (km)
Cu
Co
Mn
As
Cr
Ni
Cd
Pb
Zn
Fe
0–0.5
MIN MAX AVERAGE CV%
8.73 215.7 41.46 133.3
4.82 18.13 12.79 30.28
223.99 977.84 549.48 36.45
2.99 9.08 7.00 28.36
10.32 64.26 36.46 37.45
14.16 115.5 48.99 51.21
0.08 0.74 0.38 41.49
12.91 36.44 24.16 32.81
12.69 191.4 61.27 70.46
20,610 33,250 26,133 13.72
0.5–1
MIN MAX AVERAGE CV%
14.41 50.66 27.59 42.06
6.93 20.49 12.58 35.25
253.34 1041.2 544.05 41.36
2.62 9.66 7.13 27.30
20.58 49.77 34.19 33.36
23.91 82.35 44.13 46.99
0.26 0.88 0.47 50.43
16.63 48.08 26.76 41.74
34.04 147.2 77.79 77.71
16,005 27,970 23924.3 16.41
1–2
MIN MAX AVERAGE CV%
18.49 63.85 27.85 45.19
9.94 17.42 12.93 14.64
498.26 1023.7 651.83 22.24
6.23 9.67 8.30 11.84
23.34 53.69 33.49 22.38
30.12 61.02 42.15 24.21
0.29 0.58 0.40 17.36
17.79 95.71 27.30 66.29
36.12 129.08 63.24 35.92
19,170 34,245 26073.8 14.61
2–3
MIN MAX AVERAGE CV%
2.83 32.49 21.83 30.81
4.56 24.13 13.69 33.93
147.50 1464.5 621.94 52.33
1.76 11.22 7.57 34.14
9.19 80.76 37.48 41.05
9.70 119.2 49.50 48.80
0.05 0.54 0.38 33.48
10.69 31.80 22.80 25.38
5.85 80.82 55.30 36.44
22,585 31,250 26,250 9.13
>3
MIN MAX AVERAGE CV% ACV%
17.06 28.28 21.79 20.91 60.35
9.47 18.26 12.99 26.67 26.71
399.32 809.72 572.94 26.21 31.57
5.26 9.65 7.44 19.77 21.82
23.70 67.30 41.38 41.64 33.71
30.68 90.02 53.62 41.37 40.94
0.26 0.52 0.39 23.14 33.10
15.54 25.69 21.02 16.55 39.35
34.32 73.87 50.79 31.45 53.89
22730.0 29845.0 27058.7 9.51 13.56
Average ĐŽŶĐeŶƚraƟŽŶ (mg kg-1)
V - Coefficient of variation, ACV - average coefficient of variations.
70
Cu
60
Zn
50 40 30 20 10 0
1
2
3
4
Distance (km) Fig. 2. Concentration of Cu and Zn depending on the distance from the railroad.
is probably most associated with human activities along the railroad. Data on concentrations of heavy metals were also analyzed using analysis of variance (ANOVA). The results obtained by ANOVA showed that, for the significance level of 0.05 (α = 0.05), p-value is less than α, so the hypothesis of independence of concentration of heavy metals and distance from the railway (H0) can be rejected, which means that the concentration of heavy metals in the soil changes depending on the distance from the railroad. 3.3. Evaluation of degree of pollution Pollution index can be calculated according to Eq. (1):
Pi = Ci/ Cref
(1)
Pi is the single pollution index, Ci is the measured contamination value of heavy metal i and Cref indicates the evaluation criteria values (Official Gazette of RS 88/2010). The adopted evaluation criteria for this study were the recommended values for soil by the Ministry of Agriculture and Environmental Protection of Serbia. According to Pi values, we can determine which type of heavy metal has been excessively more in all monitored areas, and to define what are the most serious pollutants depending on the distance from the railroad. The evaluation grading standards (Hong-gui et al., 2012) of the single pollution index method are shown in Table 2. The results show that Cu, Co and Ni are the most ubiquitous heavy metals in the area near railroad. Pollution of the soil with Cu is the most visible at the distance smaller than 1 km (see Table 3). On the other hand, Co and Ni have the same pollution index at all sampling areas so it can be assumed that the railway is not the 127
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Table 2 The evaluation grading standards of the single pollution index method. Sub index
Pi < 1
1 ≤ Pi < 2
2 ≤ Pi < 3
3 ≤ Pi
Quality grade
Clean
Potential pollution
Slight pollution
Heavy pollution
Table 3 The pollution index of each heavy metal in a sampling area. Distance (km)/heavy metals
Cu
Co
Mn
As
Cr
Ni
Cd
Pb
Zn
Fe
0–1 1–2 2–3 >3
1.017 0.773 0.606 0.605
1.413 1.436 1.521 1.443
0.274 0.326 0.311 0.286
0.243 0.286 0.261 0.256
0.357 0.335 0.375 0.414
1.351 1.204 1.414 1.532
0.519 0.501 0.477 0.487
0.295 0.321 0.268 0.247
0.479 0.452 0.395 0.363
0.507 0.521 0.525 0.541
only source of heavy metals in this area and that Co and Ni are distributed at a distance of more than 1 km.
3.3.1. Nemerow pollution index The Nemerow pollution index can reflect pollution status of the surface soils by the heavy metals. The formula of Nemerow index (Pc) is shown as Eq. (2):
Pc =
(Pi )2 + (Pimax )2 2
(2)
Pi is the average value of each pollution index, Pimax is the maximum of the pollution index. According to some authors (Liu et al., 2012) the pollution level standard of Nemerow index is shown in Table 5. In accordance with the average values of Pc of the heavy metals from the sampling sites, pollution of soil near railroads with Mn, As, Cr, Cd, Pb, Zn and Fe is at the warning level. Pollutions of Cu in the soil samples distant from the railway about 0–2 km were at the light level and with increasing of distance from the railway the values of pollution index decreased (see Table 4). The Pc of Co and Ni in all soil samples were between 1 and 2 which means that all sampling sites were polluted with Co and Ni regardless of the distance from the railway. According to the Pearson’s matrix of correlation, Nemerow indices for Cu, Cd, Pb, Zn and Fe were strongly negatively related to the distances from the railroad, which indicates that railway affects the concentrations of these metals in the soil.
4. Conclusions Operations performed during the use and maintenance of trains have a relevant impact on the environment (Wierzbicka et al., 2015; Wilkomirski et al., 2012). This paper demonstrates the influence of railway on the soil quality with particular emphasis on organic pollutants like PCBs and heavy metals. In this research higher concentrations of PCBs were measured in the soil samples taken at the distance up to 1 km from the railway track. Samples with concentration higher than 0.02 ppm were taken near rail station in municipality of Ruma and Šabac. PCBs at the other samples did not exceed admissible pollution levels. The assumption is that this is a result of the activities of transhipment of goods, maintenance and washing of trains that occurs in the railway stations. Among the analyzed heavy metals, concentrations of Co and Ni were over MAC at almost all sampling sites. In the samples taken at a distances up to 1 km from railroad, concentrations of Cu, Zn, Cd and Pb were higher than those measured in soil sampled at larger distances. Nemerow index values for ten heavy metals confirm the light and medium levels of soil contamination near the railway line. Despite the fact that in most of the samples pollutants do not exceed acceptable levels of pollution (except in the case of Co and Ni), there are indications that the current amount of organic and inorganic pollutants is a potential threat to the environment, so routinely monitoring of soil in the area around the railway track and railway stations is justified. Table 5 Pollution level standard of Nemerow index. Level
Pc
Pollution level
Pollution condition
1 2 3 4 5
Pc ≤ 0.7 0.7 ≤ Pc≤1 1 ≤ Pc≤2 2 ≤ Pc≤3 3 ≤ Pc
Safety Warning Light Medium level Serious
Non-pollution Little pollution Light pollution Medium level pollution Serious pollution
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Table 4 Nemerow pollution index for ten heavy metals. Distance (km)/heavy metals
Cu
Co
Mn
As
Cr
Ni
Cd
Pb
Zn
Fe
0–1 1–2 2–3 >3
1.315 1.051 0.930 0.912
1.161 1.138 1.198 1.146
0.789 0.802 0.841 0.765
0.731 0.746 0.753 0.736
0.836 0.810 0.869 0.855
1.221 1.100 1.232 1.192
0.941 0.883 0.870 0.867
0.805 0.902 0.752 0.724
0.965 0.903 0.833 0.815
0.874 0.880 0.870 0.868
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