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Influence of Lignite Mining and Utilization on Organic Matter Budget in the Alfeios River Plain, Peloponnese (South Greece) G. Siavalas,† S. Kalaitzidis,† G. Cornelissen,‡ A. Chatziapostolou,† and K. Christanis*,† Department of Geology, UniVersity of Patras, 26500 Rio-Patras, Greece, and Norwegian Geotechnical Institute, P.O. Box 3930 UlleVål, 0806 Oslo, Norway ReceiVed March 13, 2007. ReVised Manuscript ReceiVed June 9, 2007
The Megalopolis Lignite Centre (MLC) is a lignite mining and power generation complex located in Southern Greece. In the present study, we investigate the influence of mining and combustion activities on the organic matter (OM) budget of the adjacent Alfeios River plain sediments. A total of 28 plain-sediment samples along with 13 lignite and ash samples from the MLC were collected. The sediment samples were collected from sites upstream and downstream, as well as from the vicinity of the MLC. Their OM and total organic carbon contents range from 0.9 to 43.4 and 0.2 to 24.0 wt %, respectively. The particulate OM was classified in coal-derived, carbonized particles and fresh tissues according to its origin. The different OM phases were quantified using maceral analysis on the sediments’ light fraction obtained after heavy media separations. Approximately 75 vol % of the OM was of anthropogenic origin (coal and char particles) related to mining, transport, and combustion processes at the MLC, revealing a high contamination degree. The most contaminated sites were those in the vicinity of the MLC, but upstream and downstream sites also proved to contain high concentrations of anthropogenic OM. The polycyclic aromatic hydrocarbons content of the same sediments was very low, similar to pristine areas indicating that there is no contamination from such compounds in the area.
1. Introduction The organic matter in soils and recent sediments is a complex heterogeneous mixture, consisting of compounds of diverse origin, that are distinguished in two main groups: the natural organic matter derived from the alteration of biomass during sedimentation, as well as the anthropogenic organic matter (AOM) consisting of unburned fossil-fuel particles, chars, soots, oil, surfactants, etc.1-4 The anthropogenic organic matter can be further distinguished into (a) the dissolved organic matter, which is the part diluted in surface waters, transported until deposition, and mixed with soils and sediments, and (b) the insoluble organic matter, which comprises the particulate phase.5 Coal exploitation is one of the major human activities that affect the diffusion of organic particles in soils and sediments neighboring with power generation facilities. Mining, transport, and stockpiling of coal render it susceptible to wind and surface water erosion. These processes result in the transport and deposition of coal-derived particles in recent sediments. Com* Corresponding author. Tel.: +30 2610 997568. Fax: +30 2610 997560. E-mail:
[email protected]. † University of Patras. ‡ Norwegian Geotechnical Institute. (1) Grathwohl, P. EnViron. Sci. Technol. 1990, 24, 1687-1693. (2) Luthy, R. G.; Aiken, G. R.; Brusseau, M. L.; Cunningham, S. D.; Gschwend, P. M.; Pignatello, J. J.; Reinhard, M.; Traina, S. J.; Weber, W. J.; Westall, J. C. EnViron. Sci. Technol. 1997, 31, 3341-3347. (3) Cornelissen, G.; Gustafsson, O ¨ .; Buchelli, T. D.; Jonker, M. T. O.; Koelmans, A. A.; van Noort, P. C. M. EnViron. Sci. Technol. 2005, 39, 6881-6895. (4) Oen, A. M. P. Sequestration and bioavailability of native polycyclic aromatic hydrocarbons in harbour sediments. Ph.D. Thesis, Faculty of Mathematics and Natural Sciences, University of Oslo, Oslo, Norway, 2006; p 52. (5) Faure, P.; Elie, M.; Mansuy, L.; Michels, R.; Landais, P.; Babut, M. Org. Geochem. 2004, 35, 109-122.
bustion for power generation contributes to the emission of anthropogenic organic matter in the environment as it produces large amounts of solid wastes, generally known by the term “ash”. Ash can be distinguished into two categories: (i) bottom ash or slag, which remains in the combustion chamber, and (ii) fly ash that includes fine-grained solid particles transported by the flu gases.6 Although fly ash is mainly composed of inorganic constituents, residues of organic origin may also contribute significantly. They are derived from the incomplete combustion of organic particles, generally called “chars”.7,8 The level of char in fly ash varies widely and in some power stations exceeds 5 wt %, which is the upper limit for the optimum operation of power stations.9 Existing technology reduces the stack emissions of solid particles into the environment. Nevertheless, some of them escape and are transported through air and surface waters, until certain solid compounds fall down and are deposited in soils and sediments. The disposal of the ashes in dumps may also be considered as a potential source of anthropogenic organic matter. Over the past few years, many researchers have applied various methods in order to estimate coal-derived organic particles in soils and sediments. These methods include field and stratigraphic observation,10 geochemical analyses,11-14 and (6) Swaine, D. J. In EnVironmental aspects of trace elements in coal; Swaine, D. J., Goodarzi, F., Eds.; Kluwer Academic Publ.: Dordrecht: The Netherlands, 1995; pp 204-220. (7) Griest, W. H.; Harris, L. A. Fuel 1985, 64, 821-826. (8) Taylor, G. H.; Teichmu¨ller, M.; Davis, A.; Diessel, C. F. K.; Littke, R.; Robert, P. Organic Petrology; Gebru¨der Borntraeger: Berlin, Germany, 1998; p 704. (9) Nandi, B. N.; Brown, T. D.; Lee, G. K. Fuel 1977, 56, 125-130. (10) French, P. W. EnViron. Pollut. 1998, 103, 37-43. (11) Ellenson, W. D.; Mukerjee, S.; Stevens, R. K.; Willis, R. D.; Shadwick, D. S.; Sommerville, M. C.; Lewis, R. G. EnViron. Int. 1997, 23, 643-655.
10.1021/ef070130u CCC: $37.00 © 2007 American Chemical Society Published on Web 07/25/2007
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Figure 1. Schematic geological map of the study area showing the sampling sites along the Alfeios River and its tributaries.
microscopic observation.15-18 The microscopic observation of the organic matter contained in sediments is based on the different optical features, which the organic particles reveal with dependence on their origin. Thus, microscopic observation can be a useful tool for the distinction between fresh and fossil organic matter or its combustion derivatives (char) in surface sediments. In this study, fossil fuel particles and chars are referred to as anthropogenic particles. Furthermore, the application of organic petrography techniques can lead to a quantitative approach for the presence of these particles in soils and sediments and their correlation to certain pollutants such as trace elements and/or polycyclic aromatic hydrocarbons (PAHs).16,19,20 Another interesting issue concerning the presence and origin of the organic matter in recent sediments is its relationship to certain organic pollutants with major carcinogenic properties;21 it has been shown that a specific part of insoluble organic matter, which mainly derives from combustion processes, acts as a strong sorptive phase for polycyclic aromatic hydrocarbons (12) Kruge, M. A.; Mukhopadhyay, P. K.; Lewis, C. F. M. Org. Geochem. 1998, 29, 1797-1812. (13) Rumpell, C.; Knicker, H.; Ko¨gell-Knabner, I.; Hu¨ttl, R. F. Water Air Soil Pollut. 1998, 105, 481-492. (14) Johnson, R.; Bustin, R. M. Int. J. Coal Geol. 2006, 68, 57-69. (15) Kleineidam, S. E.; Rogner, K. N.; Ligouis, B. D.; Grathwoll, P. EnViron. Sci. Technol. 1999, 33, 1637-1644. (16) Mastalerz, M.; Souch, C.; Filippeli, G. M.; Dollar, N. L.; Perkins, S. M. Int. J. Coal Geol. 2001, 46, 157-177. (17) Cornelissen, G.; Kukulska, Z.; Kalaitzidis, S.; Christanis, K.; Gustafsson, O ¨ . EnViron. Sci. Technol. 2004, 38, 3632-3640. (18) Reyes, J.; Goodarzi, F.; Sanei, H.; Stasiuk, L. D.; Duncan, W. Int. J. Coal. Geol. 2006, 65, 146-157. (19) Mukhopadhyay, P. K.; Kruge, M. A.; Lewis, C. F. M. EnViron. Geosci. 1997, 4, 137-148. (20) Kalaitzidis, S.; Christanis, K.; Cornelissen, G.; Gustafsson, O ¨ . Global NEST J. 2007, in press. (21) Flesher, J. W.; Horn, J.; Lehner, A. F. Polycycl. Aromat. Comp. 2002, 22, 379-393.
(PAHs).22-26 Furthermore, many researchers consider fossil fuel combustion for power generation one of the major sources for the release of such compounds in the environment.27-32 In the present study, the solid organic matter of the Alfeios plain sediments is characterized, with the aim to estimate the contamination of these sediments by organic particles derived from mining and combustion activities in the adjacent Megalopolis Lignite Centre. 2. Regional and Geological Setting The Alfeios River is the longest river in Peloponnese, Southern Greece, with a total length of 112 km. Its catchment occupies an area of 3600 km2 accounting for one-third of the Peloponnese peninsula. The river drains the Megalopolis Basin, which hosts the Megalopolis Lignite Centre (MLC), the second most important power installation in Greece (Figure 1). (22) Gustafsson, O ¨ .; Haghseta, K.; Chan, F.; McFarlane, A.; Gschwend, P. M. EnViron. Sci. Technol. 1997, 31, 203-209. (23) Bucheli, T. D.; Gustafsson, O ¨ . EnViron. Sci. Technol. 2000, 34, 5144-5151. (24) Xia, G.; Pignatello, J. J. EnViron. Sci. Technol. 2001, 35, 84-94. (25) Accardi-Dey, A. M.; Gschwend, P. M. EnViron. Sci. Technol. 2002, 36, 21-29. (26) Jonker, M. T. O.; Koelmans, A. A. EnViron. Sci. Technol. 2002, 36, 3725-3734. (27) Khalili, N. R.; Scheff, P. A.; Holsen, T. M. Atmos. EnViron. 1995, 29, 533-542. (28) Yunker, M. B.; Snowdon, L. R.; MacDonald, R. W.; Smith, J. N.; Fowler, M. G.; Skibo, D. N.; McLaughlin, F. A.; Danyushevskaya, A. I.; Petrova, V. I.; Ivanov, G. I. EnViron. Sci. Technol. 1996, 30, 1310-1320. (29) Yunker, M. B.; MacDonald, R. W.; Vingarzan, R.; Mitchell, R. H.; Goyette, D.; Sylvestre, S. Org. Geochem. 2002, 33, 489-515. (30) Mastral, A. M.; Calle´n, M. S. EnViron. Sci. Technol. 2000, 33, 4155-4158. (31) Zhang, Z. L.; Huang, J.; Yu, G.; Hong H. EnViron. Pollut. 2004, 130, 249-261. (32) Medeiros, P. M.; Bı´cego, M. C.; Castelao, R. M.; Del Rosso, C.; Fillman, G.; Zamboni, A. J. EnViron. Int. 2005, 31, 77-87.
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Table 1. Results of the Proximate and Ultimate Analyses of the Megalopolis Lignite and Ashes
lignite dump ash
fly ash bottom ash
a
sample #
moisturea
ashb
OMb
volatile matterb
fixed carbonb
calorific valuec
Cb
Hb
Nb
Sb
Ob
BLM1 BLM2 BLM3 AM1 AM2 AM3 AM4 FAM1 FAM2 FAM3 BAM1 BAM2 BAM3
65.0 66.2 63.8 30.7 29.2 29.3 29.7 0.2 0.2 0.5 48.5 53.1 45.5
27.0 24.7 34.6 89.1 89.5 88.8 91.9 95.5 95.7 95.5 78.7 69.4 79.3
73.0 75.3 35.4 10.9 10.5 11.2 8.2 4.5 4.3 4.5 21.3 30.6 20.7
51.1 49.5 46.5 9.8 9.2 10.9 7.3 3.8 3.5 3.6 18.4 23.9 17.7
21.9 25.8 18.9 1.1 1.3 0.3 0.8 0.7 0.8 0.9 2.9 6.7 3.0
17.0 17.9 15.7
44.7 45.3 39.0 4.9 5.3 5.1 2.4 1.9 1.7 2.9 10.7 10.7 10.3
2.9 3.0 3.7 0.8 0.5 0.7 0.4 0.1 0.1 0.1 1.4 1.4 1.2
1.7 1.6 1.6 0.2 0.1 0.1 0.1 0.1 0.1 0.3 0.3 0.6 0.3
2.4 2.3 3.0 0.4 0.3 0.4 0.9 0.6 0.7 0.5 0.3 0.3 0.4
21.3 23.1 18.1 4.6 4.3 4.9 4.3 1.8 1.7 0.7 8.6 17.6 8.5
wt %. b wt % on a dry basis. c MJ/kg on a dry basis.
The basement and the margins of the basin consist of Mesozoic limestones, dolomites, cherts, and flysch, which formed from the Upper Eocene to the Upper Oligocene. The sediments filling the basin have deposited in a tectonic graben from the Upper Pliocene until today and reflect a variety of terrestrial, fluvial, limnic, and telmatic palaeo-environments. The lignite-bearing formation was deposited in the Middle Pleistocene.33 The total thickness of the formation reaches 200 m, while the lignite layers display a maximum cumulative thickness of 45 m at the southern part of the basin.34 The extension of the deposit coincides with the areas covered by the open pit mines (Figure 1). Palaeontological data reveal that the lignite precursors were deposited in fens formed in the margins of a lake established in the central part of the basin during a warm period of the Pleistocene.35,36 In the Upper Pleistocene, the extended subsidence of the basin ceased, resulting in the establishment of fluviatile environments and the formation of the Alfeios River plain.33 The exploitation of Megalopolis lignite begun in 1969 by the Public Power Corporation (PPC) with the establishment of the MLC. Nowadays, three active open pit mines provide ca. 13.5 Mt lignite annually, which feed two power plants (Figure 1) with a total installed capacity of 850 MW. The remaining reserves are estimated approximately at 237 Mt.37 The Megalopolis lignite belongs to the mineral-rich and matrix lithotypes. It reveals high ash yields (mean: 36.7 wt %, dry basis), indicating intense clastic material influx during peat accumulation, and high sulfur contents (mean: 5.7 wt %, dry basis)34 probably due to the reduction of sulfate-rich mire waters which originated from the leaching of evaporites at greater depths. In order to reduce the SOx emissions, PPC installed a desulphurisation plant and is planning to install another one soon. 3. Materials and Methods 3.1. Sampling. Sampling included two stages: At the first stage, 13 samples from the MLC including 3 lignite samples, 3 fly ash samples, 3 slag, and 4 samples from dump ash were collected. The term “dump ash” is used in order to describe an artificial material composed of both fly and bottom ash mixed with gypsum produced from the desulphurization unit and stockpiled in external dumps. The second stage included the collection of 28 sediment samples (33) Vinken, R. Geol. Jb. 1965, 83, 97-148. (34) Sakorafa, V.; Michailidis, K. Int. J. Coal. Geol. 1997, 33, 73-91. (35) Hiltermann, H.; Lu¨ttig, G. Mitt. Int. Ver. Limnol. 1969, 17, 306314. (36) Okuda, M.; van Vugt, N.; Nakagawa, T.; Ikeya, M.; Hayashida, A.; Yasuda, Y.; Setoguchi, T. Earth Planet. Sci. Lett. 2002, 201, 143157. (37) Public Power Corporation (PPC). http://www.dei.gr/documents/ APOLOGISMOS_05. pdf (in Greek), 2006.
along the Alfeios River plain and its tributaries representing both channel and overbank deposits. The sampling sites represented sites upstream (sample nos. 9-12, 13a, 13b, 15, and 17; see Figure 1) and downstream (sample nos. 7a, 7b, 18, and 19), as well as from the vicinity of the MLC (sample nos. 1a, 1b, 1c, 2a, 2b, 3, 4a, 4b, 5, 6a, 6b, 8, 14, 16a, and 16b). From this point and on, upstream samples will be referred to as US samples, downstream samples, as DS samples, and those from the vicinity of the MLC, as VC samples. 3.2. Analytical Techniques. Proximate analysis was performed in the lignite and ash samples according to the ASTM D3174, D3175, and D3302.38-40 Ultimate analysis was performed using a C-H-N-S Carlo Erba automatic analyzer. The analyzer was calibrated using the SCP CP-1 reference material. Polished blocks were prepared from the lignite samples according to ISO 74042,41 and maceral analysis was applied on them. All sediment samples were transported to the lab, stored at +4 °C, dried at 60 °C, and sieved to pass 2 mm mesh; thereafter, the -2 mm fraction was crushed down to -500 and -250 µm grain sizes. The organic matter content was determined as weight loss after oxidation at 440 °C for 16 h.42 Total organic carbon (TOC) was measured in a C-H-N-S Carlo Erba automatic analyzer after the removal of carbonates with 1 M H2SO4-5% FeSO4. A density separation technique was applied in order to concentrate the organic matter of the sediment samples (Ø < 500 µm) and facilitate its microscopic observation. This was necessary due to the low organic matter content and the grainy nature of the samples. All samples were mixed with a ZnCl2 solution of a specific gravity of 1.8 g/cm3. The mixtures were stirred in a magnetic stirrer for 30 min and put in a supersonic bath for 10 min before they were centrifuged at 3000 rounds per min. The supernatant, accounting for the organic matter, was removed, washed with deionized water, and dried. Polished blocks were prepared from each supernatant according to ISO 7404-241 and examined under a Leica DMRX coal-petrography microscope in oil immersion under both white reflected light and blue light excitation. On each block, at least 500 macerals were determined using a Swift Prior point counter. The classification applied included the nomenclature (38) American Society for Testing and Materials (ASTM), D3174. In Annual Book of ASTM Standards, Gaseous fuels: coal and coke; Philadelphia, PA, 1989; Part 26, pp 291-294. (39) American Society for Testing and Materials (ASTM), D3175. In Annual Book of ASTM Standards, Gaseous fuels: coal and coke; Philadelphia, PA, 1989; Part 26, pp 392-395. (40) American Society for Testing and Materials (ASTM), D3302. In Annual Book of ASTM Standards, Gaseous fuels: coal and coke; Philadelphia, PA, 1989; Part 26, pp 326-332. (41) International Organization for Standardization (ISO) 7404-2. Methods for the Petrographic Analysis of Bituminous Coal and Anthracite Part 2: Method for Preparing Coal Samples; Geneva, 1985; pp 8. (42) Nelson, D. W.; Sommers, L. E. In Methods of Soil Analysis (Part 3: Chemical Methods); Sparks, D. L., Page, A. L., Helmke, P. A., Loeppert, R. H., Soltanpour, P. N., Tabatabai, M. A., Johnston, C. T., Sumner, M. E., Eds.; Soil Science Society of America Inc., American Society of Agronomy Inc.: Madison, WI, 1996; pp 961-1010.
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adopted by the International Committee for Coal and Organic Petrology,43-46 a char classification scheme,47 and a classification scheme for modern plant remnants.48 PAH determinations were performed in a Fisons FI MD800 GCMS on six selected samples (nos. 1a, 7a, 10, 12, 17, and 18) from the Alfeios plain sediments. The PAHs’ extraction was performed according to the procedures described in the work of Cornelissen and Gustafsson.49 The determined PAHs were phenanthrene (Phe), anthracene (Ant), fluoranthene (Flu), pyrene (Pyr), benzo[a]fluorene (Baf), benzo[b]fluorene (Bbf), dimethylpyrene (2Mepyr), methylpyrene (Mepyr), benzo[a]anthracene (Baa), chrysene (Chr), benzo[b]fluoranthene (Bbft), benzo[e]pyrene (BeP), benzo[a]pyrene (BaP), perylene (Per), indeno-1, 2, 3-[c, d]pyrene (Ind), and benzo[ghi]perylene (BghiP).
4. Results 4.1. Proximate and Ultimate Analyses of Lignite and Ashes. The proximate analysis (Table 1) confirms that the Megalopolis lignite is of low rank with high ash yield (28.8 wt %, on average) and a very low calorific value (mean: 16.9 MJ/ kg, on a dry basis). The volatile matter content (on a dry basis) ranges from 46.5 to 51.1 wt % (49.0 wt %, on average), and the fixed carbon, from 18.9 to 25.8 wt % (22.2 wt %, on average). The ultimate analysis of the lignite samples reveals that the carbon and nitrogen contents range from 39.0 to 45.3 and 1.6 to 1.7 wt %, respectively. The sulfur content ranges from 2.3 to 3.0 wt %. The fly and dump ash samples display on average 4.4 and 10.2 wt % OM contents, respectively. On the contrary, the OM content of the bottom ash is higher (24.2 wt %, on average) possibly due to the presence of unburned lignite. Although the amount of the produced bottom ash in MLC is far less than this of fly ash (15% vs 85%) and it does not escape through the stacks, the high OM content renders slag dumps an important source of particulate organic matter. 4.2. Organic Matter Content in the Sediments. The OM present in the Alfeios plain sediments ranges from 0.9 to 43.4 wt % (Figure 2). The highest OM contents exceeding 10% were measured in the VC samples (nos. 1a, 1b, 14, and 16b). In DS samples, the OM content displays much lower values reaching 6% in only one case (no. 7a). Even lower are the OM contents of the US samples, reaching up to 2.9% (no. 12). Proportional to the OM contents are the OC contents ranging from 0.2% to 24.0% with an average of 3.8 wt %. The OC content is higher in the VC samples with a mean of 5.6 wt %. In the DS samples, the average OC content is 3.5 wt %, while in the US samples it displays an average of 1.1 wt %. Both the OM and OC average contents are higher than those usually reported for other recent sediments worldwide.12,50-54 (43) International Committee for Coal Petrology (ICCP). International handbook of Coal Petrography, 3rd supplement to the 2nd ed.; Centre National de la Recherche Scientifique: Paris, 1993. (44) International Committee for Coal Petrography (ICCP). Fuel 1998, 77, 349-358. (45) International Committee for Coal Petrography (ICCP). Fuel 2001, 80, 459-471. (46) Sy´korova´, I.; Pickel, W.; Christanis, K.; Wolf, M.; Taylor, G. H.; Flores, D. Int. J. Coal Geol. 2005, 62, 85-106. (47) Bailey, J. G.; Tate, A.; Diessel, C. F. K.; Wall, T. F. Fuel 1990, 69, 225-239. (48) Kalaitzidis, S.; Christanis, K. In Sustaining our Peatlands, Proceedings of the 11th International Peat Congress, Quebec, Canada, 2000; Vol. 2, pp 593-603. (49) Cornelissen, G.; Gustafsson, O ¨ . EnViron. Sci. Technol. 2004, 38, 148-155. (50) Mortimer, R. J. G.; Rae, J. E. Mar. Pollut. Bull. 2000, 40, 377386. (51) Lin, S.; Hsieh, I.; Huang, K.; Wang, C. Chem. Geol. 2002, 182, 377-394.
Figure 2. Organic matter and organic carbon contents in the plain sediments of the Alfeios River.
Figure 3. Relationship between organic matter (determined after oxidation at 440 °C) vs supernatant content.
There is a significant correlation (R2 ) 0.76) between the OM content as determined by long-term oxidation with the supernatant amount of the separated sediment samples (Figure 3); this indicates that the applied density-separation technique is effective for the enrichment of organic matter in the sediment, thus facilitating the microscopic observation. 4.3. Organic Petrography. 4.3.1. Megalopolis Lignite. The maceral analysis of the Megalopolis lignite samples shows that huminite is the main maceral group with contents higher than 90 vol %. The most common macerals are attrinite and densinite (Table 2). Liptinite and inertinite display very low values (
