Environ. Sci. Technol. 2003, 37, 4569-4572
Thallium in Soils and Stream Sediments of a Zn-Pb Mining and Smelting Area JOZEF LIS,† ANNA PASIECZNA,† BOZENA KARBOWSKA,‡ WLODZIMIERZ ZEMBRZUSKI,‡ AND Z E N O N L U K A S Z E W S K I * ,‡ Polish Geological Institute, Warsaw, Poland, and Institute of Chemistry, Poznan University of Technology, PL-60-965 Poznan, Poland
Thallium was determined in 120 samples of soil and 30 samples of stream sediments from the southeastern part of the Silesian-Cracowian zinc-lead ore deposits. Soil samples were taken from topsoils (0.0-0.2 m) and bottom soils (0.8 and 1.0 m). Thallium was determined by flowinjection-differential-pulse anodic stripping voltammetry. The samples were decomposed sequentially with 73% hydrofluoric acid and a mixture of nitric acid and hydrogen peroxide. The results showed that zinc-lead ore mining as well as their processing and smelting leads to a significant increase of thallium in the top layer of soil and in stream sediments. The highest recorded concentration was 150 ppm Tl for stream sediment and 35 ppm for a soil sample. Thallium concentration in small rivers from the investigated area was by 2 orders of magnitude higher than in the reference area. The highest recorded concentration being 3.24 µg L-1.
Introduction Thallium is an element with a greater toxicity than mercury, cadmium, lead, or copper (1, 2). In geochemical systems, mostly monovalent thallium occurs, which substitutes for potassium(I) or rubidium(I) in such silicates as feldspar or mica. The thallium content in igneous rocks varies from 0.05 to 1.7 ppm (1). In hydrothermal systems, thallium is bound to sulfides such as pyrite, sphalerite, or marcasite. Weathering of these sulfides leads to thallium dispersion in sedimentary rocks as well as in iron and manganese hydroxides and organic matter, including coals. Extensive sulfide ore mining, treatment, and smelting is a major source of anthropogenic dispersion of thallium in the environment. This specifically concerns the zinc-lead ores from the Silesian-Cracowian deposits. Thallium concentration in iron sulfides from the eastern part of this region was found to be within the range of 80-1000 ppm, while in zinc sulfides it was found to be 60-280 ppm (3). Even more thallium was found in pyrites from the western part of the Silesian-Cracowian deposits (800-12 000 ppm) (4). A significant chain in the dispersion of thallium in the environment is the flotation of zinc-lead sulfide ores. Postflotation wastes can contain high thallium concentrations. The mineral melnicovite isolated from postflotation wastes contained 5000 * Corresponding author phone: (4861)6652786; fax: (4861)6652746; e-mail:
[email protected]. † Polish Geological Institute. ‡ Poznan University of Technology. 10.1021/es0346936 CCC: $25.00 Published on Web 09/11/2003
2003 American Chemical Society
ppm of thallium (5). Thallium from this source can be easily released by oxidation. An argument to support this thesis is the high concentrations of thallium found in the tap water of this region (2000 ng L-1) (6). High thallium concentration in the area is also shown by bioindicators such as magpie feathers (by 2 orders of magnitude) (7). Thallium concentration in animal organs (kidneys, liver) is of the order of 15-35 ppm i.e., by 3-4 orders of magnitude higher than those from a reference area (8, 9). Therefore, a systematic investigation of thallium concentration in the soils and stream sediments of the leadzinc sulfide ore mining and smelting area is a significant task. There has been little research on thallium concentration in soil worldwide. Several significant studies performed in the 1990s have been reviewed by Tremel et al. (10), together with their own research on thallium concentration in French arable soils. The majority of 244 French soil samples exhibited a thallium concentration within the range of 0.13-1.54 ppm, with a median value of 0.29 ppm. A slightly lower range of thallium concentrations was exhibited by 460 soil samples from Upper Austria (0.08-0.91 ppm). Eight hundred fiftythree soil samples from China contained thallium concentrations within the range between 0.29 and 1.17 ppm (11). These results show a range of thallium concentration in nonpolluted soils between 0.08 and 1.5 ppm. Less numerous measurements performed by von Laar et al. (12) as well as by Lukaszewski and Zembrzuski (13) fit well to this range. Nonpolluted soil from Saxony (Germany) contains approximately 0.5 ppm of thallium (14), while from an area of old ore mines, thallium concentration was determined as equal to 73 ppm (15). Much higher thallium concentrations were found in 22 soils from 244 samples investigated by Tremel et al. (10). The samples from the northern border of the Morvan exhibited 1.7-55 ppm of thallium. However, such high concentrations were caused by natural pedogeochemical processes. Increased thallium concentrations were related to calcareous rocks as a parent material of soils. According to the authors, the major host of thallium are sulfides dispersed in the limestone or the marl. Higher thallium concentrations were exhibited by soils from the lead-zinc exploitation zone (8.8-27.8 ppm) (16), which supports the fact that thallium is an accompanying element to lead-zinc ores and is introduced to the environment due to the processing of these ores. Therefore, the aim of this work is the systematic investigation of thallium concentrations in soils and stream sediments in the SilesianCracowian lead-zinc ore deposit area, considered as an example of thallium dispersion in the environment. Both the top (0-0.2 m) and deeper (0.8-1.0 m) layers of soil as well as stream sediments were investigated. This area shows a strong excess of zinc, lead, cadmium, and arsenic as compared to average concentrations, both in the top soil layer (0-0.2 m) and in the bottom soil (0.8-1.0 m) as well as in stream sediments (17).
Materials and Methods Site Description. The 82 km2 area of investigation is located in the southeastern part of the Silesian-Cracowian zinclead ore deposits region. The geological structure of the studied area is varied in terms of age and lithologysthe Permian and the Triassic formations are exposed on the surface or covered by Quaternary sediments. The Permian is developed as clays and conglomerates, and the Triassic is represented mainly by limestones, dolomites (including oreVOL. 37, NO. 20, 2003 / ENVIRONMENTAL SCIENCE & TECHNOLOGY
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FIGURE 1. Distribution of thallium (ppm) in soils against a background of geological structure (after ref 24) in the SilesianCracowian Zn-Pb mining and smelting area. Quaternary: (Holocene) 1 ) flood plain sands, gravel and silts; 2 ) slope-wash sands and loams; (Pleistocene) 3 ) loesses; 4 ) glaciofluvial sands and gravel. Upper Triassic: 5 ) claystones, siltstones, and limestones. Middle Triassic: 6 ) dolomites, limestones, and marls; 7 ) ore-bearing dolomites. Lower Triassic: 8 ) dolomites and marls. Permian: 9 ) claystones, siltstones, and conglomerates. 10 ) dumps. 11 ) “Boleslaw” zinc smelter. 12 ) abandoned Zn-Pb ore mines. bearing dolomites), claystones, and mudstones. The Quaternary series is composed of glaciofluvial sands and gravel as well as Pleistocene loesses and Holocene fluvial sands, gravel and slope-wash sands, and loams. The Silesian-Cracowian ore deposits belong to the Mississippi Valley type (18). The ores of industrial value are only those connected with the Middle Triassic dolomites and mainly with so-called ore-bearing dolomites (19). The main minerals of the zinc-lead ores are sphalerite, galena, pyrite, and marcasite, which appear together with calcite and Barite. The average zinc concentration in the ores is 3.3%, while lead concentration is an average 0.7%. Exploitation of the zinc-lead ores in the investigated area has been conducted since the XVI century until the present time. Outside the area, in an easterly direction, two ore mines are still active. A zinc smelter (65 000 tons of zinc per year) is located on the area together with a flotation facility. The postflotation wastes contain dolomite, calcite, and Barite as well as sulfides and oxides of iron, zinc, and lead. Sampling. Sixty sampling points were selected for soil. Sampling of soils followed a grid pattern 1750 × 1000 m (Figure 1). Two 50 sq mm cores (sampled with the Eijkelkamp Co. Sampler) were taken from each sampling point: one sample from the top level (0-0.2 m) and the second sample from a level of 0.8-1.0 m. The samples were dried and sieved with a 2 mm nylon sieve and then pulverized in an agate mortar to a fraction below 0.063 mm. Sixty sampling points along streams of the area were established approximately 1500-2000 m apart (Figure 1). The samples were dried, sieved with a 0.2 mm nylon sieve, and then pulverized in an agate mortar to a fraction below 0.063 mm. 4570
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FIGURE 2. Distribution of thallium (ppm) in stream sediments against a background of geological structure (after ref 21) in the SilesianCracowian Zn-Pb mining and smelting area. Explanationsssee Figure 1.
FIGURE 3. Thallium concentration in small rivers. Dark circle indicates the location of the ground sample investigated for mobility of thallium. Other explanationsssee Figure 1. Water samples were taken from six small rivers flowing through the investigated area (see Figure 3). Samples were immediately preserved with the addition of 0.05 M EDTA. Sample Decomposition. Sample decomposition was performed in accordance with the procedure described previously (13). The procedure was modified for the purpose of serial determination. Unlike the other authors (10, 12),
TABLE 1. Thallium Concentration (ppm) in the Investigated Soils Derived from Different Parent Rocksa topsoil 0.0-0.2 m
bottom soil 0.8-1.0 m
lithology of parent rocks
age
N
min
max
med.1
min
max
med.2
med.1/med2
flood plain sands, gravel, and silt slope-wash sands and loams loesses glaciofluvial sands and gravel dolomites, ore-bearing dolomites, limestones, and marls dumps
QH QH QP QP TR QH
6 8 6 29 7 3
0.44 0.28 0.28 0.04 0.43 6.9
1.70 14.9 0.65 2.28 6.12 29.8
0.49 1.00 0.50 0.18 2.06 22.9
0.13 0.14 0.20 0.02 0.45 17.9
1.87 35.1 1.03 0.29 4.60 19.8
0.38 0.33 0.33 0.10 1.33 19.5
1.29 3.03 1.52 1.80 1.55 1.17
a
QH - Holocene; QP - Pleistocene; TR - middle Triassic.
who used soil extracts, the total decomposition of the soil samples was used. Decomposition was performed in an open system. Toll PTFE beakers of 200 mL volume were used. Samples of 0.25 g were sequentially treated with 73% hydrofluoric acid (2.0 mL) and a mixture of 65% nitric acid (1.0 mL) and 30% hydrogen peroxide (2.5 mL) and gently evaporated after each step. The dry residue was dissolved in 1.0 mL of hot concentrated nitric acid over 2 h; during this step the beakers were covered with watch glasses. It is worth stressing that the last stage has a crucial role in the recovery of thallium during sample decomposition. The dissolved samples were supplemented with ascorbic acid (eventually 0.1 M) and EDTA (eventually 0.1 M) and adjusted to the pH 4.4 (in a 25 mL volumetric flask). Thallium Determination. Determination was performed in accordance with the procedure described previously (13). Differential-pulse adsorptive stripping voltammetry technique was used with a pulse amplitude of 50 mV. An Ecochemie (Utrecht, The Netherlands) electrochemical analyzer MICROAUTOLAB was used together with a flowthrough cell, which facilitates the medium exchange. A mercury film electrode was used as a working electrode, and a saturated calomel electrode (SCE) was the reference electrode. Thallium preconcentration was performed at the potential of -900 mV vs SCE during 60-180 s, depending on thallium concentration. Voltammograms were recorded after the medium exchange on pure 0.05 M EDTA. The results were evaluated on the basis of several standard additions. Quality Assurance. The determination was continuously monitored by using the reference material, which was soil GBW07401 (China) containing 1 ( 0.2 ppm of thallium.
Results and Discussion The results of thallium content in soils are shown in Figure 1 and summarized in Table 1. Thallium concentration in soils is very divergent and strongly depends on the lithology of the parent rocks. Significantly higher concentrations were determined in top soils than in bottom soils. The difference between the top layer and the bottom layer can serve as a measure of the anthropogenic pollution of soil with thallium. The lowest concentrations were recorded for soils developed from Quaternary glaciofluvial sands and gravel both for the bottom soils as well as for the topsoils (median equal to 0.10 ppm in the deeper level and 0.18 ppm in the top level). Bottom soils derived from the other Quaternary parent rocks such as flood plain sands, gravel and silt, slope-wash sands, and loams as well as loesses exhibit median values from 0.33 to 0.38 ppm. Much higher thallium concentrations are exhibited by bottom soils developed on zinc-lead orebearing calcareous formation of Middle Triassic. These concentrations varied from 0.45 to 4.66 ppm with a median of 1.33 ppm. The same differences caused by the lithology of parent rocks are observed for the topsoils. However, the top layer
TABLE 2. Thallium Concentration (ppm) in Stream Sediments of Rivers and Streams Collecting Sewage from Zn-Pb Processing thallium concn (ppm) river or stream
n
min
max
med
remarks
BiałaPrzemsza Sztoła and Baba Biała and Da¸ bro´ wka Warwas
5 5 5 4
2.39 2.99 12.9 1.57
25.2 5.76 23.5 147
6.51 3.74 16.0 18.3
a b c d
a Collects waters from the Eastern part of the Zn-Pb deposit area. Collects sewage from the Olkusz Zn-Pb mine. c Collects sewage from the Pomorzany Zn-Pb mine. d Collects sewage from the Bolesław Zn smelter. b
exhibited higher thallium concentration (65% on average) which is the measure of anthropogenic pollution. The highest enrichment of the top layer by thallium was observed for soils derived from slope-wash sands and loams (300%), and the lowest was observed for soil derived from flood plain sands, gravel, and silt (approximately 30%). Extremely high thallium concentrations (median approximately 20 ppm) were exhibited by samples from dumps, both from the top layer as well as from the 0.8-1.0 m level. The results of thallium content in stream sediments are collected in Figure 2. Sediments of streams flowing in the southern part of the investigated area through glaciofluvial sands and gravels contained low thallium concentration (0.02-0.17 ppm), while sediments of streams flowing through the Pleistocene loesses or the Middle Triassic formations in the northern part of the investigated area exhibited thallium concentrations within a range between 0.8 and 3.1 ppm. Sediments of the small rivers Biala Przemsza and Sztola and the Baba, Warwas, Biala, and Dabrowka streams, which collect sewage from zinc-lead ore mines, zinc smelter, and flow throughout the outcrops of ore-bearing dolomites, contained much higher thallium concentrations (Table 2). The highest concentrations were exhibited by sediments from the Warwas stream, collecting sewage from the “Boleslaw” zinc smelter (from 1.6 to approximately 150 ppm; with a median of 18.3 ppm). Thallium is probably carried out as adsorbed on colloids of zinc and manganese hydroxides. It is worth stressing that manganese concentration in sediments of the stream exceeds 14%. In the case of the Biala and Dabrowka streams, thallium is probably carried out together with highly dispersed iron(II) sulfide. Thallium concentration in sediments of these streams was within the range 12.923.5 ppm, while iron was of 3.76% and 4.12% and sulfur was of 3.85% and 6.92% from the Biala and Dabrowka streams, respectively (17). Undoubtedly, zinc-lead ores exploitation leads to a significant increase of thallium concentration in the top layer of soil and in stream sediments. A crucial factor for the potential toxic effect of thallium in the investigated soils is thallium mobility. This can be determined by a sequential extraction of soil. In the seven stage procedure, the first stage VOL. 37, NO. 20, 2003 / ENVIRONMENTAL SCIENCE & TECHNOLOGY
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describes the solubility of thallium in water and the second stage describes thallium undergoing the ion-exchange (20). These two fractions describe the most mobile thallium in the soil. The sample of ground from a waste dump located on the investigated area (see dark circle in Figure 3) showed 4% of water soluble and 12.4% of ion exchangeable thallium (21). This fact indicates a high risk of thallium pollution of the aquatic environment. The main portion of thallium from the tested ground was located in the sulfide fraction. Therefore, oxidation of sulfides leads to mobilization of thallium. The presence of mobile thallium is reflected in thallium concentration in small rivers in the investigated area. These concentrations are shown in Figure 3. The highly elevated level of thallium concentration in these rivers is obvious when compared with an average level of thallium in rivers from other areas. Thallium concentration in three large Polish rivers was determined as 5-16 ng L-1 (6). The concentrations of thallium determined in the Rivers Dabrowka, Biala, and Biala Przemsza are by 2-3 orders of magnitude higher. This explains why animal organs from the investigated area exhibit a thallium level 3-4 orders of magnitude higher than those from a reference area (7-9). The determined thallium concentrations are significantly above the thallium concentration limit given by Canadian Environmental Quality Guidelines (0.8 ppb) (22). One tap water sample from the investigated area (The “Tramp” Hotel in Bukowno) contained 0.61 µg L-1 of thallium i.e., the Maximum Contaminant Level Goal in the United States (0.5 ppb) (23) but still below the Maximum Contaminant Level (2 ppb). Polish guidelines do not indicate the thallium level.
Acknowledgments This work was supported by the Committee of Scientific Research (grant no. 9T12B04619).
Literature Cited (1) Nriagu, J. O. In Thallium in the Environment; Nriagu, J. O., Ed.; “Advances in Environmental Science and Technology” Wiley: 1998; Vol. 29. (2) Repetto, G.; Del Peso, A.; Repetto, M. In Thallium in the Environment. Nriagu, J. O., Ed.; “Advances in Environmental Science and Technology” Wiley: 1998; Vol. 29.
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(3) Gorecka, E. Archiwum. Mineralogiczne (Warsaw) 1993, 49, 23. (4) Sawlowicz, Z. Rudy Metale Niez˘ elazne. (Warsaw) 1981, 26, 355. (5) Kucha, H.; Je¸ drzejczyk. B. Mineralogia Polonica (Cracow) 1995, 26, 75. (6) Lukaszewski, Z.; Zembrzuski, W.; Piela, A. Anal. Chim. Acta 1996, 318, 159. (7) Dmowski, K. In Trace Elements - Their Distribution and Effects in the Environment; Markert and Friese, Eds.; Elsevier: 2000. (8) Dmowski, K. Acta Ornithoecologica 1999, 34, 1. (9) Dmowski, K.; Kozakiewicz, A.; Kozakiewicz, M. Ecotoxicol. Environ. Safety 1996, 41, 2. (10) Tremel, A.; Masson, P.; Sterckeman, T; Baize, D.; Mench, M. Environ. Pollut. 1997, 95, 293. (11) Wenqi, Q.; Yalei, C.; Jieshan, C. Int. J. Environ. Stud. 1992, 40, 311. (12) Von Laar, C.; Reinke, R.; Simon, J. Fresenius J. Anal. Chem. 1994, 349, 692. (13) Lukaszewski, Z.; Zembrzuski, W. Talanta 1992, 39, 221. (14) Rank, G.; Kardel, K.; Pa¨lchen, W.; Weidensdo¨rfer, H. Landesamt Umwelt Geol. 2001, 140-145. (15) Sager, M. In Thallium in the Environment; Nriagu, J. O., Ed.; “Advances in Environmental Science and Technology” Wiley: 1998; Vol. 29. (16) Schoer, J.; Nagel, U. Naturwissewnschaften 1980, 67, 261. (17) Lis, J.; Pasieczna, A. Detailed Geochemical Atlas of Upper Silesia 1:25 000. Promotional Map of ‘Slawkow’; National Institute of Geology: Warsaw, 1999. (18) Leach, D.; Viets, J. G. Geological Quarterly 1993, 37, 325. (19) Mineral resources of Poland; Przenioslo, S., Ed.; Polish Geological Institute: Warsaw, 2000. (20) Rule, J. H. Trace Metal Cation Adsorption in Soils: Selective Chemical Extractions and Biological Availability. In Adsorption and its Applications in Industry and Environmental Protection. Studies in Surface Science and Catalysis; Dabrowski, A., Ed.; Elsevier Science B.V.: 1998; Vol. 120. (21) Lukaszewski, Z.; Karbowska B.; Zembrzuski, W. Electroanalysis 2003, 15, 480. (22) Canadian Environmental Quality Guidelines. Canadian Council of Ministers of the Environment, 1999. (23) U.S. Environmental Protection Agency, Ground Water and Drinking Water, http://www.epa.gov/safewater/mcl.html. (24) Kurek, S.; Paszkowski, M.; Preidl, M. Detailed geological map of Poland 1:50,000; Polish Geological Institute: Warsaw, 1994.
Received for review July 1, 2003. Revised manuscript received July 31, 2003. Accepted August 1, 2003. ES0346936
