Environ Sci Pollut Res (2013) 20:6594–6600 DOI 10.1007/s11356-013-1719-5
RESEARCH ARTICLE
Spatial distribution of polychlorinated biphenyls in High Tatras lake sediments Barend L. van Drooge & Joan O. Grimalt & Evzen Stuchlík
Received: 23 January 2013 / Accepted: 3 April 2013 / Published online: 23 April 2013 # Springer-Verlag Berlin Heidelberg 2013
Abstract The objective of the present study was to gain insight on the spatial distribution of seven polychlorinated biphenyl (PCB) congeners in the High Tatras mountain range in Eastern Europe. Twenty high mountain lakes were sampled on their top-core sediment. Despite the relative uniform composition of PCB congeners among the lakes, there are important differences in the observed concentrations. Moderate top-core sediment concentrations of PCB congeners were observed (1.9 to 38 ng/g dw for ∑PCB) in comparison to other high mountain or Arctic areas. The variation in PCB concentrations can partly be explained by a possible altitudinal effect, resulting in higher PCB concentrations at higher (colder) altitudes. Part of this enhanced accumulation of PCBs could be caused by external factors (topography and meteorology) and internal lake factors (sediment dynamics). Many of these factors were not quantified for all individual lakes and their influence could, therefore, only be studied for some. Keywords Polychlorinated biphenyls . High mountain lake sediments . High Tatras
Introduction In the recent past, studies in European high mountain regions have revealed usefulness of lake ecosystems as sensitive Responsible editor: Constantini Samara B. L. van Drooge (*) : J. O. Grimalt Institute of Environmental Diagnostics and Water Research (IDÆA-CSIC), Jordi Girona 18, 08034 Barcelona, Catalonia, Spain e-mail:
[email protected] E. Stuchlík Department of Hydrology, Charles University, Vinicná 7, 12044 Prague, Czech Republic
environmental indicators to determine speed and direction of changing air quality on the European continent (www.mountain-lakes.org). High mountain lake systems are different from low altitude lakes at similar latitudes, since they receive pollutant input only from atmospheric transport. This input is entirely driven by long-range atmospheric transport (LRAT) as there are no local sources (van Drooge et al. 2004). Ambient temperatures are lower at these high altitudes that increase trapping efficiency of high mountain areas once semivolatile organic compounds (SOC) have been deposited or transferred from the atmosphere to other environmental compartments, such as sediments where polychlorinated biphenyls (PCBs) get buried (Grimalt et al. 2001; Meijer et al. 2006). The High Tatras, situated on the border between Poland and the Slovakian Republic, in Eastern Europe (49°10′– 49°14′N; 20°0′–20°10′E; Fig. 1), are part of a national park and there are no industrial or agricultural activities in these mountains. Summits of this steep mountain range reach altitudes of 2,655 m and are about 1,800–2,000 m above surrounding low lands. The nearest industrial areas of importance are Kosice in the south, Krakow in the north, and Ostrava in the west, all situated approximately 100 km from the mountain range. Despite lack of human activities in these mountains they were found to be moderately contaminated by PCB in fish and air samples in comparison to the mountain regions in central Europe (van Drooge et al. 2004; Vives et al. 2004), and they show relatively high polycyclic aromatic hydrocarbon (PAH) sediments loads (van Drooge et al. 2011). In a dated lake sediment core from L'adové Pleso, an increase of PCB concentrations was observed after 1954 (Grimalt et al. 2004) as a consequence of extensive use in industrial applications. Maximum concentrations were observed in the sediments from the late 1980s. The objective of the present study was to gain insight on spatial distribution of PCB concentration in lake sediments from the High Tatras. For this purpose, 20 high mountain lakes, covering an area of 10×18 km (Fig. 1), were sampled
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Fig. 1 Site map showing the location of lakes and the main ridges in the mountain range. The border between Poland and Slovakian Republic is indicated by a thick dashed line. The meteorological stations
are indicated by stars (KW Kasprowy Wierch, LS Lomnicky Stit, SP Skalnate Pleso). The numbers of individual lakes refer to codes listed in Table 1 and the text
on their top-core sediments, whereas four of these lakes were sampled on bottom-core sediments, representing environmental quality before 1850 (Appleby and Piliposian 2006). The lakes are situated between an altitude of 1,580 m (above sea level) and 2,145 m (Table 1) that, in all cases, is above the regional timberline.
The purity of the cleaned reagents was checked by ultrasonic extraction with n-hexane:dichloromethane (4:1; 3× 20 mL), concentration to 50 mL, and analysis by GC-ECD. No interferences were detected. Sodium sulfate and aluminum oxide were activated overnight at 400 and 120 °C, respectively. Sampling
Material and methods Materials Residue analysis of n-hexane, dichloromethane, isooctane, methanol, and acetone were from Merck (Darmstadt, Germany). Anhydrous sodium sulfate for analysis was also from Merck. Neutral aluminum oxide type 507C was from Fluka AG (Buchs, Switzerland). Cellulose extraction cartridges were from Whatman Ltd. (Maidstone, England, UK). Aluminum foil was rinsed with acetone and let dry at ambient temperature prior to use. Purity of the solvents was checked by gas chromatography with an electron capture detector (GC-ECD). No significant peaks should be detected for acceptance. Aluminum oxide, sodium sulfate, and cellulose cartridges were cleaned by Soxhlet extraction with hexane:dichloromethane (4:1, v/v) during 24 h before use.
Sediment samples were collected in 2001 and taken in the deepest points of the lakes using a gravity coring system (Glew, 7.5 cm diameter, 30 cm long). Immediately after sampling, sediment cores were divided in sections of 0.5 cm and stored in precleaned aluminum foil at −20 °C until analysis. Sample extraction In order to obtain the dry weight of the sediment samples, aliquots of wet weight sediment samples were lyophilized and weighted before and afterwards. For SOC analysis, about 0.1–1 g of wet sediment was extracted by sonication with methanol (20 mL; 20 min) in order to separate most of the interstitial water from the sediment. Subsequent extractions were performed with (2:1, v/v) dichloromethane:methanol (3× 20 mL; 20 min). All extracts were combined and spiked with PCB #30 and PCB #209. Then, they were
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Table 1 Characteristics of studied lakes in the High Tatras Lake code
Official name
Latitude (N)
Longitude (E)
Altitude (masl)
Area (ha)
T air estimate (°C)
∑PCB (ng/g dw)
∑PCB (ng/g OC)
TA007 TA008 TA011 TA012 TA014 TA015 TA017 TA018 TA021 TA022 TA026 TA027 TA029
Zielony Staw Gąsienicowy Zelené Krivánske Nižné Terianske Zadni Staw Polski Vyšné Terianske Zmarzly Staw Gąsienicowy Vyšné Wahlenbergovo Czarny Staw Polski Capie Vyšné Temnosmrečinské Malé Hincovo Vel'ké Hincovo Czarny Staw pod Rysami
49.2289 49.1594 49.1698 49.2134 49.1680 49.2244 49.1642 49.2046 49.1683 49.1891 49.1740 49.1797 49.1888
20.0010 20.0085 20.0143 20.0143 20.0218 20.0238 20.0271 20.0277 20.0378 20.0395 20.0585 20.0606 20.0778
1,672 2,017 1,941 1,890 2,109 1,787 2,145 1,722 2,072 1,716 1,923 1,946 1,580
3.8 4.3 4.9 6.5 0.5 0.3 5.0 12.7 2.4 5.0 2.2 18.2 20.5
1.1 −0.5 0.1 −0.4 −1.1 0.3 −1.3 0.8 −0.8 0.8 0.2 0.0 1.8
2 17 3 16 36 6 24 23 8 13 21 36 2
37 192 23 225 487 64 200 190 120 123 155 381 99
TA032 TA034 TA037 TA043 TA049 TA051 TA054
Vyšné Žabie Bielovodské L'adové Pleso v Zlomiskách Batizovské Vyšné Zbojnícke Žabie Javorové Prostredné Sivé Vel'ké Spišské
49.1942 49.1633 49.1523 49.1788 49.1912 49.1841 49.1932
20.0943 20.1077 20.1315 20.1595 20.1701 20.1768 20.1964
1,699 1,925 1,879 1,972 1,886 2,011 2,014
8.1 2.1 2.8 0.7 0.8 0.9 2.4
1.0 0.2 0.5 −0.2 −0.4 −0.4 −0.4
4 31 5 12 17 20 10
34 310 49 98 100 192 83
vacuum evaporated to almost 10 mL and hydrolyzed overnight with 20 mL of 6 % (w/w) KOH in methanol. Neutral fractions were recovered with n-hexane (3×10 mL), vacuum evaporated to almost dryness, and fractionated with a column containing 2 g of alumina. PCB congeners were collected in the first fraction of 5 mL n-hexane:dichloromethane (19:1 v/v). Active copper (1 g) was added to the fraction for removal of sulfur-containing compounds overnight. The copper was removed by filtration through glass wool and rinsed with n-hexane. Both fractions were vacuum evaporated to 0.5 mL and nitrogen concentrated to almost dryness and redissolved in isooctane prior to instrumental analysis.
respectively. Solutions of tetrachloronaphthalene and octachloronaphthalene were added to the vials prior to injection. Calibration curves (detector response vs. amount injected) were performed for each compound to be quantified. Range of linearity of the detector was evaluated from the curves generated by plotting detector signal/amount injected vs. amount injected. All measurements were performed in the ranges of linearity found for each compound. In some cases, the samples were rediluted and reinjected for fitting within the linear range of the instrument.
Instrumental PCB analysis
Quantitative data were corrected for surrogate recoveries that were 69 %±11 for PCB #30 and 82 %±11 for PCB #209. Procedural blanks were performed with each set of nine samples to check for presence of interfering peaks. All samples have been blank corrected. The method detection limits based on signal-to-noise ratio of 3 in real samples ranged from 100 to 400 pg for individual compounds.
The following PCB congeners were determined: PCB #28, #52, #101+90, #118, #153, #138, and #180. The extracts were injected into a Hewlett Packard 5890 Series II GCECD. An HP-5 fused silica capillary column (30 m length, 0.25 mm i.d., 0.25-μm film thickness) coated with 5 % phenyl 95 % methylpolysiloxane was used for the analyses. The oven temperature program started at 100 °C (hold for 1 min), increased to 120 °C at 20 °C/min, to 240 °C at 4 °C/min (hold for 12 min), and finally to 300 °C at 4 °C/min (hold for 10 min). Injector and detector temperatures were 280 and 310 °C, respectively. Helium and nitrogen were used as carrier (0.33 mL/min) and makeup (60 mL/min) gases,
Quality control
Total organic carbon analysis Sediment samples were extracted with HCl 3 N to remove inorganic carbon. Subsequently, they were cleaned with Milli-Q water until neutral pH (7±0.2) and dried at 60 °C. The determination of total organic carbon (TOC) was
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Influence of internal factors on the PCB concentrations Factors that may cause variation of PCB levels among the lake sediment are processes, such as sediment focusing, slumping, or landsliding, taking place within the lake system. Sediment focusing takes place when the bottom area of the lake is much smaller than the surface area and is normally indicated by constant high sedimentation fluxes. This is the case for Vel'ké Hincovo (TA27) (Appleby and Piliposian 2006) and may explain part of the high PCB levels found in this lake (36 ng/g dw; 381 ng/g OC). 0.35 0.30 0.25 0.20 0.15 0.10 0.05 0.00
PCB#180
The composition of the PCB congeners in the top-core lake sediments of the High Tatras are shown in Fig. 2. The composition of PCB congeners in all lakes was significantly uniform (p<0.01) and dominated by the less volatile PCB congeners, #153, #138, and #180. Similar PCB compositions were observed in the lake sediments from other mountainous areas or the Arctic (Evenset et al. 2007; Pozo et al. 2007). The lake sediment composition is in contrast with ambient air concentrations from the area, where more volatile congeners (i.e., #52 and #101+90) were the predominant compounds (van Drooge et al. 2011). In these ambient air samples, all PCB congeners are mainly present in the gas phase that suggests that diffuse air–water exchange is the dominant route of input to these lake systems (Meijer et al. 2006; van Drooge et al. 2004). Nevertheless, enhanced incorporation of the less volatile and more hydrophobic congeners to lake sediments is the consequence of their preferential absorption to atmospheric particle at low ambient temperatures (Grimalt et al. 2001) and faster deposition (Meijer et al. 2006). Once in the lake water column, the enhanced adsorption of the more hydrophobic congeners to particle leads to faster sedimentation than is the case for the
Although the profiles of PCB congeners are very similar in all top-core lake sediment samples, there are important differences in concentrations among the lakes. Both external factors, such as topographical differences, as well as internal factors, such as sedimentation rates, have influence on the final destiny of PCBs in lake sediments and are challenging the interpretation of the environmental data.
PCB#138
Relative PCB composition
Factors influencing the spatial PCB variation
PCB#153
The PCB concentrations in the lake sediments are summarized in Table 1. The bottom-core sediments at 15–17 cm depth represent preindustrial conditions before 1850 (Appleby and Piliposian 2006). The PCB concentrations in these bottom-core samples were around the detection limits, which is in agreement with the fact that PCBs were not in the environment when these sediments settled. PCBs were detected in all top-core sediment samples, except for PCB #28 that showed levels below limit of detection. The ∑PCB concentrations range from 1.9 to 38 ng/g dw considering the dry weight of the samples, and between 23 and 487 ng/g OC. These concentrations are comparable to the ones observed in other high mountain areas or the Arctic. In the Swiss Alps, ∑PCB concentrations in two alpine lakes were about 0.5 and 2.5 ng/g dw (Schmid et al. 2011), while in the Arctic, the ∑PCB was 40 ng/g dw in a lake sediment on Bjørnøya (Evenset et al. 2007). In alpine regions (Andes) on the southern hemisphere, ∑PCB concentrations ranged between 0.2 and 64 ng/g dw (Borghini et al. 2005; Pozo et al. 2007).
PCB#118
PCB concentrations
PCB#101+90
Results and discussion
less hydrophobic PCB congeners. These less hydrophobic PCBs circulate in the water column and are removed more efficiently from the lake system through the outlet of the lake and by revolatilization to the atmosphere (Meijer et al. 2006). This results in a further predominance of the less volatile and more hydrophobic congeners in the sediments and the low concentrations of the most volatile PCB #28 analyzed in this study.
PCB#52
performed by flash combustion at 1,025 °C followed by thermic conductivity detection in a CHNS Elemental Analyser EA1108. The limit of detection was 0.1 %.
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Fig. 2 Average distribution of PCB congeners (+SD) in top-core sediments
6598
Sediment slumping or landsliding takes place when unstable material of the slopes of lake or the lake's catchment is accidentally removed from its location and covers the sediment. This is normally indicated by episodes of rapid sedimentation fluxes. In the dated sediment core from L'adové Pleso (Grimalt et al. 2004), this phenomenon was observed in the top-core sediment, representing the most recent years. It showed a drop of PCB concentrations as well as radioactive Pb210 and was probably caused by a slide of inorganic material from the catchment that was not recently exposed to the atmosphere (Appleby and Piliposian 2006). Other factors, such as the surface area of the catchment area or the surface of the lake and its volume could have an effect on the fate of persistent organic pollutants. In large lakes in Switzerland, a correlation was observed between the ratio lake surface/lake volume and the polybrominated diphenyl ether concentrations in fish (Zennegg et al. 2003). In the present study, only the lake surface area was known and no correlation was observed between the PCB concentrations and the surface areas (R2 <0.05). Influence of external factors on the PCB concentrations External factors, such as the altitude and ambient air temperature, play a role in the trapping efficiency of PCB in high mountain lake systems, where higher levels are found at higher altitude (Blais et al. 1998; Grimalt et al. 2001). This is a consequence of the physicochemical properties of PCB congeners that have relatively low vapor pressures and high hydrophobicity, allowing these compounds to accumulate with decreasing temperatures and increasing altitudes. In the present study, the highest ∑PCB level of 36 ng/g dw was observed in Vel'ké Hincovo (TA27), while the lowest level of 2.1 ng/g dw was found in the sediment sample from Czarny Staw (TA29). These are two of the largest lakes in the High Tatras (~20 ha) and situated at a distance of 1.5 km from each other. However, Vel'ké Hincovo is situated at an altitude of 1,946 m on the southern slopes of the mountain range, while Czarny Staw, located nearby, is situated at 1,580 m on the northern slope (Fig. 1). Even after application of the OC, the concentrations are still 381 and 99 ng/g OC for Vel'ké Hincovo (TA27) and Czarny Staw (TA29), respectively. Comparisons of the individual lake altitudes vs. their PCB burden show moderate positive correlations for all congeners (R2 ~0.2; p< 0.05), except for PCB #52 and #101+90. This finding is in agreement with former studies (Grimalt et al. 2001), where concentrations of the more volatile PCB congeners (i.e., #52 and #101) in European mountain lake sediments did not show clear altitudinal trends, opposite to the less volatile congeners. This accumulation was controlled mainly by temperature.
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In the present study, the ambient temperatures of most of the studied lakes are unknown. However, they can be estimated by using known isotherms and temperature lapse rates from the High Tatras (Zasadni and Klapyta, 2009). In these mountains, the mean annual air isotherm of 2 °C is situated at an altitude of 1,550 m on the northern slopes and at 1,650 m on the southern slopes, while the temperature lapse rate is 0.67 °C/100 m for the eastern part of the mountain range and 0.70 °C/100 m in the northwestern part. Based on these data, the annual ambient air temperatures ranged from −1.3 to 1.8 °C, showing a temperature gradient of 4 °C. These estimated air temperatures are tentative and may contain errors, since microclimatic conditions at lake sites may result in other values. Nevertheless, they were used in this study to observe the relationship between air temperature PCB concentration and temperature (Fig. 3). No correlations were observed for PCB #52 and #101 + 90 (R2 <0.12; p>0.05), and PCB #118, #153, #138, and #180 showed moderate correlations (R2 ~0.22; p<0.05). In fact, an accumulation of the less volatile PCB congeners was observed with a decrease of the air temperature at the lake. The slope of the relationship between estimated temperature and PCB concentrations can be used to estimate the phase change pseudoenthalpies of the congeners (Grimalt et al. 2001), i.e., the energy necessary for PCBs to be transferred from the air into the lake water (~90 kJ/mol) and into the sediments (~45 kJ/mol). The obtained slopes are ~38.103 ± 17.103 K (Fig. 3) for the low volatile PCB congeners, resulting in enthalpies around 730±330 kJ/mol. Although these values show large standard deviations, the estimated pseudoenthalpies are about six times higher than expected ones (~135 kJ/mol), suggesting that the observed PCB concentration variation among the lakes can only partly be explained by the temperature gradient. The temperature effect underestimates the observed PCB concentrations, so there should be other factors involved. Internal factors that can have influence on the burial of PCB have been discussed before (see “Influence of internal factors on the PCB concentrations”) and the real effect on each individual lake is highly uncertain that may explain part of the unexplained variation among the lakes. However, there are also other external factors, such as precipitation, which have influence on the amount of PCBs entering the lake system (Pozo et al. 2007). Precipitation in these mountain areas is related to temperature by the fact that a large part of this precipitation is in the form of snow, and snow is an efficient scavenger for PCBs (Wania et al. 1999). In fact, an increase of PCB concentration was observed in the snowpack in the High Tatras with increasing altitude on a specific mountain slope (Arellano et al. 2011). Moreover, all lakes are snow and ice covered during almost 50 % of the time of the year. During the winter, the lake waters are isolated from atmospheric input, but the deposited PCBs
Environ Sci Pollut Res (2013) 20:6594–6600 3.0
6599 3.5
PCB#52
2.5
PCB#101+90
3.0
2.0
2.5
1.5 2.0 1.0 1.5 0.5 1.0
0.0 R2 = 0.08
-0.5
0.5
R2 = 0.16
0.0 -1.0 0.00363 0.00364 0.00365 0.00366 0.00367 0.00368 0.00369 0.00363 0.00364 0.00365 0.00366 0.00367 0.00368 0.00369
3.0
4.0
PCB#118
2.5
3.5
2.0
3.0
1.5
2.5
1.0
2.0
0.5
1.5
0.0
1.0
-0.5
R2 = 0.21
PCB#153
0.5
R2 = 0.24
0.0 -1.0 0.00363 0.00364 0.00365 0.00366 0.00367 0.00368 0.00369 0.00363 0.00364 0.00365 0.00366 0.00367 0.00368 0.00369 4.5
4.5
PCB#138
4.0
4.0
3.5
3.5
3.0
3.0
2.5
2.5
2.0
2.0
1.5
1.5
1.0
1.0
0.5
R2 = 0.22
0.5
PCB#180
R2 = 0.21
0.0 0.0 0.00363 0.00364 0.00365 0.00366 0.00367 0.00368 0.00369 0.00363 0.00364 0.00365 0.00366 0.00367 0.00368 0.00369
Fig. 3 Sediment LN concentrations of PCB congeners (ln ng/g OC; y-axis) vs. mean annual air temperatures (1/K; x-axis) of the studied lakes in the High Tatras. Only the significant correlations are indicated by a
solid line. The slopes of the relationship 1/T vs. Ln[PCB#] were 34.103 ± 15.103 K for #118; 41.103 ±17.103 K for #153, 38.103 ±17.103 K for #138, and 36.103 ±17.103 K for #180
are locked up in snow and ice and released at the time of spring thaw and enters the lake system. There is tendency in the High Tatras that the precipitation increases with altitude due to orographically induced precipitation. Moreover, higher precipitation loads are measured in the northwestern part of the mountain range due to the influence of air mass form the North Atlantic (Zasadni and Klapyta 2009). Nevertheless, the exact precipitation loads for each individual
lake are unknown and estimates are prone to large uncertainties. Moreover, in the mountainous terrain, snow resuspension and redeposition by wind or avalanches results in redistribution of snow and in piling of snow into topographical depressions, where the lakes are situated. All these abovementioned factors were not quantified in the present study, and their influence may be enough to explain the enhanced accumulation of the PCB congeners in the lake sediments.
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Conclusions Moderate top-core sediment concentrations of PCB congeners were observed in the High Tatras. Despite the relative uniform composition of both PCB congeners there are important differences in the observed concentrations. The differences in PCB concentrations could only partly be explained by internal factors, such as sedimentation rates and lake sedimentation dynamics (e.g., sediment focusing, slumping, or land sliding). For most of the lakes, these variables are unknown or highly uncertain. Nevertheless, a positive correlation was observed between the concentrations of less volatile PCB congeners and altitude, showing that a cold-trapping effect can be responsible for this trend. However, the observed altitudinal trends are higher than predicted by the cold-trapping effect, and other unquantified variables, which could be both external factors, such as precipitation, as well as internal factors, may cause the larger concentration variations. Acknowledgments Technical assistance from R. Mas, R. Chaler and D. Fanjul is acknowledged. Financial support for this study was provided by the EU projects EUROLIMPACS (GOCE-CT-2003-505540) and EMERGE (EVK1-CT-1999-00032), and the Consolider-Ingenio Project GRACCIE (CSD2007-00067) is acknowledged.
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