Article pubs.acs.org/est
Historical Profiles of PCB in Dated Sediment Cores Suggest Recent Lake Contamination through the “Halo Effect” Emmanuel Naffrechoux,*,† Nathalie Cottin,† Cécile Pignol,‡ Fabien Arnaud,‡ Jean-Philippe Jenny,‡ and Marie-Elodie Perga§ †
University of Savoie, LCME (Laboratory of Molecular Chemistry and Environment), 73000 Chambéry, France University of Savoie, CNRS, UMR 5204, EDYTEM, 73000 Chambéry, France § INRA (French National Institute for Agronomical Research), Alpine Research Centre for Lakes and Food Webs, University of Savoie, 74200 Thonon les Bains, France ‡
S Supporting Information *
ABSTRACT: We investigated the major sources of polychlorinated biphenyls (PCB) and interpreted the environmental fate processes of these persistent organic pollutants in the past and current PCB contamination of three large, urbanized, French peri-alpine lakes. Dated sediment cores were analyzed in order to reconstruct and compare the historical contamination in all three lakes. Stratigraphic changes of PCB contents and fluxes were considered as revealing the temporal dynamics of PCB deposition to the lakes and the distribution of the seven indicator congeners (further referred to as PCBi) as an indicator of the main contamination origin and pathway. Although located within a single PCB industrial production region, concentration profiles for the three lakes differed in timing, peak concentration magnitudes, and in the PCBi congeners compositions. PCBi fluxes to the sediment and the magnitude of the temporal changes were generally much lower in Lake Annecy (0.05−2 ng·cm−2·yr−1) as compared to Lakes Geneva (0.05−5 ng·cm−2·yr−1) and Bourget (5−290 ng·cm−2·yr−1). For all three lakes, the paramount contamination occurred in the early 1970s. In Lakes Annecy and Bourget, PCB fluxes have declined and plateaued at 0.5 and 8 ng·cm−2·yr−1, respectively, since the early 1990s. In Lake Geneva, PCB fluxes have further decreased by the end of the XXth century and are now very low. For the most contaminated lake (Lake Bourget), the high PCBi flux (5−290 ng·cm−2·yr−1) and the predominance of heavy congeners for most of the time period are consistent with a huge local input to the lake. This still high rate of Lake Bourget is explained by transport of suspended solids from one of its affluents, polluted by an industrial point source. Intermediate historical levels and PCBi distribution over time for Lake Geneva suggest a mixed contamination (urban point sources and distant atmospheric transport), while atmospheric deposition to Lake Annecy explains its lowest contamination rate. The presently low contamination levels recorded in Lake Geneva correspond to atmospheric inputs, but the recent PCBi distribution of Lake Annecy, enriched in relatively heavy congeners, reveals a contamination by the neighboring Lake Bourget, following a halo effect of about 40 km radius.
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high-altitude and high-latitude lakes.3−6 Local sources of PCB contamination (landfills or contaminated industrial soils) still persist around urbanized, temperate ecosystems, and may also interfere with these general patterns. Adequate restoration of contaminated lakes implies the necessity to track the PCB origins to target appropriate remediation measures. This study focuses on three strongly urbanized, large and deep peri-alpine lakes. All three lakes are located 60 to 120 km north of the historical site of the French industrial production of PCBs (Jarrie and Pont de Claix, Isère), where 180 kt of
INTRODUCTION
Although polychlorinated biphenyl use has been banned since 1987 in France, local fish contamination still results in consumption advisories and bans. Polychlorinated biphenyls (PCBs) present with high stability, explaining their persistence in the environment even after more than 25 years of interdiction, while their semivolatility and hydrophobicity are responsible for atmospheric long-range transport and widespread distribution. Recent studies have highlighted that PCB transport to lake ecosystems and transfer within food chains are strongly altered by climate change, through increased PCB mobilization by global distillation effects and snowmelt,1 but also by local changes in species composition and food web structures.2 Over recent years, PCB long-range transport and interaction with global warming have led to a major focus on © 2015 American Chemical Society
Received: Revised: Accepted: Published: 1303
September 9, 2014 January 5, 2015 January 7, 2015 January 7, 2015 DOI: 10.1021/es5043996 Environ. Sci. Technol. 2015, 49, 1303−1310
Article
Environmental Science & Technology PCBs were produced from 1948 to 1979 by PRODELEC.7 Over the last 5 years and in all three lakes, quantification of PCBs in fish has led to temporary or permanent consumption advisories and commercial fishing interdiction on some species (arctic char, bream, tench) (Regional Water Agency Web site www.rhone-mediterranee.eaufrance.fr/usages-et-pressions/ pollution_PCB/pcb-arretes-interdiction.php.). While all three lakes belong to the Rhône River watershed, levels of fish contamination by the seven indicator congeners (referred as PCBi) are highly variable between, but also within a single lake: from 81 to 388 ngPCBi/g ww (mean 242 ngPCBi/g ww) for bream, 25−681 (mean 199) for tench, 156−993 (mean 546) for arctic char in Lake Bourget, 10−206 (mean 38) for arctic char in Lake Annecy (Regional Water Agency Web site www. rhone-mediterranee.eaufrance.fr/usages-et-pressions/ pollution_PCB/basepcb/index.php), and 35−132 (mean 73) for arctic char in Lake Geneva.8 The overarching aim of this work was to reconstruct and compare the historical contamination in all three lakes, in order to identify the major sources of the past and current PCB contamination of these lakes.
and a mainly agricultural watershed (44 km2). Lake Saint André is a very small (2 mm). The three working cores on which contaminant analyses were performed (LEM10-P1-03 ; LDB09-P2-01, and LDA11-P102 for Lakes Geneva, Bourget, and Annecy, respectively) were sampled following annual laminations and correlated to the reference core using lithological tie points and lamina counting.10 According to the lithostratigraphic correlation with the reference cores, mean sedimentation rates in top sediments were 3.7 mm·yr−1, 4.4 mm·yr−1 and 2.3 mm·yr−1 for Lakes Geneva, Bourget, and Annecy, respectively. As a consequence, the working cores covered the 1875−2009 time periods for Lakes Bourget and Annecy and 1901−2009 for Lake Geneva. Changes from a homogeneous sediment to an annually laminated sequence in the three lakes was caused by the drastic reduction in bioturbation following hypoxia onset in 1952, 1950, and 1933 in Lakes Geneva, Bourget, and Annecy, respectively.11,12 Dating accuracy was high on the laminated part of the cores (± 2 year) and slightly lower on the bottommost homogeneous part (± 5 years) for all three lakes. The sediment core on which PCB analyses were performed for Lake Saint André was previously described in ref 13. Chemicals. Heptane, acetone, and dichloromethane were HPLC quality and purchased from Carlo Erba. Anhydrous sodium sulfate for analysis was purchased from Fisher Chemical (analytical reagent grade). Copper powder (size
