Article pubs.acs.org/est
Levels and Spatial Distribution of Persistent Organic Pollutants in the Environment: A Case Study of German Forest Soils Bernhard Aichner,*,† Bernd Bussian,‡ Petra Lehnik-Habrink,† and Sebastian Hein† †
Federal Institute for Materials Research and Testing (BAM), Richard-Willstätter-Strße 11, 12489 Berlin, Germany Federal Environment Agency (UBA), Wörlitzer Platz 1, 06844 Dessau-Roßlau, Germany
‡
S Supporting Information *
ABSTRACT: The Of/Oh-horizons of 447 forest stands in Germany were evaluated for concentrations and spatial distribution of selected polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), and organochlorine pesticides (OCPs). While concentrations of dichlorodiphenyltrichloroethane (DDT) and PCBs show similar spatial distribution patterns for all measured compounds within each compound class, significantly different distributions were identified for concentrations of low-molecular-weight PAHs [2- and 3-ring PAHs plus fluoranthene (FLA) and pyrene (PYR)] in contrast to high-molecular-weight PAHs (4−6-ring PAHs without FLA and PYR). Maxima of persistent organic pollutant (POP) concentrations could be mostly explained by specific locatable sources. Because of the slow degradation rates of these target substances, this is especially relevant for historic contamination sources, such as extensive 1980s DDT usage in the former German Democratic Republic and industrial facilities that produced hexachlorobenzene (HCB) or PCBs. A contribution of ubiquitous background pollution derived from long-range atmospheric transport is likely for some compounds in the studied area, e.g., DDT in the western part of Germany and dieldrin. However, most target compounds appear to be mainly sourced from local or regional emissions. This is supported by the absence of clear dependencies between POP concentrations and most evaluated environmental and local parameters. We suggest that these results generally reflect the distribution of POPs in densely populated and industrialized countries located in temperate regions.
1. INTRODUCTION Because of their persistence in the environment and potential toxicological effects, compounds classified as persistent organic pollutants (POPs) have been the focus of attention since the middle of the 20th century. Naturally occurring, such as polycyclic aromatic hydrocarbons (PAHs), or industrial products, such as polychlorinated biphenyls (PCBs) and organochlorine pesticides [OCPs, e.g., dichlorodiphenyltrichloroethane (DDT), dieldrin, and hexachlorobenzene (HCB)], they can be detected even in remote regions far from emission sources.1,2 Possible harmful effects on organisms range from neurotoxic to teratogenic, carcinogenic, and endocrine disruptive effects. This is especially concerning because the lipophilic properties of these substances favor their storage in the fat tissue of organisms, which consequently leads to bioaccumulation through the food chain.3 The fate of POPs, i.e., the possible pathways in the environment after release, has been subject to numerous studies. Most compounds are susceptible to long-range transport because of their relatively high volatility. Nevertheless, environmental compartments, such as soils, can act as sinks for POPs. This is mainly due to the high affinity for organic compounds to bind to organic carbon and their recalcitrance in soils.4,5 In forest stands, the scavenging effect of canopies enhances POP fluxes from air to soils.6,7 On the other hand, soils can also act as a source for some POPs by revolatilization © 2013 American Chemical Society
of compounds with relatively high vapor pressure, such as HCB, low chlorinated PCBs, or low-molecular-weight PAHs.8 POPs have been extensively studied in the atmosphere and atmospheric depositions (see refs 9 and 10) as well as in urban and agricultural soils (see refs 11−14). In contrast, soil data from forested regions are mostly available from small-scale studies only, which either cover a relatively small study area or are based on a relatively low number of sampling spots. Exceptions include data from the large-scale programs MONARPOP (e.g., see refs 15−18), the Swiss soil-monitoring network (NABO) (e.g., see ref 19), transect studies in the U.K. and Norway,20−22 and a comprehensive study conducted in the German state Bavaria.23 The MONARPOP program analyzed POP concentrations at 33 homogeneous forest stands distributed over the Alps, i.e., at comparable altitude with similar vegetation, as well as seven altitude profiles. The NABO project covered the entire area of Switzerland and also included 26 forest stands among the 105 sampling sites. U.K. and Norway transects cover relatively large gradients of latitude but report data for PCBs/polybrominated diphenyl ethers (PBDEs)21,22 and PAHs20 only, while the Bavaria study also Received: Revised: Accepted: Published: 12703
May 3, 2013 September 6, 2013 September 19, 2013 September 19, 2013 dx.doi.org/10.1021/es4019833 | Environ. Sci. Technol. 2013, 47, 12703−12714
Environmental Science & Technology
Article
Figure 1. (a) Topographic map of Germany, German states, and sampling points. (b) Landscape units according to Corine Land Cover 2006.32 Relevant urbanized areas and brown coal strip-mining districts are annotated.
topographic units: the northern German Lowlands, the central German Uplands, the Alpine Foreland of southern Germany, and the Alps in the far south, with the Zugspitze as the highest point (2962 m) (Figure 1a). About 30% of the total area is covered by forest (Figure 1b). Because of its location in the Northern Hemispheric Westerlies Zone and the influence of the Gulf Stream, the climate is moderate and temperate. The mean annual temperature is ca. 9 °C, and the mean annual precipitation (MAP) is ca. 780 mm.33 The climate in the northwest is oceanic with relatively mild winters and cool summers. In contrast, the eastern climate is relatively continental with comparably low annual rainfall (
