Environ. Sci. Technol. 2001, 35, 4597-4603
Historical PCDD Inputs and Their Source Implications from Dated Sediment Cores in Queensland (Australia) C A R O L I N E G A U S , * ,†,‡ G R E G G J . BRUNSKILL,§ ROLAND WEBER,| OLAF PA ¨ PKE,# AND JOCHEN F. MU ¨ LLER† National Research Center for Environmental Toxicology, 39 Kessels Road, Coopers Plains 4108, Queensland, Australia, School of Public Health, Griffith University, Nathan 4111, Queensland, Australia, Australian Institute of Marine Science, PMB No. 3, Townsville MVC, Queensland, Australia, Universita¨t Tu ¨ bingen, Institute for Organic Chemistry, Auf der Morgenstelle 18, 72076 Tu ¨ bingen, Germany, and Ergo Forschungsgesellschaft mbH, Geierstrasse 1, D-22305 Hamburg, Germany
Recent investigations have demonstrated the presence of an unidentified source of polychlorinated dibenzo-pdioxins (PCDDs) in the coastal zone of Queensland (Australia). The present study provides new information on the possible PCDD sources and their temporal input to this environment. Two estuarine sediment cores were collected in northern Queensland for which radiochemical chronologies were established. Core sections from different depositional ages, up to three centuries, have been analyzed for 2,3,7,8-substituted PCDDs and polychlorinated dibenzofurans (PCDFs). Variations of PCDD concentrations in the sediment cores over several centuries of depositional history were relatively small, and elevated PCDD levels were still present in sediment slices from the early 17th century. PCDD/F isomer patterns and congener profiles in sediments deposited during the last 350 years were almost identical and correlated well to the characteristic profiles observed in surface sediments and soils from the entire Queensland coastline. Profiles were dominated by higher chlorinated PCDDs, in particular octachlorodibenzodioxin (OCDD), whereas PCDF concentrations were below or near the limit of detection. These results indicate the presence of a PCDD source prior to industrialization and production of commercial organochlorine products. Further, the present study demonstrates that PCDD input patterns have been similar along an extensive but localized area over at least several centuries, contributing relatively high concentrations of PCDDs to the coastal system of Queensland.
Introduction The primary sources of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) have been identified in many * Corresponding author phone: +61 7 3274 9147; fax: +61 7 3274 9003; e-mail:
[email protected]. † National Research Center for Environmental Toxicology. ‡ Griffith University. § Australian Institute of Marine Science. | Universita ¨ t Tu ¨ bingen. # Ergo Forschungsgesellschaft mbH. 10.1021/es011086e CCC: $20.00 Published on Web 11/02/2001
2001 American Chemical Society
countries as combustion processes such as municipal waste incineration and various chemical processes that result in contaminated products and waste (1, 2). The subsequent emission to the atmosphere renders these compounds ubiquitous in the contemporary environment and result in an environmental baseline PCDD/F burden (3, 4). Therefore, sink areas such as marine ecosystems that are distant from anthropogenic PCDD/F sources may be contaminated with low background PCDD/F levels. However, during the past decade a large number of studies have contributed evidence for nonanthropogenic PCDD/F sources in the environment (e.g. refs 5-13), which may provide a natural baseline level of these compounds in specific locations. For example, Queensland, the northeastern state of Australia, is predominantly rural and known for its pristine marine environments such as the Great Barrier Reef. Few industrial or anthropogenic PCDD/F sources exist in these areas, and, as a consequence, only low contaminant concentrations would be expected in the environment. However, recent studies have demonstrated the presence of elevated levels (up to 30 ng g-1 dw) of higher chlorinated PCDDs in marine sediments and topsoil along the entire 2000 km coastline of Queensland (5, 6, 14). Remarkably, all samples exhibited similar congener profiles and identical isomer patterns, characterized by the dominance of OCDD, whereas PCDF concentrations were near or below the limit of detection. These results indicate that the PCDD source is land-based; however, the specific congener and isomer patterns could not be attributed to known technical or industrial PCDD/F sources. Similar PCDD/F signatures have been reported from elsewhere in surface sediments, soil, and kaolin clay (9, 15-17). The authors of these studies indicated that it is unlikely that anthropogenic inputs have lead to the observed contaminations, and it was suggested that natural processes may be involved in PCDD/F formations in these environments. Dated sediment cores or archived materials have been used to provide valuable information on the significance and origin of historical as well as more recent PCDD/F inputs (8, 18-20). Most retrospective PCDD/F information from archived or dated deposits indicates relatively low levels of PCDD/Fs in deposits prior to the 1900s. Such low ambient levels are then typically proceeded by significant increases in PCDD/F concentrations and concurrent changes in congener profiles with the onset of industrialization and organochlorine production (3, 19-21). These studies demonstrate that the major contributing sources to the contemporary PCDD/F burden are of anthropogenic origin. On the other hand, relatively high PCDD levels (in particular OCDD) have been reported in up to several thousand (320 pg g-1 dw) to million (2000 pg g-1 dw) year old sediment core samples from the Japanese coastal waters and the Pacific Ocean, respectively (22, 23). Similarly, relatively high concentrations of mainly OCDD (ΣPCDD/F concentrations up to 5500 pg g-1 dw) have been reported in the bottom strata of lake sediment cores from Mississippi (7). The present study was carried out to determine the temporal distribution of PCDD/Fs in the Queensland coastal environment. Congener specific PCDD/F analysis was carried out on radiochemical dated sediment cores from different depositional eras and regions to evaluate our hypothesis that the extensive PCDD contamination of Queensland may be the cause of nonanthropogenic processes. Specifically this study was aimed to assess whether (a) the specific PCDD contamination in the coastal environment is restricted to recent PCDD/F inputs, indicating anthropogenic influences since European settlement and industrialization or (b) preVOL. 35, NO. 23, 2001 / ENVIRONMENTAL SCIENCE & TECHNOLOGY
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FIGURE 1. Map of Queensland, Australia showing the sampling sites of sediment cores collected from A. Hinchinbrook area (core 1262) and B. Burdekin area (core 1260). 1900 historical contamination was present in Queensland sediments and can provide evidence for the input of nonanthropogenic derived PCDDs as well as further information on the possible formation processes involved.
Materials and Methods Location Description. Two estuarine sediment cores (AIMS 1260 and AIMS 1262) were collected in the tropics of North Queensland, Australia (Figure 1). Core 1262 (Hinchinbrook) was collected from an intertidal mangrove mud bank (18°24.5′S; 146°10.3′E) from the Hinchinbrook Channel. This area receives terrigenous sediments from the Herbert River, which drains a wet and dry tropical catchment of approximately 10 000 km2 (24). Core 1260 (Burdekin) was collected in Bowling Green Bay (19°17.9′S; 147°21.1′E), an estuarine embayment that receives terrigenous sediments mainly from the Burdekin River, draining an arid catchment of approximately 130 000 km2 (25). Both, the Herbert and Burdekin catchments are predominantly rural with only few small urban settlements (
