Sources of Bioavailable Toxic Pollutants in the Anacostia Basic Information

The polluted urban Anacostia River estuary and four of its major tributaries were monitored in summer 2001 for bioavailable EPA Priority Pollutants (PCBS, PAHS, Aroclors, pesticides and five metals) using the locally available Asiatic Clam, Corbicula fluminea. Total metal levels in clams at all sites were not significantly different from clams from the nearby control site on the Potomac at Fort Foote. PCB congenors (especially 2 5 Cl) and Aroclor totals were significantly greater than controls at Lower Beaverdam Creek (MD). Total pesticides (especially chlordane) were significently greater at the Northeast Branch. Total accumulated PAHs significantly exceeded controls at the Northeast Branch and Lower Beaverdam Creek tributaries, and also at upper and lower Anacostia estuary sites (Bladensburg Marina, Washington Gas Light and the Navy Yard). Clams placed in the Northwest Branch (MD) and Hickey Run (DC) tributaries had total pollutant levels no greater than controls. Clams placed at Hickey Run (DC) before it entered the National Arboretum grounds had only 6% survival, but when placed at the exit from the lake had 92% survival, and contaminant levels were lower than controls. Contaminants in clams at the control site suggest pollutants from the Anacostia estuary are influencing the Potomac estuary. Introduction: The Anacostia River estuary is the DC urban river with plans for improving public access and fishing. The poor biological condition of the Anacostia River estuary is receiving increasing public attention as it has a fishing advisory and depauperate benthic life (Phelps 1985), especially as it is a branch of the nearby Potomac estuary which is considered a recovery success of the Chesapeake Bay. The biological problems of the Anacostia have been known for years (Freudberg et al.1989, Cummins et al. 1991) and there have been many studies of its water and sediment chemical contaminants (Velinsky et al. 1992, Velinsky and Cummins 1994, Velinsky et al. 1994, Wade et al 1994, Syracuse Research Corporation 2000). Some studies have been done on the tributary origins of Anacostia pollutants (Warner et al. 1997, Coffin et al. 1999) and bioeffects such as sediment toxicity, tumor formation and bioaccumulation (Phelps 1990, Phelps 1991, Phelps 1993, Phelps 1995, Phelps 2001, Pinkney et al. 2000). The most serious toxic contaminants of the Anacostia from the standpoint of human health are the pesticide chlordane and PCBs which are above FDA action levels in Anacostia fish and have sponsored a fishing advisory (Velinsky and Cummins 1994, Pinkney 2001). PCBs have a number of harmful effects in biota and can come from a variety of sources including old electrical equipment (Ahlborg et al. 1994, Safe 1990, Safe 1994 Fikslin 1995). PCBs and chlordane and other persistant organic pollutants (POPs) can remain buried in sediments for years but become bioavailable through remobilization by dredging (Phelps 2001). The Anacostia Watershed Toxics Alliance (NOAA/EPA) has recently formed to study and recommend solutions to the toxic problems of the Anacostia and is proposing several remediation actions for toxics in sediments (AWTA 2002). However, for sediment toxic remediation to be successful it will be necessary to find and control ongoing sources of pollutants to the estuary. Earlier studies (Gruessner et al. 1997, Coffin 1999) suggested the major water sources to the Anacostia estuary, the Northeast and Northwest Branches (MD), contributed significant amounts of PCBs and other pollutants. A recent Anacostia watershed study (Phelps 2001) found chlordane only in sediments and Asiatic clams at the mid to upper end of the Anacostia estuary and the Northeast Branch. The use of clams to monitor these sites detected the bioavailable chlordane and suggested a Northeast Branch source. Molluscs are used for biomonitoring aquatic health worldwide because they mostly lack a cytochrome P450 system and will accumulate rather than detoxify or modify pollutants. The Asiatic clam, Corbicula fluminea, is common, widespread, resistant to toxics and has been recommended for freshwater contaminant bioaccumulation studies by the National Water Quality Assessment Program (Dougherty and Cherry 1988, Crawford and Luoma 1993, Phelps 1997). The Asiatic clam is considered an especially good accumulator of PCBÆs (Peterson et al. 1994). Translocated Asiatic clams have been used to detect organochlorines and pesticides in rivers in several countries (Elder and Mattraw 1985, Hartley and Johnston 1983, Colombo et al.1995, Smith and Ruhl 1996). Molluscs are important indicators of contaminant bioavailability. Pollutant concentrations in sediment and water are not the same as their bioavailability to living organisms (Elder and Mattraw 1984, Tatem 1986). Complexation of pollutants by organic material or ions can prevent uptake by living tissue (Sunda and Guillard 1976, Long and Morgan 1990, MacDonald et al. 2000). A recent bioavailability study found Asiatic clams did not accumulate contaminants from exposure to contaminated Anacostia sediments in the Potomac (Phelps 2000). However, clams placed on clean sand at Anacostia estuary sites accumulated water contaminants. Filter-feeding molluscs like the Asiatic clam can accumulate contaminants from water and suspended particulates but not from bed sediments (Harrison 1984, Phelps 1979, Phelps 2000). Catfish in contact with polluted Anacostia sediments have a high rate of tumors (Pinkney et al. 2000). The fish and birds of the Anacostia could be affected by bioavailable pollutants that are part of the food chain. Bioavailability information is essential to understanding the dynamics and effects of pollutants in the Anacostia. The present study uses the locally available Asiatic clam to biomonitor the bioavailable pollutants contributed by tributary subwatersheds to the Anacostia River estuary. The Asiatic clam population in the freshwater Potomac River estuary near the Anacostia has been flourishing since this invasive species was first found in 1978 (Dresler and Cory 1980, Cohen et al. 1984, Phelps 1994). The State of Maryland allows biomonitoring with Corbicula as it is now considered a naturalized species and has been reported in many Maryland rivers and streams. Corbicula in the Anacostia are small and few with no young clams, and probably entering by drift and failing to grow or reproduce (Prezant and Chalermwat 1984, Phelps 1985). Juvenile Corbicula have been used in biomonitoring toxicity in Anacostia sediment and water (Phelps 1990, Phelps 1993, Phelps and Clark 1988). Adult clams placed in the Anacostia generally survive and can be useful in bioaccumulation studies (Douherty and Cherry 1988, Phelps and Clark 1988, Phelps 2001). To assess the bioavailability of contaminants it is considered necessary to expose molluscs for six to eight weeks for tissue concentrations to reach equilibrium (Roesijadi et al.1984).