Water Resources Research Act Program

Details for Project ID 2012DC140B

Episodic ion and nutrient inputs to the Anacostia River: constructing a chemical hydrograph of an urban stream's response to periodic rainfall

Institute: District of Columbia
Year Established: 2012 Start Date: 2012-03-01 End Date: 2013-02-28
Total Federal Funds: $15,000 Total Non-Federal Funds: $33,952

Principal Investigators: Stephen MacAvoy

Abstract: The Anacostia River has been characterized as one of the most heavily polluted waterways in the United States. High concentrations of contaminants have been documented in the river's sediments (heavy metals, polycyclic aromatic hydrocarbons (PAHs) and clams (Corbicula fluminea) (PCBs, PAHs and chlordane) (Phelps 2005, 2007), plus there is a high incidence of tumors in the resident bullhead catfish (Pinkney et al. 2004). In fact, the Washington DC Department of the Environment has issued advisories against consumption of Anacostia fishes. (http://ddoe.dc.gov/ddoe/cwp/view,a,1209,q,494756.asp). These facts clearly show that the river is heavily impacted by the surrounding urban watershed; however, recent studies have found lower nitrate, ammonium and phosphorus at base-flow than would be expected in a polluted river (MacAvoy et al. 2009). In fact, the Anacostia at base-flow seems to be on the high end of "normal" for nitrate (a major form of nitrogen that is usable by plants) in an estuary (between 0.1 and 1.0 mg/l). The fact that base-flow nitrogen conditions are "normal," even in areas adjacent to combined sewage outflows, is very good news for the river and suggests that a cleaner river may be achievable in the future. However, Hwang and Foster (2008) have shown that storm-water flow after heavy precipitation events seems to flush PCB's into the Anacostia. It may be, therefore, that the nutrient loads observed by MacAvoy et al. (2009), which show base-flow conditions, do not reflect the possible periodic flushing of the watershed. Indeed, Miller et al. (2007) showed strong correlations between discharge and total nitrogen in the upper Anacostia watershed, although the correlation was much less significant once discharge was greater than 1000 cubic feet/second (discharge as measured up to 4500 cfs during episodes between 2003 and 2005). Nitrates and other compounds (such as PAHs) emitted through vehicle tailpipes and industrial processes are deposited as "dry-deposition" on impermeable surfaces, where they accumulate. Precipitation may then wash the compounds from the impermeable surfaces into the Anacostia. In this study, we propose to obtain water samples from the Anacostia hourly following precipitation events (via autosampler). These samples will have their nutrient and geochemical characteristics monitored (nitrite, nitrate, ammonia, phosphorus plus cations and anions). The water will also be examined for fatty acids to help identify bacteria in the water column. These analyses will generate a chemical response profile for the river resulting in a chemical view of the river's response to periods of heavy run off. During the same storm events that the Anacostia is exposed to, we will collect the same type of data for a relatively pristine river to the northwest of DC (the Patuxent River) as a contrast. We will determine the nutrients delivered per unit volume to the rivers and, by using flow monitors maintained by the USGS and Montgomery County Department of Environmental Protection, we will be able to estimate the total nutrients moving through the rivers. (http://www.montgomerycountymd.gov/dectmpl.asp?url=/content/dep/water/monPhysFlow.asp). The geochemical data we obtain will allow us to contrast the geochemical controls of each river in order to better assess the impact of urbanization on river chemistry. Previous work has suggested that concrete (essentially a man-made conglomerate rock) has a significant influence on the geochemistry of the Anacostia (Sarrano et al. 2010, 2011). The concrete might be altering the river in ways the river's biology has never experienced.