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Biogeochemistry Laboratory

Our Work

We examine organic contaminants and general geochemistry of freshwater systems, especially locally impacted ones such as the Anacostia River.  Urban rivers are beset with environmental problems associated with land use and human infrastructure development. We examine altered geochemistry in the river, try to determine causes and look for signs of change as regional efforts to improve the river's water quality proceed. The biogeochemical lab also examines fatty acid profiles in sediments to characterize bacterial community members. Profiles give clues to bacterial types as well as algae and diatom species.  The lab also characterizes food web structure and climate resilience using field and laboratory stable isotope studies. 

Active Projects

Exploring anomalously high calcium in suburban MD streams in the absence of bedrock carbonate and geochemical indicators of concrete dissolutionFunded by Water Resources Research Institute/US Geological Survey

The inorganic geochemical characteristics of urban rivers can be strongly influenced by development, industrial processes, altered hydrology, and other factors.  The changes shift with local characteristics but collectively the have been termed urban stream syndrome." In the Anacostia River (DC), the syndrome may manifest as high calcium and sodium from dissolving concrete, metals from industry, high nitrate from sewage, organic contaminants such as PAHs and/or synthetic chemicals such as siloxanes.

Emerging pollutants in the Anacostia River: Determining concentration of siloxanes (D4, D5, D6, and 2.4.6.8) and specific PAHs

Funded by the Water Resources Research Institute/US Geological Survey

We are investigating the occurrence and concentration of siloxanes, bibenzyl and phenanthrene at 6 locations within theAnacostia watershed and 2 locations in the Potomac.  It will test the hypothesis that siloxanes should occur in areas with more combined sewer flow (if they are derived from cosmetics). Also, both siloxanes and the PAHs should be higher in the more urban areas of the Anacostia as opposed to the suburban areas or the Potomac River sites. The Potomac River sites should have the lowest concentrations of the contaminants since the sediments will be collected in heavily forested areas at least 10 miles west of Washington DC.

Hana Bahlawan

Hana Bahlawan is a senior majoring in Environmental Science. She is also a member of the US Air Force ROTC (Lt. Col. AFROTC)! Hana is examining the concentration and distribution of a novel PAH (polycyclic aromatic hydrocarbon) called Bibenzyl which is used in flame retardants, electronics, and textile production. She is looking at both suburban and urban steam sediments that may receive different degrees of sewage input and will test for differences.
  

Laura Dudek

Laura Dudek is a junior majoring in Environmental Studies and minoring in Sociology. She is focusing on analyzing sediments collected from three sites along the Anacostia River. She will identify notable compounds and calculate the percent of organic matter and bacterial counts found within the samples.

 

Mia Fanuzzi

Mia Fanuzzi is a junior majoring in Biology. This semester she is assisting in Dr. MacAvoy’s project comparing and contrasting sediment fatty acids from sites in suburban Anacostia and Potomac. I am working on extracting and separating fatty acids and characterizing them with a GC/MS to see what these fatty acid profiles show about the different sites (bacterial species, algae, diatoms, etc). 

 

Megan Godfrey

Megan Godfrey is a senior undergraduate student at American University, majoring in Environment Science and minoring in Public Health. She came to DC from the US Virgin Islands in 2017 and after graduating in May 2021, she hopes to work for an environmental organization that focusses on the intersections between human and environmental health and environmental justice. She’s currently working on a research project in coordination with Dr. Stephen Macavoy and several other students to test the toxicity of organic contaminants in urban and suburban areas of the Anacostia and the Potomac rivers in Washington DC, using gas chromatography and a mass spectrometer to identify isolated fatty acids and study the geochemistry of the urban rivers.

Kristina Nicholas

Kristina Nicholas is an Environmental Science MS student entering her second year at American University. She received a Bachelor’s in Earth and Environmental Science from UCLA. Her research focuses on analyzing concentrations of polycyclic aromatic hydrocarbons (PAHs) and siloxanes of the Anacostia and Potomac rivers. In addition to her research work, she is a TA for an undergraduate class in the department.  

Olivia Ventresca

Olivia is responsible for extracting sediments from suburban sites in Maryland and characterizing siloxanes (emerging aquatic contaminants derived from building materials, cosmetics and industrial lubricants. She will also calculate % organic carbon and culture fecal coliform bacteria from the same sites.