PS 67-136 - Nitrogen deposition along an urban-rural land-use gradient in Baltimore, MD

Thursday, August 11, 2011
Exhibit Hall 3, Austin Convention Center
Neil D. Bettez, Cary Institute of Ecosystem Studies, Millbrook and Peter M. Groffman, Cary Institute of Ecosystem Studies, Millbrook, NY
Background/Question/Methods

Excess nitrogen (N) is a serious water-quality problem in most of the estuaries in the US. A first step in addressing this problem is to quantify the fluxes of N in coastal watersheds. This typically involves constructing input-output N budgets in which a single estimate of N deposition (usually from the nearest NADP/CASTNet site) is used. However, recent studies have documented that a portion of the emissions from mobile sources (cars and trucks, construction equipment, planes, boats, etc) is deposited near where they are produced potentially resulting in an underestimate of N inputs in urban areas. In this study we assessed this variability by measuring throughfall N deposition using mixed bed ion exchange resins in urban, suburban, agricultural and forested watersheds, along a 30 km urban-rural land use gradient in Baltimore Md. 

Results/Conclusions

Deposition was the lowest (9.65 ± 0.5 kg N ha (-1) y(-1) in the completely forested watershed. It was ~28% higher in the suburban watershed (12.40 ± 0.75 kg N ha (-1) y(-1) and 54% higher in the urban (14.62 ± 0.87 kg N ha(-1) y(-1)) and agricultural (14.88 ± 1.0 kg N ha (-1) y(-1) watersheds. These differences need to be taken into account when constructing watershed N budgets especially in urban coastal areas.

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