Figure 1 shows source loading of nitrogen and Figure 2 shows source loading of phosphorus from major rivers within the Bay's watershed. This is attributed in part to the large farming operations in Southern Pennsylvania. See Figure 3 for locations of the rivers within the watershed. The Source of Excess Nutrients in the Bay Nitrogen Nitrogen contamination of both surface water and ground water is an environmental concern. Sources of nitrogen contamination include atmospheric nitrogen, fertilizer used in commercial and suburban settings, agricultural waste, both animal and crop, and human sewage.
Surface runoff contributes nitrogen to contamination of water in streams, lakes and estuaries.
Nitrogen that is volatilized into the air as ammonia returns to surface water in the rain. In addition, nitrogen leaches into ground water and resurfaces in water feeding streams and lakes. Even if nitrogen is applied as urea or ammonia, it is rapidly converted to nitrate in soil. The ammonia is deposited into the Bay by precipitation. It is well known that excess application of nitrogen, either as manure or chemical fertilizer, can result in loss of nitrogen to surface water.