Atmospheric deposition is an example of problems associated with nonpoint source pollution (see, NPS).
In the US, the National Atmospheric Deposition Program (NADP maintains information and data on atmospheric deposition. The NADP maintain specific links to data related to: Mercury deposition, and Ammonia. Data for other forms of atmospheric deposition may be accessed HERE and HERE.
Data for Canada may be found HERE.
Global data for select years is located HERE.
Christodoulaki, S., G. Petihakis, M. Kanakidou, N. Mihalopoulos, K. Tsiaras, and G. Triantafyllou. (2013). “Atmospheric deposition in the Eastern Mediterranean. A driving force for ecosystem dynamics.” Journal of Marine Systems 109: 78-93.