Atmospheric wet and dry deposition ("acid rain") appears to be the principal source of nitrogen in twelve northern Florida watersheds that range from Pensacola to Gainesville (Escambia to Alachua Counties). The study was based on statistical analysis of chemical concentrations measured for more than ten years in weekly rainfall samples of the National Atmospheric Deposition Program, NADP, and more than twenty years of river water samples of the US Geological Survey, USGS. River fluxes of total dissolved nitrogen average close to the atmospheric deposition fluxes of nitrate and ammonium ions. Factor analysis was applied to the datasets to resolve principal components: (1) in atmospheric data, that distinguish air pollution nitrate and sulfate from sea salt sodium and chloride, and (2) in surface water data, that distinguish ground water Ca, Mg, and silica from meteoric water nitrate and sulfate. Relationships within the sets of measured concentration data suggest that, following atmospheric deposition, inorganic nitrogen undergoes biogeochemical transformation within the watersheds, which results in inorganic nitrogen being transformed to organic forms. River concentration ratios N/P in the watersheds are high, averaging twice the Redfield mole ratio N/P = 16 for aquatic plant nutrients. The results indicate that excess dissolved nitrogen could be temporarily recycled in the watersheds but not retained, so that it could eventually flow to the coastal zone where N may be a limiting nutrient for marine plants. Chemical interactions of meteoric water within the watersheds depend on geologic, hydrologic, and biogeochemical processes and are certainly complex. However, in one watershed that is geologically the simplest, separate statistical analyses of river water composition during high and low flow conditions show nitrate and sulfate to be correlated during high flow, but not during low flow, providing further evidence for an atmospheric nitrogen source and watershed transformation after deposition.