| Introduction |
Sources of anthropogenic nitrogen and patterns of depositionGlobal atmospheric nitrogen deposition has increased in response to anthropogenic fixation of nitrogen by fertilizer production (=80 Tg N yr-1), fossil fuel combustion (=20 Tg N yr-1), and cultivation of legumes (=40 Tg N yr-1). Human activities add about 140 Tg N yr-1 to the global nitrogen cycle, which is roughly equal to the annual rate of natural nitrogen fixation (Galloway et al., 1995; Jordan and Weller, 1996; Vitousek et al., 1997).
Reactive nitrogen gas has a relatively short mean residence time in the atmosphere, so it is not well mixed in the troposphere, and deposition rates vary widely between geographic regions. The map below shows estimated nitrogen deposition for 1998 (NADP, 1999) (also available in pdf). |
Introduction Sources of N Biogeochemical effects Physiological responses Community responses Case studies Future study References Links Nitrogen Cycle
