Abstract
Nitrogenous fertilizer use of the world increased rapidly in the second half of 20th century. This change has been the main cause of human-induced disturbance of global nitrogen cycles. In this paper, we focus on river nitrate transport of the world. Much of river nitrate comes from soil layers of terrestrial areas. Thus, we first estimated nitrate leaching from soil layers using a terrestrial nitrogen cycle model using datasets of nitrogen fertilizer use, climate and soil conditions, and subsequently, simulated river nitrate transport. The terrestrial nitrogen cycle model consists of several flux calculations at daily time scale. A global river channel network data was used in the river nitrate transport simulation. These calculations were carried out using datasets of 1955, 1965, 1975, 1985 and 1995. The result of 1995 was compared with mean nitrate concentration data of several large rivers observed by GEMS/Water and agreed with it reasonably. The transported nitrate at river mouth was then aggregated to see its load to oceans. Finally, comparing each year result, significant impact of fertilizer increase was found.
