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In the catchment basins of the Nagara River, Gifu Prefecture, Central Japan, many skiing grounds have been developed since the 1970s. Ammonium sulfate ((NH4)2SO4) is used as snow cement on these skiing grounds, and nitrogen pollution in the upper streams has become an issue. Inorganic nitrogen concentration and loading in a stream, where skiing ground occupies 50% of its catchments basin, showed remarkable increases in winter; the concentration being as high as 1.2 mg L-1 in winter, while 0.2 mg L-1 in other seasons without snow. Winter nitrogen loading was assumed to contribute to the annual loading by about 70%. No such specific increase in nitrogen concentration and loading has been observed in the streams of the catchment basin without skiing grounds. Over 90% of the inorganic nitrogen in the stream water was in nitrate form. It is quite likely that a great part of the ammonium is nitrified in low temperature conditions.
応用生態工学会の論文