Effect of Micrometeorology and Topography on Variation of Nitrate-Nitrogen Deposition on Precipitation in Kofu Basin

Abstract

Understanding the nitrogen dynamics in the atmosphere and nitrogen deposition into the forest is required for appropriate management of forested and headwater areas. In this study, we measured nitrate-nitrogen from rainfall from May 2012 to March 2013 at 4 points inside Kofu basin and from April 2010 to March 2013 at 3 points at the northern boundary of the basin. The amount of nitrate-nitrogen deposited in summer was larger than that in winter. Nitrogen and oxygen isotope values of nitrate were in the range of the level of atmospheric nitrate. At two sampling points in the apex of the Arakawa alluvial fan and upstream in the northern boundary of the basin, even though they are covered by mountain forest and dry field, the amounts of nitrate-nitrogen deposited were larger than that in the basin including the urban area and exceeded the standard of nitrogen saturation. In contrast, such a large deposition was not detected at another point on the northern boundary north of Kofu station and approximately 5 km southeast of the above points. Therefore, we conclude that these differences are associated with the atmospheric stream such as prevailing wind and mountain-valley wind, caused by the micrometeorology and topography.