Japan Geoscience Union Meeting 2015

Presentation information


Symbol H (Human Geosciences) » H-TT Technology & Techniques

[H-TT31] New development of environmental traceability methods

Wed. May 27, 2015 6:15 PM - 7:30 PM Convention Hall (2F)

Convener:*Takanori Nakano(Research Institute for Humanity and Nature, Inter-University Research Institute Corporation National Institutes for the Humanities), Ichiro Tayasu(Center for Ecological Research, Kyoto University)

6:15 PM - 7:30 PM

[HTT31-P05] Effects of nitrogen-saturated forests on downstream water quality in Fukuoka City

*Kenichi SHINOZUKA1, Masaaki CHIWA1, Ichiro TAYASU2, Chikage YOSHIMIZU2, Atsushi KUME1 (1.Department of Agro-environmental Sciences, Faculty of Agriculture, Kyushu University, 2.Research Institute for Humanity and Nature)

Keywords:nitrogen saturation, stream water quality, nitrogen isotope, land use

Nitrogen is often limiting nutrient for plant growth and is mainly supplied from atmosphere. Forests can act as a filter for atmospherically deposited nitrogen and maintain background concentration levels of nitrogen in streams. However, recent increases in atmospheric nitrogen deposition have resulted in a shift from net-nitrogen retention to high levels of net-nitrogen loss from forested, resulting in high nitrogen concentration stream water.
In the Tatara River Basin, Fukuoka City, nitrogen retention capacity of upland forests has decreased and nitrate concentrations in downstream water have been increasing (Chiwa et al., 2012). This study analyzed NO3-15N, NO3--δ18O in addition to NO3- concentrations in stream water in the Tatara River Basin to assess the impact of nitrogen saturation forest on downstream water quality.
In northern part of the basin, NO3- concentrations of upstream were lower than downstream. In contrast, in southern part of the basin, NO3- concentrations in upstream were lower than downstream. NO3-15N in upstream was significantly lower than downstream in both northern and southern parts of the basin. In contrast, little difference of NO3-18O was observed between upstream and downstream in both parts. It has been known that the value of δ15N and δ18O ratio due to human wastewater is 10 to 20‰ and -5 to 7‰, respectively (Kendall and others, 1995). Therefore, the different trends in NO3- concentrations from upstream to downstream between two parts could be caused by different amounts of human sewage to the downstream between two parts.