Nitrogen compounds generated by anthropogenic combustion deposits in forest watersheds and induce nitrogen saturation of the area. Because excess nitrogen is derived from atmospheric deposition, this action is expected to uniformly affect a wide area of forest soils. Geographically, heterogeneous nitrate concentration of stream water within a small area has been attributed to the tree type, geological setting and tree cut. In this article, we hypothesized that the effect of the atmospheric nitrogen deposition in the forest watershed may vary within a small area, and that such variation is induced by the degree of air mass containing a high concentration of nitrogen deposition of combustion origin. We measured major ion concentrations, including nitrate, nitrite oxygen and nitrogen stable isotope of nitrate sampled at 24 water streams in the Chichibu region, which is 50-100 km from the Tokyo metropolitan area. The nitrate concentration showed a wide range (25.6-237 μmol L −1 ) within 300 km 2 , which was explained sufficiently by the air mass advection path and its contact with the mountain's surface. The nitrate concentration showed a significant positive correlation with chloride (r=0.73; p<0.001). As chloride originates outside of the Chichibu region, the positive correlation between two ions showed that the nitrate concentration of the stream water was affected by the nitrogen compound from the Tokyo Metropolitan area as a form of atmospheric deposition. Between the nitrate concentration and the stable isotope ratio of oxygen of nitrate, there was a positive correlation until nitrate concentration of 100 μmol L −1 . When the nitrate is over 100 μmol L −1 , δ 18 O shows a stable value of ca. 5.7‰. This indicates that the nitrification proceeds when the nitrate concentration was low to middle, but the reaction slowed when the nitrate concentration became high. Oxygen stable isotope of nitrate along with a set of nitrate concentrations can be used as a good indicator of nitrogen saturation.

Deposition of atmospheric nutrients is known to alter oligotrophic ecosystems such as the open ocean, but the role of such nutrients in the further deterioration of eutrophic aquatic ecosystems is largely unknown. The Hii River watershed in Japan encompasses lagoons that have been eutrophic since 1980s. This study examined the atmospheric deposition of nitrogen and phosphorus in the Hii River watershed and the nitrogen and phosphorus concentrations in the Hii River over an 11-yr period. Total nitrogen (TN) concentrations of both precipitation and river water were significantly higher in cold months (November-March) than in warm months (April-October). Most of the TN was nitrate, which suggests that the TN source was atmospheric nitrogen from East Asia transported by seasonal winds. In contrast, total phosphorus (TP) concentrations of both precipitation and river water were significantly higher in warm months. Over time, the TN concentration in the river water showed a decreasing trend although the trend was not significant, while the TP concentration increased significantly. This was attributed to an increase in the atmospheric deposition of TP originating from East Asia since 2000. The increase in the deposition of atmospheric phosphorus might also have increased phosphorus leakage from the soils. In this work, the TN : TP ratios for both atmospheric deposition and river water indicate that changes in atmospheric nutrient deposition affect loading rates and N : P ratios. These changes, especially the latter, could have significant ecological effects in eutrophic systems by lowering the N : P ratios, which could induce cyanobacteria blooms.

This study characterizes evacuation behavior in Ibaraki Prefecture in the aftermath of the Great East Japan Earthquake and tsunamis based on geographic information, questionnaires, and interview surveys. We identified several factors on which the starting time of evacuation depended, including awareness of evacuation warnings, understanding of anticipated tsunami inundation areas (hazard maps), and distance from anticipated inundation areas. We found that those who were aware of evacuation sites, hazard maps and/or anticipated inundation areas maps, and who lived in inundated areas tended to evacuate earlier. Conversely, many residents delayed their evacuation because they chose to go home and take care of their family first. To improve future responses to likely threats, evacuation behavior and local disaster management plans must be reviewed based on the knowledge gained from this disaster.