[A-HW24] 流域圏生態系における物質輸送と循環：源流から沿岸海域まで

[AHW24-17] Long-term Phosphorus Balance Changes influenced by Anthropologic Factors in Yamato River Catchment

*Kunyang Wang¹、Shin-ichi Onodera¹、Mitsuyo Saito²、Takuya Ishida¹ (1.Graduate School of Advanced Science and Engineering, Hiroshima University、2.Graduate School of Environmental and Life Science, Okayama Universit)

キーワード：Phosphorus budget, Plant uptake, Phosphorus cycle, Soil and Water Assessment Tool, Human impact

Environmental pollution in coastal areas of Asia is usually more serious than in other areas in recent decades. This is because Asia not only has urbanization later than European and American countries, but also has a much faster population growth rate than European, American and African countries. Understanding past changes in long-term nutrient load is very important for environmental governance and warning for future situation. However, the water quality records in Asian countries usually started late, and it difficult to obtain the data in early ages. On the other hand, owing to the slow regeneration of phosphorus, this element is considered a non-renewable resource, moreover, the sources of existing phosphorus resources are also very limited. Studying the phosphorus budget at the catchment scale helps to keep balance between anthropogenic activities and the natural environment in sustainable development. In this study, the phosphorus loading in the Yamato River catchment, an urbanized coastal catchment in Asia, for 80 years from the 1940s to the 2010s is reconstructed using the Soil and Water Assessment Tool. Results show that the total phosphorus loading in the catchment peaked in the 1970s at 895 tons/year owing to untreated wastewater discharge and rapid increase in population growth. The soil surplus of phosphorus have also increased due to increased chemical fertilizer usage.