Water Pollution and Restoration in Osaka Bay; Historical Review and Scientific Evaluaion of Policies of Area-Wide Total Pollutant Load Control

Nakatsuji, Keiji; Han, Donjin; Yamane, Nobuyuki

doi:10.2208/jscej.2003.741_69

Cited by 2 publications

(2 citation statements)

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“…However, after 1985, as the area served by WWTPs in the Yamato River catchment increased rapidly, the nitrogen loading began to decrease remarkably. The nitrogen loading in scenario 1 has a similar meaning as 'potential loading' reported in a previous study [36], and both show peaks in the 1990s.…”

Section: Discussionsupporting

confidence: 75%

“…Osaka Bay is a part of the Seto Inland Sea and shows the worst water quality in this sea, particularly in the mid-1970s [35]. A study estimated longterm variations in nitrogen loading in the regions from Osaka Prefecture to Osaka Bay as 'potential loading' based on a unit of output, suggesting that the nitrogen loading peaked around 1990 [36]. Another study estimated the nitrogen loading from all rivers inflowing to Osaka Bay as the 'net loading' based on observational data recorded by the government after the 1980s, reporting that the nitrogen loading peaked in the mid-1980s and then decreased after 1990s [37].…”

Section: -2011 Modeling (Swat) Npsmentioning

confidence: 99%

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Evaluation of nitrogen loading in the last 80 years in an urbanized Asian coastal catchment through the reconstruction of severe contamination period

Wang

Onodera

Saito

2021

Environ. Res. Lett.

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Most semi-enclosed seas have experienced severe eutrophication owing to high nutrient loading from rivers during rapid population growth periods. In Japan, the coastal areas of some megacities (e.g., Tokyo and Osaka) experienced considerable economic growth during the 1960s–1970s. Therefore, determining the amount of nutrient loading during this period is essential to undertake measures for the conservation of coastal environments. However, determining the nutrient loading that occurred several decades ago is generally difficult owing to lacking water quality records. In this study, the nitrogen 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. We considered factors such as population growth, wastewater treatment plant (WWTP) construction, and changes in land and fertilizer usage in different urbanization stages. Results show that the total nitrogen loading in the catchment peaked in the 1970s at 6616 tons/year owing to untreated wastewater discharge and rapid increase in population growth. By reducing 57% of the nitrogen loading in the 2010s from the catchment, WWTPs have been instrumental in improving the water environment. The decrease in and integration of agricultural land has reduced nitrogen loading attributed to nonpoint sources; however, this reduction was not obvious because of the high fertilizer usage before the 2000s. Overall, the findings of this study provide a comprehensive understanding of the impact of rapid urbanization in an Asian coastal catchment on nitrogen loading during the high economic growth period in the past. This study will be useful for the long-term assessment of nutrient loading in other.

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Section: Discussionsupporting

confidence: 75%

Section: -2011 Modeling (Swat) Npsmentioning

confidence: 99%