5:15 PM - 7:15 PM
[AHW30-P06] Geochemical Study on Nitrogen Pollution of Surface and Groundwater in Arakawa River Fan, Saitama Prefecture, Japan
Keywords:alluvial fan, surface water, shallow groundwater, nitrogen pollution, nitrogen isotope, land use
The Arakawa River fan is about 60 km2 in area, with the Yorii Town, Saitama Prefecture, as its apex. In the fan, a sand and gravel layer with a hydraulic conductivity on the order of 10-2 cm/s and of 10-15 m thickness is distributed below a 1-2 m thick loam layer (Ishizaki and Sago, 1980). Surfacer and shallow groundwater flow northeastward through the fan, eventually flowing away to the Tone River lowland between the Arakawa River fan and the Tone River.
In the Arakawa River fan, many agricultural irrigation and drainage canals have been constructed, and a variety of agricultural activities are being conducted. In addition to field cultivation throughout the fan, the proximal area is thriving with rice cultivation, and flower cultivation, tree cultivation for landscaping and livestock raising are also active at its medial area. Many factories producing pickles of vegetables such as leeks, radishes, and cucumbers operate from the medial to the distal area of the fan, mainly in the Okabe district, and the Fukaya City (urban area) is located at the toe of the fan, spreading northwest-southeast. It is likely that surface and groundwater in the Arakawa River fan may be affected by a wide variety of pollution sources as they flow from the proximal to the toe of the fan.
In this study, based on the results of the surface water survey in July 2024 and the groundwater survey by Ishizawa et al. (2022) in July-September 2021, we investigated the reason for high nitrogen concentrations of surface and groundwater in the fan with the help of a multi-tracer method including isotopes. Furthermore, the nitrogen load to the outside of the fan via surface and groundwater is discussed.
In the Arakawa River fan, many agricultural irrigation and drainage canals have been constructed, and a variety of agricultural activities are being conducted. In addition to field cultivation throughout the fan, the proximal area is thriving with rice cultivation, and flower cultivation, tree cultivation for landscaping and livestock raising are also active at its medial area. Many factories producing pickles of vegetables such as leeks, radishes, and cucumbers operate from the medial to the distal area of the fan, mainly in the Okabe district, and the Fukaya City (urban area) is located at the toe of the fan, spreading northwest-southeast. It is likely that surface and groundwater in the Arakawa River fan may be affected by a wide variety of pollution sources as they flow from the proximal to the toe of the fan.
In this study, based on the results of the surface water survey in July 2024 and the groundwater survey by Ishizawa et al. (2022) in July-September 2021, we investigated the reason for high nitrogen concentrations of surface and groundwater in the fan with the help of a multi-tracer method including isotopes. Furthermore, the nitrogen load to the outside of the fan via surface and groundwater is discussed.