Author(s): Mitsuyo Saito; Shin-Ichi Onodera
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Keywords: Nitrate; Transport; Reduction; Coastal aquifer; Agricultural watershed
Abstract: The authors conducted the study to demonstrate the nitrate (NO 3 -) transport and reduction The authors conducted the study to demonstrate the nitrate (NO3 process in the coastal groundwater of Seto Inland Sea, southern Japan. The results are summarized as follows: 1) NO3 --N concentrations in the shallow groundwater were about 30mgL-1 in the midstream area of the catchment, whereas it decreased less than 2. 0mgL-1 in the downstream area toward the groundwater flow direction. The inverse relationship between --C and NO3 --N concentrations suggests biochemical denitrification process in the HCO3 shallow groundwater. This is also supported by the low ratio of seawater contribution (<1. 0% ), and relatively low ORP in the groundwater of the downstream area; 2) The NO3 --N concentrations in the downstream area were relatively higher in the High-flow season than --N discharge by shallow that in the Low-flow season. This result indicates that the NO3 groundwater in the High-flow is larger than that in the Low-flow season; 3) NO3 --N concentrations in deep groundwater were higher than that in shallow groundwater at the downstream area. This result suggests that leaching of organic matters from the upper sedimentary layer and groundwater recharge by the river water leads to supply of DOC to the shallow groundwater, and as a result it significantly increase denitrification process in shallow --N discharge by groundwater from the study aquifer; 4) Based on these results, NO3 catchment is estimated to be about 5. 0% of the annual nitrogen input from fertilizer application at orange groves.
Year: 2005