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Sulfate Runoff Processes during Rainfall Events in a Small Forested Catchment on the Sea of Japan Side recovering from Acidification under Climate Change
  • +6
  • Hiroyuki Sase,
  • Hiroki Yotsuyanagi,
  • Masayuki Morohashi,
  • Masaaki Takahashi,
  • Tsuyoshi Ohizumi,
  • Yayoi Inomata,
  • Shiho Yabusaki,
  • Ichiro Tayasu,
  • Hiroshi Okochi
Hiroyuki Sase
Asia Taiki Osen Kenkyu Center

Corresponding Author:sase@acap.asia

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Hiroki Yotsuyanagi
Asia Taiki Osen Kenkyu Center
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Masayuki Morohashi
Asia Taiki Osen Kenkyu Center
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Masaaki Takahashi
Niigata-ken
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Tsuyoshi Ohizumi
Asia Taiki Osen Kenkyu Center
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Yayoi Inomata
Kanazawa Daigaku
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Shiho Yabusaki
Sogo Chikyu Kankyogaku Kenkyujo
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Ichiro Tayasu
Sogo Chikyu Kankyogaku Kenkyujo
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Hiroshi Okochi
Waseda Daigaku
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Abstract

Changes in rainfall patterns due to climate change may accelerate the runoff of sulfur (S) and nitrogen (N), which are anthropogenically emitted as air pollutants and deposited and accumulated in forest soils. In this study, intensive observations were conducted in a forested catchment on the Sea of Japan side to clarify changes in stream water quality and runoff processes during rainfall events. The pH, electrical conductivity, and sulfate (SO 4 2−) concentration in the stream water decreased with increasing flow rate, whereas the nitrate (NO 3 ) concentration increased. The SO 4 2− concentration was negatively correlated with the flow rate, and the NO 3 concentration was positively correlated with the cumulative precipitation amount of each event and remarkably increased when it exceeded 10 mm. Hydrograph separations using the water isotopic parameter (deuterium excess, d-excess = δ 2H – 8 × δ 18O) showed that most of the stream flow during the rain events was derived from pre-storm water, whereas the portion derived from rainwater increased at rainfall intensities stronger than 10 mm h −1. The S isotope ratio (δ 34S) in the stream water fluctuated minimally compared to the d-excess value during rainfall events, suggesting relatively minor contributions of precipitation SO 4 2− to stream water via direct inflow. The SO 4 2− well homogenized in soil layers mainly contributed to the discharge during the rainfall events. Future climate change may further accelerate S and N runoff from forest catchments and disrupt material cycles in the ecosystem if warming causes more intense rainfall.
Submitted to Hydrological Processes
04 Mar 2024Reviewer(s) Assigned
23 Apr 2024Editorial Decision: Revise Major
05 Jun 2024Submission Checks Completed
05 Jun 2024Assigned to Editor
05 Jun 2024Reviewer(s) Assigned
16 Jun 2024Review(s) Completed, Editorial Evaluation Pending
17 Jun 2024Editorial Decision: Accept