10:00 AM - 10:15 AM
[HTT16-05] Response of forest ecosystems to reduction of atmospheric sulfur deposition
Keywords:sulfur, acidification, recovery, climate change
Sulfur oxides (SOX) derived from anthropogenic fossil fuel combustions have been causing so-called “acid rain problem” in various regions of the world. In fact, sulfate (SO42–) derived from atmospheric deposition is a major counter ion of proton (H+) in terrestrial ecosystems and sulfur deposition was a primary cause of acidification. While SOX emissions have already been enough reduced in Europe and the United States and just started declining in Asia, recovery processes from acidification are still concerned in these regions. However, dynamics of sulfur has not been investigated in terrestrial ecosystems in Asia, where recovery from acidification has just started in accordance with reduction of air pollution. To clarify the sulfur dynamics in Asia, we have been applying the isotopic analysis to rainwater, soil and soil solution, and/or stream water in forest catchments in Japan, Thailand and Malaysia. In this paper, outputs from two catchment sites in Japan will be presented mainly based on the recent publications (Sase et al. 2019, 2021) and perspectives on relevant studies may also be introduced with information on sites in Thailand and Malaysia.
Field surveys on atmospheric deposition and stream water started in Lake Ijira catchment in Gifu Prefecture (IJR) and Kajikawa catchment in Niigata Prefecture (KJK) in 1988 and 2002, respectively. For these sites, sulfur isotopic ratio (δ34S) has been determined for rainwater, soil solutions, and stream water since 2014 and 2012, respectively. The BaSO4 precipitates obtained from water samples were analyzed using a mass spectrometer equipped with an elemental analyzer, EA-IRMS (EA2500−Delta Plus by Conflo II or EA IsoLink CN – Delta Plus Advantage by Conflo IV, Thermo Fisher Scientific, USA) according to the methods described in the previous publications (Inomata et al. 2019; Sase et al. 2019, 2021).
Atmospheric S deposition at IJR and KJK decreased over the last decade, possibly reflecting reduction of both transboundary air pollution and domestic air pollution. Accordingly, pH and/or alkalinity increased with decrease of SO42– concentrations in stream water, suggesting recovery from acidification. At IJR, the sulfur outputs via stream water exceeded the atmospheric inputs significantly, larger than two times (Sase et al. 2019). On the other hand, at KJK, the outputs gradually increased and exceeded the inputs occasionally (Sase et al. 2021). The phenomena seemed to be similar, however, the isotopic evidence showed a clear difference between them. The δ34S values in stream water at IJR were stable with negative values, which were significantly lower than the range of rainwater, while the values in stream water at KJK were stable within the range of rainwater. It was suggested that the stream water at IJR was largely influenced by sources other than atmospheric deposition, such as geological (rock) sulfur (Sase et al. 2019). In the presentation, importance of a retention - release cycle of sulfur in forest ecosystems and possibility of disturbing recovery processes by climate change will also be highlighted.
This work was supported by grants from the Asia-Pacific Network for Global Change Research (ARCP2012-18NMY-Sase; ARCP2013-13CMY- Sase) and the Japan Society for the Promotion of Science (JSPS) KAKENHI Grant Numbers JP19H00955, JP19K12315 and JP18K11616.
References. Inomata et al. 2019. Science of the Total Environment; Sase et al. 2019. Biogeochemistry; Sase et al. 2021. Atmospheric Environment.
Field surveys on atmospheric deposition and stream water started in Lake Ijira catchment in Gifu Prefecture (IJR) and Kajikawa catchment in Niigata Prefecture (KJK) in 1988 and 2002, respectively. For these sites, sulfur isotopic ratio (δ34S) has been determined for rainwater, soil solutions, and stream water since 2014 and 2012, respectively. The BaSO4 precipitates obtained from water samples were analyzed using a mass spectrometer equipped with an elemental analyzer, EA-IRMS (EA2500−Delta Plus by Conflo II or EA IsoLink CN – Delta Plus Advantage by Conflo IV, Thermo Fisher Scientific, USA) according to the methods described in the previous publications (Inomata et al. 2019; Sase et al. 2019, 2021).
Atmospheric S deposition at IJR and KJK decreased over the last decade, possibly reflecting reduction of both transboundary air pollution and domestic air pollution. Accordingly, pH and/or alkalinity increased with decrease of SO42– concentrations in stream water, suggesting recovery from acidification. At IJR, the sulfur outputs via stream water exceeded the atmospheric inputs significantly, larger than two times (Sase et al. 2019). On the other hand, at KJK, the outputs gradually increased and exceeded the inputs occasionally (Sase et al. 2021). The phenomena seemed to be similar, however, the isotopic evidence showed a clear difference between them. The δ34S values in stream water at IJR were stable with negative values, which were significantly lower than the range of rainwater, while the values in stream water at KJK were stable within the range of rainwater. It was suggested that the stream water at IJR was largely influenced by sources other than atmospheric deposition, such as geological (rock) sulfur (Sase et al. 2019). In the presentation, importance of a retention - release cycle of sulfur in forest ecosystems and possibility of disturbing recovery processes by climate change will also be highlighted.
This work was supported by grants from the Asia-Pacific Network for Global Change Research (ARCP2012-18NMY-Sase; ARCP2013-13CMY- Sase) and the Japan Society for the Promotion of Science (JSPS) KAKENHI Grant Numbers JP19H00955, JP19K12315 and JP18K11616.
References. Inomata et al. 2019. Science of the Total Environment; Sase et al. 2019. Biogeochemistry; Sase et al. 2021. Atmospheric Environment.