Super typhoon induced high silica export from Arakawa River, Japan
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RESEARCH ARTICLE
Super typhoon induced high silica export from Arakawa River, Japan Atsushi Kubo 1 & Natsuki Yamahira 1 Received: 9 February 2020 / Accepted: 5 June 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Dissolved silicate (DSi) and particulate silica (PSi) concentrations were measured at Arakawa River and at sewage treatment plants (STP) during October 2018 to October 2019. These included flooding observations after super Typhoon Hagibis. At ordinary water levels, the STP effluents were found to be the largest source of DSi in the river. Although DSi concentrations during the flooding events (165 μmol L−1) decreased by about 25% compared to that of ordinary water level (221 μmol L−1), PSi was more than sixteen times higher value (301 μmol L−1) compared to that of ordinary water level (18 μmol L−1). Loading amounts of DSi and PSi (± 1 standard error) were 1.5 × 108 (± 0.1 × 108) and 0.15 × 108 (± 0.02 × 108) mol year−1, respectively, excluding the data of Typhoon Hagibis. Loading amounts during flooding events of DSi and PSi were 1.2 × 108 (± 0.1 × 108) and 2.4 × 108 (± 0.4 × 108) mol 15 days−1, respectively. Although the silica loading at ordinary water level was mainly derived from DSi, the silica loading during flooding events was extremely large due to both high level of DSi and PSi; moreover, it was higher than the annual loading amount. Keywords Dissolved silicate . Particulate silica . Flooding . Runoff . Sewage treatment plant
Introduction Dissolved silicate (DSi) in water is an essential component for some aquatic plants and organisms. Primary production of diatoms accounts for about 45% of the primary production of the entire ocean (Nelson et al. 1995; Rousseaux and Gregg 2014). Although DSi is naturally supplied to water by the weathering process, with aluminosilicates dissolved in rainwater, river water, groundwater, and seawater, human activity has also affected the silica cycle (Tréguer and De La Rocha 2013). Dams act as one of the major sinks of DSi because they increase the water residence time, inducing diatom blooms and particulate silica (PSi) sedimentation (Wei et al. 2015; Yang et al. 2018; Maavara et al. 2020). In contrast, supply from farmland, groundwater, and sewage treatment Responsible Editor: Philipp Gariguess Electronic supplementary material The online version of this article (https://doi.org/10.1007/s11356-020-09634-y) contains supplementary material, which is available to authorized users. * Atsushi Kubo [email protected] 1
Department of Geosciences, Shizuoka University, 856 Ohya, Suruga-ku, Shizuoka city, Shizuoka Prefecture 422-8529, Japan
plants (STP) is one of the sources of DSi (Van Dokkum et al. 2004; Sferratore et al. 2006; Kumagai et al. 2011). Silicate fertilizers have been applied for a long time to stabilize rice yield, but fertilizer application rates have been decreasing since the 1970s in Japan (Furumai et al. 2012). DSi concentrations in groundwater are high because some coastal aquifers consist of aluminosilicates (e.
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