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Typhoon Impacts on the Chemical Weathering Regime and Atmospheric Carbon Consumption of a High Standing Island Watershed, Taiwan
Meyer, Kevin J

2016, Master of Science, Ohio State University, Earth Sciences.
The impacts of extreme weather on watershed dynamics and chemical weathering are poorly understood and rarely documented. This study addresses the impacts of Typhoon Mindulle (2004) on the physical hydrology, chemical weathering sources, and CO2 consumption of the Choshui River, a High Standing Island watershed in Taiwan. Storm-flow runoff was determined to be largely controlled by total precipitation and precipitation intensity. Watershed slope steepness is much less important in determining runoff during periods of extremely high precipitation. Weathering sources were determined to be silicate and secondary disseminated carbonate minerals at the surface and silicate contributions from deep thermal waters. Loss on ignition analysis of collected rock samples indicate disseminated carbonate may compose a greater fraction of the surface minerology than previously identified. Strontium isotope and major ion geochemistry indicate that high precipitation causes surface minerals to control the weathering profile. These data also suggest purging of silicate solute rich soil waters during storm events, creating a greater relative contribution of silicate weathering to the solute load during periods of increased precipitation and runoff. However, this leads to depletion of this solute reservoir and carbonate weathering becomes more important to the weathering regime as the storm continues. Major ion data indicate the possibility that mica weathering (muscovite, illite, biotite, chlorite) may represent an important silicate weathering pathway in the watershed, but this determination was beyond the scope of data available. Deep thermal water represents an important contribution to river solutes during lower flow conditions.


Sulfuric acid creation through oxidation of pyrite was determined to be a major contributor to total weathering and represents ~40%–77% of weathering. The lowest contributions from sulfuric acid occur during peak flows. Carbonate weathering is dominant in the watershed (66%-86% of total weathering) and increases in contribution during the typhoon. The remaining chemical weathering comes from silicate materials. Carbonate weathering represents the majority of CO2 flux from the atmosphere during storm flow but silicate weathering is the majority during lower flow conditions. The carbonate contribution to CO2 flux is 36%–69% (31%–64% for silicates). Silicate weathering CO2 consumption for the 72 hours of storm sampling is 0.84 ton km-2, with a daily average of 0.28 ton km-2. CO2 flux from the atmosphere including carbonate weathering is substantially higher (2.51 ton km-2 for 72 hours storm measurements and 0.84 ton km-2 daily storm average). Chemical weathering mediated CO2 export rates from the atmosphere increased to a maximum of over 140 times the pre-storm rate for silicate weathering and 250 times the pre-storm rate for total weathering including carbonate minerals. The 72 hour sampling period contained only a portion of the total storm-flow and did not include the majority of the peak flow which occurred following sampling. Therefore, these consumption values are likely underestimated. Daily silicate consumption estimates during the storm-flow may contribute 0.03%–0.1% of average daily global silicate CO2 consumption from an area comprising ~0.001% of total global landmass for the days of storm activity. Therefore, extreme storm impacts on High Standing Islands globally may provide a significant but not represented contribution to the global carbon budget.
Anne Carey (Advisor)
W.Berry Lyons (Committee Member)
Matthew Saltzman (Committee Member)
133 p.

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Meyer, K. (2016). Typhoon Impacts on the Chemical Weathering Regime and Atmospheric Carbon Consumption of a High Standing Island Watershed, Taiwan. (Electronic Thesis or Dissertation). Retrieved from https://etd.ohiolink.edu/

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Meyer, Kevin. "Typhoon Impacts on the Chemical Weathering Regime and Atmospheric Carbon Consumption of a High Standing Island Watershed, Taiwan." Electronic Thesis or Dissertation. Ohio State University, 2016. OhioLINK Electronic Theses and Dissertations Center. 15 Aug 2018.

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Meyer, Kevin "Typhoon Impacts on the Chemical Weathering Regime and Atmospheric Carbon Consumption of a High Standing Island Watershed, Taiwan." Electronic Thesis or Dissertation. Ohio State University, 2016. https://etd.ohiolink.edu/

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