POTENTIAL CO2 SEQUESTRATION ASSOCIATED WITH A TYPHOON EVENT, TYPHOON MINDULLE, CHOSHUI RIVER, TAIWAN

Recent work on small mountainous rivers (SMRs) has demonstrated that they are major sources of sediment, particulate organic carbon (POC) and dissolved fluxes to the ocean. Infrequent aperiodic events such as typhoons can be responsible for the long-term water discharge and sediment delivery from SMRs. Although many studies have focused on the rapid denudation and/or geochemical delivery associated with these SMR regimes, little information is available to quantify the overall importance of aperiodic events in material delivery, in part because they are difficult to sample and study. In this presentation we show the first known semi-continuous monitoring of sediment and associated POC fluxes and dissolved Si concentrations delivered to the ocean during a typhoon. Sampling of the Choshui River in Taiwan during Typhoon Mindulle in 2004 revealed a sediment delivery of approximately 52 million tons coupled with a POC flux of approximately 4.12x10⁵ tons during a 96 hour period. The linkage of high amounts of POC with sediment concentrations capable of generating a descending hyperpycnal plume upon reaching the ocean may provide the first known evidence for the rapid delivery and burial of POC from the terrestrial system. CO₂ consumption via silicate weathering calculated from dissolved Si concentrations revealed a storm value of 1.43x10⁸ moles CO₂ consumed. Comparison of these storm POC fluxes with those delivered annually from high sediment and POC yielding localities elucidates the importance of tropical cyclone events as a primary delivery mechanism for POC fluxes from small mountainous rivers and their importance as a global sink of CO₂.