Program     Development of monitoring methods and instruments for marine environmental parameters       Poster Development of an underway instrument for accurate measurement of seawater total alkalinity P-SPS1-02-S Quanlong Li* , Xiamen University Qiu Li* , Xiamen University Presenter Email: 1834506052@qq.com Accurate measurements of total alkalinity (TA) with adequate spatial and temporal resolution is of essential importance in order to better understand the seawater carbonate system. An underway TA instrument is the best tool to achieve that goal. In this study, an underway instrument for TA measurement was built by modifying the automated TA analyzer we developed before, which was based on single-point titration and spectrophotometric pH measurement using the mixture of HCl and bromocresol as titrant. The main modification of the instrument is the use of a thermostat water bath with peltier device, inside which two coils (one for sample, the other for titrant) were installed. When sample and titrant were introduced and stayed in the coils, their temperatures were brought to 25.0 ± 0.1 °C. In addition, the instrument geometry and layout of the parts were optimized. The tests in lab showed that the instrument featured a sample throughput time of 6.65 min with high precision (±0.64; n=382) and accuracy (-2.9±1.14; n=6). The needs of seawater sample and titrant volumes for one measurement were about 32 mL and 0.9 mL, respectively. Tests in research vessel are going to be carried out.