Basic research for the technological advancement of the determination of the oceanic CO_2 variability

我们设计并建立了一种新的自动分光光度系统，用于精确分析海水中的总碱度。我们还制作并改进了软件，以适当地控制它。2005年6-7月，我们参加了日本气象厅的R/V Ryofu-Maru邮轮，沿着西北太平洋，165^ΩE，50^ΩN和28^ΩN之间，穿过西部副北极涡旋和副热带涡旋之间的过渡带，在18个水文站采集了从不同深度到1000米的海水样本。巡航结束后，我们对它们的总碱度进行了分析，证明了新系统能够进行高精度的分析，精度为±2μ摩尔·kg~(-1)(<1/1000)。此外，从总溶解无机碳(DIC)与碱度之间的性质-性质图的变化来看，我们估计该地区上层的DIC在过去13年中由于大气CO_2的吸收而增加了约15μ。我们还设计并建造了分析海水中溶解六氟硫化物(SF_6)的系统和采样瓶。通过对检测器温度、载气流速等最佳条件的考察，成功地将检测下限降至0.015毫微米/公斤。在10L精磨铝合金圆筒中制备了低浓度SF_6标准气体，并证明其浓度至少稳定了9个月。2006年10月，在西北太平洋沿137^ΩE的R/V Ryofu-Maru巡航期间，我们采集了不同深度的海水样本，成功地获得了SF6的垂直剖面，其次表层的最大浓度为1.1Femtomol/kg。

We have designed and built a new automated spectrophotometric system for precise total alkalinity analysis in seawater. We also made and improved software to properly control it. In June-July 2005, we participated in a cruise of JMA's R/V Ryofu-maru that sailed western North Pacific along, 165^ΩE between 50^ΩN and 28^ΩN across the transition zone between western sub arctic gyre and subtropical gyre, and collected seawater samples at 18 hydrographic stations from various depths down to 1000m. After the cruise we analyzed their total alkalinity and demonstrated that the new system is capable of high-precision analysis with the precision of ±2 μmol kg^<-1> (less than 1/1000). In addition, from the change in the property-property plots between total dissolved inorganic carbon (DIC) and alkalinity, we evaluated that DIC in the upper layer of this zone has increased about 15 μmol kg^<-1> during the last 13 years due to the uptake of the increasing atmospheric CO_2.We have also designed and built a system and a sampling bottle to analyze the back-ground-level hexafluorosulfide (SF_6) dissolved in seawater. We succeeded in lower the detection limit to 0.015 femto(10^<-15>)mol/kg after investigating the optimum conditions of detector-temperature, flow rate of carrier gas, and so on. We also prepared a standard gas for low level SF_6 in a finely ground 10L aluminum-alloy cylinder, and proved that its concentration is stable at least for 9 months after preparation. In the western North Pacific along 137^ΩE during the JMA's R/V Ryofu-maru cruise in October 2006, we collected seawater samples from various depths and succeeded in obtaining vertical profiles of SF_6 that showed a maximum concentration of 1.1 femtomol/kg in the subsurface layer.