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

我们设计并建造了一套用于海水总碱度精密分析的自动化分光光度系统。2005年6月~ 7月，我们参加了日本海洋厅的“两府丸”号（R/V Ryofu-maru）在北太平洋西部沿沿着165^ΩE，50^ΩN ~ 28^ΩN，穿越西副北极环流和副热带环流之间的过渡带，在1000 m以下的18个水文站采集了海水样品。巡航结束后，我们分析了它们的总碱度，并证明新系统能够进行高精度分析，精度为±2 μmol kg^<-1>（小于1/1000）。此外，根据总溶解无机碳（DIC）与碱度的性质-性质图的变化，估算出近13年来由于大气CO_2的增加，该带上层DIC增加了约15 μmol kg ~<-1>（-1）。溶解在海水中。通过<-15>对检测器温度、载气流量等条件的优化研究，成功地将检测限降低到0.015毫微微（10^）mol/kg，并在10 L细磨铝合金气瓶中制备了低水平SF_6标准气体，经实验证明，该标准气体的浓度至少可稳定9个月。2006年10月，日本海洋厅“两府丸”号考察船在北太平洋西部沿着137^ΩE海域，采集了不同深度的海水样品，成功地获得了SF_6浓度的垂直剖面图，其次表层的最大浓度为1.1毫微微摩尔/千克。

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.