We present tritium (³H) and helium isotope (δ³He) data from the South China Sea (SCS), to estimate apparent oxygen utilization rates (AOURs). The observed δ³He values are close to the theoretical solubility equilibrium value of -1.7% in the upper mixed layer, followed by an increase with depth down to ~1500 m. Below 1500 m depth, δ³He is homogenously distributed with a value of 20.9% ± 1.0%. The distribution of δ³He reveals that a significant fraction of ³He throughout the water column over the entire SCS basin is allochthonous, derived from mantle sources originated from the Pacific Ocean. By using the salinity-normalized “potential” alkalinity (NPA) as a conservative mixing tracer, ³He produced by tritium decay (tritiogenic) was separated from mantle ³He, and the apparent ³H–³He ages of the SCS water masses were subsequently calculated to be 11 ± 5 years at 100 m depth and 50 ± 4 years at 1000 m. Together with the observed dissolved oxygen concentrations, we estimated the mean AOURs and obtained values of 4.15 ± 0.27 μmol kg⁻¹·yr⁻¹ for the depth range of 100–500 m, and 0.81 ± 0.23 μmol kg⁻¹·yr⁻¹ for that between 800 and 1000 m depth. The depth-integrated AOURs between 100 and 1000 m depth, yield a spatially and temporally averaged export flux of organic carbon of 1.96 ± 0.16 mol-C·m⁻²·yr⁻¹, comparable with previous estimates based on either ²³⁸U/²³⁴Th disequilibrium or nutrient and oxygen mass balance calculations in the SCS.

我们提供了来自南海 (SCS) 的氚 ( ³ H) 和氦同位素 (δ ³ He) 数据，以估计表观氧利用率 (AOURs)。观察到的 δ ³ He 值接近于上混合层中 -1.7% 的理论溶解度平衡值，然后随着深度下降到~1500 m。在 1500 m 深度以下，δ ³ He 分布均匀，值为 20.9% ± 1.0%。δ ³ He的分布表明，³他在整个南海盆地上空的整个水体都是外来的，来源于太平洋的地幔源。通过使用盐度归一化的“潜在”碱度（NPA），其为保守的混合示踪剂，³他制作由氚衰变（tritiogenic）从地幔分离³ He和表观^3名H- ³的SCS水团的He年龄分别为随后计算为 11 ± 5 年（100 m 深度）和 50 ± 4 年（1000 m）。连同观察到的溶解氧浓度，我们估计了平均 AOURs 并获得了 4.15 ± 0.27 μmol kg ^-1 ·yr ^-1的值，对于 100-500 m 的深度范围，以及 0.81 ± 0.23 μmol kg ^-1 ·yr^-1表示 800 到 1000 m 深度之间。100 到 1000 m 深度之间的深度综合 AOURs 产生 1.96 ± 0.16 mol-C·m ^-2 ·yr ^-1的空间和时间平均有机碳输出通量，与之前基于²³⁸ U/ ^{234 的}估计值相当SCS 中的不平衡或养分和氧质量平衡计算。