We present a novel approach to detecting and quantifying a subsea release of CO₂ from within North Sea sediments, which mimicked a leak from a subsea CO₂ reservoir. Autonomous lab-on-chip sensors performed in situ measurements of pH at two heights above the seafloor. During the 11 day experiment the rate of CO₂ release was gradually increased. Whenever the currents carried the CO₂-enriched water towards the sensors, the sensors measured a decrease in pH, with a strong vertical gradient within a metre of the seafloor. At the highest release rate, a decrease of over 0.6 pH units was observed 17 cm above the seafloor compared to background measurements. The sensor data was combined with hydrodynamic measurements to quantify the amount of CO₂ escaping the sediments using an advective mass transport model. On average, we directly detected 43 ± 8% of the released CO₂ in the water column. Accounting for the incomplete carbonate equilibration process increases this estimate to up to 61 ± 10%. This technique can provide long-term in situ monitoring of offshore CO₂ reservoirs and hence provides a tool to support climate change mitigation activities. It could also be applied to characterising plumes and quantifying other natural or anthropogenic fluxes of dissolved solutes.

我们提出了一种新方法来检测和量化北海沉积物中 CO ₂的海底释放，该方法模拟了海底 CO ₂储层的泄漏。自主芯片实验室传感器在海底上方的两个高度进行 pH 值的原位测量。在第 11 天的实验中，CO _{2 的}释放速率逐渐增加。每当洋流携带 CO ₂- 富集水流向传感器，传感器测量到 pH 值下降，在海底 1 米范围内具有强烈的垂直梯度。在最高释放速率下，与背景测量值相比，在海底上方 17 厘米处观察到的 pH 值降低超过 0.6 个单位。传感器数据与流体动力学测量相结合，以使用对流质量传输模型量化从沉积物中逸出的CO ₂量。平均而言，我们直接检测到水柱中释放的 CO _{2 的}43 ± 8% 。考虑到不完全的碳酸盐平衡过程，这个估计值增加到 61 ± 10%。该技术可以提供海上 CO _{2 的}长期原位监测水库，因此提供了一种支持减缓气候变化活动的工具。它还可用于表征羽流和量化其他自然或人为溶解溶质通量。