With the aim of using side‐scan sonar (SSS) in marine monitoring at offshore CO₂ storage sites, an experiment was conducted in a bay with a flat seabed, approximately 32 m deep. CO₂ bubbles released at regulated rates between 500 and 5000 mL min⁻¹ were searched for with SSS to elucidate the detection limit, which depends on the towing speed and the altitude of SSS, and the horizontal distance between the release point and SSS. When the towing speed was less than 6 knots, SSS was able to detect CO₂ bubbles released at 1000 mL min⁻¹ (approximately 4 tonnes year⁻¹), which is an extremely small rate compared with injection rates in commercial scale storage, O(10⁶) tonnes year⁻¹. The time required for searching an area of 1 km² with SSS was estimated to be between 1.7 and 3.4 hours, assuming that SSS was towed at an altitude of 27 m. Thus, SSS was demonstrated to be serviceable for marine monitoring. pH measured at 5 m away from the release point dropped by larger than 0.05 four times during the experiment. Only one of them might have been due to the CO₂ release, and the others were due to intrusion of water from deeper layers because temperature, salinity and dissolved oxygen simultaneously changed. This indicates that bubble searching with SSS could detect smaller‐scale CO₂ leakages than locating anomalous carbonate values, although the latter is still important in case all or most of CO₂ dissolve before the emission to the sea. © 2020 Society of Chemical Industry and John Wiley & Sons, Ltd.

中文翻译：

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实验揭示了侧扫声纳检测浅海中二氧化碳气泡的能力

为了在海上CO ₂封存地点的海洋监测中使用侧扫声纳（SSS），在大约32 m深的平坦海底海湾中进行了一项实验。用SSS搜索以500至5000 mL min ^-1之间的规定速率释放的CO ₂气泡，以阐明检测极限，该极限取决于SSS的牵引速度和高度以及释放点与SSS之间的水平距离。当拖曳速度小于6节时，SSS能够检测到以1000 mL min ^-1（大约4吨年^-1）释放的CO ₂气泡，与商业规模存储中的注入速率O相比，这是非常小的比例（10 ⁶）吨年^-1。假设SSS被拖曳到27 m的高度，用SSS搜索1 km ²的区域所需的时间估计在1.7至3.4小时之间。因此，SSS被证明可用于海洋监测。在实验过程中，离释放点5 m处测得的pH值下降了四倍，大于0.05。其中只有一个可能是由于释放了CO ₂引起的，另一个是由于温度，盐度和溶解氧同时发生变化而从较深层侵入水。这表明，与定位异常碳酸盐值相比，使用SSS进行气泡搜索可以检测到更小规模的CO ₂泄漏，尽管后者对于全部或大部分CO仍然很重要₂溶解后才排放到海中。©2020年化学工业协会和John Wiley＆Sons，Ltd.