Chemical sensor measurements at the sediment surface of the Håkon Mosby mud volcano (LOOME)

Six sensor units each having a pH, dissolved oxygen (DO) and oxidation reduction potential (ORP) sensor, plus a central logger, and connection cables were purchased from RBR (Ottawa). The sensing loggers were placed at a transect across the hot spot. Unfortunately, 5 of the 7 loggers were drowned. Only the central logger, that collected the data from the 6 sensor loggers, and one of the sensor loggers remained dry and functional. The sensor was positioned at 50 m south of the frame, in the center of the hot spot. The ORP did not show interpretable signals. The DO and pH signals showed good correlation (. At the end of October 2009 both signals decreased, the pH became as low as 4, possibly indicating increased seepage, or burial in expelled sediments. In December both sensors regained seawater values and then decreased again until the end of May 2010. A pH of 4 can only be reached by very high carbondioxide levels. The dynamics of the signals indicate eruptions and sediment movements from October 2009 till the end of the deployment.本次从加拿大渥太华的RBR公司采购的设备包括6台传感器单元、1台中央数据记录器（logger）以及连接线缆，每台传感器单元均集成有pH传感器、溶解氧（dissolved oxygen, DO）传感器与氧化还原电位（oxidation reduction potential, ORP）传感器。所有传感记录器被布设至横跨热点区域的样带之上。遗憾的是，7台记录器中有5台被水淹没，仅负责采集6台传感器记录器数据的中央记录器，以及其中1台传感器记录器保持干燥且功能正常。该正常运行的传感器被部署于框架以南50米处的热点区域中心位置。氧化还原电位（ORP）未输出可解析的有效信号，溶解氧（DO）与pH信号则呈现出良好的相关性。2009年10月末，两类信号均出现下降，pH值最低降至4，这可能预示着渗流作用增强，或是沉积物被排出后的掩埋效应。同年12月，两台传感器的读数恢复至海水基准值，随后再次持续下降，直至2010年5月末。pH值降至4仅能由极高的二氧化碳浓度所导致。信号的动态变化特征表明，2009年10月至本次部署任务结束期间，该区域发生了喷发活动与沉积物运移事件。