Guo Jinjia, Lu Yuan, Cheng Kai, Song Jiaojian, Ye Wangquan, Li Nan, Zheng Ronger
Appl Opt. 2017 Oct 10;56(29):8196-8200. doi: 10.1364/AO.56.008196.
The exploitation and research of deep-sea hydrothermal vent has been an issue of great interest in ocean research in recent years. Laser-induced breakdown spectroscopy (LIBS) has great potential for ocean application due to the capabilities of stand-off, multiphase, and multielement analysis. In this work, a newly developed compact 4000 m rated LIBS system (LIBSea) is introduced with preliminary results of sea trials. The underwater system consists of an Nd:YAG single-pulsed laser operating at 1064 nm, an optical fiber spectrometer, an optics module, and an electronic controller module. The whole system is housed in an L800 mm×ϕ258 mm pressure housing with an optical window on the end cap. It was deployed on the remote operated vehicle Faxian on the research vessel Kexue, and in June 2015 was successfully applied for hydrothermal field measurements at the Manus area. The obtained results are shown that the LIBS system is capable of detecting elements Li, Na, K, Ca, and Mg in the hydrothermal area. Profiles of LIBS signals of elements K and Ca have also been obtained during the sea trial. The results show that the K emission line is gradually broadened with depth from sea surface to sea floor (1800 m or so); the K intensity shows a hump shape with maximum value at about 1050 m. The Ca emission line is rapidly broadened below 400 m and slowly narrowed to the sea floor; the Ca intensity shows no obvious change below 400 m and increases continuously to sea floor. A very interesting finding is that the small fluctuations of intensity profile curve of Ca show a degree of correlation with seawater temperature change. The sea trial results prove the performance of LIBSea. After further optimization, it is hoped to apply the LIBS system to the in situ mineral deposits and hydrothermal vent fluid detection in deep sea.
深海热液喷口的开发与研究是近年来海洋研究中备受关注的课题。激光诱导击穿光谱技术（LIBS）由于具有远距离、多相和多元素分析能力，在海洋应用方面具有巨大潜力。在这项工作中，介绍了一种新开发的额定深度为4000米的紧凑型LIBS系统（LIBSea）及其海试初步结果。该水下系统由一台工作在1064纳米的Nd:YAG单脉冲激光器、一台光纤光谱仪、一个光学模块和一个电子控制模块组成。整个系统安装在一个长800毫米×直径258毫米的耐压外壳中，端盖上有一个光学窗口。它搭载在科考船“科学”号上的遥控潜水器“发现”号上，并于2015年6月成功应用于马努斯地区的热液场测量。获得的结果表明，LIBS系统能够检测热液区中的锂、钠、钾、钙和镁元素。在海试期间还获得了钾和钙元素的LIBS信号剖面图。结果表明，钾发射线从海面到海底（约1800米）随深度逐渐变宽；钾强度呈驼峰状，在约1050米处达到最大值。钙发射线在400米以下迅速变宽，向海底缓慢变窄；钙强度在400米以下没有明显变化，向海底持续增加。一个非常有趣的发现是，钙强度剖面曲线的小波动与海水温度变化存在一定程度的相关性。海试结果证明了LIBSea的性能。经过进一步优化，有望将LIBS系统应用于深海原位矿床和热液喷口流体检测。
