收发共轴LIF系统海面乳化溢油探测与仿真研究

海面溢油污染是常见的海洋污染之一，通常以未乳化、乳化等风化状态存在，其中乳化阶段对海洋危害更加显著。因此，快速监测海面溢油信息，准确识别并评估乳化溢油污染对溢油应急处理和生态环境保护具有重要意义。激光诱导荧光(LIF)是目前有效的海面溢油探测技术之一。LIF探测系统可分为收发共轴和非共轴形式。有关收发共轴LIF系统对海面乳化溢油探测的研究较少，利用Mie散射理论计算得到溢油乳化液的吸收系数、散射系数等光学参数，建立蒙特卡罗光子传输模型对乳化溢油进行双向反射再辐射分布函数(bidirectional reflectance and reradiation distribution function, BRRDF)的仿真研究。分析浓度、厚度、油种多参数下乳化溢油的f_BRRDFcos2θ与发射接收角度的关系，进而得到基于收发共轴LIF系统海面乳化溢油探测的适宜条件。结果表明，f_BRRDFcos2θ与发射接收方位角无关，但受发射接收天顶角的影响较大，各参数下乳化溢油的f_BRRDFcos2θ其变化规律具有一定差异性。重质油包水和低浓度水包油的f_BRRDFcos2θ对天顶角的变化更敏感，轻质油包水和高浓度水包油的f_BRRDFcos2θ对较小角度(0°~45°)不敏感，之后迅速下降。因此基于收发共轴LIF系统对海面乳化溢油进行探测时，发射接收天顶角在0°~45°范围内为宜，其中在0°处系统可接收到最大光功率。另外，为验证仿真正确性，利用实验室LIF系统对乳化溢油进行收发共轴式测量荧光光谱，发现此与仿真结果具有一致性趋势。

Simulation Research on Detection of Emulsified Oil Spill on Sea Surface Based on LIF System With Coaxial Transceiver

Oil spill pollution on the sea surface is one of the most common marine pollutions, which usually exists in the state of non-emulsification, emulsification and other weathering, and the emulsification stage is more harmful to the ocean. Therefore, it is of great significance to quickly monitor the oil spill information and accurately identify and evaluate the emulsified oil spills pollution for the emergency treatment of oil spill and the restoration of the ecological environment. Laser-induced fluorescence (LIF) is recognized as one of the most effective detecting oil spills. LIF detection systems can be divided into the forms of coaxial transceiver and non-coaxial transceiver. Since there is no research on transmitting and receiving related problems in the detection of the emulsified oil spill by LIF system with coaxial transceiver, the optical parameters such as absorption coefficient and scattering coefficient of the emulsified oil spill are calculated by MIE scattering theory, and the Monte Carlo, photon transport model, is established to simulate the bidirectional reflectance and reradiation distribution functions (BRRDF) of the emulsified oil spill. The relationship between f_BRRDFcos2θ and the transmitting and receiving angle of the emulsified oil spill is analyzed under multi parameters of concentration, thickness and oil type. Then the suitable conditions for detecting oil spill on the sea surface based on an LIF system with coaxial transceiver are obtained. The results show that the f_BRRDFcos2θ is independent of the azimuth angle of transmitting and receiving. However, it is greatly affected by the zenith angle of transmitting and receiving, the variation law of f_BRRDFcos2θ of the emulsified oil spill under various parameters has certain differences. The f_BRRDFcos2θ of water-in-oil of heavy oil and oil-in-water of low concentration are more sensitive to the change of zenith angle, and the f_BRRDFcos2θ of water-in-oil of light oil and oil-in-water of high concentration are insensitive to smaller angle (0°~45°), and then decrease rapidly. Therefore, when detecting the emulsified oil spill on the sea surface based on the LIF system with a coaxial transceiver, it is advisable to transmit and receive the zenith angle within the range of 0°~45°, and the maximum optical power can be received at 0°. In addition, to verify the correctness of the simulation, the fluorescence spectra of the emulsified oil spill were measured by the laboratory LIF system. The results show that this is consistent with the simulation results.