海面溢油油包水乳化液多种探测参数的BRRDF仿真研究

海面溢油污染是最常见的污染之一，通常以不同风化状态存在于海面上，如未乳化阶段油膜，乳化阶段水包油、油包水等。因此，快速准确的监测海面溢油信息，识别、分类及定量评估不同阶段的溢油污染，对海洋污染快速治理和生态环境恢复具有重要意义。激光诱导荧光（LIF）是目前最有效的海面遥感探测技术之一。双向反射再辐射分布函数（BRRDF）通过描述目标受激发射的荧光分布来表征目标的荧光性质。目前基于LIF探测技术除对海面溢油未乳化阶段油膜和乳化阶段水包油有所研究外，尚未对乳化阶段中油包水乳化液荧光特性方面开展相关研究。鉴于此，利用米氏散射理论得到油包水乳化液的光学参数，对油包水乳化液建立蒙特卡罗光子传输模型以开展BRRDF研究，探讨与分析油包水乳化液在含油率、入射接收角度、厚度参数下f_BRRDFcosθ_rcosθ_i（荧光出射角θ_r，激光入射角θ_i）的变化，并利用实验测量的荧光光谱数据与仿真进行对比验证。结果表明，f_BRRDFcosθ_rcosθ_i值随乳化液含油率（海水表层乳化液的含油率）的升高呈下降趋势，并与实验采集到的荧光光谱数据具有一致性趋势，为基于LIF技术对海面溢油油包水乳化液含油率的推断提供依据；f_BRRDFcosθ_rcosθ_i值随θ_i的增大开始变化比较缓慢，当θ_i>65°时迅速减小，并随θ_r继续增大而持续减小，与实验采集到的光谱数据趋势相吻合，此趋势说明利用LIF技术对海面油包水乳化液进行探测时，激光入射角度不宜超过65°且垂直海面可接收到最大光信号；f_BRRDFcosθ_rcosθ_i值随乳化液厚度的升高先上升后变得平稳，说明f_BRRDFcosθ_rcosθ_i可评估海面溢油油包水乳化液的最小厚度。该研究内容为基于LIF技术探测海面溢油提供理论和技术支持。

BRRDF Simulation Research on Multiple Detection Parameters of Water-in-Oil Emulsion of Oil Spill on the Sea Surface

Oil spill pollution on the sea surface is one of the most common pollutions, which usually exists on the sea surface in different weathering states, such as oil film in the unemulsified stage, oil-in-water and water-in-oil in the emulsified stage. Therefore, rapid and accurate monitoring of oil spill information on the sea surface, and identification, classification and quantitative assessment of oil spill pollution at different stages are of great significance to the rapid control of marine pollution and the restoration of the ecological environment. Laser induced fluorescence (LIF) is currently one of the most effective technologies for remote sensing detection of the sea surfaces. The bidirectional reflectance and reradiation distribution function (BRRDF) characterizes the fluorescence properties of the target by describing the fluorescence distribution of the stimulated emission. At present, the fluorescence characteristics of water-in-oil emulsion in the emulsification stage have not been studied except oil film in the unemulsified stage and oil-in-water in the emulsification stage based on LIF detection technology. Because of this, the optical parameters of water-in-oil emulsion are obtained using the Mie scattering theory. The Monte Carlo photon transmission model of water-in-oil emulsion is established to carry out BRRDF research. The variation of f_BRRDFcosθ_rcosθ_i (the zenith angle of fluorescence emission is θ_r, and the zenith angle of laser incidence is θ_i) of water-in-oil emulsion under the parameters of oil content, incident-receiving angle, and thickness is discussed and analyzed. The experimental data of the fluorescence spectrum are compared with the simulation. The results show that the value of f_BRRDFcosθ_rcosθ_i decreases with the increase of the oil content of the emulsion (the oil content of the surface emulsion of sea-water) and has a consistent trend with the spectral data collected by the experiment, which provides the basis for inferring the oil content of water-in-oil emulsion based on LIF technology. The value of f_BRRDFcosθ_rcosθ_i first stabilizes with the increase of θ_i and decreases rapidly when θ_i>65°, and gradually decreases with the increase of θ_r, which is consistent with the trend of spectral data collected by experiments. This trend indicates that the incident angle of the laser should not exceed 65°, and the maximum optical signal can be received perpendicular to the sea surface when LIF technology is used to detect the water-in-oil emulsion on the sea surface. The value of f_BRRDFcosθ_rcosθ_i rises first and then becomes stable with the increase of emulsion thickness, which indicates that f_BRRDFcosθ_rcosθ_i can be used to evaluate the minimum thickness of water-in-oil emulsion. The research content of this paper provides theoretical and technical support for detecting oil spills on the sea surface based on LIF technology.