# WaveConv-sLSTM-KET: A Novel Framework for the Multi-Task Analysis of Oil Spill Fluorescence Spectra
## 2 Materials and Methods  
### Experimental Scheme and Data Acquisition  
The fluorescence spectra of five engine oils were collected under laboratory conditions. The samples included Shell HELIX 0W-40, Shell HELIX 5W-20, Mobil Super 4T 20W-50, Mobil Super 1000 X1 Diesel 15W-40, and Mobil 2000 5W-40. These petroleum products differ in application, viscosity, and chemical composition, leading to variations in their fluorescence spectra, including differences in intensity and characteristic peaks. The experiment involved placing equal amounts of seawater collected from the Yellow Sea of China (coordinates: 120.18\({}^{\circ}\) E, 35.82\({}^{\circ}\) N) into a Petri dish that was 7 cm in diameter. Oil samples were added in volumes of 0.2 mL, 0.4 mL, 0.6 mL, 0.8 mL, 1 mL, 1.5 mL, and 2 mL. Afterthe oil spread into a uniform film, measurements were conducted using a self-developed portable spectrometer. The experimental setup consisted of three components: a custom-built portable spectrometer with integrated transmission and reception systems, a six-axis motorized stage, and a personal computer. A schematic of the system is shown in Figure 1. The system comprises a transmission system, a reception system, and a dispersion system. The following describes the instrument components and signal acquisition process. The laser source uses a 405 nm laser diode from Thorlabs (Newton, NJ, USA), delivering an adjustable power output from 1 to 100 mW. The emitted beam passes through a transmission system composed of two cylindrical mirrors that shape the divergence angle, ensuring uniform energy distribution over long distances. After collimation, the divergence angles are reduced from 78.5 mrad and 174.5 mrad to 1.8 mrad and 3 mrad, respectively, resulting in a focal spot of approximately 72 \(\upmu\)m \(\times\) 120 \(\upmu\)m. At 60 mW of power, the beam achieves a power density of 0.885 MW/cm\({}^{2}\). The shaped beam is then directed perpendicularly onto an oil film floating on seawater. Upon receiving the laser energy, the fluorescent molecules in the oil absorb the energy, become excited, and subsequently emit fluorescence via spontaneous radiation. The reception system employs a custom-designed Cassegrain telescope with two parabolic mirrors. Featuring a primary mirror diameter of 95 mm and an effective focal length of 255 mm, the telescope efficiently collects fluorescence from the target area. It focuses the collected light onto a 35 \(\upmu\)m-wide slit and directs the signal into the dispersion system. The dispersion system uses a crossed Czerny-Turner optical path to disperse the fluorescence signal. A reflective blaze grating with 600 lines/mm and a blaze angle of 8.6\({}^{\circ}\) is used; at 500 nm, the grating achieves a blaze efficiency of 68%, meeting the application requirements. The dispersed spectral signal is then focused by a lens onto Hamamatsu TDI-CCD image sensors, known for their high sensitivity and low noise performance, which enables the precise capturing of spectral variations. A control module synchronizes the laser driver and CCD timing, allowing the CCD to perform two measurements within a single laser cycle for background correction. Each spectrometer scan takes approximately 500 milliseconds and covers a spectral range of 400-750 nm. To improve dataset diversity and reliability while better simulating real-world conditions, spectral data were collected for oil films of varying thicknesses at three laser power settings (60 mW, 70 mW, and 80 mW), with 30 samples recorded per power level. The  
Figure 1: A schematic diagram of the measurement system. spectrometer scan time was set to 5 s. The container holding the oil film and seawater was mounted on a six-axis motorized stage, which was programmed via control software to execute horizontal and vertical reciprocating motions over a 2 cm range, along with a simple harmonic tilting motion to simulate wave action.