Oil Spill Detection at Sea: Solar-Blind UV Reflection Spectroscopy and Spectrometer Applications

2026-02-28

When crude oil spills into the ocean, forming a slick, it can cause widespread hypoxia, seabird mortality, and trigger cascading ecological disasters like algal blooms. Traditional detection methods, such as thermal infrared remote sensing, are interfered with by sea temperature, while laser fluorometry is limited to nighttime operation. The discovery of the solar-blind ultraviolet (UV) band (200–300 nm) and the application of spectrometers have opened a new technological path for oil spill monitoring.

01 Solar-Blind UV Detection: Principle Analysis

Optical Properties of the Solar-Blind UV Band

Due to the strong absorption of this wavelength range by atmospheric ozone, solar background radiation near the Earth's surface in the solar-blind UV band (200–300 nm) is extremely weak, creating a natural "optical dark zone." This characteristic allows solar-blind UV reflection spectroscopy to effectively reduce ambient light interference and enhance oil signal discrimination. Experiments show that the reflectance contrast ratio between oil slicks and seawater in the 254 nm solar-blind UV band is 1.4–2.5 times, significantly higher than the 1.1–2.3 times ratio observed in the long-wave UV band (365 nm).

The 'Fingerprint Dialogue' Between Light and Oil Slicks

Treating an oil slick on the sea surface as a three-layer air-oil-water structure, when illuminated by 254 nm solar-blind UV light, reflected light from the air-oil and oil-water interfaces interferes, forming a unique "spectral fingerprint." Experiments reveal that refined oil products like 95# gasoline and diesel have a reflectance 1.4–2.5 times higher than seawater in the solar-blind UV band. Furthermore, reflectance exhibits periodic oscillation with increasing oil film thickness, eventually stabilizing at the reflectance of pure oil.

Measurement Principle of Thin-Film Interference

According to thin-film interference theory, the reflectance R of a single-layer film is calculated. Here, η₀ is the complex refractive index of air, and the characteristic matrix admittance Y is determined by the film's optical thickness δ = (2πN₁·cosθ₁·d)/λ, where N₁ = n + i·k.

Reflectance Variation Patterns

Periodic Oscillation: For thin oil films (<1 μm), reflectance oscillates approximately periodically with increasing thickness, where the period and peak values are determined by the oil's complex refractive index. For example, the reflectance oscillation period for 20# diesel at 254 nm is about 200 nm.

Thickness Saturation Effect: As oil film thickness increases, the oscillation amplitude decreases and stabilizes, approaching the reflectance of pure oil. Refined oils stabilize at 5–10 μm thickness, while crude oil stabilizes around 2–3 μm.

02 Spectrometer: Oil Spill Detection Experiments & Applications

Experimental System Setup & Parameters

Spectrometer Selection: The ATP2000 series spectrometer is recommended, with a detection range of 190–400 nm and a slit width of 50 μm, meeting high-precision detection needs in the solar-blind UV band (254 nm).
Optical Path Design: Employs vertical illumination of the oil film and collection of specularly reflected light. Testing utilizes deuterium-halogen broadband sources or 254 nm, 310 nm, and 365 nm LED sources, with a dark box design to isolate external light interference.

Oil Film Reflectance Spectroscopy Testing Procedure

Film Preparation: Add measured quantities of oil products (95# gasoline, -35# diesel, -20# diesel, light crude) to Petri dishes. Control diffusion time to create films with thicknesses ranging from 1.7 μm to 51 μm (at 1.7 μm intervals).
Spectral Acquisition: Collect 20 data sets for each oil film sample. Apply Savitzky-Golay algorithm smoothing to reduce light source fluctuation error (standard deviation < 10%).
Data Validation: Comparison between experimental data and simulations using the single-layer film characteristic matrix model shows good agreement in reflectance trends.

Extended Practical Applications

Online Dynamic Monitoring: Building on the experimental setup, integrating a fiber optic spectrometer with a deuterium-halogen source enables real-time oil spill monitoring in ports at flow rates up to 0.5 m/s, with single-sample detection time < 10 ms. Suitable for early warning around oil fields.
Airborne Remote Sensing: Leveraging UV aerial remote sensing technology, deploying fiber optic spectrometers on drones allows for rapid scanning of oil spill areas over hundreds of kilometers using solar-blind UV reflectance spectroscopy, improving coverage efficiency by over 20 times compared to traditional methods.
Oil Type & Thickness Inversion: Utilizing reflectance spectral characteristic differences of different oils in the solar-blind UV band (e.g., light crude oil shows ~20% higher reflectance peaks than 95# gasoline) and the quantitative relationship between oscillation period and thickness, both oil type and slick thickness (in the 0.1–10 μm range) can be inferred.

03 Analysis of Technical Advantages

Technical Type	Solar-Blind UV Reflection Spectroscopy	Thermal Infrared Remote Sensing	Laser-Induced Fluorescence
Detection Band	200-300 nm	8-14 μm	300-405 nm
All-Weather Capability	24/7 monitoring	Affected by sea surface temperature	Usable at night only
Thin Oil Film Sensitivity	<1 μm	Poor response	Weak signal
Equipment Cost	Low (approx. 60% lower than SAR)	Medium	High

Uniqueness of Solar-Blind UV Technology

Resistance to Background Interference: Reflectance in the solar-blind UV band is less affected by solar zenith angle. The oil-water reflectance ratio fluctuation is <15%, compared to up to 30% for long-wave UV, enabling all-weather monitoring.
Sensitivity to Thin Films: Capable of detecting ultra-thin oil films <1 μm, addressing a gap where microwave remote sensing performs poorly on thin slicks.

Experimental Data Support

Reflectance for all four tested oil types in the 254 nm solar-blind UV band was higher than seawater. Light crude oil reflectance intensity was 1.5–2.5 times that of seawater, while refined oils were 1.4–2.2 times. Reflectance showed an oscillating decline trend with increasing thickness, eventually stabilizing, consistent with single-layer film model simulations.

04 Conclusion & Technical Value

Experiments confirm that oil spill detection technology based on solar-blind UV reflection spectroscopy, coupled with high-precision reflectance data采集 (acquisition) by fiber optic spectrometers, enables integrated monitoring encompassing "presence detection, oil type classification, and thickness estimation."

Leveraging the optical advantages of the solar-blind UV band and the portability and real-time capability of fiber optic spectrometers, this technology provides a viable solution for all-weather, high-accuracy maritime oil spill monitoring. It holds significant application value for marine ecological protection and emergency response. When a beam of 254 nm UV light penetrates an oil slick, it decodes not just physical thickness but also embodies a technological commitment to protecting our blue planet.

Reference

Gong Bowen, Mao Shilei, Chen Bo. Study on Solar-blind Ultraviolet Reflection Characteristics of Simulated Offshore Oil Spill Targets[J]. Spectroscopy and Spectral Analysis, 2025,45(3): 637-644.

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