Calculation Method of Optical Parameters and Spectral Analysis of Heavy Metals in Water: A Case Study of Typical Lead Compounds
LIANG Ye-heng1, 2, 3, OUYANG Yu-chun4, XU Min-duan5, DENG Ru-ru1, 2, 3*, LEI Cong1, XU Dan6, GUO Yu1, GU Yu-ze1, LIU Rong1
1. School of Geography and Planning，Sun Yat-sen University，Guangzhou 510006，China
2. Guangdong Engineering Research Center of Water Environment Remote Sensing Monitoring，Guangzhou 510006，China
3. Southern Marine Science and Engineering Guangdong Laboratory （Zhuhai），Zhuhai 519082，China
4. China Water Resources Pearl River Planning, Surveying and Designing Limited Company，Guangzhou 510610，China
5. School of Aeronautics and Astronautics, Sun Yat-sen University，Shenzhen 518107，China
6. School of Architecture and Planning，Foshan University，Foshan 528000，China
Abstract：Remote sensing-based inversion of heavy metals in water has been a significant challenge within environmental remote sensing monitoring. One important reason is the lack of systematic measurement of optical parameters related to heavy metals. This leads to the absence or inconsistency of input parameters in the inversion models, thereby limiting scholars' ability to conduct in-depth research. In light of this, the study selected four common lead compounds in the effluent of heavy metal pollution enterprises: lead sulfate (PbSO4), lead tetraoxide (Pb3O4), lead chromate (PbCrO4), and lead sulfide (PbS). We measured their reflectance spectra in the 350~2 500 nm wavelength range and compared their spectral characteristics. Based on this, indoor and outdoor experiments were designed to combine reflectance and transmitted light, proposing a method for calculating the absorption coefficient, scattering coefficient, and extinction coefficient of the samples. The results revealed that the spectral curves of the four lead compounds each exhibited unique features with distinct discriminability. Specifically, the reflectance of PbSO4 and PbS changed little overall, with PbSO4 maintaining a reflectance above 80% for most wavelengths, with a variation range of about 17%. PbS remained below 15%, with a variation range of around 7%. The reflectance characteristics of Pb3O4 and PbCrO4 both presented more complex “S” shapes, with multiple characteristic reflection peaks and valleys. At a wavelength of 747 nm as the boundary, the reflectance values relationship among the four compounds showed complex changes before this boundary and stabilized, specifically as PbS443O4. Furthermore, taking PbSO4 as an example, the calculated absorption coefficient fluctuated around 0.001 m-1·mg-1·L in the 400~900 nm wavelength range, with local minima near 451 and 848 nm, and a local maximum near 725 nm; the scattering coefficient gradually increased from 0.019 to 0.027 m-1·mg-1·L, approximately following a line with a very small slope. This indicates that the extinction effect of PbSO4 on incident light in water is mainly due to scattering, with a minor absorption effect, and that the scattering and extinction coefficients change little with wavelength, similar to “non-selective scattering” in particle scattering types, exhibiting “large particle” scattering characteristics. The above work not only provides a reference for the selection of sensitive bands in the remote sensing inversion process, but also is the basic data necessary to realize the remote sensing inversion of lead concentration in water, provides a methodological reference for the measurement of optical parameters of other heavy metal pollutants, and further lays the foundation for the remote sensing theory of heavy metals in water.
Key words：Remote sensing of heavy metals in water;Reflectance;Scattering coefficient;Spectral analysis;Lead compounds
梁业恒，欧阳宇纯，许敏端，邓孺孺，雷 聪，徐 丹，郭 昱，谷钰泽，刘 蓉. 水中重金属的光学参数计算方法及光谱分析——以典型铅化合物为例[J]. 光谱学与光谱分析, 2025, 45(08): 2149-2155.
LIANG Ye-heng, OUYANG Yu-chun, XU Min-duan, DENG Ru-ru, LEI Cong, XU Dan, GUO Yu, GU Yu-ze, LIU Rong. Calculation Method of Optical Parameters and Spectral Analysis of Heavy Metals in Water: A Case Study of Typical Lead Compounds. SPECTROSCOPY AND SPECTRAL ANALYSIS, 2025, 45(08): 2149-2155.
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