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BIO-01  Harmful Algal Blooms
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Design of a multi-spectral sensor for accurate and real-time detection of harmful algal blooms (HABs)
Weihao Lv* , 1.Ocean College, Zhejiang University, Zhoushan, Zhejiang 316021, China
2.The Engineering Research Center of Oceanic Sensing Technology and Equipment, Ministry of Education, Zhoushan, Zhejiang 316021, China
3.Key Laboratory of Ocean Observation-Imaging Testbed of Zhejiang Province, Zhejiang University, Zhoushan, Zhejiang 316021, China
Shihan Shan, 1.Ocean College, Zhejiang University, Zhoushan, Zhejiang 316021, China
2.The Engineering Research Center of Oceanic Sensing Technology and Equipment, Ministry of Education, Zhoushan, Zhejiang 316021, China
3.Key Laboratory of Ocean Observation-Imaging Testbed of Zhejiang Province, Zhejiang University, Zhoushan, Zhejiang 316021, China |
Abstract: A multi-spectral sensor based on discrete three-dimensional fluorescence spectroscopy and absorption spectroscopy is proposed, which can realize the rapid detection of the biomass (the concentration of chlorophyll a) of HABs. Total of 13 LEDs with different center wavelengths (365, 405, 420, 430, 470, 490, 505, 525, 545, 565, 590, 610, 850 nm) were used as light sources. A reference optical path is designed to calibrate measurement deviation caused by fluctuations in the light source. Two photodiodes were used to measure the reference light and the transmitted light respectively, and two face-to-face placed silicon photomultiplier tubes were used to receive the fluorescence emitted by the sample at 660 and 680 nm respectively. The designed sensor has two measurement modes: direct reading measurement (online real-time measurement) and self-capacitance measurement (long-term offline measurement in the field). The low-power mode was designed to reduce the power consumption of the sensor, making it work continuously in the field for more than 5 months. The stability of the sensor is within ±1% when tested with ultrapure water and Rhodamine B solution. Besides, a series of standard chlorophyll-a solutions (0~200 μg/L) were also prepared to test the linearity and the precision of the sensor. The result shows that the measured fluorescence intensities are in good agreement with the concentration of chlorophyll-a solutions (correlation coefficients (R2) exceed 0.9997), and the precision of detection is within ±2 μg/L. During the actual measurement, the discrete three-dimensional fluorescence spectrum and absorption spectrum of the algal samples are obtained at the meanwhile. Based on these two spectra, the interference of yellow substance and turbidity in the algal fluorescence spectrum can also be corrected, which makes the measurement results more accurate, and the relative errors of predicted concentration of chlorophyll-a in actual algae samples are all less than 10%. Key words: multi-spectra; interference correction; in-situ detection; low-power design |
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