Pollution detection using the spectral fluorescent signatures (SFS) technique
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1
University of Vigo, Spain
This work has been developed in the Applied Physics Department at the University of Vigo within the line of research based on the treatment of the degraded water by pollutants through the use of microalgae, reducing the emissions of greenhouse gases through the absorption of CO2 in the process and the reuse of biomass as biofuel. Remote sensing techniques have contributed to a great extent to the development of oil pollution monitoring systems. However, the available detection methods, mainly designed for spaceborne and airborne long distance inspection, are too expensive and complex to be used in an operational way by relatively unskilled personnel. In the framework of DEOSOM project (European AMPERA project), an innovative water monitoring method was proposed, in two steps: early oil spill detection using a portable shipborne laser-induced fluorescence LIDAR (LIF/LIDAR), and analysis of suspicious water samples in laboratory using the Spectral Fluorescent Signature (SFS) technique. This work is focused on the second technique. This system aims to optimize the production of microalgae for biofuel and contaminant cleaning applications and was developed and tested in photo-bioreactors in the University of Vigo within the EnerBioAlgae project (SUDOE). In this project, the SFS technique was used as a diagnostic tool employing the fluorescence analyzer INSTANT-SCREENER M53UVC. The Spectral Fluorescence Signature technique (SFS) is based on compounds fluorescence properties. The fluorescence intensity of a sample is measured at different excitation and emission wavelengths to produce a 3-dimensional fluorescence matrix, which can also be presented as a 2-dimensional color image where the color shows the intensity of the fluorescence. These matrices offer qualitative and quantitative information, since they can be useful for the identification of different substances from their characteristic excitation and emission spectra of fluorescence. They also provide quantitative measurement through the use of algorithms based on libraries from previous samples. Since the different materials and compounds have different spectral signatures of fluorescence, it is possible with a single measure to analyze the different components in the sample. The reliability of this method will depend on the library of samples used. Several substances have been studied through their fluorescence response to incident light by using different methods. Firstly, different oil products have been analyzed in the laboratory, by using eight LED light sources with wavelengths ranging from 270 to 850 nm to excite the samples (Figure 1), employing a USB4000-FL Fluorescence Spectrometer to register the fluorescence spectra. On the one hand the SFS of twelve different types of oils has been obtained by exciting the samples with a 310nm LED light source (in absence of any other source of light) (Figure 2). Each sample consisted of 5 ml of distilled water and 400 μl of oil. On the other hand the SFS of oil, gasoline, engine oil and heavy oil has been acquired using all LEDs (Figure 3). Secondly, the Instant Screener M53UVC SFS analyzer has been used to obtain the SFS for screening detection of aluminium concentrations in water samples by a derivatization method. The Instant Screener (IS) presents two different software versions (UV and BIO), associated with the excitation and emission wavelength provided and registered (respectively) by the instrument. In UV software version, excitation wavelength ranges from 240 to 360 nm and fluorescence is registered from 260 to 575 nm whereas in the BIO version excitation wavelength varies from 400 to 650 nm while emission is registered from 530 to 730 nm. The study is concentrated on the development of a sensitive and selective methodology for the non-fluorescent aluminium ion detection based on the analytical derivatization reaction strategy to form a characteristic fluorescent coordination complex [1, 2]. Morin (Flavonol) was adopted as the ligand owing to its ability to react with Al3+ ion to form the stoichiometric 1:3 complex (Figure 4) with excellent fluorescent properties. On the other hand the microalgae Chlorella vulgaris was tested for growth in a photobioreactor (Figure 5) with controlled growth conditions. The system is monitored throughout software developed by the Remote Sensing laboratory (University of Vigo). It allows checking in real time all system variables, to connect a pH sensor as well and to register temperature. Besides each one of its 8 columns can be individually controlled. The SFS in BIO mode of a sample of C. vulgaris and aluminum complex are shown in Figure 6. In this image, maximum intensity value corresponds to the 465.0/690.0 nm excitation/emission wavelength for C. vulgaris and to 415.0/530.0 nm for the aluminum complex. Figure 7 shows (in UV mode) the comparison between the SFS of C. vulgaris and the aluminum complex fluorescence. Maximum value for the aluminum complex appears at 360/495 nm excitation/emission for this complex. SFSs of C. vulgaris and the aluminum complex are both, clearly different (in BIO or in UV mode) and the region of the image where the maximum value appears is also visibly characteristic. Besides, UV and BIO images can be used in a complementary manner when it comes to the discrimination of compounds.Finally, a study between absorption measurements and chlorophyll-a (through SFS) has been carried out. A total of 14 samples (obtained by a series of dilutions of a C. vulgaris culture with an initial concentration of 2.70E+07 cell/mL) (Figure 8) have been examined with the SFS analyzer Instant Screener. For absorbance measurements (Figure 9), a PX-2 lamp has been used as the exclusive source of light. The same volume (50 mL of the sample) has been used for each measurement. The signal has been obtained with a USB4000-FL spectrophotometer.
Acknowledgements
This research has been supported in part by the framework of the European Coordination Action to Foster Prevention and Best Response to Accidental Marine Pollution, Program Accidental Marine Pollution ERA-NET (AMPERA), Project Detection and Evaluation of Oil Spills by Optical Methods (DEOSOM) and also has been the result of the work within the project EnerBioAlgae (www.enerbioalgae.com) which was funded by Interreg SUDOE and led by the University of Vigo.
References
[1]. Katial, M and Prakash, S, 1977. Analytical reactions of hydroxiflavones. Talanta, Vol. 24, pp. 367-375.
[2]. Lian HZ, Kang YF, Bi SP, Yasin A, Shao DL, Chen YJ, Dai LM, Tian LC. 2003. Morin applied in speciation of aluminium in natural waters and biological samples by reversed-phase high-performance liquid chromatography with fluorescence detection. Anal Bioanal Chem., Vol. 376 (4), pp. 542–548
Keywords:
Spectral Fluorescence Siganture (SFS),
LED,
Microalgae,
aluminium complex,
oil pollution
Conference:
IMMR | International Meeting on Marine Research 2014, Peniche, Portugal, 10 Jul - 11 Jul, 2014.
Presentation Type:
Poster Presentation
Topic:
OCEANOGRAPHY AND MARITIME TECHNOLOGY
Citation:
Martín
M,
Rodríguez Prado
B,
González-Romero
E and
M. Torres
J
(2014). Pollution detection using the spectral fluorescent signatures (SFS) technique.
Front. Mar. Sci.
Conference Abstract:
IMMR | International Meeting on Marine Research 2014.
doi: 10.3389/conf.fmars.2014.02.00047
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Received:
08 May 2014;
Published Online:
18 Jul 2014.
*
Correspondence:
Ms. Mª Del Carmen Martín, University of Vigo, Vigo, Spain, maric@uvigo.es