Optical characteristics of water in stratified lakes can be used to study the pigment composition of various groups of photosynthetic organisms, its depth distribution and changes in different seasons. In the Arctic zone it is especially important to explore the evolution of natural water bodies under the influence of climate change and urbanization processes. Several water bodies on the coast of the Kandalaksha Bay of the White Sea are known as being at different stage of isolation from the Sea. In some of them the colored water layers in their chemocline zone resulted from the massive development of anoxygenic phototrophic bacteria were observed. The most numerous inhabitants of the chemocline zone are green sulfur bacteria. Besides green sulfur bacteria and purple sulfur bacteria, there were found cyanobacteria above and inside the chemocline zone. To access the pigment concentration, we measured fluorescence spectra of acetone extractions prepared from water sampled from various depths within chemocline of the lake Trekhtzvetnoe in March 2021. To increase the sensitivity of fluorescence measurements to certain pigments we acquired synchronous spectra of luminescence spectrometer performing scanning with a constant wavelength offset of 30 nm. This paper presents for the first time depth distribution of photosynthetic pigments BChl d (from green sulfur bacteria) accompanied with phycobilins (from cyanobacteria) derived from synchronous fluorescence spectra of acetone extractions prepared from water from various depths. This type of spectral measurements allowed us to receive depth distribution of cyanobacteria within the bacterial plate of green sulfur bacteria with very high depth resolution.
An important characteristic of a natural reservoir is the depth distribution of the pigment composition of various groups of photosynthetic organisms and its changes in different seasons, both qualitative and quantitative. In the Arctic zone it is especially important to explore the evolution of natural water bodies under the influence of climate change and the urbanization processes in the region. This paper presents for the first time the study of bacteriochlorophyll (BChl) depth profiles derived from optical measurements accompanied by metagenomic profiling of bacterial communities in two stratified lakes, Trekhtzvetnoe and Elovoe at the Kandalaksha coast of the White Sea. Natural water with microorganisms along with hydrological measurements was sampled from various depths during expedition in March 2021. The metagenomic studies showed that biodiversity indices in both lakes did not appear to significantly diminish with depth. According to the analysis of similarity, differences between samples grouped by the lake of origin were not statistically significant. There were significant differences when samples were grouped by layer of the water column. This suggests that stratification of bacterial communities occurred according to environmental conditions in each part of the water column (oxygenated surface layer; chemocline, and anoxic bottom layers), and was not influenced by the geographical location of the lake. Differences between bacterial communities had strong correlation to changes in redox potential and light penetration, and were weakly correlated with depth and temperature; correlation with salinity and pH was not statistically significant.
In this work, the luminescence properties of three europium complexes with ligands based on 2,2’–bipyridyldicarboxylic acid with various counterions (TFA, NO3, Cl) were studied in the form of powders and acetonitrile solutions. Their luminescence spectra were recorded at room temperature and in liquid nitrogen. We obtained and calculated the following luminescence characteristics: luminescence lifetime, relative intensities of each luminescence peak, asymmetry coefficient, radiative lifetime, internal quantum yield, luminescence quantum yield, and the effectiveness of sensitization.
The luminescent properties of two water-soluble europium complexes and two organo-soluble terbium and europium complexes with ligands based on different N-heterocyclic ligands in various mixed solvents (light and heavy water, glycerol, methanol and ethanol) were studied in this work. The absorption, emission, and excitation luminescence spectra were obtained and analyzed. We calculated the asymmetry coefficient, the luminescence quantum yield, and the luminescence lifetime at various concentrations of mixed solvents. The luminescence quenching was found more noticeable in methanol than in ethanol for all studied complexes. We observed that the luminescence quantum yield in the water-containing solvents (methanol/water, methanol/heavy water, ethanol/heavy water) is almost independent of the water or heavy water concentration. We received that heavy water has less influence on luminescence quenching than water, since the vibrational frequencies of OH groups are higher than that of OD groups. Luminescence quenching by adding glycerol to the solvent is more effective for the studied organo-soluble complexes than for water-soluble ones. This effect can be explained by the fact that the ligand of organo-soluble complexes surrounds the rare earth ion more closely, thus preventing glycerol OH groups from entering the coordination zone of the ligand.
The paper presents the results of a spectroscopic study of the "colored" water detected in the splash baths in the supralittoral zone of the Alaid Volcano (the Kuril Islands) from 2015 to 2019. The splash baths with magenta, red and red-yellow water located in different parts of the island in various summer seasons. The analysis of fluorescenсе and absorption data of the water samples revealed the presence of a large amount of bacteriochlorophyll a in the water, which is the main photosynthetic pigment of purple sulfur bacteria. The assumption of the presence of cells of microorganisms was confirmed by observations under a microscope. To determine the morphotype of microorganisms the acetonemethanol extracts from the samples were prepared and studied using spectral methods. The characteristic absorption lines of carotenoids and the monomeric form of bacteriochlorophyll identified cells as Thiocystis and Thiorhodococcus morphotypes of purple sulfur bacteria. The regular observation of water samples with microorganisms in the supralittoral zone of the Alaid Volcano leads to the conclusion that the development of the purple phototrophic bacteria is not an accidental event, but a typical phenomenon in this area. The fact that each summer season colored water were found in different places indicates a cyclical changes in living conditions of microorganisms from favorable to unfavorable habitats.
The cultures of filamentous fungi in aquatic medium release fluorescent metabolites (FM) with emission spectra that closely match the typical fluorescence bands found for soil extracts and aquatic fluorescent dissolved organic matter (FDOM). FM released from some fungal cultures show as well comparable values of fluorescent quantum yield, the blue shift of emission spectra excited in the UV, and a very close match of ultraviolet–visible absorbance spectral curves related to soil and aquatic FDOM, further strengthening the similarity of fluorophores in those aquatic material. Given the importance of microscopic filamentous fungi in the global carbon cycle, our results indicate that filamentous fungi are likely to be important sources of aquatic and soil FDOM of microbial origin.
Environmental monitoring of natural water bodies is important in the Arctic zone for studying their evolution under the influence of climate change and the urbanization processes in the region. In connection with the specific life conditions for anoxygenic phototrophic microorganisms their presence can indicate hydrogen sulfide contamination of the water reservoir and serve as a marker of hydrogen sulfide. This makes the problem of optical diagnostics of phototrophic bacteria very urgent and important. There is a number of spectral methods for determination of chlorophyll-containing microorganisms. The spectral properties of photosynthetic bacterial pigments, bacteriochlorophylls (BChls), are still poorly understood, however. For the first time we applied fluorescence spectra of BChl extracts to receive depth distribution of BChl d in the lake. Fluorescence emission spectra were measured using a Solar CM2203 luminescence spectrometer under excitation at wavelength of 425 nm, corresponding to the BChl d absorption peak. In September 2020 the maximal concentration of BChl d was found at the depth of 2.275 m (16700 mg/m3) in Lake Trekhtzvetnoye. The thickness of the bacterial plate did not exceed 5 cm, and the pigment distribution was found vertically asymmetric. We emphasize that fluorescence quantification of BChl d is more sensitive compared to spectrophotometric one, and it makes possible estimation of ultralow BChl concentrations without water sample pre-concentration.
Aquatic humic substances, or chromophoric fraction of dissolved organic matter (СDOM) in natural water have characteristic optical properties. Considerable effort has been devoted to investigate CDOM optical properties and to improve understanding of biogeochemical carbon cycles in the northern regions. However, due to rare observations up to date there is a limited amount of data available on CDOM research in the sub-Arctic zones. This work summarizes the spectral-optical properties of CDOM from several locations along two coasts of the White Sea. The absorption and fluorescence emission spectra with different excitation wavelength were measured for water sampled in August- September 2020 in the expeditions to several locations of the Karelian and Tersky Coasts, differing in geomorphology, hydrology and anthropogenic influence. The fluorescence was found excitation-dependent; we observed the “blue shift” of emission maximum along with rising the excitation wavelength for all studied CDOM samples (surface and deep coastal water). The absorption spectra are similar in shape for all studied CDOM samples, however, absorbance values reflect concentration of humic substances in some samples. In the Lobanikha Bay we did not find the significant difference in deep and surface CDOM, but in the relict lagoon in Eastern Porya Bay the CDOM was concentrated towards bottom. Those findings are important for understanding the mechanisms of the formation of optical properties of natural water with CDOM of various origins.
In this work, the luminescent properties of three europium salts with various counterions (trifluoroacetate, nitrate and chloride) are studied. Their luminescence excitation spectra at room temperature and in liquid nitrogen have been recorded and studied. Their luminescence lifetime is determined when excited in the UV and visible regions of the spectrum. The influence of counterions and the number of water molecules in the structure of europium salts on their luminescent characteristics is determined.
The work presents the results of spectroscopic study of the natural water with microorganisms from the splash baths in the Atlasov Island (the Alaid Volcano). The Alaid Volcano is the highest, northernmost and one of the most active volcanoes of the Kuril Islands, the unique object for interdisciplinary research. In 2015 within the supralittoral zone of the island the several splash pools filled with colored marine water were discovered for the first time. The paper presents the results of spectral measurements and microbiological studies performed on natural water samples taken in 2015-2017 from the supralittoral zone of the Alaid Volcano, the Kuril Islands, as well as the photosynthetic microorganisms cultivated from those samples in laboratory. The absorption spectra of the native samples and the cultures of photosynthetic bacteria cultivated from original water demonstrated pronounced maxima at 380, 590, 806, 854 nm wavelengths and the shoulders peaked at 510, 590 and 890 nm. The observed absorption maxima revealed the presence of bacteriochlorophyll а, the main photosynthetic pigment of purple sulfur bacteria, and additionally the cells of purple sulfur bacteria Thiocystis and Thiorhodococcus morphotypes were detected in water under microscope. Observation of water colored by photosynthetic microbes in different parts of the Atlasov Island within several summer seasons in 2015-2017 allowed us to conclude that the development of the purple phototrophic bacteria in the splash baths above the littoral zone is not an accidental event, but the stable phenomenon. On the other Kuril Islands similar splash baths have not been encountered yet.
The influence of the water on the stability of complexes of 6,6′-Bis(diphenylphosphinoyl)-2,2′-bipyridyl with lanthanide ions was studied. An increase in the stability value of the complexes is observed with a decrease in the ionic radius of the metal. An increasing of the water content in acetonitrile leads to decrease the stability of the complexes. Moreover the stability of the complexes became independent on ionic radii of metals.
In this work, the fluorescence quenching of two types of bioactive molecules – of the protein lysozyme and of the drug doxorubicin – by carboxylated detonation nanodiamonds in the result of their interaction has been studied. It was demonstrated that nanodiamonds effectively quench the fluorescence of lysozyme and doxorubicin but by different mechanisms. It was found that the fluorescence quenching of lysozyme by nanodiamonds is caused only by a static type of quenching while the fluorescence quenching of doxorubicin by nanodiamonds is caused by both static and dynamic types of quenching. We propose a hypothesis that the surface groups of nanodiamonds are the quenchers of the fluorescence and the variety of surface groups with which a fluorescent molecule interacts determines the fluorescence quenching mechanism. The accounting of our results will provide the insight in the nanodiamonds’ visualization as well as the possible way to track the loading and subsequent unloading of drugs from the nanodiamonds’ surface.
New types of europium complexes with 2,2’-bipyridyl-based ligands were synthesized and their photophysical properties were studied in detail. The influence of the amidic-group substituents on the stability of their complexes with lanthanides also investigated. The branching of the substituent at the amidic group decreases both the quantum yields and stability of complexes.
Investigation of proteins interactions with luminescent europium complex is interesting for the practical task of sensitive protein detection, as well as to study fundamental problems of peptide-lanthanide interplay. Presented work is devoted to examine the spectroscopic properties of europium complex (europium trinitrate (2,2'-bipyridyl-6,6'- dikarbonilazandiil)tetrakis (methylene) phosphonate) and to study its interaction with human serum albumin using various spectroscopic techniques. This complex has unique optical ability such as high values of the phosphorescence intensity in aqueous solutions, which exceeds the intensity of many other known coordination complexes of rare earth elements.
Soil fungi are actively involved in the processes of humic substances synthesis, transformation and mineralization due to production of extracellular nonspecific oxidative enzymes. The work was aimed to evaluate using spectral methods transformation dynamics for the humic product (HP) from lignosulfonate (HPligno) by filamentous soil fungal cultures Alternaria alternata and Trichoderma harzianum. Experiments showed that direct spectroscopic study of HPligno introduced into the nutrient medium and its transformation during fungal growth is challenging due to strong absorption of light by nutrient medium, development of absorbing fungal metabolites, partial utilization and destruction of HP by fungi and therefore due to the need to register tiny changes in overlapping bands. To accomplish that task we proposed a novel algorithm for processing the absorption spectra, which has not previously been used to study fungal cultures. We calculated the second-order derivative in respect to wavelength for absorption spectra measured during fungal growth and found characteristic "patterns" for introduced HP: a maximum at 270-285 and a minimum within 290-300 nm. The spectral index determined from amplitudes in the second-order derivative spectrum reflects the relative content of HP in the nutrient medium in presence of other absorbing components. We resume that two fungal strains utilized HPligno in the 0,02 and 0,1% concentrations better at 30 g/L sucrose than at 3 g/L in the medium. Thus the second-order differentiated absorption spectra helped to quantify degradation of the HPligno during fungal growth.
Imaging techniques in biology and medicine are crucial tools to obtain information on structural and functional properties of living cells and organisms. To fulfill the requirements associated with application of these techniques it appears necessary to design markers with specific characteristics. Luminescent complexes of trivalent lanthanide ions with chelating ligands are of increasing importance in biomedical applications because of their millisecond luminescence lifetime, narrow emission band, high signal-to-noise ratio and minimal photodamage to biological samples. In order to extend the available emission wavelength range the luminescent samarium chelates are highly desirable. In this study the ligands with diamides of 2,2’-bipyridin-6,6’-dicarboxylic acid were used to improve photophysical characteristics of samarium complexes. We report the luminescence characteristics of samarium complexes with novel ligands. All complexes exhibited the characteristic emission of Sm (III) ion with the lines at 565, 597, 605, 645 and 654 nm, the intensity strongly depended on the ligand. Absorption and luminescence excitation spectra of Sm (III) complexes showed main peaks in the UV range demonstrating lanthanide coordination to the ligand. The absolute lumenescence quantum yield was measured for solutions in acetonitrile with excitation at 350 nm. The largest luminescence quantum yield was found for the samarium complex Bipy 6MePy Sm (3%) being much higher that for samarium complexes reported in the literature earlier. These results prove as well that samarium chelates are potential markers for multiparametric imaging techniques.
Detection of phototropic organisms in their natural habitat using optical instruments operating under water is urgently needed for many tasks of ecological monitoring. While fluorescence methods are widely applied nowadays to detect and characterize phytoplankton communities, the techniques for detection and recognition of anoxygenic phototrophs are considered challenging. Differentiation of the forms of anoxygenic green sulfur bacteria in natural water using spectral techniques remains problematic. Green sulfur bacteria could be found in two forms, green-colored (containing BChl d in pigment compound) and brown-colored (containing BChl e), have the special ecological niche in such reservoirs. Separate determination of these microorganisms by spectral methods is complicated because of similarity of spectral characteristics of their pigments. We describe the novel technique of quantification of two forms of green sulfur bacteria directly in water using bacteriochlorophyll fluorescence without pigment extraction. This technique is noninvasive and could be applied in remote mode in the water bodies with restricted water circulation to determine simultaneously concentrations of two forms of green sulfur bacteria in their natural habitat.
We analyze the results received from two expeditions performed in August-September 2013, August-September 2014 and February 2015 in the Kandalaksha Bay of the White Sea. Depth profiles of hydrological characteristics and optical properties of water were recorded for five marine lakes being on different stages of isolation from the White Sea. Those relic lakes demonstrate a tendency to meromixis and are characterized by apparent stratification of the water bodies from the brackish top layer to the bottom salt water. Maximal concentrations of anoxygenic phototrophs (green sulfur bacteria) were found at depths close to the redox interface in all the studied lakes. To discriminate differently pigmented groups of microorganisms the fluorescence emission spectra of bacteriochlorophylls from the living cells were used. We puzzle out the data on light spectrum propagation through the water body in each lake using optical properties of water (attenuation spectra) in the UV, visible and NIR ranges, as well as direct measurements of the total irradiances at various depths. The changes in optical characteristics of water in the stratified reservoirs due to cromophoric dissolved organic matter (CDOM) and microbial pigments affect the light intensity and its spectral distribution at each water layer thus influencing the living conditions for differently pigmented phototrophic microorganisms and determining the composition of microbial community.
Hydrophobic components of cromophoric dissolved organic matter (CDOM) extracted from water samples and sediments taken in several relic basins located on Karelian shoreline of the White Sea were analyzed using spectroscopic techniques. Those water reservoirs exist at various stages of isolation from the White Sea and represent complex stratified systems of fresh and marine water layers not completely mixing trough the year. Basins separating from the White Sea are the unique natural objects for investigations of properties CDOM, its transformation in the process of turning the marine ecosystem into freshwater environment. CDOM occurring in all types of natural water represents a significant reservoir of organic carbon and plays a key role in the carbon cycle on the Earth. However, aquatic CDOM and nonliving organic matter in sediments from relic separating basins still have not been studied. The target of this work was to study absorption and fluorescence spectra of hydrophobic components of aquatic CDOM from different water depth and sediments in several separated basins of the Kandalaksha Gulf of the White Sea located near the N.A. Pertsov White Sea Biological Station.
The development of new complexes of rare earth elements (REE) with chelating organic ligands opens up the possibility of purposeful alteration in the composition and structure of the complexes, and therefore tuning their optical properties. New ligands possessing two pyridine rings in their structure were synthesized to improve coordination properties and photophysical characteristics of REE compounds. Complexes of trivalent europium with novel chelating ligands were investigated using luminescence and absorption spectroscopy, as well as atomic force microscopy. Luminescence properties of new compounds were studied both for solutions and films deposited on the solid support. All complexes exhibit the characteristic red luminescence of Eu (III) ion with the absolute lumenescence quantum yield in polar acetonitrile solution varying from 0.21 to 1.45 % and emission lifetime ranged from 0.1 to 1 ms. Excitation spectra of Eu coordination complexes correspond with absorption bands of chelating ligand. The energy levels of the triplet state of the new ligands were determined from the phosphorescence at 77 K of the corresponding Gd (III) complexes. The morphology of films of europium complexes with different substituents in the organic ligands was investigated by atomic force microscopy (AFM). It strongly depends both on the type of substituent in the organic ligand, and the rotation speed of the spin-coater. New europium complexes with chelating ligands containing additional pyridine fragments represent outstanding candidates for phosphors with improved luminescence properties.
As a result of a recent years study on the Karelia shore of the White Sea more than ten relict lakes in different stages of separation from the sea have been discovered. Five of them are located close to the Nikolai Pertsov White Sea Biological Station of Moscow State University. Such separated lakes are interesting to explore for their firm vertical stratification. Water layers differ not only by temperature, salinity and other physic and chemical characteristics and optical properties, but also by ibhabiting microorganisms and by the quality of dissolved organic matter. To study phototropic organisms in water sampled from different depths we used spectroscopic techniques. Identification of the main bands in the absorption and fluorescence spectra showed that there are two main groups of photosynthetic organisms in the redox zone (chemocline): unicellular algae containing chlorophyll a and green sulfur bacteria with bacteriochlorophylls c, d, e. Spectral data were compared with physical and chemical characteristics of the water layer (temperature, salinity, pH, dissolved oxygen and sunlight illumination at certain depth). It gave an opportunity to compare vertical profiles of oxygen and hydrogen sulphide concentration with the number and distribution of oxygenic and anoxygenic phototrophic microorganisms. Maximum abundance of both algae and green sulfur bacteria were achieved within the redox zone. Typical thickness of the layer with the highest concentration of microorganisms did not exceed 10-20 cm.
Research is initiated to study water samples from stratified water basins in the Kandalaksha Gulf of the White Sea at
different stages of their separation from the sea. The objects of research are lakes Elovoe and Nizhnee Ershovskoe
located close to the Nikolai Pertsov White Sea Biological Station. Depth profiles of physico-chemical characteristics
such as temperature, salinity, pH and dissolved oxygen were measured. Brightly colored green water layers were found
in both lakes. Concentrations of photosynthetic organisms were estimated using absorption and fluorescence spectra of
water samples from various depths.
The results of Raman spectroscopy research of aqueous ethanol solutions with various mixing ratios are presented. The
analysis of the behavior of Raman spectra with changes in ethanol concentration from 0 to pure ethanol is given. The
analysis of contour of stretching OH-band provided information about changes in hydrogen bonding along with increases
in ethanol concentration. Obtained results showed that the maximum strength of H-bonding in aqueous ethanol solution
corresponded to an ethanol concentration of 15...20 % w/w. The observed strengthening of H-bonding strongly supports
the hypothesis of clathrate-like structures. These results were supported by application of MCR-ALS method.
Non-living dissolved organic matter (DOM) is the largest organic carbon pool in natural waters and plays a central role in the biogeochemistry of a variety of elements. Colloidal matter makes up a significant portion of the bulk DOM in aquatic environments, but is still poorly characterized. Fluorescence emission spectra excited at 270, 310 and 355 nm and absorbance values were measured for the colloidal fraction CF with particles size ranging between 5 and 200 nm, for the fraction F5 with molecules smaller 5 nm, and for DOM filtered with the 0.2 μm pore size filter. For all DOM fractions the "blue shift" of fluorescence maximum position was observed with excitation at 310 nm compared to excitation at 270 or 355 nm. With river water samples it was found that DOM contains about 40% of organic matter in colloidal fraction; that emission maximum wavelength is 5...10 nm longer for CF than for F5; that fluorescence quantum yield is decreasing in 12% for CF and increasing in 30% for F5 compared to the original DOM samples. We confirmed that bigger DOM nanoparticles have red-shifted fluorescence emission and lower fluorescence quantum yield compared to DOM nanoparticles smaller 5 nm.
Phototrophic purple sulphur bacteria represent an important constituent of coastal zone biota and a crucial link of sulphur cycling in the nature. Purple bacteria are widespread in the environment occurring almost in every water basin and also in soil. The spectroscopic research was performed in vivo on purple sulphur bacteria Chromatium sp. in different culture development stages and illumination conditions during culture growth. Possibilities of purple bacteria quantification in vivo using absorbance and fluorescence intensities are described. The experiments revealed the possibility of application of the intensities ratio of porphyrin pigments emission to cell blue fluorescence for the estimation of the culture physiological status. These findings may be used for improvement of remote sensing techniques of ecological monitoring.
The effect of fluorescence saturation under laser pulsed excitation appears as a non-linear response of emission signal versus intensity of excitation. The saturation becomes important when the rate of molecular excitation exceeds the rate of their deactivation. Typically the effect is noticeable when excitation photon flux ((rho) ) exceeds 1023 . . . 1024 cm-2s-1. We present the theory of fluorescence saturation under laser pulsed excitation for both quasi-stationary and non-stationary cases, as well as the experimental study on fluorescence saturation for of organic dyes in aqueous and ethanol solutions and in polymer film.
The effect of fluorescence saturation is caused by limited life-time of molecules in excited state, and appears as a non-linear dependence of detected fluorescence signal versus excitation intensity under laser pulsed irradiation of the sample. It is noticeable at conditions of 1024 exciting photons per second per square centimeter, which we usually have for laboratory laser fluorimeter. Spectroscopy of saturated fluorescence is a promising tool for studying such spectral molecular characteristics, as fluorescence life- time, absorption cross-section, constant of singlet-singlet annihilation, and their changes due to molecular interaction. The work presents the theory of the effect considering the cases of different intermolecular interaction (quenching mechanisms, singlet-singlet annihilation) and describes the experimental results on florescence saturation for several organic dyes in water.
KEYWORDS: Data modeling, Luminescence, Data analysis, Defense and security, Maritime surveillance, Radar, Microwave radiation, Radiometry, Laser scanners, 3D scanning
By the end of 1993 the Federal Ministries of Transport and Defence put a second generation maritime surveillance system into service for long-term operation in the North Sea and the Baltic Sea. The system consists of a DO 228-212 aircraft and of a side-looking airborne radar, a microwave radiometer, a UV/IR line scanner, and a laser fluorosensor. The main purpose of the laser fluorosensor is the detection and classification of oil spills on the sea surface. In addition, dissolved organic matter and phytoplankton pigments can be investigated while the aircraft is performing long-range surveillance flights. The hydrographic data are analyzed by geostatistical algorithms, which exploit the spatial correlation of the data to estimate the 2D distribution and the prediction variance of the examined property. As an additional information about the reliability of the results, the prediction variance is accessible. In this way, a detailed illustration of hydrographic conditions in coastal waters can be achieved. In this article, we discuss problems that arise if the condition of statistical uniformity is not met by the data. A possible way to handle these data is demonstrated on a data set measured in the North Sea.
Natural organic compounds are present in significant concentration in all types of water. The spectroscopic study of dissolved organic matter and its major components is important for applications of lidar remote sensing techniques for water quality measurements. In this paper, fluorescence emission and excitation spectra, as well as absorption spectra for commercially available analogues of major components of gelbstoff are analyzed and compared with spectra of natural water samples of different origin.
Airborne laser fluorosensor measurements of hydrographic parameters have been performed in the German Bight and in the Baltic Sea. The results are compared with data measured with a luminescence spectrometer on board research vessels. Fluorescence spectra excited at different excitation wavelengths (on board the ship) give us information on fluorescent gelbstoff components in natural water. These ground truth data have proved the remotely detected data of gelbstoff in coastal waters. Recent measurements made in the Canary Islands region demonstrate that gelbstoff fluorescence can be registered also in clear open ocean waters with low concentrations of this material.
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