mgr Henryk Toczek

Uniwersytet Morski
Wydzia³ Mechaniczny, Katedra Fizyki
ul. Morska 81-87, pok. C109/C118
81-225 Gdynia
tel.: (+48 58) 55 86 384

Publikacje wg Journal Citation Reports

Haule K., Freda W., Darecki M., Toczek H., 2017. Possibilities of optical remote sensing of dispersed oil in coastal waters. ESTUARINE COASTAL AND SHELF SCIENCE, vol. 195, p. 76-87.

This study is intended to be one of the first steps in assessing the feasibility of remote sensing of dispersed oil in seawater. All optically active seawater constituents, including oil droplets, shape the water-leaving light flux and contribute to a commonly measured apparent optical variable known as remote sensing reflectance (Rrs). Radiative transfer simulations were performed in visible bands for natural seawater in the coastal zone of the Southern Baltic Sea and for a model of seawater polluted by dispersed Petrobaltic crude oil characterised by different droplet size distributions. Our model was supplied by simultaneous in situ measurements of inherent optical properties and the Rrs of natural seawater. The optical description of dispersed oil was based on previous experiments and new application of the Mie solution to the Petrobaltic crude oil of a log-normal size distribution characterised by peak diameters ranging from 0.5 to 500 gm. The results of radiative transfer modelling showed that the typically considered concentration of 1 ppm of oil droplets can locally affect the remote sensing reflectance, causing up to a 6-fold increase or 2-fold decrease, depending on the droplet size distribution. It was demonstrated that the optically significant oil droplet sizes (giving at least 5% contribution to the total scattering coefficient) are <100 gm, as long as oil concentration does not exceed 5 ppm. Moreover, we discussed the influence of dispersed oil droplets on the performance of remote sensing algorithms based on absolute R-rs values or band ratios. Oil dispersion that consists mostly of submicron droplets in a concentration of 1 ppm had the ability to increase blue/green Rrs ratios up to 32%, whereas oil dispersions dominated by micrometre-sized droplets tended to decrease such ratios by up to 18%. Blue/red Rrs ratios were most strongly affected by dispersed Petrobaltic oil, causing a 9%-54% decrease for droplet size distributions characterised by a peak diameter of up to 100 gm. These findings demonstrate why these parameters are considered to be the most useful in the potential remote sensing algorithms. (C) 2016 Elsevier Ltd. All rights reserved.

Freda W., Piskozub J., Toczek H., 2015. Polarization imaging over sea surface - a method for measurements of Stokes components angular distribution. Journal of the European Optical Society, vol. 10, 15060.

This article describes a method for determining the angular distribution of light polarization over a roughened surface of the sea. Our method relies on measurements of the Stokes vector elements using a polarization imaging camera that operates using the Division of Focal Plane (DoFP) method. It uses special monochrome CCD array in which the neighbouring cells, instead of recording different colours (red green and blue), are equipped with micropolarizers of four directions (0, 45, 90 and 135 degrees).
We combined the camera with a fish-eye lens of Field of View (FoV) > 180 deg. Such a large FoV allowed us to crop out the fragment of the frame along the circular horizon, showing a view covering all directions of the hemisphere. Because of complicated optical design of the fish-eye lens (light refraction on surfaces of parts of the lens) connected to the sensor we checked the accuracy of the measurement system. A method to determine the accuracy of measured polarization is based on comparison of the experimentally obtained rotation matrix with its theoretical form. Such a comparison showed that the maximum error of Stokes vector elements depended on zenith angle and reached as much as 24% for light coming from just above the horizon, but decreased rapidly with decreasing zenith angle to the value of 12% for the angles 10 off the edge of FoV.
Moreover we present the preliminary results prepared over rough sea surface. These results include total intensity of light, Degree of Linear Polarization (DoLP) and their standard deviations. The results have been averaged over one thousand frames of a movie. These results indicate that the maximum polarization is observed near the reflection of the sun, and the signal coming from below the surface may be observed at zenith angles far from the vertical direction.

Haule K., Darecki M., Toczek H., 2015. Light penetration in seawater polluted by dispersed oil: results of radiative transfer modelling. Journal of the European Optical Society, vol. 10, 15052.

The downwelling light in seawater is shaped by natural seawater constituents as well as by some external substances which can occur locally and temporally. In this study we focused on dispersed oil droplets which can be found in seawater after an oil spill or in the consequence of intensive shipping, oil extraction and transportation. We applied our modified radiative transfer model based on Monte Carlo code to evaluate the magnitude of potential influence of dispersed oil droplets on the downwelling irradiance and the depth of the euphotic zone. Our model was validated on the basis of in situ measurements for natural (unpolluted) seawater in the Southern Baltic Sea, resulting in less than 5% uncertainty. The optical properties of dispersed Petrobaltic crude oil were calculated on the basis of Mie theory and involved into radiative transfer model. We found that the changes in downwelling light caused by dispersed oil depend on several factors such as oil droplet concentration, size distribution, and the penetration depth (i.e. vertical range of oil droplets occurrence below sea surface). Petrobaltic oil droplets of submicron sizes and penetration depth of 5 m showed a potentially detectable reduction in the depth of the euphotic zone of 5.5% at the concentration of only 10 ppb. Micrometer-sized droplets needed 10 times higher concentration to give a similar effect. Our radiative transfer model provided data to analyse and discuss the influence of each factor separately. This study contributes to the understanding of the change in visible light penetration in seawater affected by dispersed oil.

Drozdowska V., Freda W., Baszanowska E., Rud¼ K., Darecki M., Heldt J. R., Toczek H., 2013. Spectral properties of natural and oil polluted Baltic seawater - results of measurements and modelling. The European Physical Journal Special Topics vol. 222, issue 9, pp. 2157-2170.

Seawater in addition to natural components such as living and non-living organic matter contains also components artificially introduced into the marine environment, such as oil substances. These components, present in the surface layer of the sea, can significantly affect radiative transfer processes. Therefore, taking into account these processes in remote sensing measurements can improve assessment of the environment. To improve local seawater optical models, it is necessary to measure the luminescence properties of all components of seawater as well as the water leaving radiance values. Additionally, substances which form the surface microlayer (surfactants - surface active agents) can affect both the dynamic characteristics of the fluxes (in particular the gas exchange and marine aerosol production) as well as inherent optical properties of surface seawater. This paper contains both the results of research focused on introducing of an efficient method for identifying oils by their fluorescence spectra as well as a marine experiment on the identification of luminescent properties of surfactants - sampled in different regions of the Baltic Sea. Moreover, the aim of the presented study is to assess the impact of the oil emulsion to spectral water leaving signal. Those results are obtained both from running Monte Carlo radiative transfer code and from approximated formulas.

Baszanowska E., Zielinski O., Otremba Z., Toczek H., 2013. Influence of oil-in-water emulsions on fluorescence properties as observed by excitation-emission spectra. Journal of the European Optical Society, vol. 8, 13069.

Oil poses a major threat to marine ecosystems. This work describes a set of studies focused on introducing an efficient method for the identification of oil in the form of oil emulsions through fluorescence spectra analyses. Hence the concept of classification of oil pollution in seawater based on fluorescence spectroscopy using a high sensitive fluorimeter suitable for laboratory and in situ measurements is introduced. We consider that this approach, in the future, will make it possible to collect specific fluorescence information allowing us to build a base of the oil standards. Here we examined excitation-emission fluorescence spectra (EEMs) of water containing oil-in-water emulsion prepared artificially under laboratory conditions. Water polluted with oil-in-water emulsion was studied with the objective to estimate differences in three-dimensional fluorescence spectra. Studies included various types of oils and oil concentrations. Essential differences in fluorescence spectra for various oils are indicated.

Rud¼ K., Darecki M., Toczek H., 2013. Modelling the influence of oil content on optical properties of seawater in the Baltic Sea. Journal of the European Optical Society, vol. 8, 13063.

The accuracy and correct interpretation of optical parameters of seawater depend on the complete information osn the interactions between seawater components and the light field. Among components influencing the radiative transfer, the droplets of oil can cause over- or underestimation of modelled and measured optical quantities, especially in closed seas and coastal zones. Oil content in the Baltic Sea varies from several ppb in the open sea to several ppm in estuaries or ship routes. Oil droplets become additional absorbents and attenuators in seawater causing changes in apparent optical properties. These changes can potentially enable remote optical detection of oil-in-water emulsion in visible bands. To demonstrate potential possibilities of such optical remote sensing, a study of inherent optical properties of two types of crude oil emulsion was conducted, i.e. high absorptive and strongly scattering Romashkino, and low absorptive and weakly scattering Petrobaltic. First, the calculations of spectral absorption and scattering coefficients as well as scattering phase functions for oil emulsions were performed on the basis of Lorentz-Mie theory for two different oil droplets size distributions corresponding to a fresh and 14-days aged emulsions. Next, radiative transfer theory was applied to evaluate the contribution of oil emulsion to remote sensing reflectance Rrs(ė). Presented system for radiative transfer simulation is based on Monte Carlo code and it involves optical tracing of virtual photons. The model was validated by comparison of Rrs(ė) simulated for natural seawater to Rrs(ė) from in situ measurements in Baltic Sea. The deviation did not exceed 10% for central visible wavelengths and stayed within 5% for short and long wavelengths. The light Petrobaltic crude oil in concentration of 1 ppm causes typically a 10-30% increase of Rrs while the heavy Romashkino reduces Rrs for 30-50%.

Stelmaszewski A., Król T., Toczek H., 2009. Light scattering in Baltic crude oil - seawater emulsion. Oceanologia No. 51 (3), 405-414.

The paper discusses the scattering of radiation by a Baltic crude oil - seawater emulsion. The scattering spectrum calculated using the Mie solution in the spectral range from 380 nm to 730 nm is compared with the measured spectrum of light scattered through a right angle. Spectra in the wavelength range from 210 nm to 730 nm were measured using a spectrofluorimeter for fresh and stored samples of the Baltic crude oil emulsion. Scattering increases with wavelength in the UV range and then decreases slightly with the wavelength of visible light. The result of the calculation is similar to the measured spectra. Both the calculated and measured spectra display numerous relative extremes throughout the spectra area. Light scattering in the emulsion decreases during storage as the oil concentration in the medium diminishes. The results also demonstrate that the single scattering model describes the phenomenon correctly.

Otremba Z., Toczek H., 2002. Degradation of crude oil film on the surface of seawater: the role of luminous, biological and aquatorial factors. Polish Journal of Environmental Studies Vol. 11, No. 5, 555-559.

Samples of water were collected from the port of Gdynia and the Gulf of Gdansk (Southern Baltic Sea), and were artificially covered by oil film and stored at a constant temperature. One part of samples was stored in darkness and the second batch was placed under artificial light. Change in the composition of oil on the water surface was determined by means of gas chromatography. Results indicate a greater rate of degradation for the film which covered port water than water from the Gulf of Gdansk. It was revealed that light decreases the rate of biodegradation of an oil film.

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