Janusz Slawinski

Changes in the Luminescent Properties of Humic Acids Induced by UV Radiation

AbstractHumic acids (HA) are complex, dark, paramagnetic biopolymers, ubiquitus in the soil and aquatic ecosystems. Due to their peculiar properties (multifluorophore system capable of excitation energy transfer, continuous featureless absorption over a wide spectral range, and paramagnetism), HA play an important role as an efficient target for UV solar radiation, O2, and O3—detrimental environmental factors which affect the Earths biosphere. Photooxidation of HA causes changes in the absorption and luminescence properties of HA which may be of significant importance for environmental photophysics and photochemistry. We have studied effects of UV irradiation on the degradation of several commercial HA (Fluka, Merck, and Serva). Aqueous, aerated alkaline solutions of HA (0.1–0.4 g/L in 0.006–0.1 M Na2CO3) were irradiated with an electrodeless Hg (254-nm) lamp in a flow system during several hours. After different times of irradiation, solutions were assayed by means of fluorescence (Fl), absorption (UV–Vis), and chemiluminescence (CL) spectroscopy. The data obtained indicate that the free radical-mediated degradative photooxidation of HA macromolecules is accompanied by a very weak, long-lived chemiluminescence (340–800 nm), a gradual decrease in absorbancy with characteristic changes in color coefficients Q4/6, Q2.7/6.0, and Q2.7/4.0, and an increase in the intensity of Fl emission (340- to 560-nm) and excitation (250- to 400-nm) spectra. Processes undergoing these changes are intrinsically associated with the generation of excited states and reactive oxygen species

Chemiluminescence of cereal products. II. Chemiluminescence spectra

({\text{ROS}} \cdot {\text{, O}}_{\text{2}}^ - ,{\text{ OH}} \cdot {\text{, RO}}_{\text{2}} \cdot ,{\text{ H}}_{\text{2}} {\text{O}}_{\text{2}} ,{\text{ and O}}_{\text{2}}^{\text{*}} ;{\text{ }}^{\text{1}} \Delta _{\text{g}} ,{\text{ }}^{\text{1}} \sum {_{\text{g}}^{\text{ + }} } )

CHEMILUMINESCENCE OF CEREAL PRODUCTS. III. TWO-DIMENSIONAL PHOTOCOUNT IMAGING OF CHEMILUMINESCENCE

. These processes are expected to play a vital role in the natural environment, e.g., HA-photosensitized decomposition of xenobiotics and solar energy transfer in symbiotic hydrobionts.

Model studies of zinc bonding with humic acid in the presence of UV-VIS-NIR radiation

Living systems spontaneously emit ultraweak light (ultraweak photon emission, UPE) during the process of metabolic reactions associated with the normal physiological state. Stress factors and pathological states change parameters of that emission, such as intensity, yield, temporal, statistical and spectral characteristics. Thus, properties of UPE are inherently associated with and derived from biochemical and biophysical excitation processes. UPE can be considered as a holistic expression of the perturbation of the physiological state of the bio-system and may carry information on the bioenergetics, kinetics and character of biochemical and physiological processes, functioning of the regulatory feedback systems and the degree of perturbation by internal and external factors. This article presents an overview of the fundamentals of UPE and its relation to physiological processes.

Use of a CCD-monitored chemiluminescence imaging for sensing of the UV-and ozone-induced degradation of humus substances

Spectra of ultraweak chemiluminescence (CL) accompanying auto-oxidation and hydration of cereal products have been measured using single photon counting and cut-off filters. The spectra cover the 380–880 nm spectral range with maxima centred around 600 nm. Analytically pure air-dried carbohydrates like agar, cellulose and nitrocellulose give emission too weak for spectral measurements. The emission from water pure carbohydrates is on average 4–12 times higher and emission spectra are similar to those from cereal products. The effect of free radical scavengers, SOD and O*2 (1Δg)-quenchers on CL spectra indicates a contribution of radical reactions with the participation of excited carbonyls, O2− and excited molecular oxygen dimoles. Moreover, possible mechanisms of chemi-excitation due to a cooperative H-bond formation during the hydration of carbohydrates and/or recombination of trapped radicals and electron-holes are discussed. It is also postulated that the excitation energy transfer to natural sensitizers occuring in cereal products may account for non-specific broad spectra and differences in the intensity of CL.

Secondary Ultraweak Luminescence from Humic Acids Induced by γ-Radiation

Biological organisms are open systems as they exchange energy E, information Inf and mass m with their environment (Fig. 1). They achieve the degree of spaciotemporal order (infrastructure) necessary for survival through the flow of metabolic free energy ΔG. To maintain this order and a steady-state (a dynamic equilibrium) requires that the rate of entropy S production inside the open system dS i / dt is balanced by the rate of external entropy S e production as shown in Fig. 1:

Chemiluminescence methods for the evaluation of degradative processes in soil organic matter

Two-dimensional (2-D) spatial distributions of ultra-weak chemiluminescence (photon imaging) from auto-oxidizing and water-hydrated cereal food products were measured by means of a high-sensitivity 2-D photon counting system—an intensified charge coupled device (CCD) camera. The 2-D images obtained reveal the dynamics and emission patterns of very slow auto-oxidation reactions and much faster processes of water penetration into cereal products. The enhancement of chemiluminescence by the addition of water appears to involve complex processes with an inhomogenous spatial and energy distribution within cereal products. The effect of antioxidants, free radical promoters and scavengers suggests that oxidative radical reactions contribute significantly to the observed chemiluminescence. The possible involvement of hydrophilic interactions, H2O-biopolymers and recombination of trapped radicals is also discussed.

Degradation of humic acids by UV-radiation and ozone

Model experiments were performed to determine the influence of UV-VIS-NIR radiation on zinc bonded with humic acid (HA). The samples of HA or HA-65Zn radioisotope were overlayed on quartz sand in a glass column and subjected to elution that simulated natural conditions. The zinc concentration was chosen to that occurring in the sewage of the Central Sewage Work in Poznań. Zinc was washed with water to simulate the influence of rain. The recovery of injected radiotraces ions in the eluates was found to depend on pH, zinc and HA concentrations and on radiation exposure. The results help to evaluate the migration behavior of zinc in the presence of HA and UV-VIS-NIR radiation. From the first part of the investigation appears that radiation induces a degradation of HA-Zn layer and that the degradation process depends on pH of the environment. A decrease in pH causes an increase in photodegradation and the degree of zinc binding in the humic layer. Simultaneously, the ultra-weak luminescence (UWL) of plants was monitored to estimate the influence of zinc and HA on their development. The results show effects of HA and zinc on UWL and growth of bean and watercress which characterize the rate of plants metabolism and perturbation of their homeostasis. It was observed that high concentrations of zinc ions and HA considerably affect the development process of the plants.