Goraczko Wieslaw, Slawiński Janusz
Faculty of Chemical Technology, Radio- and Photochemistry Department, Poznan University of Technology, Poznan, Poland.
Nonlinearity Biol Toxicol Med. 2004 Jul;2(3):245-58. doi: 10.1080/15401420490507468.
Humic substances (HSs) are products of biochemical transformations of plant and animal residues that make up a major fraction of the organic carbon of soil and aquatic systems in the environment. Because radioisotopes occur in the Earth's crust and because the entire biosphere is continuously exposed to cosmic radiation, ionizing radiation continually interacts with HSs. This chronic irradiation could have a significant ecological impact. However, very few publications are available that address possible consequences of chronic exposure of HSs to ionizing radiation from terrestrial and cosmic sources. This study was conducted to investigate possible impacts of exposure of HSs to ionizing radiation.Dried humic acid (HA) or its associated aqueous solution (in 0.1 M Na(2)CO(3)) were exposed to absorbed gamma-radiation in high doses of 1-90 kGy using a (60)Co source. Following the gamma-ray exposures, a secondary, ultraweak radiation emanation with wavelengths in the spectral range lambda= 340-650 nm was recorded as a long-lived chemiluminescence (CL) from the aqueous solutions; however, the CL was not observed after irradiating dry HA.Absorption spectra (for lambda=240-800 nm) of irradiated solutions indicated that polymerization/degradation processes were operating on the HA macromolecules. The effect of specific CL enhancers (luminol and lucigenin) on the intensity and kinetics of the CL implicated the participation of reactive oxygen species and free radicals in the CL and polymerization/degradation processes. For the range of absorbed doses used (1-10 kGy), the intensity of the induced CL was nonlinearly related to dose, suggesting that complex radical formation mechanisms were involved.
腐殖质（HSs）是动植物残体生物化学转化的产物，在环境中构成土壤和水生系统有机碳的主要部分。由于放射性同位素存在于地壳中，且整个生物圈持续受到宇宙辐射，电离辐射不断与腐殖质相互作用。这种长期辐射可能产生重大的生态影响。然而，很少有出版物探讨腐殖质长期暴露于来自陆地和宇宙源的电离辐射可能产生的后果。本研究旨在调查腐殖质暴露于电离辐射的可能影响。使用钴-60源，将干燥的腐殖酸（HA）或其相关水溶液（在0.1M碳酸钠中）暴露于1-90kGy的高剂量吸收伽马辐射下。伽马射线照射后，记录到水溶液发出波长在λ=340-650nm光谱范围内的二次超微弱辐射，作为一种长寿命化学发光（CL）；然而，照射干燥的HA后未观察到化学发光。照射后溶液的吸收光谱（λ=240-800nm）表明，HA大分子上发生了聚合/降解过程。特定化学发光增强剂（鲁米诺和光泽精）对化学发光强度和动力学的影响表明，活性氧物种和自由基参与了化学发光及聚合/降解过程。在所使用的吸收剂量范围内（1-10kGy），诱导化学发光的强度与剂量呈非线性关系，这表明涉及复杂的自由基形成机制。
