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Ultraweak chemiluminescence from gamma-irradiated humic acids

Goraczko W., Slawinski J.

Nukleonika

2004

Vol. 49, nr 4

143-147

Dried humic acid and its aqueous solution in 0.1 M Na2CO3 were gamma-irradiated with 1 90 kGy from 60Co. Thereafter, a secondary ultraweak radiation in the spectral range of gamma = 340 650 nm from aqueous solutions was recorded as long-lived chemiluminescence (CL). Only for absorbed doses lower than 10 kGy low intensity signals of the CL decay were measurable. For absorbed doses higher than 40 kGy residual flat and weak signals are observed. Humic acid irradiated in the dry form did not reveal statistically significant CL. Absorption spectra (gamma = 240 800 nm) of irradiated solutions indicated the occurrence of a dominant degradation process of the humic acid macromolecular components. The effect of H2O2 and CL enhancers (luminol and lucigenin) on the intensity and kinetics of CL proved the participation of reactive oxygen species and the free radical mechanism in the CL and degradation processes. The dose-effect relationship (i.e. gamma-radiation absorbed dose vs. intensity of gamma-radiation-induced CL) showes a non-linear shape, especially in the range of 1-10 kGy, which suggests complex radical mechanisms. A possible ecological significance of the observed phenomena is briefly discussed.

Model radioisotope experiments on the influence of acid rain on 65Zn binding with humic acid

Koczorowska E., Mieloch M., Slawinski J.

Nukleonika

2002

Vol. 47, nr 4

167-171

Acid rain formed first of all from sulphur oxide emitted by natural and anthropogenic sources, may change the biological equilibrium and the metal stoppage in the soil. The model experiments were performed to determine the influence of acid rain on zinc bond with humic acid (HA). The samples were prepared in glass columns with quartz sand and overlaid HA or HA+65Zn radioisotope that simulates natural conditions. Then, solutions of H2SO4 were introduced into the sand HA layer. Zinc was washed with diluted (10 4 10 3 M) sulphuric acid as the simulation of acid rain. The recovery of injected radiotracer ions in eluates was found to depend on pH of simulated acid rain. The results help to evaluate the migration behaviour of zinc in the presence of HA and H2SO4. The model studies illustrate the considerable influence of sulphuric acid on chemical degradation of HA.