The spectroscopic studies of humic acid extracted from sediment collected at different seasons.

Goczałkowice Reservoir is the biggest water reservoir in the south of Poland. For our studies bottom sediments were collected from eight different places of the reservoir at various seasons of the year. EPR spectroscopy was applied to analyse both quantitatively and qualitatively the humic acids (HA) present in the samples. EPR spectra of the extracted HA exhibited broad lines from the paramagnetic metal ions and narrow lines from free radicals. The values of the free radical concentration obtained for HA amounted to 1.14-13.6 × 1016 spin g(-1) depending on the season and the place of sample collection. The values of the g factor obtained for HA were of the range 2.0027-2.0035. The EPR studies show that HA extracted from bottom sediment collected at various points of the Goczałkowice Reservoir exhibit similar physical-chemical properties. It was also observed that the depth of the reservoir affects the content of the oxygen functional groups as well as the free radical concentration in HA. The identification of the functional groups was done by means of IR. UV/VIS spectroscopy was used to estimate the maturity of the HA.