ИСТИНА

A number of commercial HPs produced from coalified materials (brown coal BC, leonardite Le, lignite Li and humalite Hu), plant-originated resources peat (Pe), sapropel (Sa) and organic waste material (OW) were examined in respect to their chemical composition and structure. Five selected HPs (two from BC, two from Pe and one from lignosulphonate) were then tested for their detoxication ability in sets of incubation experiments with soils, polluted with lead (320 mg kg-1), copper (660 mg kg-1), and phosphogypsum (3.3 and 7.5 w%). Toxicants were applied to model soil mixture (20% of kaolin, 10% of peat and 70% of sand; ISO 11268-1) together with suspensions of HPs at rates giving 0.0025, 0.005, 0.010 and 0.020 w%. Patterns of C and N distribution in HPs show that the ones from coalified materials contain higher amount of C and minor amount of N, whereas products from Pe, Sa and OW are significantly higher in N and lower in C. Advanced investigations of molecular structure of humic acids extracted from selected HPs were performed; results are discussed in presentation. Under conditions of pollution all HPs modified availability of toxicants in soils. For Pb content of water extractable species decreased in treatments with HPs up to 57-77% to polluted control. For Cu a smaller decrease was observed for all the HPs (70-94%) except the one from lignosulphonate which increased mobility of Cu (129%). In contrast, in experiments with phosphogypsum mobilization of available Sr and Ca was observed. All the HPs increased content of AAB-extractable Sr on 8-24% and Ca on 24-32%, in both cases being the highest for the Pe-product. The results show that detoxication ability of humic products towards heavy metals is unequal and depends both on organic matter origin and properties of HPs and the chemical nature of a toxicant.