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The wood protection industry has refined their products from chrome-, copper-, and arsenate-based wood preservatives toward solely copper-based preservatives in combination with organic biocides. One of these is Cu-HDO, containing the chelation product of copper and N-cyclohexyldiazenium dioxide (HDO). In this study, the fate of isotope-labeled (13C) and nonlabeled (12C) Cu-HDO incorporated in wood sawdust mixed with soil was investigated. HDO concentration was monitored by high-pressure liquid chromatography. The total carbon and the δ13C content of respired CO2, as well as of the soil-wood-sawdust mixture, were determined with an elemental analyzer-isotopic ratio mass spectrometer. The concentration of HDO decreased significantly after 105 days of incubation, and after 24 days the 13CO2 concentration respired from soil increased steadily to a maximum after 64 days of incubation. Phospholipid fatty acid-stable isotope probing (PFA-SIP) analysis revealed that the dominant PFAs C19:0d8,9, C18:0, C18:1ω7, C18:2ω6,9, C17:1d7,8, C16:0, and C16:1ω7 were highly enriched in their δ13C content. Moreover, RNA-SIP identified members of the phylum Acidobacteria and the genera Phenylobacterium and Comamonas that were assimilating carbon from HDO exclusively. Cu-HDO as part of a wood preservative effectively decreased fungal wood decay and overall microbial respiration from soil. In turn, a defined bacterial community was stimulated that was able to metabolize HDO completely.
The influence of humin preparations obtained from low-moor peat by the mechanochemical method on the changes in the microflora number and hydrocarbon composition in oil-polluted soils was studied. The intense growth of the microorganisms in number especially in the oil-polluted soil was observed upon the application of humin acids (at a concentration of 0.005 wt %) extracted from mechanically processed peat. In this case, the content of the extracted bitumoids decreased down to 40 wt %. The soil microflora stimulated by the humin preparations was shown to have highly destructive oil-oxidizing activity reflected in the indices of the hydrocarbon biodegradation. The mechanochemical activation of peat allows raising the efficiency of extracting the humic acids and can be a reason for increasing the availability of their individual components and parts of molecules, including micro- and macroelements that are used by microbial cells as sources of nutrition and energy.