Detoxification of oil-contaminated soils by using humic acids

Abstract

Abstract The paper deals with the study of the effect of peat mechanoactivation on the structure and biostimulating and detoxifying properties of isolated humic acids (HA) in of oil-contaminated soil. It is shown that the mechanical activation of peat leads to an increase in the HA yield by a factor of 2-3. In this case, the changes in the fragment composition of HA are observed. Hence, the percentage of aromatic and oxidized alkyl fragments increases, while the amount of oxygen-containing functional groups decreases. The binding of petroleum organic compounds occurs due to the presence of an aromatic skeleton in the structure of HA. The increase in the proportion of aromatic fragments in the structure of mechanically activated HAs increases their affinity for hydrophobic oil compounds, thereby providing them a detoxifying ability. The maximum detoxifying ability of mechanically activated HA determines their biostimulating properties in the wheat seed germination experiment. The biostimulating effect from the use of mechanically activated HA samples is manifested itself to a greater degree in the increase in the height of the sprout stem and the dry mass of the aerial part of the plant. The processes of biodegradation of oil in the soil in the presence of HA are investigated. It is shown that the amount of bitumoids extracted from the soil in the presence of HA is reduced by 30%. The content of hydrocarbons in bitumoids decreases by 50% due to the biodegradation of low molecular weight alkanes. At the same time, the degree of branching of hydrocarbon chains increases, which suggests a microbiological activity. An increase in alcohol-benzene resins in the composition of bitumoids indicates the stimulation of hydrocarbon-oxidizing bacteria by humic acids. According to the data of IR spectroscopy, the content of paraffin hydrocarbons has decreased during the destruction of oil by soil microflora.