Suchergebnisse

In industrialized society, large amounts of oily sediments from contaminated sites as well asoily sludge from industrial processes need to be treated in sustainable way. Nowadaysbiological treatment is becoming more important. The purpose of biotreatment is to decreasethe concentration of organic pollutants (e.g. oil) in soil or compost by mineralizing hazardouschemicals into harmless compounds such as carbon dioxide or some other gas or inorganicsubstance, water, and cell material. Whereas hydrocarbons are generally well degradable,some organic compounds (e.g. PAH) are less degradable; and some (heavy metals) can not bedegraded. However, resistant compounds can be transformed through sorption, methylation,and complexation, and change in valence state, which affect mobility and bioavailability. Theuse of oil-compost depends on legislative limits, and response of vegetation. Oil-content mayhave a negative effect on plant root system even in low concentrations. Heavy metals mayinhibit the growth, but in the other hand, the plants are also known in uptaking heavy metalsand other contaminants, known as phytoremediation. This may create a situation, wherevegetation cover acts as additional treatment system for matured oil-composts. The objectiveof this study was to examine the effect of hydrocarbon residues in different substances(compost and soil mixtures) on soil model plants (Raphanus sativus) germination andphytomass production. The germination study demonstrated that the plants germination andbiomass production was highly dependent on compost decomposition degree, nutrient contentand biological properties of soil. On less matured compost, the germination and growth wassuppressed. The phytomass production experiment showed that plants in oil compost haddecreased height, taproot mass and above ground phytomass. The application of complexmineral fertilizers increased the volume of abovementioned parameters. ; In industrialized society, large amounts of oily sediments from contaminated sites as well asoily sludge from industrial processes need to be treated in sustainable way. Nowadaysbiological treatment is becoming more important. The purpose of biotreatment is to decreasethe concentration of organic pollutants (e.g. oil) in soil or compost by mineralizing hazardouschemicals into harmless compounds such as carbon dioxide or some other gas or inorganicsubstance, water, and cell material. Whereas hydrocarbons are generally well degradable,some organic compounds (e.g. PAH) are less degradable; and some (heavy metals) can not bedegraded. However, resistant compounds can be transformed through sorption, methylation,and complexation, and change in valence state, which affect mobility and bioavailability. Theuse of oil-compost depends on legislative limits, and response of vegetation. Oil-content mayhave a negative effect on plant root system even in low concentrations. Heavy metals mayinhibit the growth, but in the other hand, the plants are also known in uptaking heavy metalsand other contaminants, known as phytoremediation. This may create a situation, wherevegetation cover acts as additional treatment system for matured oil-composts. The objectiveof this study was to examine the effect of hydrocarbon residues in different substances(compost and soil mixtures) on soil model plants (Raphanus sativus) germination andphytomass production. The germination study demonstrated that the plants germination andbiomass production was highly dependent on compost decomposition degree, nutrient contentand biological properties of soil. On less matured compost, the germination and growth wassuppressed. The phytomass production experiment showed that plants in oil compost haddecreased height, taproot mass and above ground phytomass. The application of complexmineral fertilizers increased the volume of abovementioned parameters.

The decomposition of fresh crop residues added to soil for agricultural purposes is complex. This is due to di erent factors that influence the decomposition process. In field conditions, the incorporation of crop residues into soil does not always have a positive e ect on aggregate stability. The aim of this study was to investigate the decomposition e ects of residues from two di erent cover crops (Brassica napus var. oleifera and Secale cereale) and one main crop (wheat straw) on soil aggregate stability. A 105-day incubation experiment was conducted in which crop residues were mixed with sandy loam soil at a rate of 6 g C kg􀀀1 of soil. During the incubation, there were five water additions. The decomposition e ects of organic matter on soil conditions during incubation were evaluated by determining the soil functional groups; carbon dioxide (CO2), nitrous oxide (N2O), and methane (CH4) emissions; soil microbial biomass carbon (MBC); and water-stable aggregates (WSA). The functional groups of the plant residues and the soil were analyzed using Fourier transform infrared spectroscopy (FTIR) and a double exponential model was used to estimate the decomposition rates. The results show that the decomposition rate of fresh organic materials was correlated with the soil functional groups and the C/N ratio. Oilseed rape and rye, with lower C/N ratios than wheat straw residues, had faster decomposition rates and higher CO2 and N2O emissions than wheat straw. The CO2 and N2O flush at the start of the experiment corresponded to a decrease of soil aggregate stability (from Day 3 to Day 10 for CO2 and from Day 19 to Day 28 for N2O emissions), which was linked to higher decomposition rates of the labile fraction. The lower decomposition rates contributed to higher remaining C (carbon) and higher soil aggregate stability. The results also show that changes in the soil functional groups due to crop residue incorporation did not significantly influence aggregate stability. Soil moisture (SM) negatively influenced the aggregate stability and greenhouse gas emissions (GHG) in all treatments (oilseed rape, rye, wheat straw, and control). Irrespective of the water addition procedure, rye and wheat straw residues had a positive e ect on water-stable aggregates more frequently than oilseed rape during the incubation period. The results presented here may contribute to a better understanding of decomposition processes after the incorporation of fresh crop residues from cover crops. A future field study investigating the influence of incorporation rates of di erent crop residues on soil aggregate stability would be of great interest. ; The research was funded by the European Union's European Regional Development Fund (Estonian University of Life Sciences ASTRA project [2014-2020.4.01.16-0036] "Value-chain based bio-economy") and the Horizon 2020 project iSQAPER [project number 635750].