Browsing by Subject "bioremediation"

Sort by: Order: Results:

Now showing items 1-3 of 3
  • Chen, Yongchen (Helsingfors universitet, 2013)
    Soil contamination with oily products poses great healthy and environmental risks to the polluted sites. The remediation difficulty mainly comes from the complexity of hydrocarbons. Different kinds of remediation technologies have been applied for hydrocarbon removal from soil. New technologies especially in situ bioremediation technologies are emerging constantly. Soil assessment is a key step in the remediation processes since it provides information about the contamination level and potential risks. In the present study, hydrocarbon contaminated soil samples were collected from two sites (one site was contaminated by weathered oily sludge waste with some vegetated plots; the other was contaminated with fuel oil with short-chain hydrocarbons). The samples were analyzed for physicochemical properties and hydrocarbon degraders were enumerated. Four degrading strains were isolated from the samples and their 16S rRNA genes were sequenced. The samples and isolates were investigated to check the existence of three catabolic genes involved in petroleum degradation. The objective was to reveal the intrinsic bioremediation potential of contaminated soils by investigating the key remediation “players” i.e. the degrader microorganisms and catabolic genes. The coexistence of abundant degraders and diverse catabolic genes give the soil a good potential for bioremediation. In addition, the relationships between degrader counts, genes detection and soil contamination levels can reveal how the contaminants affect the indigenous microbial community. The differences between vegetated and nonvegetated plots can also suggest if vegetation with legumes has good potential for hydrocarbon bioremediation. According to the results, both sites were moderately contaminated with different hydrocarbon composition. In the landfarming site, the TPH depletion in vegetated fields was higher than the unvegetated bulk soil areas. However, the degrading microorganism counts had no significant differences between vegetated and nonvegetated plots. The hydrocarbon contamination level had no correlation with the degrader counts. In subsurface soils where aeration was quite limited, degrading microorganisms were much lower than those in surface soils. Catabolic genes were detected from the isolated strains but rarely from the contaminated soil samples. The contaminants co-extracted with soil DNA may inhibit the PCR-based gene detection. With more primer sets or primers targeting broader genetic diversity ranges, more detection results can be expected.
  • Raitosalo, Amanda (Helsingin yliopisto, 2020)
    Heavy traffic and transportation of crude oil makes the Baltic Sea vulnerable to accidental oil spills. Currently mechanical removal is the recommended response method in the Baltic Sea region. However, in bad weather conditions, mechanical oil removal can be challenging, and it may be justifiable to consider alternative response methods in order to protect valuable natural sites. Chemical dispersants are mixtures of surfactants and solvents and are used to treat spilled oil in marine environments. Dispersants break oil slicks into small droplets, which are more readily available for microbial biodegradation. Large-scale studies on the effects of dispersants on microbial communities and biodegradation rates have not been conducted in the Baltic Sea. During this 40-day microcosm study, native microbial communities from the Gulf of Finland were exposed to crude oil, dispersant or their combination. Additional nutrients were not supplied during the study. The experiment was carried out at 10 °C, and samples were collected at days 1, 2, 5, 14 and 40. The amount and expression of genes related to microbial abundance, oil biodegradation and nutrient cycling was assessed by quantitative PCR. Extracellular enzymatic activities of microbes were studied utilizing high throughput robotics. The results indicated that microbial response was primarily elevated in samples containing dispersant. Dispersant was degraded almost completely during the study period. Biodegradation of C21-40 hydrocarbons in crude oil was not enhanced with the addition of dispersant. On genetic level, the abundance and expression of alkane monooxygenase gene (alkB) was elevated in samples with dispersant, whereas the abundance and expression of polycyclic aromatic ring-hydroxylating dioxygenase gene (PAH-RHD) was enhanced also in samples containing crude oil.
  • Mikkonen, Anu; Yläranta, Kati; Tiirola, Marja; Dutra, Lara Ambrosio Leal; Salmi, Pauliina; Romantschuk, Martin; Copley, Shelley; Ikäheimo, Jukka; Sinkkonen, Aki (2018)
    The xenobiotic priority pollutant pentachlorophenol has been used as a timber preservative in a polychlorophenol bulk synthesis product containing also tetrachlorophenol and trichlorophenol. Highly soluble chlorophenol salts have leaked into groundwater, causing severe contamination of large aquifers. Natural attenuation of higher-chlorinated phenols (HCPs: pentachlorophenol + tetrachlorophenol) at historically polluted sites has been inefficient, but a 4-year full scale in situ biostimulation of a chlorophenol-contaminated aquifer by circulation and re-infiltration of aerated groundwater was remarkably successful: pentachlorophenol decreased from 400 μg L−1 to