34 thavamani-palanisami
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Thavamani Palanisami conducted a study on bioremediating soils contaminated with chemical mixtures, specifically PAHs and heavy metals. The objectives were to understand the biochemodynamics of PAHs and their interactions with other chemicals, and develop suitable remediation methods. Methods included characterizing contaminated soils, evaluating toxicity of PAH and metal mixtures, and enriching and isolating PAH-degrading bacteria resistant to metals. Results showed isolated cultures could degrade PAHs in the presence of toxic levels of cadmium. The cultures have potential for bioremediating actual contaminated soils. Ongoing work includes microcosm studies, effects on gene expression, and elucidating PAH-metal interactions.
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34 thavamani-palanisami
- 1. Thavamani Palanisami BIOREMEDIATION OF SOILS CONTAMINATED with CHEMICAL MIXTURES
- 2. Acknowledgements To my supervisory committee: Prof. Megharaj Mallavarpu, Director, CERAR Prof. Ravi Naidu, Managing Director CRC CARE Mr. Ross Mcfarland, National Practice Leader, HLA ENSR CERAR ENVIROPACIFIC SERVICES
- 3. Structure Introduction Objective of the study Methods Results Conclusion Work in progress
- 4. Introduction • Almost all contaminated soils contain a mixture of toxic substances • However, current focus of toxicological studies and remediation is single toxic substances; • Mixed contaminated systems can be extremely toxic to environment and a challenge to remediate. • One example of such a system is the gas work sites containing PAHs and other inorganic toxic chemicals. The adverse effect of mixed chemicals is demonstrated by the recent death of Heath Ledger from ingestion of mixture of tablets
- 5. Introduction.. ctd • Successful remediation of PAH contaminated soils requires a thorough understanding of both the biochemo-dynamics of PAHs as single series compound as well as its interaction with other chemicals present at gas work sites
- 6. Objective To study the science underpinning the bioremediation of certain mixed contaminants (specifically PAHs and heavy metals) and develop suitable remediation methods for mixed contaminated soils. Cd, CN
- 7. Milestones addressed Research Milestones 2.2.2. Laboratory based development of bioremediation technology for organic contaminants 2.2.3. Isolation of novel metal(loid) resistant, organic contaminant detoxifying microbes. Commercial milestones 2.3.1 Isolation of novel aerobic and anaerobic POP degrading microorganisms 2.3.2. Isolation and characterisation of novel POP degrading microorganisms
- 8. Methods • Characterization of contaminated soils. • Evaluation of toxicity and bioavailability in spiked soils with known concentrations of PAHs and metals • Testing the toxicity of selected PAHs and metals using novel scientifically-defensible methods. • Enrichment and isolation of PAH degrading bacteria that are highly resistant to selected metals. • Bioremediation of PAHs in liquid as well as soil microcosm using MGP site soils
- 9. Results I. Soil Characterisation • 9 gas work contaminated soils were investigated • Considerable variation in the concentration of PAHs and metals in the study soils PAHs (mg/kg) Heavymetals(mg/kg) LMW HMW Pb Zn Cr As Cd Ni Cu 790 1884 277 183 159 6 47 92 39 (107-2299) (201-6345) (93-671) (63-488) (33-378) (4.5-8.5) (8-112) (28-229) (18-57) LMW- Low molecular weight PAHs (up to 3 benzene rings in structure); HMW- High molecular weight PAHs (more than 4 benzene rings in structure)
- 10. II.PAH degradation in presence of Cd by pure culture • Model PAH compounds : Phenanthrene and Pyrene Metal : Cadmium • Experiment was conducted in a modified microbial media optimised for maximum free Cd • Parameters recorded: Growth, Protein, PAH concentration • Experiment was conducted in duplicate and repeated twice
- 13. Co-degradation
- 14. Conclusion •Isolated cultures were able degrade PAHs in presence of toxic levels of cadmium •The isolated cultures have potential to apply in bioremediation of MGP site soils
- 15. Work in progress • Bioremediation of MGP site soils in microcosm • Effect of PAH-metals on gene expression of earthworm • Elucidating interactions of PAH-Metals • PAH degradation pathway • Algal diversity in MGP soils and its role in PAH degradation
Editor's Notes
- Good morning, My name is Thava, I m doing my second year Phd in CERAR Crc Care. I m happy to present my research update on “Bioremediation of soils contaminated with Chemical mixtures”. In this broad topic our compounds of aim are PAH and Metals.
- Before I start my presentation, I would like to thank my supervisory committee for their outstanding support and “help to explore this unexplored topic”. Also my sincere thanks to all my funding bodies CRC CARE, AU-DEST,UNISA and CERAR. OK let us go to the presentation.
- The over view of my today’s presentation is a , Brief introduction about mixed contaminants, main objective of my study, Overall methods of my research, then I will be talking a brief about one of our degradation study, Sofar conclusion of the study. Finally work/ experiments in progress.
- Soil contamination is a major problem in the latest century. In Severity, Now almost all soils contain a mixture of toxic substance. However current focus of toxicological and remediation studies is single toxic substances only.Unlike sinlge contaminant problem, mixed contaminated systems can be extremely toxic to environment and a challenge to remediate. One fine example of such a system is the gaswork sites, which contains loads of PAHs and other inorganic chemicals esp metals. The adverse effect of mixed chemicals is well demonstrated by recent death of Heath Ledger from ingestion of mixture of tablets(6). cocktail of hypnotic-type drugs prescribed to Heath Ledger for anxiety and insomnia had the potential to make a sleeping person dangerously unresponsive.
- Being an unexplored topic , our main objective is to study the science underpinning the bioremediation of mixed contaminants specfically PAHs and heavy metals) and develop a suitable remediation methods.
- Mixed contaminant research is one of the major milestones in CRC CARE. Our topic supports various milestones . Namely two research milestones 2.2.2…. And 2.2.3. this topic also addresses the two commercial milestones as well,2.3.1… and 2.3.2.
- The over all methodology of my topic is 1.Characterisation of contaminated soils-We faced a great difficulty in getting real contaminated soils, after amost 1.5 we got few soils from former MGP sites. All the soils were completely characterised for its physicochemical and biological properties.I will be giving a brief about characterisation in later slides. 2. Evaluation…..While waiting for contaminated soils, we have spiked uncontaminated soils into 19 different concent of PAHs and metals. The toxicity and bioavailability were evaluated.3.testing ….. We have used some of the novel toxicity testing methods to study interaction between PAH-metals. 4. Enrichement and iso…. Enrichment cultures were set up in selected MGP site soils, subcultured every 14days over few months. 5.Finally the bioremediation of PAHs in liquid as well as soil microcosm.
- 9 gas work site soils were investigated, we have found a considerable variation in the conc of PAHs and metals in the study soil. Here is the range of concentrations of PAHs and metals. Soils have very high concen of HMW than LMW, As LMW compounds are highly volatile might be degraded or disappeared over time(site is >90yr old). Among heavymetals, lead,zinc cadmium and chromium were found in high concentration.
- We have isolated few mixed cultures and one pure culture and tested for metal resistance, PAH degradation in liquid media. To study PAH degradation in presence of metals we tried several microbial media. However the toxicity was under estimated due to high PO4,SO4 and other metal complexing chemicals. We have optimised the modified and optimised in such condition where free Cd++ is >90%, without affecting the PAH degradation. Here we are presenting the degradation study done with one pure culture.
- PHE is a 3 ring LMW compound composite of phenyl and anthracene. The pure culture completely degraded PHE in 3-4 days. Degradation rate in presence of cd was intially bit slower, however on 2 nd day on par with PHE alone and 3 rd day faster than PHE alone. The culture showed a positive effect in presence of cadmium and it doesn’t affected the PHE degradation. The degradation rate was monitored and supported by OD. 4 th day was the highest OD upt 0.8nm in Phe+cd. Sometimes color change during degradation may over estimate the OD. So the Protein conc was measured at the same time and confirms the culture growth.
- Unlike PHE, Pyrene is a HMW consisting of four fused benzene rings. Solubility is only 0.135mg/l. The degradation pyrene when compared to PHE is slightly slower. Though the degradation was only 80% in 15-20days, the pureculture once again showed a great tolerance to cd without losing its degradation potential. Here you can see degradation in PY+Cd much higher than PY alone. Once again the OD and Protein concentration very well supports the culture growth&degradation.
- To improve the PY degradation we did another study, with Phe and PY together. By adding PHE together culture growth was improved and started utilising Phe as well as PY. One 3 rd day Phe was completely degraded, then the bugs started utilising PY as carbon source, at the end 100% degradation was achieved in 15 th day. Here also cadmium has positive effect on PAH degradation. This is in short about our degradation study, this was extended to other HMW PAHs as well. In our latest results, the pure culture improved its degradation rate, now it can degrade PYR completely within 10days. [Pyrene-2d,4d,10d,15d20d-Phe-1,2,3,4,5]
- We have completed the similar experiments with other cultures as well.The main conclusion drawn from the liquid culture degradation study is the isolated cultures were able to degrade PAHs in presence of toxic levels of cadmium. The isolated cultures have potential to apply in bioremediation of MGP site soils.
- These are all the work in progress. We have started a bioremediation study in microcosm level using MGP site soils and degradation is being monitored periodically. When we did toxicity studies in MGP soils, some of the moderately contaminated soils havent shown much effect on mortality,to explore the real toxicity we started using molecular techniques to study the effect of PAH-metals on gene expression. Other two important works are Elucidating interactions of PAH-metals based on our experimental results and if possible to study the degradation pathway in presence of metals. When we characterised the collected MGP site soils, we have isolated and purified several algal species from highly contaminated soils, planning to look at the role of algae in PAH degradation.