Microbial turnover and incorporation of organic compounds in oil sand mining reclamation sites
Abstract
Microorganisms play an important role in the development of new soils and in the reclamation of disturbed landscapes. Especially in hydrocarbon-contaminated soils their ability to degrade organic matter and pollutants makes them essential to re-establish full ecosystem functionality. Microbes are also involved in the mobilization of nutrients for plant growth and in the production of greenhouse gases. Reclamation sites from oil sand mining activities in Alberta, Canada, contain residual bitumen as well as other hydrocarbons. So, these areas provide a great opportunity to study microbial degradation of residual contaminants from oil sand. To get an impression of degradation rates as well as metabolic pathways, incubation experiments were performed in the lab. We measured microbial turnover (catabolic metabolism) and incorporation (anabolic metabolism) rates of different common organic compounds in samples from differently treated reclamation sites - with plant cover and without plant cover. About 10 g of sample material was suspended in 10 mL of a solution that mimics the in-situ concentration of dissolved ions. Radioactively labelled 14C-acetate was added as a common substrate, whereas 14C-naphthenic acid was chosen to investigate the microbial community's capability to utilize a typical hydrocarbon pollutant in oil sand tailings as a nutrient source. To test for the influence of fertilizers on microbial activity, phosphate, nitrate and potassium were added to some samples in different combinations. Incubations were run over two different time periods (7 and 14 days). At the end of each incubation experiment, the amount of produced 14CO2, 14C incorporated into the cells and the remaining unreacted 14C in the slurry were measured. First results show that most of the added 14C-acetate is used for respiration as it is mostly released as 14CO2. In upper soil layers only about 3% of 14C is incorporated into cells, whereas in deeper horizons with lower cell abundances about 14% of 14C is used to build up biomass. The results also show that microorganisms use 14C-naphthenic acid as a carbon source, but at a lower rate. About half of the degraded naphthenic acid is incorporated into cells; the other half is released as 14CO2. The results give an impression of how fast and to what amount microorganisms can degrade residual oil compounds. Additionally, our study allows for rough estimates of greenhouse gas emissions of reclamation areas.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2013
- Bibcode:
- 2013AGUFM.B43B0479L
- Keywords:
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- 0418 BIOGEOSCIENCES Bioremediation;
- 0448 BIOGEOSCIENCES Geomicrobiology;
- 0432 BIOGEOSCIENCES Contaminant and organic biogeochemistry;
- 0486 BIOGEOSCIENCES Soils/pedology