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Title: EFFECTS OF SORPTION ON THE BIODEGRADATION OF 2-METHYLPYRIDINE IN AQUEOUS SUSPENSIONS OF REFERENCE CLAY MINERALS

Author
item OLOUGHLIN, EDWARD - TYNDALL AFB RESEARCH LAB
item TRAINA, SAMUEL - OHIO STATE UNIV
item SIMS, GERALD

Submitted to: Environmental Toxicology and Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/14/2000
Publication Date: N/A
Citation: N/A

Interpretive Summary: Among the most important pollutants detected in surface and groundwater near fossil fuel conversion facilities are the alkylpyridines (nitrogen containing organic solvents), the most common of which is 2-methylpyridine (2-MP). Through readily degraded by soil microorganisms, 2-MP often persists in sediments, possibly due to inability of microorganisms to access the compound. Studies were conducted to determine the bioavailability of 2-MP to a soil bacterium in the presence and absence of common soil minerals which might adsorb and thus reduce the availability of the compound. Results of the studies showed that the presence of soil minerals with a great affinity for 2-MP decreased microbial degradation of the compound suggesting a role of minerals in reducing the bioavailability and thus increasing the presistence of this compound in the environment. These results illustrate the need to consider bioavailability when designing projects for bioremediation of these pollutants. The results ma also be extrapolated to certain pesticides with high affinity for soil solids. The impact of this work is to provide a framework for making site management decisions that will reduce offsite contamination by these and related compounds, and for planning facilities and approaches for bioremediation of pollutants with similar environmental behavior.

Technical Abstract: The effects of sorption on the bioavailability of 2-methylpyridine (2-MP) were investigated by determining the biodegradation of 2-MP by an Arthrobacter sp. in aqueous suspensions of reference clay minerals and a synthetic cation exchange resin. Adsorption of 2-MP on kaolinite, illite, hectorite, montmorillonite, and Dowex was determined by the batch equilibrium method. In general, adsorption of 2-MP was positively correlated with the cation exchange capacity of the sorbent, suggesting that sorption of 2-MP on clay minerals occurs through a cation exchange reaction via the 2-methylpyridinum ion. The biodegradation of 2-MP was most rapid in the kaolinite suspensions followed by the controls> illite>> Dowex> hectorite/montmorillonite. With the exception of kaolinite, adsorption of 2-MP on clay minerals and Dowex reduced the rate of biodegradation. The degree of attenuation was positively correlated with the fraction of 2-MP sorbed, suggesting that sorbed 2-MP was not directly available for degradation. Desorption was not rate limiting in suspensions containing hectorite, montmorillonite, or Dowex; however, desorption may have become limiting in the kaolinite and illite suspensions. The results of this study clearly indicate that adsorption can directly affect the degradation of 2-MP in complex mineral systems.