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Nutrient level, microbial activity, and alachlor transformation in aerobic aquatic systems
Charles W Knapp1, David W Graham, Gina Berardesco
1Department of Civil and Environmental Engineering, University of Kansas, 4002 Learned Hall, 66045, Lawrence, KS, USA
Water Research
|October 22, 2003
Summary
Alachlor herbicide degrades in water primarily through biotic processes. Efficient transformation requires both eubacterial and eukaryotic microbial activity, especially in nutrient-rich, hypereutrophic aquatic systems.
Area of Science:
- Environmental Chemistry
- Aquatic Ecology
- Microbiology
Background:
- Alachlor is a common herbicide found in surface waters.
- Its environmental fate is influenced by various factors in aquatic systems.
Purpose of the Study:
- To investigate the primary mechanisms affecting alachlor fate in aquatic environments.
- To assess the impact of fertility and microbial activity on alachlor transformation.
Main Methods:
- Field experiments using large mesocosms (n=39) and smaller microcosms (n=16).
- Mesocosms evaluated alachlor disappearance under varying nutrient conditions (oligotrophic to hypereutrophic).
- Microcosms used microbial inhibitors to block eubacterial, eukaryotic, and universal microbial activity.
Main Results:
- Alachlor transformation rate coefficients ranged from 0.006 to 0.042 day⁻¹.
- Highest transformation rates were observed in hypereutrophic waters.
- Alachlor transformation was >90% biotic, requiring both eubacterial and eukaryotic activity for efficient biotransformation.
Conclusions:
- Alachlor transformation in aquatic systems is primarily a biotic process.
- Efficient alachlor biotransformation depends on the metabolic activity of both major microbial domains (eubacterial and eukaryotic).
- Nutrient levels, particularly in hypereutrophic waters, influence alachlor degradation rates.