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Updated: Jun 23, 2026

Determination of the Settling Rate of Clay/Cyanobacterial Floccules
Published on: June 11, 2018
Atrazine biodegradation modulated by clays and clay/humic acid complexes
Pascale Besse-Hoggan1, Tatiana Alekseeva, Martine Sancelme
1Laboratoire de Synthèse et Etude de Systèmes à Intérêt Biologique, UMR-CNRS 6504, Université Blaise Pascal, 63177 Aubière Cedex, France. Pascale.Besse@univ-bpclermont.fr
Soil clay properties significantly impact pesticide fate. Humic acid enhances atrazine sorption, affecting its biodegradation rate, which is limited by desorption but surprisingly increases with Layered Double Hydroxide (LDH) due to bacterial cell adsorption.
Area of Science:
- Environmental Chemistry
- Soil Science
- Microbiology
Background:
- Pesticide fate in soil is governed by sorption processes influencing transfer and bioavailability.
- Cationic (Ca-bentonite) and anionic (Layered Double Hydroxide - LDH) clays exhibit distinct interactions with ionizable pesticides like atrazine (AT).
Purpose of the Study:
- To investigate the sorption behavior of atrazine (AT) on modified clays (Ca-bentonite and LDH) with varying humic acid (HA) content.
- To evaluate the impact of these clay-HA-AT interactions on AT biodegradation by Pseudomonas sp. ADP.
Main Methods:
- Sorption experiments using Ca-bentonite and LDH modified with humic acid (HA).
- Analysis of atrazine (AT) biodegradation and metabolite formation using Pseudomonas sp. ADP.
- Investigation of the role of bacterial cell adsorption on clay particles.
Main Results:
- Ca-bentonite showed significant AT sorption, while LDH exhibited minimal interaction.
- Humic acid (HA) addition to clays enhanced AT sorption.
- Biodegradation rates were modulated by sorption capacity and limited by desorption.
- Surprisingly, AT biodegradation increased significantly with LDH, attributed to bacterial cell adsorption.
Conclusions:
- Clay properties and humic acid content critically influence pesticide sorption and bioavailability.
- Desorption rates are a key limiting factor for pesticide biodegradation.
- Bacterial cell adsorption onto clay particles can enhance the degradation of non-sorbed pesticides, impacting environmental fate predictions.
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