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The breakdown of malathion in soil and soil components
1Biological Laboratory, University of Kent, CT2 7NJ, Canterbury, Kent, England.
Microbial Ecology
|November 16, 2013
Summary
The organophosphorus insecticide malathion rapidly breaks down in soil, primarily due to its organic matter content. Microbial metabolism plays a lesser role, especially in soils with low organic matter.
Area of Science:
- Environmental Chemistry
- Soil Science
- Pesticide Degradation
Background:
- Organophosphorus insecticides like malathion are widely used in agriculture.
- Understanding pesticide degradation pathways in soil is crucial for environmental risk assessment.
- The role of soil components in pesticide breakdown requires detailed investigation.
Purpose of the Study:
- To investigate the disappearance of malathion from silt loam soil and its components.
- To determine the influence of soil organic matter and microbial activity on malathion degradation.
- To identify the primary factors responsible for rapid malathion breakdown in soil.
Main Methods:
- Malathion degradation was studied in nonsterile, sterile (autoclaved, sodium azide-treated), and irradiated soil samples.
- Experiments were conducted on whole soil, separated soil fractions (sand, silt, clay), and organic matter components.
- Half-lives and time for 90% decomposition were measured under various conditions.
Main Results:
- Malathion breakdown was rapid in the presence of organic matter and organo-mineral complexes (half-life ~1-2 days).
- Degradation was significantly slower in soil fractions lacking organic matter and negligible in autoclaved components.
- Microbial activity contributed to breakdown, but was slower than degradation mediated by organic matter components.
Conclusions:
- Colloidal organic matter, or associated fractions, is the most significant factor in rapid malathion breakdown in this soil.
- Microbial metabolism is a slower degradation pathway, more relevant in soils low in organic matter.
- A stable exoenzyme within the organic matter is suggested as the catalytic component responsible for malathion degradation.
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