Dissipation dynamics of fipronil in tropical paddy (Oryza sativa L.) soil: unravelling its persistence and metabolism under varying moisture regime.
Preethu DC, Ashoka KR, Bhagyalakshmi T, Yogananda SB, Vijaykumar L
Soil Health
Rice paddies managed with less water — a common drought-response strategy — linger longer with fipronil residues and concentrate a more toxic breakdown compound in the soil your food grows in.
Researchers tracked what happens to a common rice pesticide (fipronil) in tropical paddy fields under different watering conditions. They found that keeping fields flooded helps break down the pesticide faster, while drier soils and added compost cause it to stick around longer. The pesticide also transforms into a more harmful form in well-oxygenated, drier soils, though by harvest time the rice grains themselves were safe to eat.
Key Findings
Fipronil dissipated fastest under flooded conditions, with residues dropping from 0.70 µg/g on day 1 to 0.01 µg/g by day 30, compared to 1.37 µg/g dropping to only 0.03 µg/g under drier field-capacity conditions.
Organic matter amendment extended fipronil's soil half-life from 11.87 days (flooded, no organic matter) up to 13.75 days (drier soil with organic matter), and up to 20.82 days in unplanted soil.
The toxic breakdown product fipronil sulfone peaked at 0.82 µg/g in drier soils versus 0.60 µg/g in flooded soils, indicating that water-saving irrigation practices increase exposure to this more hazardous metabolite.
chevron_right Technical Summary
A field study in tropical paddy fields found that fipronil insecticide breaks down faster in flooded rice paddies than in drier soils, and that adding organic matter to soil slows its breakdown. Crucially, rice grain residues at harvest fell below safety limits, but a more toxic breakdown product accumulates in drier, oxygen-rich soil conditions.
Abstract Preview
Fipronil, a phenylpyrazole insecticide, is widely used for the management of rice pests; however, its environmental fate and potential risks in tropical paddy ecosystems to food safety under varyin...
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