Charcoal-like soil additive locks pesticides away from groundwater
Zhao J, Gong J, Li J, Hu Y, Tang S
Soil Health
If you've ever worried about pesticide runoff from a treated lawn or field reaching a nearby stream or well, this shows a simple soil amendment made from charred plant waste can stop that leaching almost completely.
Neonicotinoid pesticides are notorious for washing straight through soil into groundwater because they don't stick well to dirt. Researchers found that mixing biochar (a charcoal-like material made from burning plant matter) into soil makes these pesticides bind so strongly they barely move at all, boosting the soil's grip on them more than 20 times over. Even a small amount of biochar, about 1% of the soil's weight, was enough to stop the pesticides from leaching through in lab column tests.
Key Findings
3% biochar amendment increased soil adsorption capacity for thiamethoxam and clothianidin by over 20-fold compared to untreated soil.
A biochar dosage threshold of ≥1% (w/w) achieved complete interception of freshly applied pesticides in soil column leaching tests and eliminated remobilization of aged residues.
Adsorption followed pseudo-second-order kinetics and the Freundlich isotherm, driven by chemisorption mechanisms including pore-filling and π-π interactions, and promoted formation of stable soil-biochar-pesticide aggregates.
chevron_right Technical Summary
Adding biochar to soil can trap common pesticides called neonicotinoids so tightly that they stop leaching into groundwater, with just 1% biochar by weight enough to block fresh pesticide runoff entirely.
Abstract Preview
Original paper
Immobilization mechanisms and transport fate of neonicotinoids in biochar-amended soils: insights into sorption-desorption hysteresis.
The widespread use of neonicotinoid pesticides, characterized by high water solubility and low soil adsorption, poses a significant threat to groundwater quality due to their high leaching potentia...
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