Paraquat behavior in Costa Rican soils and residues in coffee

• Published in: Journal of agricultural and food chemistry Vol. 38; no. 10; pp. 1985 - 1988
• Main Authors: Constenla, Manuel A, Riley, Dave, Kennedy, Steve H, Rojas, Carlos E, Mora, Luis E, Stevens, John E. B
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 01.10.1990
• Subjects: ADSORCION; ADSORPTION; BIODEGRADACION; BIODEGRADATION; Biological and medical sciences; CAFE; COFFEE; Coffee, tea and other stimulative beverage industries; COSTA RICA; deactivation capacity; Food industries; Fundamental and applied biological sciences. Psychology; HERBICIDAS; HERBICIDE; HERBICIDES; MICROBIAL DEGRADATION; PARACUAT; PARAQUAT; PERSISTENCE; RESIDU; RESIDUES; RESIDUOS; SOIL; SOL; SUELO; Assay; Degradation; Soils; Residue; Pesticides; Paraquat; Coffee; Chemical contamination
• ISSN: 0021-8561; 1520-5118
• DOI: 10.1021/jf00100a022

Soil from 20 Costa Rican coffee plantations was analyzed for adsorption of the herbicide paraquat. A wheat bioassay was used to determine soil adsorption capacities which generally ranged from 100 500 mg/kg soil. Adsorption coefficients ranged from 140 2990. Even though large amounts of paraquat were adsorbed, these amounts were less than expected for the amounts applied to the crops, which is mostly due to photodegradation. Soil residues were usually less than 1% of the wheat bioassay values. Residues in the coffee beans and berries were either negligible or nondetectable and were well below EPA tolerance levels. It is concluded that paraquat can be safely used for hundreds of years before harmful residue levels are reached.