title: A toxicity view of the pesticide picloram when immobilized onto a silica gel surface.
abstract: The pesticide picloram (4-amino-3,5,6-trichloropicolinic acid) was anchored onto silica gel to yield a new surface. Isothermal microcalorimetry was applied to study the toxic effects caused to microbial activity of a typical Brazilian agricultural soil by application of free and immobilized picloram. The activity of the microorganisms in 1.50 g of soil sample was stimulated by addition of 6.0 mg of glucose plus 6.0 mg of ammonium sulfate under 34.8% controlled humidity at 298.15+/-0.02 K. The activity was recorded through power-time curves for increasing amounts of the active principle, varying from zero to 10.00 microg g(-1). The increasing amounts of picloram, either free or immobilized, caused a decrease of the original thermal effect. The calorimetric data showed that the anchored pesticide presented a much lower toxic effect than the free picloram on the microbial activity.
authors.affiliation: Instituto de Química, Universidade de Brasília, Caixa Postal 04478, 70919-970 Brasília, Distrito Federal, Brazil. agsprado@unb.br
authors.forename: Alexandre G S
authors.initials: AG
authors.lastname: Prado
authors.forename: Claudio
authors.initials: C
authors.lastname: Airoldi
mesh_terms: D001419:Bacteria / Q000187:drug effects* / Q000378:metabolism*; D002151:Calorimetry / Q000379:methods*; D004305:Dose-Response Relationship, Drug; D004734:Energy Metabolism / Q000187:drug effects; D004784:Environmental Monitoring / Q000379:methods; D006540:Herbicides / Q000737:chemistry / Q000633:toxicity*; D006801:Humans; D008567:Membranes, Artificial; D010846:Picloram / Q000737:chemistry / Q000633:toxicity*; D058428:Silica Gel; D012822:Silicon Dioxide; D012988:Soil Microbiology; D012989:Soil Pollutants / Q000633:toxicity*
chemical_list: D006540:Herbicides; D008567:Membranes, Artificial; D012989:Soil Pollutants; D058428:Silica Gel; D012822:Silicon Dioxide; D010846:Picloram